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Sample records for quarter-filled layered organic

  1. Photoinduced melting and charge order in quarter-filled organic conductors: Itinerant electron systems with competing interactions

    NASA Astrophysics Data System (ADS)

    Yonemitsu, Kenji; Maeshima, Nobuya; Tanaka, Yasuhiro; Miyashita, Satoshi

    2009-02-01

    Photoinduced charge dynamics in one- and two-dimensional organic conductors are studied theoretically in extended Peierls-Hubbard models. For quasi-one-dimensional (EDO-TTF)2PF6, photoinduced change in the charge order pattern from (0110) to (1010) is accompanied by probe-energy-dependent oscillations of conductivity. This is caused by coexistence of charge order and delocalized electrons. For quasi-two-dimensional α-(BEDT-TTF)2I3 and θ-(BEDT-TTF)2RbZn(SCN)4, photoinduced melting of the horizontal-stripe charge order proceeds easier in the α-type salt than in the θ-type salt. This is because the charge order in the θ-type salt is more strongly stabilized by electron-phonon interactions.

  2. Single-pole ladder at quarter filling

    NASA Astrophysics Data System (ADS)

    Aristov, D. N.; Kiselev, M. N.; Kikoin, K.

    2007-06-01

    We study the ground state and excitation spectrum of a quasi-one-dimensional system consisting of a pole and rungs oriented in opposite directions (“centipede ladder,” CL) at quarter filling. The spin and charge excitation spectra are found in the limits of small and large longitudinal hoppings t‖ compared to the on-rung hopping rate t⊥ and exchange coupling I⊥ . At small t‖ , the system with ferromagnetic on-rung exchange demonstrates instability against dimerization. Coherent propagation of charge-transfer excitons is possible in this limit. At large t‖ , CL behaves like two-orbital Hubbard chain, but the gap opens in the charge excitation spectrum, thus reducing the symmetry from SU(4) to SU(2). The spin excitations are always gapless and their dispersion changes from quadratic magnonlike for ferromagnetic on-rung exchange to linear spinonlike for antiferromagnetic on-rung exchange in weak longitudinal hopping limit.

  3. Entanglement entropies of the quarter filled Hubbard model

    NASA Astrophysics Data System (ADS)

    Calabrese, Pasquale; Essler, Fabian H. L.; Läuchli, Andreas M.

    2014-09-01

    We study Rényi and von Neumann entanglement entropies in the ground state of the one dimensional quarter-filled Hubbard model with periodic boundary conditions. We show that they exhibit an unexpected dependence on system size: for L = 4mod 8 the results are in agreement with expectations based on conformal field theory, while for L = 0mod 8 additional contributions arise. We show that these can be understood in terms of a ‘shell-filling’ effect and we develop a conformal field theory approach to calculate the additional contributions to the entropies. These analytic results are found to be in excellent agreement with density matrix renormalization group computations for weak Hubbard interactions. We argue that for larger interactions the presence of a marginal irrelevant operator in the spin sector strongly affects the entropies at the finite sizes accessible numerically and we present an effective way to take them into account.

  4. One-dimensional Kondo lattice model at quarter filling

    NASA Astrophysics Data System (ADS)

    Xavier, J. C.; Miranda, E.

    2008-10-01

    We revisit the problem of the quarter-filled one-dimensional Kondo lattice model, for which the existence of a dimerized phase and a nonzero charge gap had been reported by Xavier [Phys. Rev. Lett. 90, 247204 (2003)]. Recently, some objections were raised claiming that the system is neither dimerized nor has a charge gap. In the interest of clarifying this important issue, we show that these objections are based on results obtained under conditions in which the dimer order is artificially suppressed. We use the incontrovertible dimerized phase of the Majumdar-Ghosh point of the J1-J2 Heisenberg model as a paradigm with which to illustrate this artificial suppression. Finally, by means of extremely accurate density-matrix renormalization-group calculations, we show that the charge gap is indeed nonzero in the dimerized phase.

  5. Coulomb-induced pairing in a quarter-filled band model for κ-(BEDT-TTF)2X

    NASA Astrophysics Data System (ADS)

    de Silva, W. Wasanthi; Gomes, Niladri; Mazumdar, Sumit; Clay, R. Torsten

    κ -(BEDT-TTF)2X is a two dimensional organic charge transfer solid superconductor with a hole density of one half per (BEDT-TTF) molecule. With one hole per dimer of molecules, the material is frequently described using an effective 1 / 2 -filled band Hubbard model on an anisotropic triangular lattice. Within this effective model a metal to antiferromagnetic (AFM) semiconductor phase transition is found. Calculations beyond the mean field level, however, have shown absence of superconductivity within the model. We present the results of correlated-electron calculations on the κ-lattice for up to 64 BEDT-TTF molecules using the Constrained Path Monte Carlo (CPMC) and Path Integral Renormalization Group (PIRG) methods over a wide range of carrier density. We show that superconducting pair-pair correlations in this model are enhanced by electron-electron (e-e) interactions for d-wave pairing symmetry uniquely for hole density close to quarter-filling. Our results indicate that this enhancement of superconductivity is not related to the presence of AFM order, but to the strong tendency to spin-singlet formation in the quarter-filled band. Supported by DOE Grant DE-FG02-06ER46315 and NSF-CHE-151475.

  6. Organic photovoltaic cells utilizing ultrathin sensitizing layer

    DOEpatents

    Rand, Barry P.; Forrest, Stephen R.

    2011-05-24

    A photosensitive device includes a series of organic photoactive layers disposed between two electrodes. Each layer in the series is in direct contact with a next layer in the series. The series is arranged to form at least one donor-acceptor heterojunction, and includes a first organic photoactive layer comprising a first host material serving as a donor, a thin second organic photoactive layer comprising a second host material disposed between the first and a third organic photoactive layer, and the third organic photoactive layer comprising a third host material serving as an acceptor. The first, second, and third host materials are different. The thin second layer serves as an acceptor relative to the first layer or as a donor relative to the third layer.

  7. Photoinduced melting of charge order in a quarter-filled electron system coupled with different types of phonons

    NASA Astrophysics Data System (ADS)

    Yonemitsu, Kenji; Maeshima, Nobuya

    2007-08-01

    Photoinduced melting of charge order is calculated by using the exact many-electron wave function coupled with classically treated phonons in the one-dimensional quarter-filled Hubbard model with Peierls and Holstein types of electron-phonon couplings. The model parameters are taken from recent experiments on (EDO-TTF)2PF6 (EDO-TTF=ethylenedioxy-tetrathiafulvalene) with a (0110) charge order, where transfer integrals are modulated by molecular displacements (bond-coupled phonons) and site energies by molecular deformations (charge-coupled phonons). The charge-transfer photoexcitation from (0110) to (0200) configurations and that from (0110) to (1010) configurations have different energies. The corresponding excited states have different shapes of adiabatic potentials as a function of these two phonon amplitudes. The adiabatic potentials are shown to be useful in understanding differences in the photoinduced charge dynamics and the efficiency of melting, which depend not only on the excitation energy but also on the relative phonon frequency of the bond- and charge-coupled phonons.

  8. Organic photovoltaic cells utilizing ultrathin sensitizing layer

    DOEpatents

    Forrest, Stephen R.; Yang, Fan; Rand, Barry P.

    2011-09-06

    A photosensitive device includes a plurality of organic photoconductive materials disposed in a stack between a first electrode and a second electrode, including a first continuous layer of donor host material, a second continuous layer of acceptor host material, and at least one other organic photoconductive material disposed as a plurality of discontinuous islands between the first continuous layer and the second continuous layer. Each of these other photoconductive materials has an absorption spectra different from the donor host material and the acceptor host material. Preferably, each of the discontinuous islands consists essentially of a crystallite of the respective organic photoconductive material, and more preferably, the crystallites are nanocrystals.

  9. Quarter-filled systems with frustration: Candidate for correlated electron superconductivity

    NASA Astrophysics Data System (ADS)

    Gomes, Niladri; de Silva, W. Wasanthi; Dutta, Tirthankar; Clay, R. Torsten; Mazumdar, Sumit

    A necessary condition for superconductivity (SC) driven by electron correlation is that electron electron (e-e) interactions enhance superconducting pair-pair correlations, relative to the non-interacting limit. We present the results of high-precision calculations of superconducting pair-pair correlations on four different frustrated lattices over the complete range of carrier density 0 < ρ < 1 in each case. We find that pair correlations are enhanced relative to the noninteracting limit only for density ρ equal to or close to 0 . 5 (1 / 4 filling). At all other ρ pair correlations are suppressed by interactions. This enhancement is due to the proximity to a spin-gapped paired-electron crystal (PEC) state that occurs at ρ = 0 . 5 . Our theory explains the pseudogap observed at high temperatures in many organic superconductors. The remarkable bandfilling specificity is an essential ingredient to understanding the mechanism of superconductivity in the two-dimensional organic charge-transfer solids as well as the many different families of other unconventional superconductors that share this bandfilling. Supported by DOE Grant DE-FG02-06ER46315 and NSF-CHE-151475.

  10. Gate Control of Electronic Phases in a Quarter-Filled Manganite

    PubMed Central

    Hatano, T.; Ogimoto, Y.; Ogawa, N.; Nakano, M.; Ono, S.; Tomioka, Y.; Miyano, K.; Iwasa, Y.; Tokura, Y.

    2013-01-01

    Electron correlation often produces a variety of electrically insulating states caused by self-organization of electrons, which are particularly stable at commensurate fillings. Although collapsing such ordered states by minute external stimuli has been a key strategy toward device applications, it is difficult to access their true electronic phase boundaries due to the necessity of fine-tuning of material parameters. Here, we demonstrate the ambipolar resistance switching in Pr1−xSrxMnO3 thin films (x = 0.5; an effectively 1/4-filled state) by quasi-continuous control of the doping level x and band-width W using gate-voltage and magnetic field, enabled by the extreme electric-field formed at the nanoscale interface generated in an electrolyte-gated transistor. An electroresistance peak with unprecedented steepness emerges on approaching a critical point in the x-W phase diagram. The technique opens a new route to Mott-insulator based transistors and to discovering singularities hitherto unnoticed in conventional bulk studies of strongly correlated electron systems. PMID:24104858

  11. Organic doping of rotated double layer graphene

    NASA Astrophysics Data System (ADS)

    George, Lijin; Jaiswal, Manu

    2016-05-01

    Charge transfer techniques have been extensively used as knobs to tune electronic properties of two- dimensional systems, such as, for the modulation of conductivity mobility of single layer graphene and for opening the bandgap in bilayer graphene. The charge injected into the graphene layer shifts the Fermi level away from the minimum density of states point (Dirac point). In this work, we study charge transfer in rotated double-layer graphene achieved by the use of organic dopant, Tetracyanoquinodimethane. Naturally occurring bilayer graphene has a well-defined A-B stacking whereas in rotated double-layer the two graphene layers are randomly stacked with different rotational angles. This rotation is expected to significantly alter the interlayer interaction. Double-layer samples are prepared using layer-by-layer assembly of chemical vapor deposited single-layer graphene and they are identified by characteristic resonance in the Raman spectrum. The charge transfer and distribution of charges between the two graphene layers is studied using Raman spectroscopy and the results are compared with that for single-layer and A-B stacked bilayer graphene doped under identical conditions.

  12. Two-layer organic photovoltaic cell

    SciTech Connect

    Tang, C.W.

    1986-01-13

    A thin-film, two-layer organic photovoltaic cell has been fabricated from copper phthalocyanine and a perylene tetracarboxylic derivative. A power conversion efficiency of about 1% has been achieved under simulated AM2 illumination. A novel feature of the device is that the charge-generation efficiency is relatively independent of the bias voltage, resulting in cells with fill factor values as high as 0.65. The interface between the two organic materials, rather than the electrode/organic contacts, is crucial in determining the photovoltaic properties of the cell.

  13. Organic electronic devices with multiple solution-processed layers

    DOEpatents

    Forrest, Stephen R.; Lassiter, Brian E.; Zimmerman, Jeramy D.

    2015-08-04

    A method of fabricating a tandem organic photosensitive device involves depositing a first layer of an organic electron donor type material film by solution-processing of the organic electron donor type material dissolved in a first solvent; depositing a first layer of an organic electron acceptor type material over the first layer of the organic electron donor type material film by a dry deposition process; depositing a conductive layer over the interim stack by a dry deposition process; depositing a second layer of the organic electron donor type material over the conductive layer by solution-processing of the organic electron donor type material dissolved in a second solvent, wherein the organic electron acceptor type material and the conductive layer are insoluble in the second solvent; depositing a second layer of an organic electron acceptor type material over the second layer of the organic electron donor type material film by a dry deposition process, resulting in a stack.

  14. Organic electronic devices with multiple solution-processed layers

    DOEpatents

    Forrest, Stephen R.; Lassiter, Brian E.; Zimmerman, Jeramy D.

    2016-07-05

    A method for fabricating an organic light emitting device stack involves depositing a first conductive electrode layer over a substrate; depositing a first set of one or more organic layers, wherein at least one of the first set of organic layers is a first emissive layer and one of the first set of organic layers is deposited by a solution-based process that utilizes a first solvent; depositing a first conductive interlayer by a dry deposition process; and depositing a second set of one or more organic layers, wherein at least one of the second set of organic layers is a second emissive layer and one of the second set of organic layers is deposited by a solution-based process that utilizes a second solvent, wherein all layers that precede the layer deposited using the second solvent are insoluble in the second solvent.

  15. Global Phase Diagram in Layered Organic Conductors

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Guo, Yaowu

    2014-03-01

    Layered organic superconductors serve as model systems for Mott physics with geometrical frustration. The global phase diagram of such system is obtained by using Gutzwiller variational method to study a Hubbard model including a spin exchange coupling term. Five possible candidates of ground state are obtained respectively, including a spin liquid insulating state at large on-site Coulomb repulsion U and large lattice frustration t'/t, an antiferromagnetic state at large U and small t'/t , two Gossamer superconducting states at medium U with either gapless dx 2 - y 2-wave (small t'/t) or gapped d +id-wave symmetry (large t'/t) , and a metallic Fermi liquid state at small U. Moreover, we study the evolution of double occupancy number d in terms of different U and t'/t parameters mimicking the pressure effect. Our results are qualitatively consistent with main experimental results in organic superconductors. -/abstract- Billing ID: 814549 Member I

  16. Organic light emitting device having multiple separate emissive layers

    SciTech Connect

    Forrest, Stephen R.

    2012-03-27

    An organic light emitting device having multiple separate emissive layers is provided. Each emissive layer may define an exciton formation region, allowing exciton formation to occur across the entire emissive region. By aligning the energy levels of each emissive layer with the adjacent emissive layers, exciton formation in each layer may be improved. Devices incorporating multiple emissive layers with multiple exciton formation regions may exhibit improved performance, including internal quantum efficiencies of up to 100%.

  17. Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit

    2014-01-15

    A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4′-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigated through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.

  18. Organic photosensitive optoelectronic device having a phenanthroline exciton blocking layer

    DOEpatents

    Thompson, Mark E.; Li, Jian; Forrest, Stephen; Rand, Barry

    2011-02-22

    An organic photosensitive optoelectronic device, having an anode, a cathode, and an organic blocking layer between the anode and the cathode is described, wherein the blocking layer comprises a phenanthroline derivative, and at least partially blocks at least one of excitons, electrons, and holes.

  19. Novel solutions for thin film layer deposition for organic materials

    NASA Astrophysics Data System (ADS)

    Keiper, Dietmar; Long, Michael; Schwambera, Markus; Gersdorff, Markus; Kreis, Juergen; Heuken, Michael

    2011-03-01

    Innovative systems for carrier-gas enhanced vapor phase deposition of organic layers offer advanced methods for the precise deposition of complex thin-film layer stacks. The approach inherently avoids potential short-comings from solvent-based polymer deposition and offers new opportunities. The process operates at low pressure (thus avoiding complex vacuum setups), and, by employing AIXTRON's extensive experience in freely scalable solutions, can be adapted to virtually any production process and allows for R&D and production systems alike. Deposition of organic layers and stacks recommends the approach for a wide range of organic small molecule and polymer materials (including layers with gradual change of the composition), for conductive layers, for dielectric layers, for barrier systems, for OLED materials, and surface treatments such as oleophobic / hydrophobic coatings. With the combination of other vapor phase deposition solutions, hybrid systems combining organic and inorganic materials and other advanced stacks can be realized.

  20. Interplane transport effects in layered organic conductors.

    SciTech Connect

    Symington, J. A.; Singleton, J.; Harrison, N.; Clayton, N.; Schlueter, J. A.; Kurmoo, M.; Day, P.

    2000-08-22

    Detailed studies of the magnetic field orientation on magnetic quantum oscillations in two charge transfer salts of the molecule ET have been carried out. .After all conventional mechanisms affecting quantum oscillations have been accounted for, we find that the amplitude of the oscillations has an underlying dependence exp({minus}{alpha} tan 0), where {theta} is the angle between the normal to the highly-conducting layers and the magnetic field, and a is a constant.

  1. Organic electrophosphorescence device having interfacial layers

    DOEpatents

    Choulis, Stelios A.; Mathai, Mathew; Choong, Vi-En; So, Franky

    2010-08-10

    Techniques are described for forming an organic light emitting diode device with improved device efficiency. Materials having at least one energy level that is similar to those of a phosphorescent light emitting material in the diode are incorporated into the device to directly inject holes or electrons to the light emitting material.

  2. Film-coupled nanoparticles by atomic layer deposition: Comparison with organic spacing layers

    SciTech Connect

    Ciracì, Cristian Mock, Jack J.; McGuire, Felicia; Liu, Xiaojun; Smith, David R.; Chen, Xiaoshu; Oh, Sang-Hyun

    2014-01-13

    Film-coupled nanoparticle systems have proven a reliable platform for exploring the field enhancement associated with sub-nanometer sized gaps between plasmonic nanostructures. In this Letter, we present a side-by-side comparison of the spectral properties of film-coupled plasmon-resonant, gold nanoparticles, with dielectric spacer layers fabricated either using atomic layer deposition or using organic layers (polyelectrolytes or self-assembled monolayers of molecules). In either case, large area, uniform spacer layers with sub-nanometer thicknesses can be accurately deposited, allowing extreme coupling regimes to be probed. The observed spectral shifts of the nanoparticles as a function of spacer layer thickness are similar for the organic and inorganic films and are consistent with numerical calculations taking into account the nonlocal response of the metal.

  3. Structural templating of multiple polycrystalline layers in organic photovoltaic cells

    SciTech Connect

    Lassiter, Brian E; Lunt, Richard R; Renshaw, Kyle; Forrest, Stephen R.

    2010-09-01

    We demonstrate that organic photovoltaic cell performance is influenced by changes in the crystalline orientation of composite layer structures. A 1.5 nm thick self-organized, polycrystalline template layer of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) orients subsequently deposited layers of a diindenoperylene exciton blocking layer, and the donor, copper phthalocyanine (CuPc). Control over the crystalline orientation of the CuPc leads to changes in its frontier energy levels, absorption coefficient, and surface morphology, resulting in an increase of power conversion efficiency at 1 sun from 1.42 ± 0.04% to 2.19 ± 0.05% for a planar heterojunction and from 1.89 ± 0.05% to 2.49 ± 0.03% for a planar-mixed heterojunction.

  4. Structural templating of multiple polycrystalline layers in organic photovoltaic cells.

    PubMed

    Lassiter, Brian E; Lunt, Richard R; Renshaw, C Kyle; Forrest, Stephen R

    2010-09-13

    We demonstrate that organic photovoltaic cell performance is influenced by changes in the crystalline orientation of composite layer structures. A 1.5 nm thick self-organized, polycrystalline template layer of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) orients subsequently deposited layers of a diindenoperylene exciton blocking layer, and the donor, copper phthalocyanine (CuPc). Control over the crystalline orientation of the CuPc leads to changes in its frontier energy levels, absorption coefficient, and surface morphology, resulting in an increase of power conversion efficiency at 1 sun from 1.42 ± 0.04% to 2.19 ± 0.05% for a planar heterojunction and from 1.89 ± 0.05% to 2.49 ± 0.03% for a planar-mixed heterojunction. PMID:21165074

  5. Resistance to forced airflow through layers of composting organic material.

    PubMed

    Teixeira, Denis Leocádio; de Matos, Antonio Teixeira; Melo, Evandro de Castro

    2015-02-01

    The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of organic residues submitted to two stages of biochemical degradation, and to evaluate the static pressure drop of airflow thought the material layer. Measurements of static pressure drop in the layers of sugarcane bagasse and coffee husks mixed with poultry litter on day 0 and after 30 days of composting were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m(3) s(-1) m(-2). Static pressure gradient and specific airflow rate data were properly fit to the Shedd, Hukill & Ives and Ergun models, which may be used to predict the static pressure gradient of air to be blown through the organic residue layers. However, the Shedd model was that which best represented the phenomenon studied. The static pressure drop of airflow increased as a power of the material layer thickness and showed tendency for decreasing with the biochemical degradation time of the organic material. PMID:25536861

  6. Single-layer graphene cathodes for organic photovoltaics

    SciTech Connect

    Cox, Marshall P.; Gorodetsky, Alon A.; Kim, Bumjung; Kim, Keun Soo; Jia, Zhang; Kim, Philip; Nuckolls, Colin; Kymissis, Ioannis

    2011-01-01

    A laminated single-layer graphene is demonstrated as a cathode for organic photovoltaicdevices. The measured properties indicate that graphene offers two potential advantages over conventional photovoltaic electrode materials; work function matching via contact doping, and increased power conversion efficiency due to transparency. These findings indicate that flexible, light-weight all carbon solar cells can be constructed using graphene as the cathode material.

  7. On the source of organic acid aerosol layers above clouds.

    PubMed

    Sorooshian, Armin; Lu, Miao-Ling; Brechtel, Fred J; Jonsson, Haflidi; Feingold, Graham; Flagan, Richard C; Seinfeld, John H

    2007-07-01

    During the July 2005 Marine Stratus/Stratocumulus Experiment (MASE) and the August-September 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed aerosols and cumulus clouds in the eastern Pacific Ocean off the coast of northern California and in southeastern Texas, respectively. An on-board particle-into-liquid sampler (PILS) quantified inorganic and organic acid species with < or = 5-min time resolution. Ubiquitous organic aerosol layers above cloud with enhanced organic acid levels were observed in both locations. The data suggest that aqueous-phase reactions to produce organic acids, mainly oxalic acid, followed by droplet evaporation is a source of elevated organic acid aerosol levels above cloud. Oxalic acid is observed to be produced more efficiently relative to sulfate as the cloud liquid water content increases, corresponding to larger and less acidic droplets. As derived from large eddy simulations of stratocumulus underthe conditions of MASE, both Lagrangian trajectory analysis and diurnal cloudtop evolution provide evidence that a significant fraction of the aerosol mass concentration above cloud can be accounted for by evaporated droplet residual particles. Methanesulfonate data suggest that entrainment of free tropospheric aerosol can also be a source of organic acids above boundary layer clouds. PMID:17695910

  8. Analysis of Charge Carrier Transport in Organic Photovoltaic Active Layers

    NASA Astrophysics Data System (ADS)

    Han, Xu; Maroudas, Dimitrios

    2015-03-01

    We present a systematic analysis of charge carrier transport in organic photovoltaic (OPV) devices based on phenomenological, deterministic charge carrier transport models. The models describe free electron and hole transport, trapping, and detrapping, as well as geminate charge-pair dissociation and geminate and bimolecular recombination, self-consistently with Poisson's equation for the electric field in the active layer. We predict photocurrent evolution in devices with active layers of P3HT, P3HT/PMMA, and P3HT/PS, as well as P3HT/PCBM blends, and photocurrent-voltage (I-V) relations in these devices at steady state. Charge generation propensity, zero-field charge mobilities, and trapping, detrapping, and recombination rate coefficients are determined by fitting the modeling predictions to experimental measurements. We have analyzed effects of the active layer morphology for layers consisting of both pristine drop-cast films and of nanoparticle (NP) assemblies, as well as effects on device performance of insulating NP doping in conducting polymers and of specially designed interlayers placed between an electrode and the active layer. The model predictions provide valuable input toward synthesis of active layers with prescribed morphology that optimize OPV device performance.

  9. Inverted organic photovoltaic device with a new electron transport layer

    PubMed Central

    2014-01-01

    We demonstrate that there is a new solution-processed electron transport layer, lithium-doped zinc oxide (LZO), with high-performance inverted organic photovoltaic device. The device exhibits a fill factor of 68.58%, an open circuit voltage of 0.86 V, a short-circuit current density of −9.35 cm/mA2 along with 5.49% power conversion efficiency. In addition, we studied the performance of blend ratio dependence on inverted organic photovoltaics. Our device also demonstrates a long stability shelf life over 4 weeks in air. PMID:24674457

  10. Layered structures of organic/inorganic hybrid halide perovskites

    NASA Astrophysics Data System (ADS)

    Huan, Tran Doan; Tuoc, Vu Ngoc; Minh, Nguyen Viet

    2016-03-01

    Organic-inorganic hybrid halide perovskites, in which the A cations of an ABX3 perovskite are replaced by organic cations, may be used for photovoltaic and solar thermoelectric applications. In this contribution, we systematically study three lead-free hybrid perovskites, i.e., methylammonium tin iodide CH3NH3SnI3 , ammonium tin iodide NH4SnI3 , and formamidnium tin iodide HC (NH2)2SnI3 by first-principles calculations. We find that in addition to the commonly known motif in which the corner-shared SnI6 octahedra form a three-dimensional network, these materials may also favor a two-dimensional (layered) motif formed by alternating layers of the SnI6 octahedra and the organic cations. These two motifs are nearly equal in free energy and are separated by low barriers. These layered structures features many flat electronic bands near the band edges, making their electronic structures significantly different from those of the structural phases composed of three-dimension networks of SnI6 octahedra. Furthermore, because the electronic structures of HC (NH2)2SnI3 are found to be rather similar to those of CH3NH3SnI3 , formamidnium tin iodide may also be promising for the applications of methylammonium tin iodide.

  11. Soil moisture sensor calibration for organic soil surface layers

    NASA Astrophysics Data System (ADS)

    Bircher, S.; Andreasen, M.; Vuollet, J.; Vehviläinen, J.; Rautiainen, K.; Jonard, F.; Weihermüller, L.; Zakharova, E.; Wigneron, J.-P.; Kerr, Y. H.

    2015-12-01

    This paper's objective is to present generic calibration functions for organic surface layers derived for the soil moisture sensors Decagon ECH2O 5TE and Delta-T ThetaProbe ML2x, using material from northern regions, mainly from the Finish Meteorological Institute's Arctic Research Center in Sodankylä and the study area of the Danish Center for Hydrology HOBE. For the Decagon 5TE sensor such a function is currently not reported in literature. Data were compared with measurements from underlying mineral soils including laboratory and field measurements. Shrinkage and charring during drying were considered. For both sensors all field and lab data showed consistent trends. For mineral layers with low soil organic matter (SOM) content the validity of the manufacturer's calibrations was demonstrated. Deviating sensor outputs in organic and mineral horizons were identified: for the Decagon 5TE apparent relative permittivities at a given moisture content decreased for increased SOM content, which was attributed to an increase of bound water in organic materials with large surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger non-linearity in the sensor response and signal saturation in the high level data. The derived calibration fit functions between sensor response and volumetric water content hold for samples spanning a wide range of humus types with differing SOM characteristics. This strengthens confidence in their validity under various conditions, rendering them highly suitable for large-scale applications in remote sensing and land surface modeling studies. Agreement between independent Decagon 5TE and ThetaProbe time series from an organic surface layer at the Sodankylä site was significantly improved when the here proposed fit functions were used. Decagon 5TE data also well-reflected precipitation events. Thus, Decagon 5TE network data from organic surface layers at the Sodankylä and HOBE sites are

  12. Soil moisture sensor calibration for organic soil surface layers

    NASA Astrophysics Data System (ADS)

    Bircher, Simone; Andreasen, Mie; Vuollet, Johanna; Vehviläinen, Juho; Rautiainen, Kimmo; Jonard, François; Weihermüller, Lutz; Zakharova, Elena; Wigneron, Jean-Pierre; Kerr, Yann H.

    2016-04-01

    This paper's objective is to present generic calibration functions for organic surface layers derived for the soil moisture sensors Decagon ECH2O 5TE and Delta-T ThetaProbe ML2x, using material from northern regions, mainly from the Finnish Meteorological Institute's Arctic Research Center in Sodankylä and the study area of the Danish Center for Hydrology (HOBE). For the Decagon 5TE sensor such a function is currently not reported in the literature. Data were compared with measurements from underlying mineral soils including laboratory and field measurements. Shrinkage and charring during drying were considered. For both sensors all field and lab data showed consistent trends. For mineral layers with low soil organic matter (SOM) content the validity of the manufacturer's calibrations was demonstrated. Deviating sensor outputs in organic and mineral horizons were identified. For the Decagon 5TE, apparent relative permittivities at a given moisture content decreased for increased SOM content, which was attributed to an increase of bound water in organic materials with large specific surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger nonlinearity in the sensor response and signal saturation in the high-level data. The derived calibration fit functions between sensor response and volumetric water content hold for samples spanning a wide range of humus types with differing SOM characteristics. This strengthens confidence in their validity under various conditions, rendering them highly suitable for large-scale applications in remote sensing and land surface modeling studies. Agreement between independent Decagon 5TE and ThetaProbe time series from an organic surface layer at the Sodankylä site was significantly improved when the here-proposed fit functions were used. Decagon 5TE data also well-reflected precipitation events. Thus, Decagon 5TE network data from organic surface layers at the Sodankylä and

  13. Nucleation and Early Stages of Layer-by-Layer Growth of Metal Organic Frameworks on Surfaces

    PubMed Central

    2015-01-01

    High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5–10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface. PMID:26709359

  14. The Orientation of Luminescent Excitons in Layered Organic Nanomaterials

    NASA Astrophysics Data System (ADS)

    Schuller, Jon; Karavelli, Sinan; He, Keliang; Yang, Shyuan; Shan, Jie; Kymissis, John; Zia, Rashid

    2012-02-01

    A fundamental understanding of optoelectronics in organic semiconductors is complicated by the diversity of excitons which can exist within a single material system. Measurements that distinguish between different exciton types are crucial for a complete understanding of organic materials. By fitting experimental curves of angle-, polarization-, and energy-dependent PL to analytical Purcell calculations we quantify the relative dipole moments for in-plane and out-of-plane oriented excitons in organic and inorganic layered nanomaterials. In mono- and bi-layers of Molybdenum Disulfide (MoS2) and Graphene Oxide the luminescence arises only from in-plane oriented excitons. In the perylene derivative PTCDA, however, we show that PL arises from both in-plane and out-of-plane excitons. We observe a difference in emission frequency between the dipole orientations which indicates the existence of two distinct exciton species: an in-plane oriented Frenkel exciton and an out-of-plane oriented Charge Transfer exciton. Based on these results we devise and implement a method for isolating luminescence from either exciton species. We observe different temporal dynamics for the two distinct excitons, highlighting the power of this technique for fundamental studies of organic materials.

  15. Polyaniline-based organic memristive device fabricated by layer-by-layer deposition technique

    NASA Astrophysics Data System (ADS)

    Erokhina, Svetlana; Sorokin, Vladimir; Erokhin, Victor

    2015-09-01

    Memristors and memristive devices represent a splendid area of research due to the unique possibilities for the realization of new types of computer hardware elements and mimicking several essential properties of the nervous system of living beings. The organic memristive device was developed as an electronic single-device analogue of the synapse, suitable for the realization of circuits allowing Hebbian type of learning. This work is dedicated to the realization of the active channel of organic memristive devices by polyelectrolyte self-assembling (layer-by-layer technique). Stable and reproducible electrical characteristics of the device were obtained when the thickness of the active channel was more than seven bilayers. The device revealed rectifying behaviour and the presence of hysteresis—important properties for the realization of neuromorphic systems with synapse-like properties of the individual elements. Compared to previously reported results on organic memristive devices fabricated using other methods, the present device does not require any additional doping that is usually performed through acid treatment. Such a behaviour is extremely important for the cases in which biological systems (nervous cells, slime mould, etc.) must be interfaced with the system of organic memristive devices, since acid treatment can kill living beings. [Figure not available: see fulltext.

  16. Organic and inorganic-organic thin film structures by molecular layer deposition: A review.

    PubMed

    Sundberg, Pia; Karppinen, Maarit

    2014-01-01

    The possibility to deposit purely organic and hybrid inorganic-organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic-organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  17. Organic and inorganic–organic thin film structures by molecular layer deposition: A review

    PubMed Central

    Sundberg, Pia

    2014-01-01

    Summary The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  18. Organic photovoltaic device with interfacial layer and method of fabricating same

    SciTech Connect

    Marks, Tobin J.; Hains, Alexander W.

    2013-03-19

    An organic photovoltaic device and method of forming same. In one embodiment, the organic photovoltaic device has an anode, a cathode, an active layer disposed between the anode and the cathode; and an interfacial layer disposed between the anode and the active layer, the interfacial layer comprising 5,5'-bis[(p-trichlorosilylpropylphenyl)phenylamino]-2,2'-bithiophene (PABTSi.sub.2).

  19. Carrier modulation layer-enhanced organic light-emitting diodes.

    PubMed

    Jou, Jwo-Huei; Kumar, Sudhir; Singh, Meenu; Chen, Yi-Hong; Chen, Chung-Chia; Lee, Meng-Ting

    2015-01-01

    Organic light-emitting diode (OLED)-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML), also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI) for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance. PMID:26193252

  20. TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

    DOEpatents

    Marks, Iobin J.; Hains, Alexander W.

    2011-02-15

    The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode; an active organic layer comprising an electron-donating organic material and an electron-accepting organic material; and an interfacial layer formed between the anode and active organic layer, where the interfacial layer comprises a hole-transporting polymer characterized with a hole-mobility higher than that of the electron-donating organic material in the active organic layer, and a small molecule that has a high hole-mobility and is capable of crosslinking on contact with air.

  1. Organic self-assembled layer-by-layer thin films for second-order nonlinear optics

    NASA Astrophysics Data System (ADS)

    Guzy, Matthew T.

    Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of chi(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices. In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation

  2. Layer-by-layer deposited organic/inorganic hybrid multilayer films containing noncentrosymmetrically orientated azobenzene chromophores.

    PubMed

    Kang, En-Hua; Bu, Tianjia; Jin, Pengcheng; Sun, Junqi; Yang, Yanqiang; Shen, Jiacong

    2007-07-01

    Organic/inorganic hybrid multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by the sequential deposition of ZrO2 layers by a surface sol-gel process and subsequent layer-by-layer (LbL) adsorption of the nonlinear optical (NLO)-active azobenzene-containing polyanion PAC-azoBNS and poly(diallyldimethylammonium chloride) (PDDA). Noncentrosymmetric orientation of the NLO-active azobenzene chromophores was achieved because of the strong repulsion between the negatively charged ZrO(2) and the sulfonate groups of the azobenzene chromophore in PAC-azoBNS. Regular deposition of ZrO(2)/PAC-azoBNS/PDDA multilayer films was verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. Both UV-vis absorption spectroscopy and transmission second harmonic generation (SHG) measurements confirmed the noncentrosymmetric orientation of the azobenzene chromophores in the as-prepared ZrO2/PAC-azoBNS/PDDA multilayer films. The square root of the SHG signal (I(2omega)(1/2)) increases with the increase of the azobenzene graft ratio in PAC-azoBNS as the number of deposition cycles of the ZrO(2)/PAC-azoBNS/PDDA films remains the same, while the second-order susceptibility chi(zzz)(2) of the film decreases with the increase of the azobenzene graft ratio. Furthermore, the present method was successfully extended to realize the noncentrosymmetric orientation of azobenzene chromophores in multilayer films when small organic azobenzene compounds with carboxylic acid and/or hydroxyl groups at one end and sulfonate groups at the other end were used. The present method was characterized by its simplicity and flexibility in film preparation, and it is anticipated to be a facile way to fabricate second-order nonlinear optical film materials. PMID:17555337

  3. Anisotropic Josephson-vortex dynamics in layered organic superconductors

    NASA Astrophysics Data System (ADS)

    Yasuzuka, S.; Uji, S.; Satsukawa, H.; Kimata, M.; Terashima, T.; Koga, H.; Yamamura, Y.; Saito, K.; Akutsu, H.; Yamada, J.

    2010-06-01

    To study the anisotropic Josephson-vortex dynamics in the d-wave superconductors, the interplane resistance has been measured on layered organic superconductors κ-(ET)2Cu(NCS)2 and β-(BDA-TTP)2SbF6 under magnetic fields precisely parallel to the conducting planes. For κ-(ET)2Cu(NCS)2, in-plane angular dependence of the Josephson-vortex flow resistance is mainly described by the fourfold symmetry and dip structures appear when the magnetic field is applied parallel to the b- and c-axes. The obtained results have a relation to the d-wave superconducting gap symmetry. However, the absence of in-plane fourfold anisotropy was found for β-(BDA-TTP)2SbF6. The different anisotropic behavior is discussed in terms of the interlayer coupling strength.

  4. Current-voltage characteristics of organic semiconductors: Interfacial control between organic layers and electrodes

    NASA Astrophysics Data System (ADS)

    Kondo, Takeshi

    2007-12-01

    Current-voltage (I-V) characteristics of organic molecular glasses and solution processable materials embedded between two electrodes were studied to find materials possessing high charge-carrier mobilities and to design organic memory devices. The comparison studies between TOF, FET and SCLC measurements confirm the validity of using analyses of I-V characteristics to determine the mobility of organic semiconductors. Hexaazatrinaphthylene derivatives tri-substituted by electron withdrawing groups were characterized as potential electron transporting molecular glasses. The presence of two isomers has important implications for film morphology and effective mobility. The statistical isomer mixture of hexaazatrinaphthylene derivatized with pentafluoro-phenylmethyl ester is able to form amorphous films, and electron mobilities with the range of 10--2 cm2/Vs are observed in their I-V characteristics. Single-layer organic memory devices consisting of a polymer layer embedded between an Al electrode and ITO modified with Ag nanodots (Ag-NDs) prepared by a solution-based surface assembly demonstrated a potential capability as nonvolatile organic memory device with high ON/OFF switching ratios of 10 4. This level of performance could be achieved by modifying the ITO electrodes with some Ag-NDs that act as trapping sites, reducing the current in the OFF state. Based upon the observed electrical characteristics, the currents of the low-resistance state can be attributed to a tunneling through low-resistance pathways of metal particles originating from the metal top electrode in the organic layer and that the high-resistance state is controlled by charge trapping by the metal particles including Ag-NDs. In an alternative approach, complex films of AgNO3: hexaazatrinaphthylene derivatives were studied as the active layers for all-solution processed and air-stable organic memory devices. Rewritable memory effects were observed in the devices comprised of a thin polymer

  5. New electronic and magnetic properties emerging from adsorption of organized organic layers.

    PubMed

    Naaman, Ron; Vager, Zeev

    2006-05-21

    New electronic and magnetic properties are induced by the adsorption of closed packed monolayers on solid substrates. For many thiolated molecules self-assembled on gold, a surprisingly large paramagnetism is observed. In the case where the layers are made from chiral molecules, in addition an unexpectedly large electronic dichroism is observed, which manifests itself as spin specific electron transmission. This dichroism was observed for monolayers made from polyalanine and from DNA. Self-assembled monolayers of double-stranded DNA oligomers on gold interact with polarized electrons similarly to a strong and oriented magnetic field. The direction of the field for right-handed DNA is away from the substrate. Moreover, the layer shows very high paramagnetic susceptibility. Interestingly, thiolated single-stranded DNA oligomers on gold do not show this effect. All the observations can be rationalized by assuming organization induced charge transfer between the substrate and the organic layer. The charge transfer results in spin alignment of the transferred electrons/holes. While for achiral molecules the spin alignment varies among the domains, in the case of monolayer made from chiral molecules the alignment is the same across the entire sample. When magnetic field is applied, large magnetic moment is observed that results from orbital magnetism. PMID:16688303

  6. Organic photovoltaic cell incorporating electron conducting exciton blocking layers

    SciTech Connect

    Forrest, Stephen R.; Lassiter, Brian E.

    2014-08-26

    The present disclosure relates to photosensitive optoelectronic devices including a compound blocking layer located between an acceptor material and a cathode, the compound blocking layer including: at least one electron conducting material, and at least one wide-gap electron conducting exciton blocking layer. For example, 3,4,9,10 perylenetetracarboxylic bisbenzimidazole (PTCBI) and 1,4,5,8-napthalene-tetracarboxylic-dianhydride (NTCDA) function as electron conducting and exciton blocking layers when interposed between the acceptor layer and cathode. Both materials serve as efficient electron conductors, leading to a fill factor as high as 0.70. By using an NTCDA/PTCBI compound blocking layer structure increased power conversion efficiency is achieved, compared to an analogous device using a conventional blocking layers shown to conduct electrons via damage-induced midgap states.

  7. Probing the tropical tropopause layer for organic and inorganic bromine

    NASA Astrophysics Data System (ADS)

    Werner, Bodo; Pfeilsticker, Klaus; Atlas, Elliot; Cheung, Ross; Chipperfield, Martyn; Colosimo, Fedele; Deutschmann, Tim; Elkins, Jim; Fahey, David; Feng, Wu; Festa, James; Gao, Ru-Shan; Hossaini, Ryan; Navarro, Maria; Raecke, Rasmus; Scalone, Lisa; Spolaor, Max; Thornberry, Troy; Tsai, Catalina; Stutz, Jochen

    2016-04-01

    Bromine chemistry impacts the levels of ozone in the upper troposphere and the stratosphere. An accurate quantitative understanding of the sources, sinks, and chemical transformation of bromine species is thus important to understand the photochemistry and budget of bromine in the tropical upper troposphere, tropopause layer and lowermost stratosphere (UT/TTL/LS). These regions are also known to serve as a gateway for delivery of ozone depleting gases to the stratosphere. CH3Br, halons, short-lived organic bromine precursors (VSLS), such as CHBr3, CH2Br2, and possibly inorganic product gases have been identified as the main bromine gases delivered to the stratosphere. However, many important details of the transport and delivery of VSLS and inorganic bromine compounds through the TTL are still uncertain. Moreover, a number of chemical processes, including the transformation of the source gases and cycling of inorganic bromine species at low ambient temperature and on ice particles are also poorly understood. The presentation reports measurements of CH4, O3, NO2, and BrO performed by different instruments and techniques during the 2013 NASA-ATTREX flights in the TTL and LS. The interpretation of our measurements is supported by chemical transport model (SLIMCAT) simulations. SLIMCAT results, in conjunction with extensive radiative transfer calculations using the Monte Carlo model McArtim, also are used to improve retrieval of O3, NO2, and BrO concentrations from limb scattered sunlight measurements made with the Differential Optical Absorption Spectroscopy (DOAS) technique during ATTREX. The chemical transport model also allows us to attribute observed concentration variations to transport and to photochemical processes. When properly accounting for the transport-related concentration variations in methane and ozone, we find that measured BrO mostly agrees with model simulations. An exception are regions where the contribution of the short-lived CH2Br2 or the

  8. Encapsulation methods and dielectric layers for organic electrical devices

    DOEpatents

    Blum, Yigal D; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijan

    2013-07-02

    The disclosure provides methods and materials suitable for use as encapsulation barriers and dielectric layers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device with a dielectric layer comprising alternating layers of a silicon-containing bonding material and a ceramic material. The methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

  9. Organic light emitting diode with light extracting layer

    DOEpatents

    Lu, Songwei

    2016-06-14

    A light extraction substrate includes a glass substrate having a first surface and a second surface. A light extraction layer is formed on at least one of the surfaces. The light extraction layer is a coating, such as a silicon-containing coating, incorporating nanoparticles.

  10. Tunable photochemical properties of a covalently anchored and spatially confined organic polymer in a layered compound

    NASA Astrophysics Data System (ADS)

    Matsui, Hiroshi; Oaki, Yuya; Imai, Hiroaki

    2016-05-01

    A covalently anchored and spatially confined organic polymer was formed in a layered compound with a surface-modified layer. The resultant anchored and confined polymer showed tunable photochemical properties with the incorporation of a variety of guest molecules originating from the specific incorporation states. The layer surface of an inorganic layered compound was modified by an organic molecule with vinyl groups. The precursor layered composite accommodated N-vinylcarbazole (VCz), a vinyl monomer, in the hydrophobic interlayer space. The introduction of VCz induced the simultaneous exfoliation of the layered structures and copolymerization with vinyl groups on the layer surface. The covalently anchored and spatially confined poly(N-vinylcarbazole) (PVCz) with tunable photochemical properties was formed in a layered structure. The present study shows the versatile potential of polymers with anchored and confined states in surface-functionalized layered composites.A covalently anchored and spatially confined organic polymer was formed in a layered compound with a surface-modified layer. The resultant anchored and confined polymer showed tunable photochemical properties with the incorporation of a variety of guest molecules originating from the specific incorporation states. The layer surface of an inorganic layered compound was modified by an organic molecule with vinyl groups. The precursor layered composite accommodated N-vinylcarbazole (VCz), a vinyl monomer, in the hydrophobic interlayer space. The introduction of VCz induced the simultaneous exfoliation of the layered structures and copolymerization with vinyl groups on the layer surface. The covalently anchored and spatially confined poly(N-vinylcarbazole) (PVCz) with tunable photochemical properties was formed in a layered structure. The present study shows the versatile potential of polymers with anchored and confined states in surface-functionalized layered composites. Electronic supplementary

  11. The effect of the hole injection layer on the performance of single layer organic light-emitting diodes

    SciTech Connect

    Wenjin, Zeng; Ran, Bi; Hongmei, Zhang E-mail: iamwhuang@njupt.edu.cn; Wei, Huang E-mail: iamwhuang@njupt.edu.cn

    2014-12-14

    Efficient single-layer organic light-emitting diodes (OLEDs) were reported based on a green fluorescent dye 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7–tetramethyl-1H,5H,11H-(1) benzopyropyrano (6,7-8-I,j)quinolizin-11-one (C545T). Herein, poly(3,4-ethylenedioxy thiophene) poly(styrene sulfonate) were, respectively, applied as the injection layer for comparison. The hole transport properties of the emission layer with different hole injection materials are well investigated via current-voltage measurement. It was clearly found that the hole injection layers (HILs) play an important role in the adjustment of the electron/hole injection to attain transport balance of charge carriers in the single emission layer of OLEDs with electron-transporting host. The layer of tris-(8-hydroxyquinoline) aluminum played a dual role of host and electron-transporting materials within the emission layer. Therefore, appropriate selection of hole injection layer is a key factor to achieve high efficiency OLEDs with single emission layer.

  12. Organic crystal light-emitting transistors combined with a metal oxide layer

    NASA Astrophysics Data System (ADS)

    Obara, Keiji; Higashihara, Shohei; Yamao, Takeshi; Hotta, Shu

    2016-03-01

    We improved organic light-emitting transistors (OLETs) characterized by aluminum-doped zinc oxide (AZO) layer insertion between organic and gate insulator layers using organic oligomer semiconductor crystals. (i) To ensure firm contact between the crystal and the AZO layer, we shaped the AZO layer into a rectangle (250 × 500 µm2) and covered it with a vapor-phase-grown crystal. (ii) To enhance contact between the crystal and the AZO layer, we placed the crystal used as a mask on the patternless AZO layer and etched parts of AZO not covered with the crystal with hydrochloric acid vapor. We completed OLETs by forming electron- and hole-injection contacts on the crystal. We modified these contacts with an oxide and/or a carbonate. The devices showed bright light emission from the part of the crystal sandwiched between the electron- and hole-injection contacts located on the AZO layer.

  13. Organic diode with high rectification ratio made of electrohydrodynamic printed organic layers

    NASA Astrophysics Data System (ADS)

    Ali, Shawkat; Bae, Jinho; Lee, Chong Hyun

    2016-03-01

    In this paper, an all-printed organic diode to reveal a high rectification ratio (˜1.2 × 104) is proposed using organic heterojunction materials N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) and fullerene (C60). The proposed organic diode is fabricated as a structure of ITO/TPD/C60/Al on a glass substrate through an all-printed electrohydrodynamic (EHD) technique, which has an effective area of 2 × 2 mm2. The threshold voltage of the forward bias is 1.2 V and the current density reaches 550 mA/cm2 at 3 V. The device is characterized by current voltage I-V at temperature 30°C to 120°C, and junction capacitance is analyzed at 4 kHz frequency at ±2 V. To verify the successful construction of all layers deposited through the EHD technique, morphology analysis was carried out with FE-SEM. From these measured electrical characteristics, suitability for rectification purposes in printed electronics is confirmed. [Figure not available: see fulltext.

  14. LAYER I NEOCORTICAL ECTOPIA: CELLULAR ORGANIZATION AND LOCAL CORTICAL CIRCUITRY

    PubMed Central

    Gabel, Lisa Ann

    2011-01-01

    Focal cortical dysplasia (FCD) are associated with neurological disorders and cognitive impairments in humans. Molecular layer ectopia, clusters of misplaced cells in layer I of the neocortex, have been identified in patients with developmental dyslexia and psychomotor retardation. Mouse models of this developmental disorder display behavioral impairments and increased seizure susceptibility. Although there is a correlation between cortical malformations and neurological dysfunction, little is known about the morphological and physiological properties of cells within cortical malformations. In the present study we used electrophysiological and immunocytochemical analyses to examine the distribution of neuronal and non-neuronal cell types within and surrounding layer I neocortical ectopia in NXSMD/EiJ mice. We show that cells within ectopia have membrane properties of both pyramidal and a variety of nonpyramidal cell types, including fast-spiking cells. Immunocytochemical analysis for different interneuronal subtypes demonstrates that ectopia contain nonpyramidal cells immunoreactive for calbindin-D28K (CALB), parvalbumin (PARV), and calretinin (CR). Ectopia also contain astrocytes, positive for glial fibrillary acidic protein (GFAP) and oligodendrocyte precursor cells positive for NG2 proteoglycan (NG2). Lastly, we provide electrophysiological and morphological evidence to demonstrate that cells within ectopia receive input from cells within layers I, upper and deeper II/III, and V and provide outputs to cells within deep layer II/III and layer V, but not layers I and upper II/III. These results indicate that ectopia contain cells of different lineages with diverse morphological and physiological properties, and appear to cause disruptions in local cortical circuitry. PMID:21256119

  15. Thin-Layer Chromatography: The "Eyes" of the Organic Chemist

    ERIC Educational Resources Information Center

    Dickson, Hamilton; Kittredge, Kevin W.; Sarquis, Arlyne

    2004-01-01

    Thin-layer chromatography (TLC) methods are successfully used in many areas of research and development such as clinical medicine, forensic chemistry, biochemistry, and pharmaceutical analysis as TLC is relatively inexpensive and has found widespread application as an easy to use, reliable, and quick analytic tool. The usefulness of TLC in organic…

  16. Organic photosensitive cells having a reciprocal-carrier exciton blocking layer

    DOEpatents

    Rand, Barry P.; Forrest, Stephen R.; Thompson, Mark E.

    2007-06-12

    A photosensitive cell includes an anode and a cathode; a donor-type organic material and an acceptor-type organic material forming a donor-acceptor junction connected between the anode and the cathode; and an exciton blocking layer connected between the acceptor-type organic material of the donor-acceptor junction and the cathode, the blocking layer consisting essentially of a material that has a hole mobility of at least 10.sup.-7 cm.sup.2/V-sec or higher, where a HOMO of the blocking layer is higher than or equal to a HOMO of the acceptor-type material.

  17. Efficiency enhancement in small molecular organic photovoltaic devices employing dual anode interfacial layers

    NASA Astrophysics Data System (ADS)

    Fleetham, Tyler; O'Brien, Barry; Mudrick, John P.; Xue, Jiangeng; Li, Jian

    2013-10-01

    We demonstrated enhanced efficiency in small molecule organic photovoltaic devices using dual organic interfacial layers of PEDOT:PSS followed by tetracene between the ITO anode and the organic donor material. The use of a small molecular templating layer, such as tetracene, proved to increase the molecular stacking of the subsequent phthalocyanine (Pc) based donor materials. Upon application in planar heterojunction devices of ZnPc and C60, an enhancement of over 80 percent in the donor contribution to the external quantum efficiency was observed attributed to the combination of exciton blocking by the higher band gap tetracene layer and enhanced exciton diffusion and charge transport resulting from the increased crystallinity.

  18. Optical and electrical properties of bi-layers organic devices

    NASA Astrophysics Data System (ADS)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  19. Ambipolar charge transport in "traditional" organic hole transport layers.

    PubMed

    Khademi, S; Song, J Y; Wyatt, P B; Kreouzis, T; Gillin, W P

    2012-05-01

    Organic semiconductors are often labeled as electron or hole transport materials due to the primary role they perform in devices. However, despite these labels we have shown using time-of-flight that two of the traditional "hole transport materials" TPD and NPB are actually excellent electron transporters the electron transport properties of which are comparable to those for holes. PMID:22467553

  20. Liquid exfoliation of alkyl-ether functionalised layered metal-organic frameworks to nanosheets.

    PubMed

    Foster, Jonathan A; Henke, Sebastian; Schneemann, Andreas; Fischer, Roland A; Cheetham, Anthony K

    2016-08-18

    We report the synthesis of a 2D-layered metal-organic framework incorporating weakly interacting chains designed to aid exfoliation of the layers into nanosheets. Dispersion of the nanosheets exposes labile metal-sites which are shown to exchange solvent molecules allowing the nanosheets to act as sensors in suspension. PMID:27452790

  1. Material properties and field-effect transistor characteristics of hybrid organic/graphene active layers

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun; Lee, Jongho; Chowdhury, Sk. Fahad; Akinwande, Deji; Dodabalapur, Ananth

    2012-10-01

    We report on the material properties and device characteristics of field-effect transistors (FETs) consisting of hybrid mono-layer graphene/organic semiconductor active layers. By capping with selected organic and polymeric layers, transformation of the electronic characteristics of mono-layer graphene FETs was observed. The off-state current is reduced while the on-state current and field-effect mobility are either unaffected or increased after depositing π-conjugated organic semiconductors. Significantly, capping mono-layer graphene FETs with fluoropolymer improved the on-off current ratio from 5 to 10 as well as increased the field-effect mobility by factor of two compared to plain graphene FETs. Removal of π-conjugated organic semiconductors or fluoropolymer from graphene FETs results in a return to the original electronic properties of mono-layer graphene FETs. This suggests that weak reversible electronic interactions between graphene and π-conjugated organic semiconductors/fluoropolymer favorably tune the material and electrical characteristics of mono-layer graphene.

  2. High efficiency electrophosphorescent red organic light-emitting devices with double-emission layers

    NASA Astrophysics Data System (ADS)

    Xie, Wenfa; Zhao, Yi; Li, Chuannan; Liu, Shiyong

    2007-08-01

    High efficiency electrophosphorescent red organic light-emitting devices with double-emission layers (DELs) have been fabricated with a changing of the hole blocking layer. Bis(1-(phenyl)isoquinoline) iridium (III) acetylanetonate [Ir(piq) 2(acac)] as the red emitting dopant is doped into both 4,4'-bis( N-carbazolyl)biphenyl (CBP) host and hole blocking layers. The DELs devices show significantly improved efficiency compared to the conventional devices with a single emitting layer. The maximum power efficiency of 4.05 lm/W at 5 V, which is about 25% greater than that of the device with a single emitting layer, is obtained in a device with 2,2',2″-(1,3,5-phenylene) tris(1-phenyl-1 H-benzimidazole) (TPBI) as hole blocking layer. We attribute it to the excitons-collected effect of the doped TPBI layer and the excellent electron transport performance of TPBI.

  3. The Role of Organic Capping Layers of Platinum Nanoparticles in Catalytic Activity of CO Oxidation

    SciTech Connect

    Park, Jeong Y.; Aliaga, Cesar; Renzas, J. Russell; Lee, Hyunjoo; Somorjai, Gabor A.

    2008-12-17

    We report the catalytic activity of colloid platinum nanoparticles synthesized with different organic capping layers. On the molecular scale, the porous organic layers have open spaces that permit the reactant and product molecules to reach the metal surface. We carried out CO oxidation on several platinum nanoparticle systems capped with various organic molecules to investigate the role of the capping agent on catalytic activity. Platinum colloid nanoparticles with four types of capping layer have been used: TTAB (Tetradecyltrimethylammonium Bromide), HDA (hexadecylamine), HDT (hexadecylthiol), and PVP (poly(vinylpyrrolidone)). The reactivity of the Pt nanoparticles varied by 30%, with higher activity on TTAB coated nanoparticles and lower activity on HDT, while the activation energy remained between 27-28 kcal/mol. In separate experiments, the organic capping layers were partially removed using ultraviolet light-ozone generation techniques, which resulted in increased catalytic activity due to the removal of some of the organic layers. These results indicate that the nature of chemical bonding between organic capping layers and nanoparticle surfaces plays a role in determining the catalytic activity of platinum colloid nanoparticles for carbon monoxide oxidation.

  4. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage.

    PubMed

    Cai, Ronggang; Kassa, Hailu G; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H; Ruzié, Christian; van Breemen, Albert J J M; Gelinck, Gerwin H; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M

    2016-03-21

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. PMID:26927694

  5. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H.; Ruzié, Christian; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2016-03-01

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices.Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction

  6. Improved Performance of Organic Light-Emitting Field-Effect Transistors by Interfacial Modification of Hole-Transport Layer/Emission Layer: Incorporating Organic Heterojunctions.

    PubMed

    Song, Li; Hu, Yongsheng; Zhang, Nan; Li, Yantao; Lin, Jie; Liu, Xingyuan

    2016-06-01

    Organic heterojunctions (OHJs) consisting of a strong electron acceptor 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) and an electron donor N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB) were demonstrated for the first time that they can be implemented as effective modification layers between hole transport layer (HTL) and emission layer in the heterostructured organic light-emitting field effect transistors (OLEFETs). The influence of both HAT-CN/NPB junction (npJ) and NPB/HAT-CN junction (pnJ) on the optoelectronic performance of OLEFETs were conscientiously investigated. It is found that both the transport ability of holes and the injection ability of holes into emissive layer can be dramatically improved via the charge transfer of the OHJs and that between HAT-CN and the HTL. Consequently, OLEFETs with pnJ present optimal performance of an external quantum efficiency (EQE) of 3.3% at brightness of 2630 cdm(-2) and the ones with npJs show an EQE of 4.7% at brightness of 4620 cdm(-2). By further utilizing npn OHJs of HAT-CN/NPB/HAT-CN, superior optoelectronic performance with an EQE of 4.7% at brightness of 8350 cdm(-2) and on/off ratio of 1 × 10(5) is obtained. The results demonstrate the great practicality of implementing OHJs as effective modification layers in heterostructured OLEFETs. PMID:27215694

  7. The organic interlamellar layer in abalone nacre: Formation and mechanical response.

    PubMed

    López, Maria Isabel; Meyers, Marc André

    2016-01-01

    The interlamellar organic layer plays a key role in establishing the tensile mechanical response of nacre, while changing the compressive response in only a marginal manner. We conduct observations on the epithelial layer of the abalone foot in direct contact with the extrapallial layer where the deposition process takes place and identify cilia, microvilli, and secretory cells which determine the deposition of chitin to form the interlamellar organic layer. On the basis of these observations we propose a mechanism for the deposition of interlamellar organic layers. We show that the fraction of pores, as well as their diameter, grow rapidly as the interlamellar layer is extended uniaxially or biaxially, and compare these calculations with the observed values. In the calculations we assume a Poisson's ratio equal to zero in the plane of the lamellae. This assumption is justified by the thickness of the organic layer (20-50 nm) being equal to twice the diameter of the chitin fibrils; consequently the expansion of the membrane occurs at a constant thickness. As an illustration of this effect, an externally applied strain of 0.5 increases the initial pore diameter (typically equal to 20-50 nm) to a value of ten times (0.2-0.5 μm). These calculations explain the observations of large pores reported in the literature and interpret them as the result of externally applied loads. PMID:26478281

  8. Current–voltage characteristics of organic heterostructure devices with insulating spacer layers

    DOE PAGESBeta

    Yin, Sun; Nie, Wanyi; Mohite, Aditya D.; Saxena, Avadh; Smith, Darryl L.; Ruden, P. Paul

    2015-09-01

    The dark current density in donor/acceptor organic planar heterostructure devices at a given forward voltage bias can either increase or decrease when an insulating spacer layer is added between the donor and acceptor layers. The dominant current flow process in these systems involves the formation and subsequent recombination of interfacial exciplex states. If the exciplex recombination rate limits current flow, an insulating interface layer decreases the dark current. However, if the exciplex formation rate limits the current, an insulating interface layer may increase the dark current. As a result, we present a device model to describe this behavior, and wemore » discuss relevant experimental data.« less

  9. Current–voltage characteristics of organic heterostructure devices with insulating spacer layers

    SciTech Connect

    Yin, Sun; Nie, Wanyi; Mohite, Aditya D.; Saxena, Avadh; Smith, Darryl L.; Ruden, P. Paul

    2015-09-01

    The dark current density in donor/acceptor organic planar heterostructure devices at a given forward voltage bias can either increase or decrease when an insulating spacer layer is added between the donor and acceptor layers. The dominant current flow process in these systems involves the formation and subsequent recombination of interfacial exciplex states. If the exciplex recombination rate limits current flow, an insulating interface layer decreases the dark current. However, if the exciplex formation rate limits the current, an insulating interface layer may increase the dark current. As a result, we present a device model to describe this behavior, and we discuss relevant experimental data.

  10. Intercalation of stable organic radicals into layered saponite clay.

    PubMed

    Hemme, Wilhelm L; Fujita, Wataru; Awaga, Kunio; Eckert, Hellmut

    2009-10-14

    2-(3- and 4-N-methylpyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-N-oxide (abbreviated as m- and p-MPYNN), the butyl derivative (m- and p-BuPYNN), 4-(N-ethylammonium)-2,2,5,5-tetramethylpiperidin-1-oxyl (ETEP) and N,N,N',N'-Tetramethyl-1,4-phenylenediamine radical cation (TMPD(+)) have been successfully intercalated into saponite clay. The amount of intercalated material has been determined via UV/VIS spectroscopy, elemental analysis and EPR spectroscopy, and the expansion of the layer distance from approximately 12.0 to ca. 15 A has been measured by X-ray powder diffraction. The magnetic properties of these materials, which result from the interplay of the modified intermolecular interactions between the guest species, and the additional interaction with the host lattice, have been characterized by magnetic susceptibility, EPR and solid state NMR measurements. While the (29)Si and (27)Al NMR spectra show little influence of the radical species on the local structural environments of the nuclei in the host lattice, the guest-host interaction manifests itself in significant line-broadening and (in some cases) resonance displacements of the (1)H NMR signals belonging to the molecular radical cations. In the case of TMPD(+) intercalates, the NMR and EPR data indicate predominant radical dimerization within the interlayer space. PMID:19771362

  11. A novel hybrid inorganic-organic single layer barrier for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Mandlik, Prashant

    Organic light-emitting diodes (OLEDs) suffer rapid degradation upon exposure to moisture or oxygen and require a permeation barrier to extend their lifetime. The goal of this project was to prepare an ultra-hermetic encapsulation barrier for OLEDs that can be prepared by a simple, environmentally friendly process. The approach was to employ plasma-enhanced chemical vapor deposition (PE-CVD) of hexamethyl disiloxane (HMDSO, a non-toxic and inexpensive organo-siloxane) and O2, to grow thin SiO2-like barrier films directly on OLEDs. The encapsulation barrier discovered during the project is a flexible, homogeneous, single-layer barrier film grown in a single PE-CVD chamber. The barrier material is a single-phase hybrid with part-inorganic and part-polymeric character. The OLEDs coated with this barrier film were stored at 65°C in 85% relative humidity, an accelerated environmental test. These OLEDs keep functioning after more than one year of accelerated storage tests, surpassing any existing encapsulation barrier including the glass plate encapsulation. Barrier film when deposited on a steel foil substrate can be flexed between 1-2% tensile strains. Infrared absorption, wetting contact angle of water, indentation hardness, Young's modulus, and atomic force micrographs reflect the barrier as a homogeneous SiO2-like film with residual silicone character. The permeation through the bulk of the barrier film is so slow that it exposes two secondary modes of moisture permeation. A relatively rapid degradation associated with particulate inclusions in the barrier, and the very slow degradation caused by permeation along barrier-substrate interfaces. Even though it is prepared by a simple and inexpensive process, this film has shown superior barrier performance than multilayer barrier (alternate inorganic-polymeric films), the current encapsulation technology, which requires a complicated and costly process.

  12. Associations between and development of welfare indicators in organic layers.

    PubMed

    Hinrichsen, L K; Riber, A B; Labouriau, R

    2016-06-01

    The retail market share of organic eggs in Denmark is high, and the consumers expect high animal welfare standards in the organic production. Documentation of animal welfare is important, however, knowledge about the associations between animal-based welfare indicators is limited. The aims of the study were to investigate the associations between selected welfare indicators at two ages (peak and end of lay), and to examine the development with age of the chosen welfare indicators. The chosen welfare indicators were Ascaridia galli (roundworm) infection, Heterakis sp. (caecal worm) infection, keel bone damages, back feathering, body feathering, foot damages, comb colour and wounds on the body. An observational study with 12 organic egg farms was conducted in 2012 and 2013 with a total of 214 hens assessed individually at the peak and the end of lay. Insufficient data were obtained on helminth infection at the peak of lay. At the end of lay, all helminth infected hens were positive for A. galli, and only three of them had in addition a Heterakis sp. infection. Foot damages, pale combs and wounds on the body occurred at frequencies <5% and were therefore, together with the prevalence of Heterakis sp. infection, left out of the analysis of associations. A graphical model was used to analyse the associations between the remaining clinical welfare indicators, A. galli infection, housing systems and age of the hens at end of lay. A. galli infection was only directly associated with back feathering at end of lay (P=0.011) with an increased incidence of A. galli infection in hens with good back feathering. Between the two visits, the prevalence of hens with keel bone damages increased (P<0.001), and the plumage condition deteriorated (P<0.001), whereas the number of hens with plantar abscess (P=0.037) and pale combs (P=0.020) decreased. No significant differences were found for other foot damages or for skin damage. In conclusion, back feathering at end of lay provided

  13. New evidence of an organic layer on marine aerosols

    NASA Astrophysics Data System (ADS)

    Tervahattu, Heikki; Hartonen, Kari; Kerminen, Veli-Matti; Kupiainen, Kaarle; Aarnio, Päivi; Koskentalo, Tarja; Tuck, Adrian F.; Vaida, Veronica

    2002-04-01

    An extraordinary episode of fine particles (diameter mainly <2.5 μm) occurred in Helsinki, southern Finland, at the end of February 1998. The air masses came from the North Atlantic Ocean and passed over France, Germany, and southern Scandinavia. Particles were collected during the episode as well as before and after it. Uncoated particle samples were adhered to an indium substrate and were studied by a scanning electron microscope (SEM) coupled with an energy dispersive X-ray microanalyzer (EDX). A great proportion of the particles behaved differently than aerosols previously studied by microscopic techniques. The particles (size mainly 0.5-1 μm) did not exhibit solid shape. They were ``bubbling'' or ``pulsating'' continually, enlarging in one part and shrinking in another. Some particles were broken down, especially when the beam of the electron microscope was focused on them. EDX analyses showed that the particles contained much carbon together with oxygen, sulfur, and sodium. Ion analyses by ion chromatography revealed high concentrations of sodium, sulfate, nitrate, and ammonium. The particles were identified as marine sea-salt aerosols, which had accumulated anthropogenic emissions and lost chloride during their flow through continental polluted air. The shape fluctuations and the high carbon content observed by SEM/EDX led to the conclusion that the aerosols were enclosed by an organic membrane. Direct insertion probe/mass spectrometry investigations showed remarkable amounts of fragmented aliphatic hydrocarbons, which were considered as an evidence of a lipid membrane on the surface of the particles. The impact of the posited organic film on the properties of sea-salt particles, as well as on Earth's climate, is discussed.

  14. Device physics of single layer organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Crone, B. K.; Campbell, I. H.; Davids, P. S.; Smith, D. L.; Neef, C. J.; Ferraris, J. P.

    1999-11-01

    We present experimental and device model results for electron only, hole only, and bipolar organic light-emitting diodes fabricated using a soluble poly (p-phenylene vinylene) based polymer. Current-voltage (I-V) characteristics were measured for a series of electron only devices in which the polymer thickness was varied. The I-V curves were described using a device model from which the electron mobility parameters were extracted. Similarly, the hole mobility parameters were extracted using a device model description of I-V characteristics for a series of hole only devices where the barrier to hole injection was varied by appropriate choices of hole injecting electrode. The electron and hole mobilities extracted from the single carrier devices are then used, without additional adjustable parameters, to describe the measured current-voltage characteristics of a series of bipolar devices where both the device thickness and contacts were varied. The model successfully describes the I-V characteristics of single carrier and bipolar devices as a function of polymer thickness and for structures that are contact limited, space charge limited, and for cases in between. We find qualitative agreement between the device model and measured external luminance for a thickness series of devices. We investigate the sensitivity of the device model calculations to the magnitude of the bimolecular recombination rate prefactor.

  15. Distinct temperature sensitivity of soil carbon decomposition in forest organic layer and mineral soil

    PubMed Central

    Xu, Wenhua; Li, Wei; Jiang, Ping; Wang, Hui; Bai, Edith

    2014-01-01

    The roles of substrate availability and quality in determining temperature sensitivity (Q10) of soil carbon (C) decomposition are still unclear, which limits our ability to predict how soil C storage and cycling would respond to climate change. Here we determined Q10 in surface organic layer and subsurface mineral soil along an elevation gradient in a temperate forest ecosystem. Q10 was calculated by comparing the times required to respire a given amount of soil C at 15 and 25°C in a 350-day incubation. Results indicated that Q10 of the organic layer was 0.22–0.71 (absolute difference) higher than Q10 of the mineral soil. Q10 in both the organic layer (2.5–3.4) and the mineral soil (2.1–2.8) increased with decreasing substrate quality during the incubation. This enhancement of Q10 over incubation time in both layers suggested that Q10 of more labile C was lower than that of more recalcitrant C, consistent with the Arrhenius kinetics. No clear trend of Q10 was found along the elevation gradient. Because the soil organic C pool of the organic layer in temperate forests is large, its higher temperature sensitivity highlights its importance in C cycling under global warming. PMID:25270905

  16. CMOS color image sensor with overlaid organic photoconductive layers having narrow absorption band

    NASA Astrophysics Data System (ADS)

    Takada, Shunji; Ihama, Mikio; Inuiya, Masafumi; Komatsu, Takashi; Saito, Takahiro

    2007-02-01

    At EI2006, we proposed the CMOS image sensor, which was overlaid with organic photoconductive layers in order to incorporate in it large light-capturing ability of a color film owing to its multiple-layer structure, and demonstrated the pictures taken by the trial product of the proposed CMOS image sensor overlaid with an organic layer having green sensitivity. In this study, we have tried to get the optimized spectral sensitivity for the proposed CMOS image sensor by means of the simulation to minimize the color difference between the original Macbeth chart and its reproduction with the spectral sensitivity of the sensor as a parameter. As a result, it has been confirmed that the proposed CMOS image sensor with multiple-layer structure possesses high potential capability in terms of imagecapturing efficiency when it is provided with the optimized spectral sensitivity.

  17. Detailed analysis of bathocuproine layer for organic solar cells based on copper phthalocyanine and C60

    NASA Astrophysics Data System (ADS)

    Huang, Jiang; Yu, Junsheng; Lin, Hui; Jiang, Yadong

    2009-04-01

    The electrical characteristics of double heterojunction organic solar cells with various thicknesses of bathocuproine (BCP) as an exciton-blocking layer (EBL) were studied. A theoretical analysis using optical transfer matrix theory was carried out to obtain insight into how the EBL influences light-absorbing and exciton-transporting properties in the organic layers. The results showed that by employing an 8-10 nm BCP layer exciton density was increased by 46%. By using an improved equivalent circuit model, photovoltaic characteristics were parametrized and modeled, which revealed that the thin BCP layer <10 nm did not affect the charge collection process. The mechanism of metallic cathode influence on solar cells was also discussed.

  18. Organic matter control of mercury and lead toxicity in mor layers.

    PubMed

    Akerblom, Staffan; Bringmark, Lage; Nilsson, Mats

    2010-07-01

    This study evaluated the effect of organic matter composition on Hg and Pb toxicity for heterotrophic respiration in mor layers in long-term in vitro dose-response experiments. Pb proved to be a more potent toxin than Hg at comparable metal additions. The degree of litter decomposition and fragmentation and background Hg concentration levels were key factors determining metal toxicity. Higher sensitivity to metal additions in the fermentation layer than in litter and humification layers was corroborated. The role of organic matter composition was further examined in litter after structural disintegration by milling, which significantly increased the sensitivity of heterotrophic respiration to metal additions. A threshold value causing 5% reduction in heterotrophic respiration was estimated at 800 microg Hg kg(-1). In boreal forests in the northern hemisphere, the mean regional Hg concentrations in mor layers amount to approximately half this threshold value. PMID:20236702

  19. Design and application of carbon nanomaterials for photoactive and charge transport layers in organic solar cells

    NASA Astrophysics Data System (ADS)

    Jin, Sunghwan; Jun, Gwang Hoon; Jeon, Seokwoo; Hong, Soon Hyung

    2016-04-01

    Commercialization of organic solar cell (OSC) has faltered due to their low power conversion efficiency (PCE) compared to inorganic solar cell. Low electrical conductivity, low charge mobility, and short-range light absorption of most organic materials limit the PCE of OSCs. Carbon nanomaterials, especially carbon nanotubes (CNTs) and graphenes, are of great interest for use in OSC applications due to their high electrical conductivity, mobility, and unique optical properties for enhancing the performance of OSCs. In this review, recent progress toward the integration of carbon nanomaterials into OSCs is described. The role of carbon nanomaterials and strategies for their integration into various layers of OSCs, including the photoactive layer and charge transport layer, are discussed. Based on these, we also discuss the prospects of carbon nanomaterials for specific OSC layers to maximize the PCE.

  20. Enhanced gypsum scaling by organic fouling layer on nanofiltration membrane: Characteristics and mechanisms.

    PubMed

    Wang, Jiaxuan; Wang, Lei; Miao, Rui; Lv, Yongtao; Wang, Xudong; Meng, Xiaorong; Yang, Ruosong; Zhang, Xiaoting

    2016-03-15

    To investigate how the characteristics of pregenerated organic fouling layers on nanofiltration (NF) membranes influence the subsequent gypsum scaling behavior, filtration experiments with gypsum were carried out with organic-fouled poly(piperazineamide) NF membranes. Organic fouling layer on membrane was induced by bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), respectively. The morphology and components of the scalants, the role of Ca(2+) adsorption on the organic fouling layer during gypsum crystallization, and the interaction forces of gypsum on the membrane surface were investigated. The results indicated that SA- and HA-fouled membranes had higher surface crystallization tendency along with more severe flux decline during gypsum scaling than BSA-fouled and virgin membranes because HA and SA macromolecules acted as nuclei for crystallization. Based on the analyses of Ca(2+) adsorption onto organic adlayers and adhesion forces, it was found that the flux decline rate and extent in the gypsum scaling experiment was positively related to the Ca(2+)-binding capacity of the organic matter. Although the dominant gypsum scaling mechanism was affected by coupling physicochemical effects, the controlling factors varied among foulants. Nevertheless, the carboxyl density of organic matter played an important role in determining surface crystallization on organic-fouled membrane. PMID:26799710

  1. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

    PubMed

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2015-06-30

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance. PMID:26080437

  2. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells

    PubMed Central

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J.; Chang, Robert P. H.; Facchetti, Antonio; Marks, Tobin J.

    2015-01-01

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor–inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance. PMID:26080437

  3. Surface-confined single-layer covalent organic framework on single-layer graphene grown on copper foil.

    PubMed

    Xu, Lirong; Zhou, Xin; Tian, Wei Quan; Gao, Teng; Zhang, Yan Feng; Lei, Shengbin; Liu, Zhong Fan

    2014-09-01

    The integration of 2D covalent organic frameworks (COFs) with atomic thickness with graphene will lead to intriguing two-dimensional materials. A surface-confined covalently bonded Schiff base network was prepared on single-layer graphene grown on copper foil and the dynamic reaction process was investigated with scanning tunneling microscopy. DFT simulations provide an understanding of the electronic structures and the interactions between the surface COF and graphene. Strong coupling between the surface COF and graphene was confirmed by the dispersive bands of the surface COF after interaction with graphene, and also by the experimental observation of tunneling condition dependent contrast of the surface COF. PMID:25145927

  4. Solution-Processed Small Molecular Organic Light-Emitting Devices with a Mixed Single Layer

    NASA Astrophysics Data System (ADS)

    Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki

    2011-01-01

    We investigated the characteristics of solution-processed mixed-single-layer organic light-emitting devices (OLEDs) by mixing an electron injection material, a hole transport material, and a dopant material based on 5,6,11,12-tetraphenylnaphthacene (rubrene). The mixed-single-layer OLEDs showed better performance by optimizing the solution concentration and mixing ratio of organic materials. The performance was further improved by mixing chloroform (95 wt %) and toluene (5 wt %) as a solvent. The maximum luminance and power efficiency obtained were 12,400 cd/m2 and 1.1 lm/W, respectively. The mixed-single-layer OLEDs by solution process can be expected as an alternative route to the fabrication of small-molecular OLEDs with reduced cost of devices and avoiding the complexities of the co-evaporation of multiple organic materials in the vacuum deposition process.

  5. Assembly and organization of poly(3-hexylthiophene) brushes and their potential use as novel anode buffer layers for organic photovoltaics.

    PubMed

    Alonzo, José; Kochemba, W Michael; Pickel, Deanna L; Ramanathan, Muruganathan; Sun, Zhenzhong; Li, Dawen; Chen, Jihua; Sumpter, Bobby G; Heller, William T; Kilbey, S Michael

    2013-10-01

    Buffer layers that control electrochemical reactions and physical interactions at electrode/film interfaces are key components of an organic photovoltaic cell. Here the structure and properties of layers of semi-rigid poly(3-hexylthiophene) (P3HT) chains tethered at a surface are investigated, and these functional systems are applied in an organic photovoltaic device. Areal density of P3HT chains is readily tuned through the choice of polymer molecular weight and annealing conditions, and insights from optical absorption spectroscopy and semiempirical quantum calculation methods suggest that tethering causes intrachain defects that affect co-facial π-stacking of brush chains. Because of their ability to modify oxide surfaces, P3HT brushes are utilized as an anode buffer layer in a P3HT-PCBM (phenyl-C₆₁-butyric acid methyl ester) bulk heterojunction device. Current-voltage characterization shows a significant enhancement in short circuit current, suggesting the potential of these novel nanostructured buffer layers to replace the PEDOT:PSS buffer layer typically applied in traditional P3HT-PCBM solar cells. PMID:23955069

  6. Luminous efficiency enhancement in blue phosphorescent organic light-emitting diodes with an electron confinement layers

    NASA Astrophysics Data System (ADS)

    Kang, Jin Sung; Yoon, Ju-An; Yoo, Seung Il; Kim, Jin Wook; Yi, Seungjun; Zhu, Furong; Cheah, Kok Wai; Kim, Woo Young

    2015-09-01

    This study reports the results of blue phosphorescent organic light emitting diodes (PHOLEDs) employing an electron confinement layer (ECL), tris-(phenylpyrazole)iridium (Ir(ppz)3) and a hole confinement layer (HCl), 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene (TPBi). The electrical and optical characteristics of PHOLEDs with different emissive layers, including current density, luminance, and luminous efficiency, were analyzed. The thickness of the individual emissive layer was optimized, however, and the total thickness of the emitting region was kept constant at 300 Å. This work reveals that the effective electron confinement, due to a large energy level offset between the electron confinement and emitting layers, helps to improve hole-electron current balance in the emitting region. The maximum external quantum efficiency of 23.40% at 1500 cd/m2 was achieved for PHOLEDs with an ECL, which is 60% higher than the structural identical control device without ECL.

  7. Performance improvement of rubrene-based organic light emitting devices with a mixed single layer

    NASA Astrophysics Data System (ADS)

    Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki

    2010-09-01

    We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by using 4,4'-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl ( α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the J - V characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower than Al/Alq3 interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed single-layer device.

  8. Separation and electrical properties of self-organized graphene/graphite layers

    NASA Astrophysics Data System (ADS)

    Mailian, Manuel R.; Mailian, Aram R.

    2015-02-01

    Intrinsic layered structure of graphite is the source of ongoing and expanding search of ways of obtaining low-cost and promising graphite thin layers. We report on a novel method of obtaing and seperating rubbed graphite sheets by using water soluble NaCl substrate. The electrical behavior of sheets was characterized by current-voltage measurements. An in-plane electrical anisotropy depending on rubbing direction is discovered. Optical microscopy observations combined with discovered non-linear electrical behavior revealed that friction leads to the formation of sheet makeup which contain an optically transparent lamina of self-organized few-layer graphene.

  9. The effect of interfacial layers on charge transport in organic solar cell

    NASA Astrophysics Data System (ADS)

    Mbuyise, Xolani G.; Tonui, Patrick; Mola, Genene Tessema

    2016-09-01

    The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.

  10. Ultraviolet-ozone-treated PEDOT:PSS as anode buffer layer for organic solar cells

    PubMed Central

    2012-01-01

    Ultraviolet-ozone-treated poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)was used as the anode buffer layer in copper phthalocyanine (CuPc)/fullerene-based solar cells. The power conversion efficiency of the cells with appropriated UV-ozone treatment was found to increase about 20% compared to the reference cell. The improved performance is attributed to the increased work function of the PEDOT:PSS layer, which improves the contact condition between PEDOT:PSS and CuPc, hence increasing the extraction efficiency of the photogenerated holes and decreasing the recombination probability of holes and electrons in the active organic layers. PMID:22901365

  11. Organic solar cells with graded absorber layers processed from nanoparticle dispersions

    NASA Astrophysics Data System (ADS)

    Gärtner, Stefan; Reich, Stefan; Bruns, Michael; Czolk, Jens; Colsmann, Alexander

    2016-03-01

    The fabrication of organic solar cells with advanced multi-layer architectures from solution is often limited by the choice of solvents since most organic semiconductors dissolve in the same aromatic agents. In this work, we investigate multi-pass deposition of organic semiconductors from eco-friendly ethanol dispersion. Once applied, the nanoparticles are insoluble in the deposition agent, allowing for the application of further nanoparticulate layers and hence for building poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct absorber layers with vertically graded polymer and conversely graded fullerene concentration. Upon thermal annealing, we observe some degrees of polymer/fullerene interdiffusion by means of X-ray photoelectron spectroscopy and Kelvin probe force microscopy. Replacing the common bulk-heterojunction by such a graded photo-active layer yields an enhanced fill factor of the solar cell due to an improved charge carrier extraction, and consequently an overall power conversion efficiency beyond 4%. Wet processing of such advanced device architectures paves the way for a versatile, eco-friendly and industrially feasible future fabrication of organic solar cells with advanced multi-layer architectures.

  12. Hormonal Regulation of Organic and Phosphoric Acid Release by Barley Aleurone Layers and Scutella.

    PubMed Central

    Drozdowicz, Y. M.; Jones, R. L.

    1995-01-01

    The release of acid from the aleurone layer and scutellum of barley (Hordeum vulgare L. cv Himalaya) was investigated. Aleurone layers isolated from mature barley grains acidify the external medium by releasing organic and phosphoric acids. Gibberellic acid and abscisic acid stimulate acid release 2-fold over control tissue incubated in 10 mM CACl2. Gibberellic acid causes medium acidification by stimulating the release of phosphoric and citric acids, whereas abscisic acid stimulates the release of malic acid. The accumulation of these acids in the incubation medium buffers the medium against changes in pH, particularly between pH 4 and 5. The amounts of amino acids that accumulate in the medium are low (2-12 nmol/layer) compared to other organic and phosphoric acids (100-500 nmol/layer). The scutellum does not play a major role in medium acidification but participates in the uptake of organic acids. The organic acid composition of the starchy endosperm changes after 3 d of imbibition; malic, succinic, and lactic acids decrease, whereas citric and phosphoric acids remain unchanged or increase. These results indicate that during postgerminative growth, the acidity of the starchy endosperm is maintained by acid production by the aleurone layer. PMID:12228509

  13. Organic solar cells with graded absorber layers processed from nanoparticle dispersions.

    PubMed

    Gärtner, Stefan; Reich, Stefan; Bruns, Michael; Czolk, Jens; Colsmann, Alexander

    2016-03-28

    The fabrication of organic solar cells with advanced multi-layer architectures from solution is often limited by the choice of solvents since most organic semiconductors dissolve in the same aromatic agents. In this work, we investigate multi-pass deposition of organic semiconductors from eco-friendly ethanol dispersion. Once applied, the nanoparticles are insoluble in the deposition agent, allowing for the application of further nanoparticulate layers and hence for building poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct absorber layers with vertically graded polymer and conversely graded fullerene concentration. Upon thermal annealing, we observe some degrees of polymer/fullerene interdiffusion by means of X-ray photoelectron spectroscopy and Kelvin probe force microscopy. Replacing the common bulk-heterojunction by such a graded photo-active layer yields an enhanced fill factor of the solar cell due to an improved charge carrier extraction, and consequently an overall power conversion efficiency beyond 4%. Wet processing of such advanced device architectures paves the way for a versatile, eco-friendly and industrially feasible future fabrication of organic solar cells with advanced multi-layer architectures. PMID:26952692

  14. Carrier transport in multilayer organic photodetectors: I. Effects of layer structure on dark current and photoresponse

    NASA Astrophysics Data System (ADS)

    Xue, Jiangeng; Forrest, Stephen R.

    2004-02-01

    In this and the following article (Parts I and II, respectively), we discuss carrier transport in multilayer organic photodetectors. In Part I, we analyze carrier tunneling in multilayer organic photodetectors, both within the organic active region and at the anode/organic interface. The external quantum efficiency of an organic photodetector whose individual layers in the active region are ⩽30 Å thick shows an activation energy of ⩽0.1 eV, suggesting that the photogenerated carriers tunnel through the potential wells formed by the multilayer stack. In such photodetectors, electron tunneling injection from the anode into the organic active region dominates the dark current at T⩾200 K. Fitting of the dark current-voltage characteristics using a semiclassical tunneling model leads to barrier heights in agreement with experimental data. In Part II, the effects of anode preparation on performance of multilayer organic photodetectors are discussed.

  15. A water-processable organic electron-selective layer for solution-processed inverted organic solar cells

    SciTech Connect

    Chen, Dongcheng; Zhou, Hu; Cai, Ping; Sun, Shi; Ye, Hua; Su, Shi-Jian Cao, Yong

    2014-02-03

    A triazine- and pyridinium-containing water-soluble material of 1,1′,1″-(4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl)) tris(methylene)tripyridinium bromide (TzPyBr) was developed as an organic electron-selective layer in solution-processed inverted organic solar cells due to its strong anti-erosion capacity against non-polar organic solvents commonly used for the active layer. Ohmic-like contact with the adjacent active materials like fullerene derivatives is speculated to be formed, as confirmed by the work-function measurements with scanning Kelvin probe and ultraviolet photoelectron spectroscopy techniques. Besides, considering the deep highest occupied molecular orbital energy level of TzPyBr, excellent hole-blocking property of the electron-selective layer is also anticipated. The inverted organic photovoltaic devices based on the TzPyBr/ITO (indium tin oxide) bilayer cathode exhibit dramatically enhanced performance compared to the control devices with bare ITO as the cathode and even higher efficiency than the conventional type devices with ITO and Al as the electrodes.

  16. Highly sensitive multi-layer pressure sensor with an active nanostructured layer of an organic molecular metal

    NASA Astrophysics Data System (ADS)

    Laukhin, V.; Lebedev, V.; Laukhina, E.; Rovira, C.; Veciana, J.

    2016-03-01

    This work addresses to the modern technologies that need to be instrumented with lightweight highly sensitive pressure sensors. The paper presents the development of a new plain flexible thin pressure sensor using a nanostructured layer of the highly sensitive organic piezoresistive metal β-(BEDT-TTF)2I3 as an active component; BEDT-TTF=bis (ethylenedithio)tetrathiafulvalene. The original construction approach permits one to operate the developed sensor on the principle of electrical resistance variations when its piezoresistive layer is elongated under a pressure increase. The pressure sensing element and a set of gold electrodes were integrated into one compact multi-layer design. The construction was optimized to enable one generic design for pressure ranges from 1 to 400 bar. The pressure tests showed that the sensor is able to control a small pressure change as a well definite electrical signal. So the developed type of the sensors is very attractive as a new generation of compact, lightweight, low-cost sensors that might monitor pressure with a good level of measurement accuracy.

  17. Exclusion of metal oxide by an RF sputtered Ti layer in flexible perovskite solar cells: energetic interface between a Ti layer and an organic charge transporting layer.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Nazeeruddin, Mohammad Khaja; Shin, Hyung-Shik

    2015-04-14

    In this work, the effects of a titanium (Ti) layer on the charge transport and recombination rates of flexible perovskite solar cells were studied. Ti as an efficient barrier layer was deposited directly on PET-ITO flexible substrates through RF magnetic sputtering using a Ti-source and a pressure of ∼5 mTorr. A Ti coated PET-ITO was used for the fabrication of a flexible perovskite solar cell without using any metal oxide layer. The fabricated flexible perovskite solar cell was composed of a PET-ITO/Ti/perovskite (CH3NH3PbI3)/organic hole transport layer of 2,2',7,7'-tetrakis [N,N'-di-p-methoxyphenylamine]-9,9'-spirobifluorene (spiro-OMeTAD)-Li-TFSI/Ag. A high conversion efficiency of ∼8.39% along with a high short circuit current (JSC) of ∼15.24 mA cm(-2), an open circuit voltage (VOC) of ∼0.830 V and a high fill factor (FF) of ∼0.66 was accomplished by the fabricated flexible perovskite solar cell under a light illumination of ∼100 mW cm(-2) (1.5 AM). Intensity-modulated photocurrent (IMPS)/photovoltage spectroscopy (IMVS) studies demonstrated that the fabricated flexible perovskite solar cell considerably reduced the recombination rate. PMID:25747794

  18. High Efficiency Alternating Current Driven Organic Light Emitting Devices Employing Active Semiconducting Gate Layers

    NASA Astrophysics Data System (ADS)

    Smith, Gregory; Xu, Junwei; Carroll, David

    2015-03-01

    In this work, we describe the role of semiconductor-polymer interfaces in alternating current (AC) driven organic electroluminescent (EL) devices. We implement inorganic semiconducting materials between the external contact and the active layers in organic light EL devices. Precise control of capacitance and charge injection is required to realize bright and efficient large area AC driven devices. We show how this architecture results in active gating to the polymer layers, resulting in the novel ability to control the capacitance and charge injection characteristics. We propose a model based on band bending at the semiconductor-polymer interface. Furthermore, we elucidate the influence of the semiconductor-polymer interface on the internally coupled magnetic field generated in an alternating current driven organic light emitting device configuration. Magnetic fields can alter the ratios of singlet and triplet populations, and we show that internal generation of a magnetic field can dramatically alter the efficiency of light emission in organic EL devices.

  19. Photoluminescence emission from Alq3 organic layer in metal-Alq3-metal plasmonic structure

    NASA Astrophysics Data System (ADS)

    Huang, Bohr-Ran; Liao, Chung-Chi; Fan, Wan-Ting; Wu, Jin-Han; Chen, Cheng-Chang; Lin, Yi-Ping; Li, Jung-Yu; Chen, Shih-Pu; Ke, Wen-Cheng; Chen, Nai-Chuan

    2014-06-01

    The emission properties of an organic layer embedded in a metal-organic-metal (MOM) structure were investigated. A partially radiative odd-SPW as well as a non-radiative even-SPW modes are supported by hybridization of the SPW modes on the opposite organic/metal interface in the structure. Because of the competition by this radiative SPW, the population of excitons that recombine to form non-radiative SPW should be reduced. This may account for why the photoluminescence intensity of the MOM sample is higher than that of an organic-metal sample even though the MOM sample has an additional metal layer that should intuitively act as a filter.

  20. Effect of layered structures on the location of emissive regions in organic electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Aminaka, Ei-ichiro; Tsutsui, Tetsuo; Saito, Shogo

    1996-06-01

    Effect of layered structures on the location of emissive regions was studied in four types of organic electroluminescent (EL) devices: a single-layered (SL) device consisting only of an emissive layer (EML), two types of double-layered (DL-H and DL-E) devices in which a hole-transport layer (HTL) or an electron-transport layer (ETL) is attached to an EML, and a triple-layered (TL) device in which an EML is sandwiched between a HTL and an ETL. As EML, HTL and ETL material, 9, 10-bis[4-(diphenylamino)styryl]anthracene, 4,4'-bis[(3-methylphenyl)phenylamino]biphenyl and 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene, respectively, were used. Within EML layers, a thin sensing layer doped with a squarilium dye, 2,4-bis[4-diethylamino)-2- hydroxyphenyl]cycrobutenediylium-1,3-dioxide was inserted. The change in emission intensity from the dopant, when the location of the sensing layer was systematically varied, gave information on emissive regions in each type of EL device. The emissive region in the SL device extended through the EML, and that in the DL-H device resided near the HTL/EML boundary. On the contrary, those in the DL-E and TL devices were located within a 10-nm-wide region adjacent to the EML/ETL boundary. Moreover, the emission efficiencies of the DL-E and TL devices were found to be higher than those of the SL and DL-H devices. It was experimentally demonstrated that the carrier recombination within the narrow region adjacent to the EML/carrier transport layer boundary gave high emission efficiency.

  1. Phosphorus Speciation of Forest-soil Organic Surface Layers using P K-edge XANES Spectroscopy

    SciTech Connect

    J Prietzel; J Thieme; D Paterson

    2011-12-31

    The phosphorus (P) speciation of organic surface layers from two adjacent German forest soils with different degree of water-logging (Stagnosol, Rheic Histosol) was analyzed by P K-edge XANES and subsequent Linear Combination Fitting. In both soils, {approx}70% of the P was inorganic phosphate and {approx}30% organic phosphate; reduced P forms such as phosphonate were absent. The increased degree of water-logging in the Histosol compared to the Stagnosol did not affect P speciation.

  2. Phosphorus speciation of forest-soil organic surface layers using P K-edge XANES spectroscopy

    SciTech Connect

    Prietzel, Jörg; Thieme, Jürgen; Paterson, David

    2012-02-07

    The phosphorus (P) speciation of organic surface layers from two adjacent German forest soils with different degree of water-logging (Stagnosol, Rheic Histosol) was analyzed by P K-edge XANES and subsequent Linear Combination Fitting. In both soils, {approx} 70% of the P was inorganic phosphate and {approx} 30% organic phosphate; reduced P forms such as phosphonate were absent. The increased degree of water-logging in the Histosol compared to the Stagnosol did not affect P speciation.

  3. Photoconductive properties of organic-inorganic hybrid films of layered perovskite-type niobate.

    PubMed

    Saruwatari, Kazuko; Sato, Hisako; Idei, Tomochika; Kameda, Jun; Yamagishi, Akihiko; Takagaki, Atsushi; Domen, Kazunari

    2005-06-30

    A hybrid film of layered niobate and an organic amphiphile was prepared by the Langmuir-Blodgett (LB) method. Trimethylammonium-exchanged perovskite-type niobates ((CH(3))(3)NHSr(2)Nb(3)O(10)) were exfoliative to form an aqueous suspension. A monolayer of octadecylamine was produced on such an aqueous dispersion as a template for a hybrid film. A hybrid film was transferred as a Y-type LB film onto a hydrophilic glass plate or an ITO substrate. The structure of a deposited film was investigated with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic force microscopy (AFM) measurements, indicating a layer-by-layer structure with a single or double sheet of niobate as an inorganic composite. From the cyclic voltammogram on an ITO electrode modified with the Y-type 10 layered film, the lower edge of the conduction band of a niobate layer was determined to be - 0.6 V (vs Ag/AgCl). ac impedance and dc measurements were carried out on 1, 5, and 10-layered LB films (2 mm (electrode spacing) x 8 mm (width)) with aluminum electrodes. The freshly deposited samples behaved as an insulator under the illumination of 280 nm light (2.04 x 10(16) quanta s(-1)). Photoconductivities appeared, however, when they were preirradiated with a 150 W Xe lamp (ca. 2 x 10(18) quanta s(-1)) for 0.5-8.5 h. The process was denoted as photomodification. From the FT-IR and XRD results, it was deduced that the photomodification of LB films caused the decomposition of organic templates (octadecylammonium) accompanied by the collapse of layer-by-layer structures. dc analyses on the 5- and 10-layered films after photomodification also showed that they behaved as a photosemiconductor under UV light illumination. PMID:16852536

  4. Small-molecule organic solar cells with multiple-layer donor

    NASA Astrophysics Data System (ADS)

    Arisawa, Kenta; Harafuji, Kenji

    2015-09-01

    Small-molecule organic solar cells (OSCs) with a multifunction three-layer donor are experimentally investigated to achieve higher power conversion efficiency. The proposed OSC has an indium tin oxide (ITO, anode)/three-layer donor/fullerene (C60, acceptor, 40 nm)/bathocuproine (BCP, cathode buffer, 10 nm)/Ag (cathode, 100 nm) structure. The three-layer donor is composed of 3-nm-thick pentacene/20-nm-thick copper phthalocyanine (CuPc)/5-nm-thick aluminum phthalocyanine chloride (ClAlPc). The OSC achieves a power conversion efficiency of 1.79%, which is 1.7 times as large as that for an OSC with a single-layer donor of 20-nm-thick CuPc. Atomic force microscopy observation is carried out to clarify in detail the surface morphology at typical organic layers. The acceptor C60 is in contact not only with ClAlPc but also with CuPc due to the vertical and wall-like growth of the ClAlPc layer. The open-circuit voltage for the OSC with the ClAlPc/C60 contact is 0.56 V, compared with 0.47 V for the OSC with the CuPc/C60 contact. The thin pentacene layer is uniformly grown on the ITO and serves to achieve a high short-circuit current density Jsc by lowering the barrier height for hole transport between ITO and CuPc. Jsc for the OSC with the thin pentacene layer is 5.60 mA/cm2, compared with 4.32 mA/cm2 for the OSC without the thin pentacene layer.

  5. Uric Acid Spherulites in the Reflector Layer of Firefly Light Organ

    PubMed Central

    Goh, King-Siang; Sheu, Hwo-Shuenn; Hua, Tzu-En; Kang, Mei-Hua; Li, Chia-Wei

    2013-01-01

    Background In firefly light organs, reflector layer is a specialized tissue which is believed to play a key role for increasing the bioluminescence intensity through reflection. However, the nature of this unique tissue remains elusive. In this report, we investigated the role, fine structure and nature of the reflector layer in the light organ of adult Luciola cerata. Principal Findings Our results indicated that the reflector layer is capable of reflecting bioluminescence, and contains abundant uric acid. Electron microscopy (EM) demonstrated that the cytosol of the reflector layer's cells is filled with densely packed spherical granules, which should be the uric acid granules. These granules are highly regular in size (∼700 nm in diameter), and exhibit a radial internal structure. X-ray diffraction (XRD) analyses revealed that an intense single peak pattern with a d-spacing value of 0.320 nm is specifically detected in the light organ, and is highly similar to the diffraction peak pattern and d-spacing value of needle-formed crystals of monosodium urate monohydrate. However, the molar ratio evaluation of uric acid to various cations (K+, Na+, Ca2+ and Mg2+) in the light organ deduced that only a few uric acid molecules were in the form of urate salts. Thus, non-salt uric acid should be the source of the diffraction signal detected in the light organ. Conclusions In the light organ, the intense single peak diffraction signal might come from a unique needle-like uric acid form, which is different from other known structures of non-salt uric acid form. The finding of a radial structure in the granules of reflector layer implies that the spherical uric acid granules might be formed by the radial arrangement of needle-formed packing matter. PMID:23441187

  6. Isolation and characterization of nanosheets containing few layers of the Aurivillius family of oxides and metal-organic compounds

    SciTech Connect

    Sreedhara, M.B.; Prasad, B.E.; Moirangthem, Monali; Murugavel, R.; Rao, C.N.R.

    2015-04-15

    Nanosheets containing few-layers of ferroelectric Aurivillius family of oxides, Bi{sub 2}A{sub n−1}B{sub n}O{sub 3n+3} (where A=Bi{sup 3+}, Ba{sup 2+} etc. and B=Ti{sup 4+}, Fe{sup 3+} etc.) with n=3, 4, 5, 6 and 7 have been prepared by reaction with n-butyllithium, followed by exfoliation in water. The few-layer samples have been characterized by Tyndall cones, atomic force microscopy, optical spectroscopy and other techniques. The few-layer species have a thickness corresponding to a fraction of the c-parameter along which axis the perovskite layers are stacked. Magnetization measurements have been carried out on the few-layer samples containing iron. Few-layer species of a few layered metal-organic compounds have been obtained by ultrasonication and characterized by Tyndall cones, atomic force microscopy, optical spectroscopy and magnetic measurements. Significant changes in the optical spectra and magnetic properties are found in the few-layer species compared to the bulk samples. Few-layer species of the Aurivillius family of oxides may find uses as thin layer dielectrics in photovoltaics and other applications. - Graphical abstract: Exfoliation of the layered Aurivillius oxides into few-layer nanosheets by chemical Li intercalation using n-BuLi followed by reaction in water. Exfoliation of the layered metal-organic compounds into few-layer nanosheets by ultrasonication. - Highlights: • Few-layer nanosheets of Aurivillius family of oxides with perovskite layers have been generated by lithium intercalation. • Few-layer nanosheets of few layered metal-organic compounds have been generated by ultrasonication. • Few-layer nanosheets of the Aurivillius oxides have been characterized by AFM, TEM and optical spectroscopy. • Aurivillius oxides containing Fe show layer dependent magnetic properties. • Exfoliated few-layer metal-organic compounds show changes in spectroscopic and magnetic properties compared with bulk materials.

  7. Organic field-effect transistors based on a crosslinkable polymer blend as the semiconducting layer

    NASA Astrophysics Data System (ADS)

    Yan, He; Yoon, Myung-Han; Facchetti, Antonio; Marks, Tobin J.

    2005-10-01

    For fabrication of top-gate polymer-based organic field-effect transistors (OFETs), it is essential that the semiconducting layer remain intact during spin coating of the overlying dielectric layer. This requirement severely limits the applicable solvent and materials combinations. We show here that a crosslinkable polymer blend consisting of a p-type semiconducting polymer {e.g., TFB; poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine]} and an electroactive crosslinkable silyl reagent {e.g., TPDSi2; 4,4'-bis[(p-trichloro-silylpropylphenyl)phenylamino]biphenyl} is effective as the semiconducting layer in a top-gate bottom-contact OFET device. The TFB +TPDSi2 semiconducting blend is prepared by spin-coating in ambient. The crosslinking process occurs during spin-coating in air and is completed by curing at 90 °C, which renders the resulting film insoluble in common organic solvents and allows subsequent deposition of dielectric layers from a wide range of organic solvents. We also show that the presence of TPDSi2 in the semiconductor layer significantly reduces typical TFB-source-drain threshold voltages in bottom-contact devices, likely due to favorable interfacial TPDSi2-gold electrode interactions.

  8. Bioavailability of Hydrophobic Organic Compounds in Thin-Layered Capped Sediments

    PubMed Central

    Meric, Dogus; Alshawabkeh, Akram N.; Shine, James P.; Sheahan, Thomas C.

    2014-01-01

    The effect of a thin sand capping layer (7.5 cm) on the bioavailability of hydrophobic organic compounds (HOCs, i.e., PCBs and naphthalene) was studied using oligochaete worms, and the results compared to previously obtained bioavailability tests with a reactive core mat (RCM) cap. The study investigated the difference in HOC concentration in worms exposed to: a) a grab sample of sediment used as sampled for PCBs and spiked for PAHs; b) an initially clean mixture of sand and organic matter (biouptake layer) directly overlying the sediment; and c) the biouptake layer placed on top of the RCM-capped sediment. Benchscale experiments were performed to induce pore fluid flux through the sediment and into the overlying layer(s). Principal component analysis (PCA) was used to assess PCB homolog group concentrations. Results indicate that the thin sand cap alone reduced the average bioavailability of PCBs by a factor of 100 compared to direct exposure, but had no effect on the bioavailability of naphthalene. However, worms exposed to the RCM-protected biouptake layer show virtually the same HOC concentrations as those in the background worm samples, indicating effective isolation by the RCM. PMID:24374187

  9. Organic membranes determine the pattern of the columnar prismatic layer of mollusc shells.

    PubMed

    Checa, Antonio G; Macías-Sánchez, Elena; Harper, Elizabeth M; Cartwright, Julyan H E

    2016-05-11

    The degree to which biological control is exercised compared to physical control of the organization of biogenic materials is a central theme in biomineralization. We show that the outlines of biogenic calcite domains with organic membranes are always of simple geometries, while without they are much more complex. Moreover, the mineral prisms enclosed within the organic membranes are frequently polycrystalline. In the prismatic layer of the mollusc shell, organic membranes display a dynamics in accordance with the von Neumann-Mullins and Lewis Laws for two-dimensional foam, emulsion and grain growth. Taken together with the facts that we found instances in which the crystals do not obey such laws, and that the same organic membrane pattern can be found even without the mineral infilling, our work indicates that it is the membranes, not the mineral prisms, that control the pattern, and the mineral enclosed within the organic membranes passively adjusts to the dynamics dictated by the latter. PMID:27147096

  10. In situ intercalation dynamics in inorganic-organic layered perovskite thin films.

    PubMed

    Ahmad, Shahab; Kanaujia, Pawan K; Niu, Wendy; Baumberg, Jeremy J; Vijaya Prakash, G

    2014-07-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson-Mehl-Avrami-Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  11. Permafrost and organic layer interactions over a climate gradient in a discontinuous permafrost zone

    SciTech Connect

    Johnson, Kristopher D; Harden, Jennifer; McGuire, A. David; Clark, Mark; Yuan, Fengming; Finley, Andrew

    2013-01-01

    Permafrost is tightly coupled to the organic layer, an interaction that mediates permafrost degradation in response to regional warming. We analyzed changes in permafrost occurrence (PF) and organic layer thickness (OLT) in more than 3000 soil pedons across a mean annual temperature (MAT) gradient. Cause and effect relationships between PF, OLT, and other topographic factors were investigated using structural equation modeling in a multi-group analysis. Groups were defined by slope, soil texture type, and shallow v. deep organic layers. Permafrost probability sharply increased by 0.32 for every 10-cm OLT increase in shallow OLT soils (OLTs) due to an insulation effect, but PF decreased in deep OLT soils (OLTd) by 0.06 for every 10-cm increase. As temperature warmed, sandy soils varied little in PF or OLT, but PF in loamy and sandy soils decreased substantially. The change in OLT was more heterogeneous across soil types in some there was no change while in others OLTs soils thinned and/or OLTd soils thickened as temperature warmed. Furthermore, the rate of thickening with warming for OLTd soils was on average almost 4 times greater than the rate of thinning for OLTs soils across all soil types. If soils follow a trajectory of warming that mimics the spatial gradients found today, then heterogeneities of permafrost degradation and organic layer thinning and thickening should be considered in the regional carbon balance.

  12. Enantiospecific spin polarization of electrons photoemitted through layers of homochiral organic molecules.

    PubMed

    Niño, Miguel Ángel; Kowalik, Iwona Agnieszka; Luque, Francisco Jesús; Arvanitis, Dimitri; Miranda, Rodolfo; de Miguel, Juan José

    2014-11-26

    Electrons photoemitted through layers of purely organic chiral molecules become strongly spin-polarized even at room temperature and for double-monolayer thicknesses. The substitution of one enantiomer for its mirror image does not revert the sign of the spin polarization, rather its direction in space. These findings might lead to the obtention of highly efficient spin filters for spintronic applications. PMID:25183637

  13. In Situ Intercalation Dynamics in Inorganic–Organic Layered Perovskite Thin Films

    PubMed Central

    2014-01-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic–organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson–Mehl–Avrami–Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  14. Slot waveguide ring resonators coated by an atomic layer deposited organic/inorganic nanolaminate.

    PubMed

    Autere, A; Karvonen, L; Säynätjoki, A; Roussey, M; Färm, E; Kemell, M; Tu, X; Liow, T Y; Lo, G Q; Ritala, M; Leskelä, M; Honkanen, S; Lipsanen, H; Sun, Z

    2015-10-19

    In this study, slot waveguide ring resonators patterned on a silicon-on-insulator (SOI) wafer and coated with an atomic layer deposited nanolaminate consisting of alternating layers of tantalum pentoxide and polyimide were fabricated and characterized. To the best of our knowledge, this is the first demonstration of atomic layer deposition (ALD) of organic materials in waveguiding applications. In our nanolaminate ring resonators, the optical power is not only confined in the narrow central air slot but also in several parallel sub-10 nm wide vertical polyimide slots. This indicates that the mode profiles in the silicon slot waveguide can be accurately tuned by the ALD method. Our results show that ALD of organic and inorganic materials can be combined with conventional silicon waveguide fabrication techniques to create slot waveguide ring resonators with varying mode profiles. This can potentially open new possibilities for various photonic applications, such as optical sensing and all-optical signal processing. PMID:26480355

  15. Charge generation layers for solution processed tandem organic light emitting diodes with regular device architecture.

    PubMed

    Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Lemmer, Uli; Colsmann, Alexander

    2015-04-22

    Tandem organic light emitting diodes (OLEDs) utilizing fluorescent polymers in both sub-OLEDs and a regular device architecture were fabricated from solution, and their structure and performance characterized. The charge carrier generation layer comprised a zinc oxide layer, modified by a polyethylenimine interface dipole, for electron injection and either MoO3, WO3, or VOx for hole injection into the adjacent sub-OLEDs. ToF-SIMS investigations and STEM-EDX mapping verified the distinct functional layers throughout the layer stack. At a given device current density, the current efficiencies of both sub-OLEDs add up to a maximum of 25 cd/A, indicating a properly working tandem OLED. PMID:25832776

  16. A randomly nano-structured scattering layer for transparent organic light emitting diodes.

    PubMed

    Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

    2014-09-21

    A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. PMID:25099663

  17. Multilayer organic electrophosphorescent white light-emitting diodes without exciton-blocking layer

    NASA Astrophysics Data System (ADS)

    Lei, Gangtie; Wang, Liduo; Qiu, Yong

    2006-03-01

    We demonstrate high-efficiency white organic light-emitting diodes with two emissive layers, in which different hosts are employed. With the energy gap of the two hosts, there was no exciton-blocking layer between the emissive layers to confine the diffusion of excitons. The phosphorescent dye, bis[(4,6-difluorophenyl)-pyridinato-N, C2'] (picolinato) Ir(III) and bis (1-phenyl-isoquinoline) (acetylacetonate) iridium (III) [Ir(pic)2acac] were employed as guests, while N,N'-dicarbazolyl-1, 4-dimethene-benzene and 4, 4'-N, N'-dicarbazole-biphenyl were employed as hosts, respectively. The device exhibited white emission by controlling the thickness of the emissive layers and the maximum current efficiency and luminance were 10.5cd/A and 22000cd/m2, respectively.

  18. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    SciTech Connect

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin; Eun Lee, Song; Kwan Kim, Young; Hwa Yu, Hyeong; Turak, Ayse; Young Kim, Woo

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  19. Optimisation of the material properties of indium tin oxide layers for use in organic photovoltaics

    SciTech Connect

    Doggart, P.; Bristow, N.; Kettle, J.

    2014-09-14

    The influence of indium tin oxide [(In{sub 2}O{sub 3}:Sn), ITO] material properties on the output performance of organic photovoltaic (OPV) devices has been modelled and investigated. In particular, the effect of altering carrier concentration (n), thickness (t), and mobility (μ{sub e}) in ITO films and their impact on the optical performance, parasitic resistances and overall efficiency in OPVs was studied. This enables optimal values of these parameters to be calculated for solar cells made with P3HT:PC{sub 61}BM and PCPDTBT:PC{sub 71}BM active layers. The optimal values of n, t and μ{sub e} are not constant between different OPV active layers and depend on the absorption spectrum of the underlying active layer material system. Consequently, design rules for these optimal values as a function of donor bandgap in bulk-heterojunction active layers have been formulated.

  20. Tuning the Microcavity of Organic Light Emitting Diodes by Solution Processable Polymer-Nanoparticle Composite Layers.

    PubMed

    Preinfalk, Jan B; Schackmar, Fabian R; Lampe, Thomas; Egel, Amos; Schmidt, Tobias D; Brütting, Wolfgang; Gomard, Guillaume; Lemmer, Uli

    2016-02-01

    In this study, we present a simple method to tune and take advantage of microcavity effects for an increased fraction of outcoupled light in solution-processed organic light emitting diodes. This is achieved by incorporating nonscattering polymer-nanoparticle composite layers. These tunable layers allow the optimization of the device architecture even for high film thicknesses on a single substrate by gradually altering the film thickness using a horizontal dipping technique. Moreover, it is shown that the optoelectronic device parameters are in good agreement with transfer matrix simulations of the corresponding layer stack, which offers the possibility to numerically design devices based on such composite layers. Lastly, it could be shown that the introduction of nanoparticles leads to an improved charge injection, which combined with an optimized microcavity resulted in a maximum luminous efficacy increase of 85% compared to a nanoparticle-free reference device. PMID:26744904

  1. Molecular Interdiffusion between Stacked Layers by Solution and Thermal Annealing Processes in Organic Light Emitting Devices.

    PubMed

    Ohisa, Satoru; Pu, Yong-Jin; Yamada, Norifumi L; Matsuba, Go; Kido, Junji

    2015-09-23

    In organic light emitting devices (OLEDs), interfacial structures between multilayers have large impacts on the characteristics of OLEDs. Herein, we succeeded in revealing the interdiffusion in solution processed and thermal annealed OLEDs by neutron reflectometry. We investigated interfaces between a polymer under layer and small molecules upper layer. The small molecules diffused into the swollen polymer layer during the interfacial formation by the solution process, but the polymer did not diffuse into the small molecules layer. At temperatures close to the glass transition temperatures of the materials, asymmetric molecular diffusion was observed. We elucidated the effects of the interdiffusion on the characteristics of OLEDs. Partially mixing the interface improved the current efficiencies due to suppressed triplet-polaron quenching at the interface. Controlling and understanding the interfacial structures of the miultilayers will be more important to improve the OLED characteristics. PMID:26331696

  2. A randomly nano-structured scattering layer for transparent organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

    2014-08-01

    A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs.A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs. Electronic supplementary information (ESI) available: Simulation results of total (bottom and top) radiance of TOLEDs with the RSL depending on HTL and ETL thicknesses. See DOI: 10.1039/c4nr01520g

  3. Effects of dust particles and layer properties on organic electronic devices fabricated by stamping

    NASA Astrophysics Data System (ADS)

    Cao, Yifang; Kim, Changsoon; Forrest, Stephen R.; Soboyejo, Wole

    2005-08-01

    The mechanical properties of organic semiconductor thin films are determined using nanoindentation. The measured mechanical properties are incorporated into finite element simulations of deformation that arise during cathode patterning of organic electronic devices by pressure stamping methods. Simulations show that dust particles interposed between the stamp and film surface affect the evolution of contact areas when silicon or compliant polydimethyl-siloxane stamp dies are employed. We also examine the effects of the transferred metal layer thickness and stamp bulk modulus. Experimental and modeling results are found to be in good agreement. The implications of the results are discussed for the fabrication of a range of organic electronic devices.

  4. Spatial organization of excitatory synaptic inputs to layer 4 neurons in mouse primary auditory cortex.

    PubMed

    Kratz, Megan B; Manis, Paul B

    2015-01-01

    Layer 4 (L4) of primary auditory cortex (A1) receives a tonotopically organized projection from the medial geniculate nucleus of the thalamus. However, individual neurons in A1 respond to a wider range of sound frequencies than would be predicted by their thalamic input, which suggests the existence of cross-frequency intracortical networks. We used laser scanning photostimulation and uncaging of glutamate in brain slices of mouse A1 to characterize the spatial organization of intracortical inputs to L4 neurons. Slices were prepared to include the entire tonotopic extent of A1. We find that L4 neurons receive local vertically organized (columnar) excitation from layers 2 through 6 (L6) and horizontally organized excitation primarily from L4 and L6 neurons in regions centered ~300-500 μm caudal and/or rostral to the cell. Excitatory horizontal synaptic connections from layers 2 and 3 were sparse. The origins of horizontal projections from L4 and L6 correspond to regions in the tonotopic map that are approximately an octave away from the target cell location. Such spatially organized lateral connections may contribute to the detection and processing of auditory objects with specific spectral structures. PMID:25972787

  5. Spatial organization of excitatory synaptic inputs to layer 4 neurons in mouse primary auditory cortex

    PubMed Central

    Kratz, Megan B.; Manis, Paul B.

    2015-01-01

    Layer 4 (L4) of primary auditory cortex (A1) receives a tonotopically organized projection from the medial geniculate nucleus of the thalamus. However, individual neurons in A1 respond to a wider range of sound frequencies than would be predicted by their thalamic input, which suggests the existence of cross-frequency intracortical networks. We used laser scanning photostimulation and uncaging of glutamate in brain slices of mouse A1 to characterize the spatial organization of intracortical inputs to L4 neurons. Slices were prepared to include the entire tonotopic extent of A1. We find that L4 neurons receive local vertically organized (columnar) excitation from layers 2 through 6 (L6) and horizontally organized excitation primarily from L4 and L6 neurons in regions centered ~300–500 μm caudal and/or rostral to the cell. Excitatory horizontal synaptic connections from layers 2 and 3 were sparse. The origins of horizontal projections from L4 and L6 correspond to regions in the tonotopic map that are approximately an octave away from the target cell location. Such spatially organized lateral connections may contribute to the detection and processing of auditory objects with specific spectral structures. PMID:25972787

  6. Molecular simulation of dispersion and mechanical stability of organically modified layered silicates in polymer matrices

    NASA Astrophysics Data System (ADS)

    Fu, Yao-Tsung

    The experimental analysis of nanometer-scale separation processes and mechanical properties at buried interfaces in nanocomposites has remained difficult. We have employed molecular dynamics simulation in relation to available experimental data to alleviate such limitations and gain insight into the dispersion and mechanical stability of organically modified layered silicates in hydrophobic polymer matrices. We analyzed cleavage energies of various organically modified silicates as a function of the cation exchange capacity, surfactant head group chemistry, and chain length using MD simulations with the PCFF-PHYLLOSILICATE force field. The range of the cleavage energy is between 25 and 210 mJ/m2 upon the molecular structures and packing of surfactants. As a function of chain length, the cleavage energy indicates local minima for interlayer structures comprised of loosely packed layers of alkyl chains and local maxima for interlayer structures comprised of densely packed layers of alkyl chains between the layers. In addition, the distribution of cationic head groups between the layers in the equilibrium state determines whether large increases in cleavage energy due to Coulomb attraction. We have also examined mechanical bending and failure mechanisms of layered silicates on the nanometer scale using molecular dynamics simulation in comparison to a library of TEM data of polymer nanocomposites. We investigated the energy of single clay lamellae as a function of bending radius and different cation density. The layer energy increases particularly for bending radii below 20 nm and is largely independent of cation exchange capacity. The analysis of TEM images of agglomerated and exfoliated aluminosilicates of different CEC in polymer matrices at small volume fractions showed bending radii in excess of 100 nm due to free volumes in the polymer matrix. At a volume fraction >5%, however, bent clay layers were found with bending radii <20 nm and kinks as a failure mechanism

  7. Different materials as a cathode modification layer on the impact of organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Jian; Huang, Qiuyan; Yu, Junsheng; Jiang, Yadong

    2010-10-01

    Organic thin film solar cells based on conjugated polymer or small molecules have showed an interesting approach to energy conversion since Tang reported a single donor-accepter hetero-junction solar cell. The power conversion efficiency of organic solar cells has increased steadily over last decade. Small-molecular weight organic double heterojunction donor-acceptor layer organic solar cells (OSC) with a structure of indium-tin-oxide (ITO)/CuPc(200Å)/C60(400Å)/x/Ag(1000Å), using CuPc(copper Phthalocyanine)as donor layer, and Alq3(8-Hydroxyquinoline aluminum salt), BCP(Bromocresol purple sodium salt) and Bphen(4'7-diphyenyl-1,10-phenanthroline) as cathode modification layer, respectively were fabricated. The performance of OSC was studied as a function of the different materials as an cathode modification layer to optimize the structure. The current-voltage characteristic of the solar cell under AM1.5 solar illumination at an intensity of 100 mw/cm2 showed that the power conversion efficiency (PCE) was dependent of the different materials of the cathode modification layer. the efficiency along with the different materials as an cathode modification layer will diminish under that standard solar illumination(AM1.5)was obtained. Using a double heterostructure of ITO/CuPc(200Å)/C60(400Å)/Alq3(60Å)/Ag(1000Å) with high-vacuum evaporation technology, the efficiency was 0.587%.the efficiency was 0.967% when the material of the cathode modification layer was BCP, with the structure of ITO/CuPc(200Å)/C60(400Å)/BCP(35Å)/Ag(1000Å), and the efficiency was 0.742% when the material of the cathode modification layer was Bphen, with the structure of ITO/CuPc(200Å)/C60(400Å)/ Bphen(50Å)/Ag(1000Å).Using different materials as a cathode modification layer, it can be seen that the material which matches the energy level could even eventually be able to improve the energy conversion efficiency more.

  8. Adsorptive and photocatalytic removal of phenol by layered niobates organically modified through intercalation and silylation.

    PubMed

    Kiba, Shosuke; Haga, Jun-ichi; Hashimoto, Sachika; Nakato, Teruyuki

    2010-12-01

    Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed. PMID:21121337

  9. Self-aligned metallization on organic semiconductor through 3D dual-layer thermal nanoimprint

    NASA Astrophysics Data System (ADS)

    Jung, Y.; Cheng, X.

    2014-09-01

    High-resolution patterning of metal structures on organic semiconductors is important to the realization of high-performance organic transistors for organic integrated circuit applications. The traditional shadow mask technique has a limited resolution, precluding sub-micron metal structures on organic semiconductors. Thus organic transistors cannot benefit from scaling into the deep sub-micron region to improve their dc and ac performances. In this work, we report an efficient multiple-level metallization on poly (3-hexylthiophene) (P3HT) with a deep sub-micron lateral gap. By using a 3D nanoimprint mold in a dual-layer thermal nanoimprint process, we achieved self-aligned two-level metallization on P3HT. The 3D dual-layer thermal nanoimprint enables the first metal patterns to have suspending side-wings that can clearly define a distance from the second metal patterns. Isotropic and anisotropic side-wing structures can be fabricated through two different schemes. The process based on isotropic side-wings achieves a lateral-gap in the order of 100 nm (scheme 1). A gap of 60 nm can be achieved from the process with anisotropic side-wings (scheme 2). Because of the capability of nanoscale metal patterning on organic semiconductors with high overlay accuracy, this self-aligned metallization technique can be utilized to fabricate high-performance organic metal semiconductor field-effect transistor.

  10. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers

    NASA Astrophysics Data System (ADS)

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M.; Zacharias, Margit; Asplund, Maria

    2016-01-01

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ±0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system.

  11. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers

    PubMed Central

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M.; Zacharias, Margit; Asplund, Maria

    2016-01-01

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ±0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system. PMID:26791399

  12. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers.

    PubMed

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M; Zacharias, Margit; Asplund, Maria

    2016-01-01

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ± 0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system. PMID:26791399

  13. Understanding the Internal Structure of Layered Organic Compounds deposited on mineral surface using Neutron Reflectivity

    NASA Astrophysics Data System (ADS)

    Ambaye, Haile; Jagadamma, Sindhu; Petridis, Loukas; Mayes, Melanie; Lauter, Valeria

    2013-03-01

    Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore the understanding of the structure and function of the OC-soil mineral interface is of high importance. To study the internal structure, films with different combination of simple OC compounds, natural organic matter (NOM), Bi-layers of SA (Stearic Acid) on Glucose and NOM/Hydrophilic-NOM/Hydrophobic-NOM were deposited onto sapphire using spin coating. The phobic and phylic fractions of the NOM are operationally separated by exchange resins. We obtained detailed structural depth profile of the films using the depth-sensitive technique of the neutron reflectometry. The neutron reflectivity data were collected at the MAGICS Reflectometer at Spallation Neutron Source at the ORNL. Self-assembled ordering of SA in a repeating bi-layer structure was observed when it was deposited on NOM, phylic-NOM and Glucose. However, when SA was added to phobic-NOM no ordering of SA was detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM/Hydrophilic-NOM and Glucose. Our results reveal that the OC-mineral interface form complex layering and that the sequence of the layering depends on the compounds. The work was supported by ORNL (LDRD), BES and DOE.

  14. The formation of organic (propolis films)/inorganic (layered crystals) interfaces for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Drapak, S. I.; Bakhtinov, A. P.; Gavrylyuk, S. V.; Kovalyuk, Z. D.; Lytvyn, O. S.

    2008-10-01

    Propolis (honeybee glue) organic films were prepared from an alcoholic solution on the surfaces of inorganic layered semiconductors (indium, gallium and bismuth selenides). Atomic force microscopy (AFM) and X-ray diffraction (XRD) are used to characterize structural properties of an organic/inorganic interfaces. It is shown that nanodimensional linear defects and nanodimensional cavities of various shapes are formed on the van der Waals (VDW) surfaces of layered crystals as a result of chemical interaction between the components of propolis (flavonoids, aminoacids and phenolic acids) and the VDW surfaces as well as deformation interaction between the VDW surfaces and propolis films during their polymerization. The nanocavities are formed as a result of the rupture of strong covalent bonds in the upper layers of layered crystals and have the shape of hexagons or triangles in the (0001) plane. The shape, lateral size and distribution of nanodimensional defects on the VDW surfaces depends on the type of crystals, the magnitude and distribution of surface stresses. We have obtained self-organized nanofold structures of propolis/InSe interface. It is established that such heterostructures have photosensitivity in the infrared range hν<1.2 eV (the values of energy gap are 1.2 eV for InSe and 3.07 eV for propolis films at room temperature).

  15. Permafrost and organic layer interactions over a climate gradient in a discontinuous permafrost zone

    USGS Publications Warehouse

    Johnson, Kristofer D.; Harden, Jennifer W.; McGuire, A. David; Clark, Mark; Yuan, Fengming; Finley, Andrew O.

    2013-01-01

    Permafrost is tightly coupled to the organic soil layer, an interaction that mediates permafrost degradation in response to regional warming. We analyzed changes in permafrost occurrence and organic layer thickness (OLT) using more than 3000 soil pedons across a mean annual temperature (MAT) gradient. Cause and effect relationships between permafrost probability (PF), OLT, and other topographic factors were investigated using structural equation modeling in a multi-group analysis. Groups were defined by slope, soil texture type, and shallow (<28 cm) versus deep organic (≥28 cm) layers. The probability of observing permafrost sharply increased by 0.32 for every 10-cm OLT increase in shallow OLT soils (OLTs) due to an insulation effect, but PF decreased in deep OLT soils (OLTd) by 0.06 for every 10-cm increase. Across the MAT gradient, PF in sandy soils varied little, but PF in loamy and silty soils decreased substantially from cooler to warmer temperatures. The change in OLT was more heterogeneous across soil texture types—in some there was no change while in others OLTs soils thinned and/or OLTd soils thickened at warmer locations. Furthermore, when soil organic carbon was estimated using a relationship with thickness, the average increase in carbon in OLTd soils was almost four times greater compared to the average decrease in carbon in OLTs soils across all soil types. If soils follow a trajectory of warming that mimics the spatial gradients found today, then heterogeneities of permafrost degradation and organic layer thinning and thickening should be considered in the regional carbon balance.

  16. Improved performance of polymer solar cells by using inorganic, organic, and doped cathode buffer layers

    NASA Astrophysics Data System (ADS)

    Taohong, Wang; Changbo, Chen; Kunping, Guo; Guo, Chen; Tao, Xu; Bin, Wei

    2016-03-01

    The interface between the active layer and the electrode is one of the most critical factors that could affect the device performance of polymer solar cells. In this work, based on the typical poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) polymer solar cell, we studied the effect of the cathode buffer layer (CBL) between the top metal electrode and the active layer on the device performance. Several inorganic and organic materials commonly used as the electron injection layer in an organic light-emitting diode (OLED) were employed as the CBL in the P3HT:PCBM polymer solar cells. Our results demonstrate that the inorganic and organic materials like Cs2CO3, bathophenanthroline (Bphen), and 8-hydroxyquinolatolithium (Liq) can be used as CBL to efficiently improve the device performance of the P3HT:PCBM polymer solar cells. The P3HT:PCBM devices employed various CBLs possess power conversion efficiencies (PCEs) of 3.0%-3.3%, which are ca. 50% improved compared to that of the device without CBL. Furthermore, by using the doped organic materials Bphen:Cs2CO3 and Bphen:Liq as the CBL, the PCE of the P3HT:PCBM device will be further improved to 3.5%, which is ca. 70% higher than that of the device without a CBL and ca. 10% increased compared with that of the devices with a neat inorganic or organic CBL. Project supported by the National Natural Science Foundation of China (Grant No. 61204014), the “Chenguang” Project (13CG42) supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation, China, and the Shanghai University Young Teacher Training Program of Shanghai Municipality, China.

  17. Efficient Light Extraction from Organic Light-Emitting Diodes Using Plasmonic Scattering Layers

    SciTech Connect

    Rothberg, Lewis

    2012-11-30

    Our project addressed the DOE MYPP 2020 goal to improve light extraction from organic light-emitting diodes (OLEDs) to 75% (Core task 6.3). As noted in the 2010 MYPP, “the greatest opportunity for improvement is in the extraction of light from [OLED] panels”. There are many approaches to avoiding waveguiding limitations intrinsic to the planar OLED structure including use of textured substrates, microcavity designs and incorporating scattering layers into the device structure. We have chosen to pursue scattering layers since it addresses the largest source of loss which is waveguiding in the OLED itself. Scattering layers also have the potential to be relatively robust to color, polarization and angular distributions. We note that this can be combined with textured or microlens decorated substrates to achieve additional enhancement.

  18. Small molecular phosphorescent organic light-emitting diodes using a spin-coated hole blocking layer

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Duan, Lian; Zhang, Deqiang; Hou, Liudong; Qiao, Juan; Wang, Liduo; Qiu, Yong

    2012-02-01

    Small molecular green phosphorescent organic light-emitting diodes (OLEDs) have been studied using a solution processed polyethyleneoxide (PEO) hole blocking layer (HBL) and a Cs2CO3/Al cathode. PEO is soluable in alcoholic solvents and allows the fabrication of multilayer OLEDs by successive spin-coating. The current efficiency of the optimized OLED with the PEO HBL increases from 18.8 cd/A to 32.1 cd/A, and the turn-on voltage reduces from 4.8 V to 3.4 V, compared with the device without the PEO HBL. Photovoltaic measurements indicate that the injection barrier for electron is reduced by inserting the PEO layer. X-ray photoelectron spectroscopy measurements further reveal that improvement in device performance is due to the partial penetration of Cs into the PEO layer.

  19. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells.

    PubMed

    Ambade, Swapnil B; Ambade, Rohan B; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S; Mane, Rajaram S; Lee, Soo-Hyoung

    2016-03-01

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs. PMID:26864170

  20. A novel structure of directly patterned isolating layer for organic thin-film transistor-driven organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Kai; Lin, Tsung-Hsien; Yan, Jing-Yi; Lee, Tzu-Wei; Shen, Yu-Yuan; Yeh, Shu-Tang; Tseng, Mei-Rurng; Wu, Po-Sheng; Lin, Kuo-Tong; Chen, Chia-Hsun; Ho, Jia-Chong

    2007-09-01

    Mono-chrome phosphorescence Organic light emitting diodes (OLEDs) operated by organic thin-film transistors (OTFTs) with a 32×32 array are fabricated with a novel method, and the results reveal a fabulous demonstration. The later isolation, which segregated source/drain electrodes and an OLED cathode, was designed in our OTFT-OLED pixel. In the OTFT-OLED process; we used the polymer isolating layer which was deposited by spin coating and patterned by traditional photo-lithography before the organic semiconductor and OLED deposition. However, the residue polymer affect of OTFT electric properties which have poor mobility (5×10-4 cm2/V-s), a lower on/off ratio (~103), and a positive threshold voltage (4.5 V), and devices, have poor uniformity. Using UV-Ozone treatment could enhance OTFT mobility (2×10-2 cm2/V-s) and permit higher devices uniformity, but the threshold voltage would still have a positive 5.1 V. This threshold voltage was not a good operation mode for display application because this operation voltage was not fit for our driving systems. In order to overcome this problem, a new structure of OTFT-OLED pixel was designed and combined with a new-material isolating layer process. This new process could fabricate an OTFT-OLED array successfully and have a nice uniformity. After the isolating layer process, OTFT devices have a higher mobility (0.1×10-2 cm2/V-s), a higher on-off ratio (~107) a lower threshold voltage (-9.7 V), and a higher devices uniformity.

  1. Calcium chloride electron injection/extraction layers in organic electronic devices

    SciTech Connect

    Qu, Bo E-mail: qhgong@pku.edu.cn; Gao, Zhi; Yang, Hongsheng; Xiao, Lixin; Chen, Zhijian; Gong, Qihuang E-mail: qhgong@pku.edu.cn

    2014-01-27

    Nontoxic calcium chloride (CaCl{sub 2}) was introduced into organic electronic devices as cathode buffer layer (CBL). The turn-on voltage and maximum luminance of organic light-emitting diode (OLED) with 1.5 nm CaCl{sub 2} was 3.5 V and 21 960 cd/m{sup 2}, respectively. OLED with 1.5 nm CaCl{sub 2} possessed comparable electroluminescent characteristics to that of the commonly used LiF. Moreover, the performance of the organic photovoltaic device with 0.5 nm CaCl{sub 2} was comparable to that of the control device with LiF. Therefore, CaCl{sub 2} has the potential to be used as the CBL for organic electronic devices.

  2. More stable hybrid organic solar cells deposited on amorphous Si electron transfer layer

    SciTech Connect

    Samiee, Mehran; Modtland, Brian; Dalal, Vikram L.; Aidarkhanov, Damir

    2014-05-26

    We report on defect densities, performance, and stability of organic/inorganic hybrid solar cells produced using n-doped inorganic amorphous silicon-carbide layers as the electron transport layer (ETL). The organic material was poly-3-hexyl-thiophene (P3HT) and heterojunction was formed using phenyl-C{sub 71}-Butyric-Acid-Methyl Ester (PCBM). For comparison, inverted solar cells fabricated using Cs{sub 2}CO{sub 3} as ETL were fabricated. Defect densities and subgap quantum efficiency curves were found to be nearly identical for both types of cells. The cells were subjected to 2xsun illumination and it was found that the cells produced using doped a-Si as ETL were much more stable than the cells produced using Cs{sub 2}CO{sub 3}.

  3. More stable hybrid organic solar cells deposited on amorphous Si electron transfer layer

    NASA Astrophysics Data System (ADS)

    Samiee, Mehran; Modtland, Brian; Aidarkhanov, Damir; Dalal, Vikram L.

    2014-05-01

    We report on defect densities, performance, and stability of organic/inorganic hybrid solar cells produced using n-doped inorganic amorphous silicon-carbide layers as the electron transport layer (ETL). The organic material was poly-3-hexyl-thiophene (P3HT) and heterojunction was formed using phenyl-C71-Butyric-Acid-Methyl Ester (PCBM). For comparison, inverted solar cells fabricated using Cs2CO3 as ETL were fabricated. Defect densities and subgap quantum efficiency curves were found to be nearly identical for both types of cells. The cells were subjected to 2xsun illumination and it was found that the cells produced using doped a-Si as ETL were much more stable than the cells produced using Cs2CO3.

  4. Quantifying the Distribution and Landscape Controls of Peatlands and Organic Layer Thickness within Alaska

    NASA Astrophysics Data System (ADS)

    Wylie, B. K.; Pastick, N.; Jorgenson, T.; Nield, S.; Johnson, K. D.

    2014-12-01

    The northern circumpolar region is estimated to contain 50 % of the global belowground carbon pool and is experiencing climate change at rates higher than anywhere else globally. Surface organic horizons associated with these immense carbon pools are important to ecosystem functioning in terms of soil moisture and temperature regulations, permafrost degradation, successional trajectories, and soil respiration levels. However, fire-induced changes to surface organics and their distribution are poorly understood, especially on landscape scales. These ambiguities make future predictions uncertain for these significant carbon pools, which have the potential for significant feedbacks to global warming. Moreover, given the significant impacts and increasing severity and amount of fires in boreal systems, the spatial quantification of post-fire surface organic thickness is important for ecosystem model calibrations and comparisons, and can improve future projections of vegetation types and albedo, carbon stocks and fluxes, and future thaw depths. Here we present the results of pioneering studies that quantified the distribution and controls of peatlands and soil organic layer thickness in Alaska through the use of statistical models, field data, spatial analyses, and remote sensing (Landsat). Our empirical modeling approach enabled us to produce medium-resolution (30-m pixels) maps of peatlands and organic layer thickness throughout Alaska, which is important for land management practices and enhances the understanding of the risk and feedbacks associated with fires and climate feedbacks.

  5. Artificially MoO3 graded ITO anodes for acidic buffer layer free organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Min; Kim, Seok-Soon; Kim, Han-Ki

    2016-02-01

    We report characteristics of MoO3 graded ITO anodes prepared by a RF/DC graded sputtering for acidic poly(3,4-ethylene dioxylene thiophene):poly(styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs). Graded sputtering of the MoO3 buffer layer on top of the ITO layer produced MoO3 graded ITO anodes with a sheet resistance of 12.67 Ω/square, a resistivity of 2.54 × 10-4 Ω cm, and an optical transmittance of 86.78%, all of which were comparable to a conventional ITO anode. In addition, the MoO3 graded ITO electrode showed a greater work function of 4.92 eV than that (4.6 eV) of an ITO anode, which is beneficial for hole extraction from an organic active layer. Due to the high work function of MoO3 graded ITO electrodes, the acidic PEDOT:PSS-free OSCs fabricated on the MoO3 graded ITO electrode exhibited a power conversion efficiency 3.60% greater than that of a PEDOT:PSS-free OSC on the conventional ITO anode. The successful operation of PEDOT:PSS-free OSCs indicates simpler fabrication steps for cost-effective OSCs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable OSCs.

  6. Charge transport and device physics of layered-crystalline organic semiconductors (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tatsuo

    2015-10-01

    Here we present and discuss our recent investigations into the understanding of microscopic charge transport, novel film processing technologies, and a development of layered-crystalline organic semiconductors for high performance OTFTs. We first discuss the microscopic charge transport in the OTFTs, as investigated by field-induced electron spin resonance spectroscopy. The technique can detect signals due to tiny amount of field-induced carriers, accumulated at the semiconductor-insulator interfaces. Following aspects are presented and discussed; 1) Carrier motion within the crystalline domains can be understood in terms of the trap-and-release transport, 2) charge trap states are spatially extended over several sites depending on the trap levels, and 3) the intra- and inter-domain transport can be discriminated by anisotropic electron spin resonance measurements. Next we discuss novel print production technologies for organic semiconductors showing high layered crystallinity. The concept of "printed electronics" is now regarded as a realistic paradigm to manufacture light-weight, thin, and impact-resistant electronics devices, although production of highly crystalline semiconductor films may be incompatible with conventional printing process. We here present printing techniques for manufacturing high performance OTFTs; 1) double-shot inkjet printing for small-molecule-based semiconductors, and 2) push-coating for semiconducting polymers. We demonstrate that both processes are useful to manufacture high quality semiconductor layers with the high layered crystallinity.

  7. Formation of mixed organic layers by stepwise electrochemical reduction of diazonium compounds.

    PubMed

    Santos, Luis; Ghilane, Jalal; Lacroix, Jean Christophe

    2012-03-28

    This work describes the formation of a mixed organic layer covalently attached to a carbon electrode. The strategy adopted is based on two successive electrochemical reductions of diazonium salts. First, bithiophene phenyl (BTB) diazonium salt is reduced using host/guest complexation in a water/cyclodextrin (β-CD) solution. The resulting layer consists of grafted BTB oligomers and cyclodextrin that can be removed from the surface. The electrochemical response of several outer-sphere redox probes on such BTB/CD electrodes is close to that of a diode, thanks to the easily p-dopable oligo(BTB) moieties. When CD is removed from the surface, pinholes are created and this diode like behavior is lost. Following this, nitrophenyl (NP) diazonium is reduced to graft a second component. Electrochemical study shows that upon grafting NP insulating moieties, the diode-like behavior of the layer is restored which demonstrates that NP is grafted predominately in the empty spaces generated by β-CD desorption. As a result, a mixed BTB/NP organic layer covalently attached to a carbon electrode is obtained using a stepwise electrochemical reduction of two diazonium compounds. PMID:22385504

  8. Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

    DOEpatents

    Forrest, Stephen; Kanno, Hiroshi

    2009-08-25

    The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

  9. Improving performance of inverted organic solar cells using ZTO nanoparticles as cathode buffer layer

    NASA Astrophysics Data System (ADS)

    Tsai, Meng-Yen; Cheng, Wen-Hui; Jeng, Jiann-Shing; Chen, Jen-Sue

    2016-06-01

    In this study, a low-temperature solution-processed zinc tin oxide (ZTO) films are successfully utilized as the cathode buffer layer in the inverted organic P3HT:PCBM bulk heterojunction solar cells. ZTO film cathode buffer layer with an appropriate Sn-doping concentration outperforms the zinc oxide (ZnO) film with an improved power conversion efficiency (1.96% (ZTO film) vs. 1.56% (ZnO film)). Furthermore, ZTO nanoparticles (NPs) are also synthesized via low-temperature solution route and the device with ZTO NPs buffer layer exhibits a significant improvement in device performance to reach a PCE of 2.60%. The crystallinity of the cathode buffer layer plays an influential factor in the performance. From impedance spectroscopy analysis, a correlation between short circuit current (Jsc), carrier life time (τavg) and, thus, PCE is observed. The interplay between composition and crystallinity of the cathode buffer layers is discussed to find their influences on the solar cell performance.

  10. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    NASA Astrophysics Data System (ADS)

    Sang, Jing; Aisawa, Sumio; Hirahara, Hidetoshi; Kudo, Takahiro; Mori, Kunio

    2016-04-01

    Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag+ ion to Ag0. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  11. Uncovering the role of cathode buffer layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Qi, Boyuan; Zhang, Zhi-Guo; Wang, Jizheng

    2015-01-01

    Organic solar cells (OSCs) as the third generation photovoltaic devices have drawn intense research, for their ability to be easily deposited by low-cost solution coating technologies. However the cathode in conventional OSCs, Ca, can be only deposited by thermal evaporation and is highly unstable in ambient. Therefore various solution processible cathode buffer layers (CBLs) are synthesized as substitute of Ca and show excellent effect in optimizing performance of OSCs. Yet, there is still no universal consensus on the mechanism that how CBL works, which is evidently a critical scientific issue that should be addressed. In this article detailed studies are targeted on the interfacial physics at the interface between active layer and cathode (with and without treatment of a polar CBL) by using ultraviolet photoelectron spectroscopy, capacitance-voltage measurement, and impedance spectroscopy. The experimental data demonstrate that CBL mainly takes effect in three ways: suppressing surface states at the surface of active layer, protecting the active layer from being damaged by thermally evaporated cathode, and changing the energy level alignment by forming dipole moments with active layer and/or cathode. Our findings here provide a comprehensive picture of interfacial physics in devices with and without CBL.

  12. Uncovering the role of cathode buffer layer in organic solar cells.

    PubMed

    Qi, Boyuan; Zhang, Zhi-Guo; Wang, Jizheng

    2015-01-01

    Organic solar cells (OSCs) as the third generation photovoltaic devices have drawn intense research, for their ability to be easily deposited by low-cost solution coating technologies. However the cathode in conventional OSCs, Ca, can be only deposited by thermal evaporation and is highly unstable in ambient. Therefore various solution processible cathode buffer layers (CBLs) are synthesized as substitute of Ca and show excellent effect in optimizing performance of OSCs. Yet, there is still no universal consensus on the mechanism that how CBL works, which is evidently a critical scientific issue that should be addressed. In this article detailed studies are targeted on the interfacial physics at the interface between active layer and cathode (with and without treatment of a polar CBL) by using ultraviolet photoelectron spectroscopy, capacitance-voltage measurement, and impedance spectroscopy. The experimental data demonstrate that CBL mainly takes effect in three ways: suppressing surface states at the surface of active layer, protecting the active layer from being damaged by thermally evaporated cathode, and changing the energy level alignment by forming dipole moments with active layer and/or cathode. Our findings here provide a comprehensive picture of interfacial physics in devices with and without CBL. PMID:25588623

  13. Geochemical drivers of organic matter decomposition in the active layer of Arctic tundra

    NASA Astrophysics Data System (ADS)

    Herndon, E.; Roy Chowdhury, T.; Mann, B.; Graham, D. E.; Wullschleger, S. D.; Gu, B.; Liang, L.

    2014-12-01

    Arctic tundra soils store large quantities of organic carbon that are susceptible to decomposition and release to the atmosphere as CO2 and CH4. Decomposition rates are limited by cold temperatures and widespread anoxia; however, ongoing changes in soil temperature, thaw depth, and water saturation are expected to influence rates and pathways of organic matter decomposition. In order to predict greenhouse gas releases from high-latitude ecosystems, it is necessary to identify how geochemical factors (e.g. terminal electron acceptors, carbon substrates) influence CO2 and CH4 production in tundra soils. This study evaluates spatial patterns of aqueous geochemistry in the active layer of low- to high-centered polygons located at the Barrow Environmental Observatory in northern Alaska. Pore waters from saturated soils were low in sulfate and nitrate but contained abundant Fe which may serve a major terminal electron acceptor for anaerobic microbial metabolism. Relatively high concentrations of soluble Fe accumulated in the middle of the active layer near the boundary between the organic and mineral horizon, and we infer that Fe-oxide reduction and dissolution in the mineral horizon produced soluble Fe that diffused upwards and was stabilized by complexation with dissolved organic matter. Fe concentrations in the bulk soil were higher in organic than mineral horizons due to the presence of these organic-Fe complexes and Fe-oxide precipitates. Dissolved CH4 increased with increasing proportions of dissolved Fe(III) in saturated soils from transitional and low-centered polygons. The opposite trend was observed in drier soils from flat- and high-centered polygons where deeper oxidation fronts may inhibit methanogenesis. Using multiple spectroscopic and molecular methods (e.g. UV-Vis, Fourier transform infrared, ultrahigh resolution mass spectrometry), we also observed that pore waters from the middle of the active layer contained more aromatic organics than in mineral

  14. Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Jitsui, Yusuke; Ohtani, Naoki

    2012-10-01

    We performed transmission electron microscope (TEM) observation of organic-inorganic hybrid thin films fabricated by the sol-gel reaction and used as the active layers of organic light-emitting diodes. The cross-sectional TEM images show that the films consist of a triple-layer structure. To evaluate the composition of these layers, the distribution of atoms in them was measured by energy-dispersive X-ray fluorescence spectroscopy. As a result, most of the organic emissive material, poly(9,9-dioctyl-fluorene-co- N-4-butylphenyl-diphenylamine (TFB), was found to be distributed in the middle layer sandwiched by SiO and SiO2 layers. The surface SiO layer was fabricated due to the lack of oxygen. This means that the best sol-gel condition was changed due to the TFB doping; thus, the novel best condition should be found.

  15. Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodes.

    PubMed

    Jitsui, Yusuke; Ohtani, Naoki

    2012-01-01

    We performed transmission electron microscope (TEM) observation of organic-inorganic hybrid thin films fabricated by the sol-gel reaction and used as the active layers of organic light-emitting diodes. The cross-sectional TEM images show that the films consist of a triple-layer structure. To evaluate the composition of these layers, the distribution of atoms in them was measured by energy-dispersive X-ray fluorescence spectroscopy. As a result, most of the organic emissive material, poly(9,9-dioctyl-fluorene-co-N-4-butylphenyl-diphenylamine (TFB), was found to be distributed in the middle layer sandwiched by SiO and SiO2 layers. The surface SiO layer was fabricated due to the lack of oxygen. This means that the best sol-gel condition was changed due to the TFB doping; thus, the novel best condition should be found. PMID:23095451

  16. Engineered Molecular Layers For Organic Electronic Applications: A Confocal Scanning Raman Spectroscopy (CSRS) Investigation

    SciTech Connect

    Paez-Sierra, Beynor-Antonio; Kolotovska, Viktoriia; Rangel-Kuoppa, Victor-Tapio

    2011-12-23

    We present CSRS maps of magnetically modified vanadyl phthalocyanine (VOPc) thin films forming conduction channels in organic field-effect transistors (OFETs). The VOPc films with a nominal thickness of about 100 nm were produced by organic molecular beam deposition in high vacuum. During the growth conditions the substrates were exposed to a magnetic field (B) from a bar magnet. The CSRS maps revealed significant changes of the organic fields upon preparation conditions. The highest field effect mobility, electrical current and anisotropy of the CSRS-topography is achieved in layers grown with B parallel to the substrate plane, while intermediate and lowest values are achieved in devices grown with B perpendicular to the substrate and without, respectively.

  17. Structure, Optical Absorption, and Performance of Organic Solar Cells Improved by Gold Nanoparticles in Buffer Layers.

    PubMed

    Yang, Yingguo; Feng, Shanglei; Li, Meng; Wu, Zhongwei; Fang, Xiao; Wang, Fei; Geng, Dongping; Yang, Tieying; Li, Xiaolong; Sun, Baoquan; Gao, Xingyu

    2015-11-11

    11-Mercaptoundecanoic acid (MUA)-stabilized gold nanoparticles (AuNPs) embedded in copper phthalocyanine (CuPc) were used as a buffer layer between a poly(3-hexyl-thiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction and anodic indium-tin oxide (ITO) substrate. As systematic synchrotron-based grazing incidence X-ray diffraction (GIXRD) experiments demonstrated that the AuNPs present in the buffer layer can improve the microstructure of the active layer with a better lamella packing of P3HT from the surface to the interior, UV-visible absorption spectrum measurements revealed enhanced optical absorption due to the localized surface plasma resonance (LSPR) generated by the AuNPs. The device of ITO/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/CuPc:MUA-stabilized AuNPs/P3HT:PCBM/LiF/Al was found with over 24% enhancement of power conversion efficiency (PCE) in comparison with reference devices without AuNPs. This remarkable improvement in PCE should be partially attributed to LSPR generated by the AuNPs and partially to improved crystallization as well as preferred orientation order of P3HT due to the presence of the AuNPs, which would promote more applications of metal NPs in the organic photovoltaic devices and other organic multilayer devices. PMID:26477556

  18. Density of states determination in organic donor-acceptor blend layers enabled by molecular doping

    NASA Astrophysics Data System (ADS)

    Fischer, Janine; Ray, Debdutta; Kleemann, Hans; Pahner, Paul; Schwarze, Martin; Koerner, Christian; Vandewal, Koen; Leo, Karl

    2015-06-01

    Charge carrier transport is a key parameter determining the efficiency of organic solar cells, and is closely related to the density of free and trapped states. For trap characterization, impedance spectroscopy is a suitable, non-invasive method, applicable to complete organic semiconductor devices. In order to contribute to the capacitive signal, the traps must be filled with charge carriers. Typically, trap filling is achieved by illuminating the device or by injecting charge carriers through application of a forward bias voltage. However, in both cases, the exact number of charge carriers in the device is not known and depends strongly on the measurement conditions. Here, hole trap states of the model blend layer ZnPc:C60 are filled by weak p-doping, enabling trap characterization in a blend layer at a controlled hole density. We evaluate impedance spectra at different temperatures in order to determine the density of occupied states (DOOS) directly from the capacitance-frequency spectra by assuming a simple energy diagram. The reconstructed DOOS distribution is analyzed at different doping concentrations and device thicknesses and compared to thermally stimulated current measurements performed on the same devices. In both methods, a pronounced Gaussian peak at about 0.4 eV below the transport level is found as well as deep, exponential tail states, providing a deeper insight into the density of states distribution of this donor-acceptor blend layer. Additionally, the effect of doping-induced trap filling on the solar cell characteristics is studied in these devices.

  19. Performance of organic photovoltaics using an ytterbium trifluoride n-type buffer layer

    NASA Astrophysics Data System (ADS)

    Ji, Chan Hyuk; Jang, Ji Min; Oh, Se Young

    2016-03-01

    Ytterbium trifluoride (YbF3) was used as an n-type cathode buffer layer in conventional poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PC60BM) bulk heterojunction (BHJ) organic photovoltaic cells. This buffer layer acts as an electron-transport layer and improves the open circuit voltage ( V oc), power conversion efficiency (PCE), and interfacial durability of the device. The physical properties and performance of the device were studied using impedance spectroscopy, photocurrent measurements, ultraviolet photoelectron spectroscopy, and atomic force microscopy. The PCE reached to 3.2% with a 65% fill factor under 1 sun irradiation. The PCE decreased to half of its original value after 120 h at room temperature in air or 24 h at 70°C in air. Comparison with Yb and TiOx cathode buffer layers reveals that YbF3 has superior performance and longevity. These findings suggest that YbF3 has the potential to replace costly device encapsulation. [Figure not available: see fulltext.

  20. Nickel Oxide as an Inorganic Hole Transport Layer in Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Bailey, Brian; Widjonarko, N. Edwin; Berry, Joseph J.; Shaheen, Sean E.; Ginley, David S.; Olson, Dana C.

    2009-10-01

    This work explores the use of nickel oxide as a hole transport layer in organic photovoltaics (OPV). The purpose of the hole transport layer (HTL) is to provide an energetic barrier to electrons at the anode of the OPV device, while facilitating extraction of holes. At present, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) is commonly used in this layer of the device, but it suffers from inherent problems in phase separation of the PEDOT and PSS components leading to non-uniform conductivity, incompatibility with various transparent conducting oxides due to its acidity, and high rate of water uptake that can accelerate degradation of interfaces and surrounding layers. Inorganic metal oxides such as nickel oxide present a potential solution to these problems. Using pulsed laser deposition (PLD) to deposit nickel oxide films, we show OPV device performance to be tunable by varying deposition parameters. Parameters explored include oxygen partial pressure during PLD, substrate temperature, film thickness, and post PLD surface treatments. These tune physical properties of the film such as work function and conductivity, which were measured directly, and in device performance.

  1. Tri-Metal Layered Semitransparent Electrode for Red Phosphorescent Organic Light-Emitting Diodes.

    PubMed

    Lee, Jae Woo; Lee, Ho Won; Lee, Song Eun; Yang, Hyung Jin; Lee, Sung Kyu; Hwang, Kyo Min; Park, Soo Na; Yoon, Seung Soo; Kim, Young Kwan

    2015-10-01

    In this paper, we fabricated tri-metal layered thin film semitransparent electrodes consisting of a thin conductive metal layer, sandwiched between two nickel layers. An equal red phosphorescent organic light-emitting diode (PHOLED) structure was deposited on the anodes of indium tin oxide (ITO) and three types of tri-metal layers (Ni/Al/Ni, Ni/Cu/Ni, and Ni/Ag/Ni, thickness of 3/7/3 nm in common) on a glass substrate. The optical and electrical performances of the device using Ni/Ag/Ni were improved more than the performances of the other devices due to the micro-cavity effect in accordance with the various electrode characteristics. Moreover, we fabricated the same red PHOLED structures on a flexible substrate, as a consequence, showed competitive emission characteristics compared to the devices fabricated on a glass substrate. Therefore, this study could succeed to additional research on flexible display panel and light-emitting devices with ITO-free electrodes. PMID:26726477

  2. All-solution-processed inverted organic solar cell with a stacked hole-transporting layer

    NASA Astrophysics Data System (ADS)

    Lin, Wen-Kai; Su, Shui-Hsiang; Liu, Che-Chun; Yokoyama, Meiso

    2014-11-01

    In this study, inverted organic solar cells (IOSCs) have been fabricated and characterized. A sol-gel zinc oxide (ZnO) film is used as a hole-blocking layer (HBL). Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and copper phthalocyanine (CuPc) are used as a hole-transporting layer (HTL). The HBL, active layer, and HTL films are fabricated by spin-coating technique. The anode is fabricated from Ag nanoparticles by drop titration using a Pasteur burette. Experimental results show that the PEDOT:PSS/CuPc stacked HTL provides a stepwise hole-transporting energy diagram configuration, which subsequently increases the charge carrier transporting capability and extracts holes from the active layer to the anode. The characteristics of the IOSCs were optimized and exhibited an open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of 0.53 V, 6.13 mA/cm2, 37.53%, and 1.24%, respectively, under simulated AM1.5G illumination of 100 mW/cm2. Hence, a solution process is feasible for fabricating low-cost and large-area solar energy devices.

  3. Attractive mechanical properties of a lightweight highly sensitive bi layer thermistor: polycarbonate/organic molecular conductor

    NASA Astrophysics Data System (ADS)

    Laukhina, E.; Lebedev, V.; Rovira, C.; Laukhin, V.; Veciana, J.

    2016-03-01

    The paper covers some of the basic mechanical characteristics of a recently developed bi layer thermistor: polycarbonate/(001) oriented layer of organic molecular conductor α’-(BEDT-TTF)2IxBr3-x, were BEDT-TTF=bis(ethylenedithio)tetrathiafulvalen. The nano and macro mechanical properties have been studied in order to use this flexible, low cost thermistor in sensing applications by proper way. The nano-mechanical properties of the temperature sensitive semiconducting layer of α’-(BEDT-TTF)2IxBr3-x were tested using nanoindentation method. The value of Young's modulus in direction being perpendicular to the layer plan was found as 9.0 ±1.4 GPa. The macro mechanical properties of the thermistor were studied using a 5848 MicroTester. The tensile tests showed that basic mechanical characteristics of the thermistor are close to those of polycarbonate films. This indicates a good mechanical strength of the developed sensor. Therefore, the thermistor can be used in technologies that need to be instrumented with highly robustness lightweight low cost temperature sensors. The paper also reports synthetic details on fabricating temperature sensing e-textile. As the temperature control is becoming more and more important in biomedical technologies like healthcare monitoring, this work strongly contributes on the ongoing research on engineering sensitive conducting materials for biomedical applications.

  4. Automatic inspection of a residual resist layer by means of self-organizing map

    NASA Astrophysics Data System (ADS)

    Philippe, Zaki Sabit Fawzi; Robert, Stéphane; Bayard, Bernard

    2016-05-01

    Photolithography allows large-scale fabrication of nanocomponents in the semiconductor industry. This technique consists of manufacturing a desired pattern on a photoresist film transferred onto the substrate during the etching process. Therefore, the mask quality is essential for reliable etching. For example, the presence of a residual layer of resist might be considered as a mask defect and can lead to the failure of the etching process. We propose the use of a Kohonen self-organizing map for automatic detection of a residual layer from an ellipsometric signature. The feasibility of the suggested inspection by the use of a classification technique is discussed and simulations are carried out on a 750-nm period grating.

  5. Characteristics of blue organic light emitting diodes with different thick emitting layers

    NASA Astrophysics Data System (ADS)

    Li, Chong; Tsuboi, Taiju; Huang, Wei

    2014-08-01

    We fabricated blue organic light emitting diodes (called blue OLEDs) with emitting layer (EML) of diphenylanthracene derivative 9,10-di(2-naphthyl)anthracene (ADN) doped with blue-emitting DSA-ph (1-4-di-[4-(N,N-di-phenyl)amino]styryl-benzene) to investigate how the thickness of EML and hole injection layer (HIL) influences the electroluminescence characteristics. The driving voltage was observed to increase with increasing EML thickness from 15 nm to 70 nm. The maximum external quantum efficiency of 6.2% and the maximum current efficiency of 14 cd/A were obtained from the OLED with 35 nm thick EML and 75 nm thick HIL. High luminance of 120,000 cd/m2 was obtained at 7.5 V from OLED with 15 nm thick EML.

  6. Lifetime enhanced phosphorescent organic light emitting diode using an electron scavenger layer

    NASA Astrophysics Data System (ADS)

    Hong, Seokhwan; Kim, Ji Whan; Lee, Sangyeob

    2015-07-01

    We demonstrate a method to improve lifetime of a phosphorescent organic light emitting diode (OLED) using an electron scavenger layer (ESL) in a hole transporting layer (HTL) of the device. We use a bis(1-(phenyl)isoquinoline)iridium(III)acetylacetonate [Ir(piq)2(acac)] doped HTL to stimulate radiative decay, preventing thermal degradation in HTL. The ESL effectively prevented non-radiative decay of leakage electron in HTL by converting non-radiative decay to radiative decay via a phosphorescent red emitter, Ir(piq)2(acac). The lifetime of device (t95: time after 5% decrease of luminance) has been increased from 75 h to 120 h by using the ESL in a phosphorescent green-emitting OLED.

  7. Influence of inserting a thin fullerene layer on pentacene organic thin-film transistor

    NASA Astrophysics Data System (ADS)

    Li, Yu-Chang; Lin, Yu-Ju; Wei, Chia-Yu; Chou, Dei-Wei; Tsao, Chun-Ho; Wang, Yeong-Her

    2012-03-01

    The performance of organic thin-film transistors (TFTs) with a pentacene/fullerene(C60)/pentacene (PCP) sandwich structure is presented. Using a 3.5 nm-thick C60 layer inserted between the pentacene films, the obtained hole mobility is improved by more than six times. By applying atomic force microscopy, x-ray diffraction, Raman spectrum, and transmission line method analysis, one can reasonably infer that the smoother surface of the pentacene film covered with thin C60 layer delays the phase transformation of the upper pentacene film, resulting in stronger intermolecular coupling and the reduction of channel resistance of the PCP TFTs from 3.03 to 1.72 MΩ, and, therefore, improving the device performance.

  8. Simulation of mixed-host emitting layer based organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Yap, S. S.; Tou, T. Y.

    2015-04-01

    `SimOLED' simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq3) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq3 of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  9. Lifetime enhanced phosphorescent organic light emitting diode using an electron scavenger layer

    SciTech Connect

    Hong, Seokhwan; Kim, Ji Whan; Lee, Sangyeob

    2015-07-27

    We demonstrate a method to improve lifetime of a phosphorescent organic light emitting diode (OLED) using an electron scavenger layer (ESL) in a hole transporting layer (HTL) of the device. We use a bis(1-(phenyl)isoquinoline)iridium(III)acetylacetonate [Ir(piq){sub 2}(acac)] doped HTL to stimulate radiative decay, preventing thermal degradation in HTL. The ESL effectively prevented non-radiative decay of leakage electron in HTL by converting non-radiative decay to radiative decay via a phosphorescent red emitter, Ir(piq){sub 2}(acac). The lifetime of device (t{sub 95}: time after 5% decrease of luminance) has been increased from 75 h to 120 h by using the ESL in a phosphorescent green-emitting OLED.

  10. Alternating Current Driven Organic Light Emitting Diodes Using Lithium Fluoride Insulating Layers

    PubMed Central

    Liu, Shang-Yi; Chang, Jung-Hung; -Wen Wu, I.; Wu, Chih-I

    2014-01-01

    We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m2 obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage. PMID:25523436

  11. Improved oxidation resistance of organic/inorganic composite atomic layer deposition coated cellulose nanocrystal aerogels

    SciTech Connect

    Smith, Sean W.; Matthews, David J.; Conley, John F.; Buesch, Christian; Simonsen, John

    2014-07-01

    Cellulose nanocrystal (CNC) aerogels are coated with thin conformal layers of Al{sub 2}O{sub 3} using atomic layer deposition to form hybrid organic/inorganic nanocomposites. Electron probe microanalysis and scanning electron microscopy analysis indicated the Al{sub 2}O{sub 3} penetrated more than 1500 μm into the aerogel for extended precursor pulse and exposure/purge times. The measured profile of coated fiber radius versus depth from the aerogel surface agrees well with simulations of precursor penetration depth in modeled aerogel structures. Thermogravimetric analysis shows that Al{sub 2}O{sub 3} coated CNC aerogel nanocomposites do not show significant thermal degradation below 295 °C as compared with 175 °C for uncoated CNC aerogels, an improvement of over 100 °C.

  12. High efficiency yellow organic light-emitting diodes with optimized barrier layers

    NASA Astrophysics Data System (ADS)

    Mu, Ye; Zhang, Shiming; Yue, Shouzhen; Wu, Qingyang; Zhao, Yi

    2015-12-01

    High efficiency Iridium (III) bis (4-phenylthieno [3,2-c] pyridinato-N,C2‧) acetylacetonate (PO-01) based yellow organic light-emitting devices are fabricated by employing multiple emission layers. The efficiency of the device using 4,4‧,4″-tris(N-carbazolyl) triphenylamine (TCTA) as potential barrier layer (PBL) outperforms those devices based on other PBLs and detailed analysis is carried out to reveal the mechanisms. A forward-viewing current efficiency (CE) of 65.21 cd/A, which corresponds to a maximum total CE of 110.85 cd/A is achieved at 335.8 cd/m2 in the optimized device without any outcoupling enhancement structures.

  13. The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

    NASA Astrophysics Data System (ADS)

    Jafarov, Elchin; Schaefer, Kevin

    2016-03-01

    Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. Initializing the frozen permafrost carbon with the observed soil carbon distribution from the Northern Circumpolar Soil Carbon Database reduces the uncertainty associated with the modeling of the permafrost carbon feedback. To improve permafrost thermal and carbon dynamics we implemented a dynamic surface organic layer with vertical carbon redistribution, and introduced dynamic root growth controlled by active layer thickness, which improved soil carbon exchange between frozen and thawed pools. These changes increased the initial amount of simulated frozen carbon from 313 to 560 Gt C, consistent with observed frozen carbon stocks, and increased the spatial correlation of the simulated and observed distribution of frozen carbon from 0.12 to 0.63.

  14. Absorption and quasiguided mode analysis of organic solar cells with photonic crystal photoactive layers.

    PubMed

    Tumbleston, John R; Ko, Doo-Hyun; Samulski, Edward T; Lopez, Rene

    2009-04-27

    We analyze optical absorption enhancements and quasiguided mode properties of organic solar cells with highly ordered nanostructured photoactive layers comprised of the bulk heterojunction blend, poly-3-hexylthiophene/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and a low index of refraction conducting material (LICM). This photonic crystal geometry is capable of enhancing spectral absorption by approximately 17% in part due to the excitation of quasiguided modes near the band edge of P3HT:PCBM. A nanostructure thickness between 200 nm and 300 nm is determined to be optimal, while the LICM must have an index of refraction approximately 0.3 lower than P3HT:PCBM to produce absorption enhancements. Quasiguided modes that differ in lifetime by an order of magnitude are also identified and yield absorption that is concentrated in the P3HT:PCBM flash layer. PMID:19399146

  15. Improving the efficiency of organic solar cells by varying the material concentration in the photoactive layer

    NASA Astrophysics Data System (ADS)

    Latimer, Kevin Anthony

    increased overall device efficiency. A photoactive layer solution prepared with 30 mg P3HT and 24 mg PC61BM, when implemented in an organic solar cell, produced the optimal electrical, physical, and optical characteristics.

  16. Plasmonically sensitized metal-oxide electron extraction layers for organic solar cells

    PubMed Central

    Trost, S.; Becker, T.; Zilberberg, K.; Behrendt, A.; Polywka, A.; Heiderhoff, R.; Görrn, P.; Riedl, T.

    2015-01-01

    ZnO and TiOx are commonly used as electron extraction layers (EELs) in organic solar cells (OSCs). A general phenomenon of OSCs incorporating these metal-oxides is the requirement to illuminate the devices with UV light in order to improve device characteristics. This may cause severe problems if UV to VIS down-conversion is applied or if the UV spectral range (λ < 400 nm) is blocked to achieve an improved device lifetime. In this work, silver nanoparticles (AgNP) are used to plasmonically sensitize metal-oxide based EELs in the vicinity (1–20 nm) of the metal-oxide/organic interface. We evidence that plasmonically sensitized metal-oxide layers facilitate electron extraction and afford well-behaved highly efficient OSCs, even without the typical requirement of UV exposure. It is shown that in the plasmonically sensitized metal-oxides the illumination with visible light lowers the WF due to desorption of previously ionosorbed oxygen, in analogy to the process found in neat metal oxides upon UV exposure, only. As underlying mechanism the transfer of hot holes from the metal to the oxide upon illumination with hν < Eg is verified. The general applicability of this concept to most common metal-oxides (e.g. TiOx and ZnO) in combination with different photoactive organic materials is demonstrated. PMID:25592174

  17. Reversible and selective solvent adsorption in layered metal-organic frameworks by coordination control.

    PubMed

    Yin, Xinbo; Chen, Haohong; Song, Yuna; Wang, Yang; Li, Qiaowei; Zhang, Lijuan

    2014-01-01

    With various functionalities in the framework and high thermal stability, metal-organic frameworks (MOFs) have been extensively studied for the applications in adsorption and separation. In last decade, synthesizing new MOFs with desired structures and improved chemical stability to meet these applications has drawn great attention. In this report, by using an organic ligand with azolate moiety, benzo-bis(imidazole) (H2BBI), we synthesized two new 2D layered MOF structures with distinct topologies. Framework 1 {[Zn2Cl2(BBI)(MSM)2]n, MSM=methylsulfonylmethane}, constructed from tetrahedral Zn(II) and BBI, maintains its structure in organic solvents, such as methanol and benzene, and even in water. Meanwhile, framework 2 {[Cd2Cl2(BBI)(DMSO)2]n, DMSO=dimethyl sulfoxide} differs from framework 1, and is assembled from trigonal bipyramidal Cd(II) and square planar BBI. By removing the DMSO molecules coordinated to Cd(II) (25 weight% of the structure), 2 could transform to 3 {[Cd2Cl2(BBI)]n}, which was further characterized by high-resolution powder X-ray diffraction. The solvent-free 3 retains the original connectivity within each layer, and is capable of reversible and selective adsorption of DMSO molecules. The bistable four- and five-coordinated geometry exchange of Cd(II) is the origin of this adsorption with improved selectivity and capacity. PMID:24183447

  18. Synthesis of carbon nano-structures using organic-molecule intercalated taeniolite layered silicates

    NASA Astrophysics Data System (ADS)

    Maezumi, Takaaki; Wada, Noboru

    2015-03-01

    By calcinating organic-molecule intercalated taeniolite layered silicates, carbon nano-structures were made between the 2:1 layered silicate sheets. Raman scattering, XRD, TGA and SEM were used to characterize the samples. Large taeniolite crystals (NaLiMg2Si4O10F) were first prepared by melting appropriate chemicals at high temperatures using a platinum crucible. Then, the taeniolite crystals made were cation-exchanged with Li+, K+, NH4+,Ca2+ + and Mg2+ in salt solution. Finally, various organic molecules such as ethylene glycol, pyridine and so on were intercalated into the taeniolite crystals, and calcinated under a N2 atmosphere at about 1000K. The resulting crystals are usually gray or black. X-ray (00l) diffraction patterns suggested that the carbon structures may be monolayer thick (i.e., graphene-like). Raman scattering spectra which exhibited a sharp G-band peak with a high G-band/D-band ratio indicated that the carbon structures were relatively well crystallized. Cation and organic-molecule dependence on the carbon structures will be discussed. In addition, evidence for stage-2 taeniolite will be presented.

  19. Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

    NASA Astrophysics Data System (ADS)

    Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

    2015-09-01

    We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10-2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost.

  20. Design of Bicontinuous Donor/Acceptor Morphologies for Use as Organic Solar Cell Active Layers

    NASA Astrophysics Data System (ADS)

    Kipp, Dylan; Mok, Jorge; Verduzco, Rafael; Ganesan, Venkat

    Two of the primary challenges limiting the marketability of organic solar cells are i) the smaller device efficiency of the organic solar cell relative to the conventional silicon-based solar cell and ii) the long term thermal instability of the device active layer. The achievement of equilibrium donor/acceptor morphologies with the characteristics believed to yield high device performance characteristics could address each of these two challenges. In this work, we present the results of a combined simulations and experiments-based approach to investigate if a conjugated BCP additive can be used to control the self-assembled morphologies taken on by conjugated polymer/PCBM mixtures. First, we use single chain in mean field Monte Carlo simulations to identify regions within the conjugated polymer/PCBM composition space in which addition of copolymers can lead to bicontinuous equilibrium morphologies with high interfacial areas and nanoscale dimensions. Second, we conduct experiments as directed by the simulations to achieve such morphologies in the PTB7 + PTB7- b-PNDI + PCBM model blend. We characterize the results of our experiments via a combination of transmission electron microscopy and X-ray scattering techniques and demonstrate that the morphologies from experiments agree with those predicted in simulations. Accordingly, these results indicate that the approach utilized represents a promising approach to intelligently design the morphologies taken on by organic solar cell active layers.

  1. Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

    PubMed Central

    Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

    2015-01-01

    We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10–2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost. PMID:26416434

  2. A futuristic approach towards interface layer modifications for improved efficiency in inverted organic solar cells

    SciTech Connect

    Tiwari, J. P. E-mail: tiwarijp@mail.nplindia.org; Ali, Farman; Sharma, Abhishek; Chand, Suresh; Pillai, Sriraj; Parakh, Sonal

    2014-01-27

    Inverted polymer Solar Cells of the classical poly (3-hexylthiophene) (P3HT):(6,6)-phenyl-C{sub 61}butyric acid methyl ester (PC{sub 61}BM) blend on indium tin oxide substrates were fabricated, which shows improved device performance, by using a facile solution–processed ZnO-polyelectrolytes [poly (diallyldimethylammonium chloride) (PDADMAC), Poly (acrylic acid sodium salt) (PAS), poly (4-styrenesulfonic acid) (PSS), and Polyvinylpyrrolidone (PVP)] nanocomposite as a cathode interface layer compared to devices using pristine ZnO as cathode buffer layer in ambient conditions. The devices with different combinations of polyelectrolyte with ZnO show different improvements in the device efficiency. The combinations of ZnO with PVP and PDADMAC show highest amount of improvements in the efficiency by a factor of ∼17–19. The improvement of the efficiency may be due to various phenomena, such as the passivation of ZnO surface as well as bulk traps, work function modification, improved energy level alignment, improved electronic coupling of the inorganic/organic interface, improved light harvesting, and decrease of surface as well as bulk charge recombination in the device. The introduction of polyelectrolyte into ZnO inhibits the aggregation of ZnO nanoparticles yielding the large area ZnO nanoclusters; and hence, forming the uniform film of ZnO resulting in the modifications of morphology as well as electronic structure of ZnO-polyelectrolyte nano-composite favouring better electronic coupling between cathode and active layer and hence enhancing the current and, consequently, the efficiency. This simple low temperature ZnO-polyelectrolyte nanocomposite based protocol proposed for cathode interface layer modification may be very much useful for roll to roll industrial manufacturing of organic solar cells.

  3. White organic light-emitting diodes with ultra-thin mixed emitting layer

    NASA Astrophysics Data System (ADS)

    Jeon, T.; Forget, S.; Chenais, S.; Geffroy, B.; Tondelier, D.; Bonnassieux, Y.; Ishow, E.

    2012-02-01

    White light can be obtained from Organic Light Emitting Diodes by mixing three primary colors, (i.e. red, green and blue) or two complementary colors in the emissive layer. In order to improve the efficiency and stability of the devices, a host-guest system is generally used as an emitting layer. However, the color balance to obtain white light is difficult to control and optimize because the spectrum is very sensitive to doping concentration (especially when a small amount of material is used). We use here an ultra-thin mixed emitting layer (UML) deposited by thermal evaporation to fabricate white organic light emitting diodes (WOLEDs) without co-evaporation. The UML was inserted in the hole-transporting layer consisting of 4, 4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) instead of using a conventional doping process. The UML was formed from a single evaporation boat containing a mixture of two dipolar starbust triarylamine molecules (fvin and fcho) presenting very similar structures and thermal properties and emitting in complementary spectral regions (orange and blue respectively) and mixed according to their weight ratio. The composition of the UML specifically allows for fine tuning of the emission color despite its very thin thickness down to 1 nm. Competitive energy transfer processes from fcho and the host interface toward fvin are key parameters to control the relative intensity between red and blue emission. White light with very good CIE 1931 color coordinate (0.34, 0.34) was obtained by simply adjusting the UML film composition.

  4. A futuristic approach towards interface layer modifications for improved efficiency in inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Tiwari, J. P.; Pillai, Sriraj; Parakh, Sonal; Ali, Farman; Sharma, Abhishek; Chand, Suresh

    2014-01-01

    Inverted polymer Solar Cells of the classical poly (3-hexylthiophene) (P3HT):(6,6)-phenyl-C61butyric acid methyl ester (PC61BM) blend on indium tin oxide substrates were fabricated, which shows improved device performance, by using a facile solution-processed ZnO-polyelectrolytes [poly (diallyldimethylammonium chloride) (PDADMAC), Poly (acrylic acid sodium salt) (PAS), poly (4-styrenesulfonic acid) (PSS), and Polyvinylpyrrolidone (PVP)] nanocomposite as a cathode interface layer compared to devices using pristine ZnO as cathode buffer layer in ambient conditions. The devices with different combinations of polyelectrolyte with ZnO show different improvements in the device efficiency. The combinations of ZnO with PVP and PDADMAC show highest amount of improvements in the efficiency by a factor of ˜17-19. The improvement of the efficiency may be due to various phenomena, such as the passivation of ZnO surface as well as bulk traps, work function modification, improved energy level alignment, improved electronic coupling of the inorganic/organic interface, improved light harvesting, and decrease of surface as well as bulk charge recombination in the device. The introduction of polyelectrolyte into ZnO inhibits the aggregation of ZnO nanoparticles yielding the large area ZnO nanoclusters; and hence, forming the uniform film of ZnO resulting in the modifications of morphology as well as electronic structure of ZnO-polyelectrolyte nano-composite favouring better electronic coupling between cathode and active layer and hence enhancing the current and, consequently, the efficiency. This simple low temperature ZnO-polyelectrolyte nanocomposite based protocol proposed for cathode interface layer modification may be very much useful for roll to roll industrial manufacturing of organic solar cells.

  5. High Efficiency Organic/Silicon-Nanowire Hybrid Solar Cells: Significance of Strong Inversion Layer

    PubMed Central

    Yu, Xuegong; Shen, Xinlei; Mu, Xinhui; Zhang, Jie; Sun, Baoquan; Zeng, Lingsheng; Yang, Lifei; Wu, Yichao; He, Hang; Yang, Deren

    2015-01-01

    Organic/silicon nanowires (SiNWs) hybrid solar cells have recently been recognized as one of potentially low-cost candidates for photovoltaic application. Here, we have controllably prepared a series of uniform silicon nanowires (SiNWs) with various diameters on silicon substrate by metal-assisted chemical etching followed by thermal oxidization, and then fabricated the organic/SiNWs hybrid solar cells with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). It is found that the reflective index of SiNWs layer for sunlight depends on the filling ratio of SiNWs. Compared to the SiNWs with the lowest reflectivity (LR-SiNWs), the solar cell based on the SiNWs with low filling ratio (LF-SiNWs) has a higher open-circuit voltage and fill factor. The capacitance-voltage measurements have clarified that the built-in potential barrier at the LF-SiNWs/PEDOT:PSS interface is much larger than that at the LR-SiNWs/PEDOT one, which yields a strong inversion layer generating near the silicon surface. The formation of inversion layer can effectively suppress the carrier recombination, reducing the leakage current of solar cell, and meanwhile transfer the LF-SiNWs/PEDOT:PSS device into a p-n junction. As a result, a highest efficiency of 13.11% is achieved for the LF-SiNWs/PEDOT:PSS solar cell. These results pave a way to the fabrication of high efficiency organic/SiNWs hybrid solar cells. PMID:26610848

  6. Actomyosin dynamics drive local membrane component organization in an in vitro active composite layer.

    PubMed

    Köster, Darius Vasco; Husain, Kabir; Iljazi, Elda; Bhat, Abrar; Bieling, Peter; Mullins, R Dyche; Rao, Madan; Mayor, Satyajit

    2016-03-22

    The surface of a living cell provides a platform for receptor signaling, protein sorting, transport, and endocytosis, whose regulation requires the local control of membrane organization. Previous work has revealed a role for dynamic actomyosin in membrane protein and lipid organization, suggesting that the cell surface behaves as an active composite composed of a fluid bilayer and a thin film of active actomyosin. We reconstitute an analogous system in vitro that consists of a fluid lipid bilayer coupled via membrane-associated actin-binding proteins to dynamic actin filaments and myosin motors. Upon complete consumption of ATP, this system settles into distinct phases of actin organization, namely bundled filaments, linked apolar asters, and a lattice of polar asters. These depend on actin concentration, filament length, and actin/myosin ratio. During formation of the polar aster phase, advection of the self-organizing actomyosin network drives transient clustering of actin-associated membrane components. Regeneration of ATP supports a constitutively remodeling actomyosin state, which in turn drives active fluctuations of coupled membrane components, resembling those observed at the cell surface. In a multicomponent membrane bilayer, this remodeling actomyosin layer contributes to changes in the extent and dynamics of phase-segregating domains. These results show how local membrane composition can be driven by active processes arising from actomyosin, highlighting the fundamental basis of the active composite model of the cell surface, and indicate its relevance to the study of membrane organization. PMID:26929326

  7. Controlled current matching in small molecule organic tandem solar cells using doped spacer layers

    NASA Astrophysics Data System (ADS)

    Schueppel, Rico; Timmreck, Ronny; Allinger, Nikola; Mueller, Toni; Furno, Mauro; Uhrich, Christian; Leo, Karl; Riede, Moritz

    2010-02-01

    Current matching of the subcells is crucial to optimize the performance of tandem solar cells. Due to the thin film optics of organic solar cells, the position of the two subcells relative to the reflecting electrode becomes a very important issue. This is demonstrated for an indium tin oxide (ITO)/pin/pii/Al structure with thin intrinsic absorbing layers consisting of zinc-phthalocyanine and fullerene C60 and a metal-free lossless recombination contact between the subcells. By keeping the thickness of the absorbing layers constant and changing only the thickness of the inner p-doped transparent layer in 16 steps from 0to186nm, the distance of the ITO-sided subcell from the reflecting electrode (Al) is systematically varied. Thus, the p-doped layer works as an optical spacer between both subcells. The influence of its thickness on the thin film optics is shown in optical simulations and confirmed with current-voltage measurements. If both subcells are separated only by the recombination contact, they are positioned in the first interference maximum of the incident light and the currents of the individual subcells nearly matches. By increasing the spacer layer thickness, the ITO-sided subcell is moved to the first interference minimum, limiting the measured short circuit current density jsc of the tandem solar cell to about 1/2 of its initial value without spacer. At a spacer thickness of about 140nm, jsc recovers in the second interference maximum to nearly its original value. Within this series, an almost constant high fill factor of about 59% as well as a constant open circuit voltage of 1.06V is observed, showing that the Ohmic losses in the spacer are negligible. The power conversion efficiency of these devices reaches nearly 4% in the first and approximately 3.6% in the second interference maximum, respectively, in an outdoor test at 1sun. Furthermore, it is shown that for thicker absorber layers, an optimized current density cannot be reached in the first

  8. Layered zirconium phosphonate with inorganic–organic hybrid structure: Preparation and its assembly with DNA

    SciTech Connect

    Liu, Li-Min; Lu, Guo-Yuan; Jiang, Li-Ping; Zhu, Jun-Jie

    2014-07-01

    An aminoethoxy-functionalized zirconium phosphonate (Zr(O{sub 3}POCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}·3H{sub 2}O), abbreviated as ZrRP (R=OCH{sub 2}CH{sub 2}NH{sub 2}), with layered structure has been synthesized. This layered compound possesses the characteristic of inorganic–organic hybrid, due to the covalently linked aminoethoxy in the host layer. The anion exchanged property of this zirconium phosphonate is suitable for the direct intercalation of negatively charged DNA, which is different from these reported zirconium phosphates or zirconium phosphonates. As a precursor, this prepared zirconium phosphonate was utilized to fabricate a novel DNA/ZrRP binary hybrid via a delamination-reassembly procedure. The release behavior of DNA from the DNA/ZrRP composite was investigated at different medium pH, because the combination between zirconium phosphonate sheets and DNA was pH-dependent sensitively. Moreover, the helical conformation of DNA was almost retained after the intercalation and release process. These properties of the DNA/ZrRP composite suggested the potential application of layered zirconium phosphonate as a non-viral vector in gene delivery. - Graphical abstract: The intercalation of DNA into zirconium phosphonate and the release of DNA from the interlayer of zirconium phosphonate. - Highlights: ●A layered aminoethoxy-functionalized zirconium phosphonate has been synthesized. ●DNA was intercalated directly into the prepared zirconium phosphonate. ●A novel zirconium phosphonate/DNA binary hybrid was fabricated. ●DNA can be reversibly released from the interlayer of zirconium phosphonate. ●The intercalation/release processes do not induce the denaturalization of DNA.

  9. Temperature and layer thickness dependent in situ investigations on epindolidione organic thin-film transistors

    PubMed Central

    Lassnig, R.; Striedinger, B.; Jones, A.O.F.; Scherwitzl, B.; Fian, A.; Głowacl, E.D.; Stadlober, B.; Winkler, A.

    2016-01-01

    We report on in situ performance evaluations as a function of layer thickness and substrate temperature for bottom-gate, bottom-gold contact epindolidione organic thin-film transistors on various gate dielectrics. Experiments were carried out under ultra-high vacuum conditions, enabling quasi-simultaneous electrical and surface analysis. Auger electron spectroscopy and thermal desorption spectroscopy (TDS) were applied to characterize the quality of the substrate surface and the thermal stability of the organic films. Ex situ atomic force microscopy (AFM) was used to gain additional information on the layer formation and surface morphology of the hydrogen-bonded organic pigment. The examined gate dielectrics included SiO2, in its untreated and sputtered forms, as well as the spin-coated organic capping layers poly(vinyl-cinnamate) (PVCi) and poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE, from the class of polynorbornenes). TDS and AFM revealed Volmer-Weber island growth dominated film formation with no evidence of a subjacent wetting layer. This growth mode is responsible for the comparably high coverage required for transistor behavior at 90–95% of a monolayer composed of standing molecules. Surface sputtering and an increased sample temperature during epindolidione deposition augmented the surface diffusion of adsorbing molecules and therefore led to a lower number of better-ordered islands. Consequently, while the onset of charge transport was delayed, higher saturation mobility was obtained. The highest, bottom-contact configuration, mobilities of approximately 2.5 × 10−3cm2/Vs were found for high coverages (50 nm) on sputtered samples. The coverage dependence of the mobility showed very different characteristics for the different gate dielectrics, while the change of the threshold voltage with coverage was approximately the same for all systems. An apparent decrease of the mobility with increasing coverage on the

  10. Quasi-equilibrium hopping drift and field-stimulated diffusion in ultrathin layers of organic materials

    SciTech Connect

    Korolev, N. A.; Nikitenko, V. R. Ivanov, D. V.

    2011-02-15

    Hopping transport (drift and diffusion) of charge carriers is studied by numerical Monte Carlo simulation at the quasi-equilibrium initial energy distribution of charge carriers in ultrathin disordered organic semiconductor and insulator films (thinner than 100 molecular layers). The effect of variations in the film thickness, the degree of energy disorder, and the applied field strength on the drift mobility and diffusion coefficient is analyzed. It is found that, as the film thickness is increased, the mobility substantially decreases and follows the power law. The diffusion coefficient significantly differs from that obtained previously in the limit of large thicknesses. This result must be taken into consideration in the analysis of experimental data.

  11. Layered and segmented system organization (LASSO) for highly reliable inventory monitoring systems (IMS)

    SciTech Connect

    Mangan, Dennis L.; Matter, John C.; Waddoups, I.; Abhold, M. E.; Chiaro, P.

    2002-01-01

    The Trilateral Initiative is preparing for International Atomic Energy Agency (LUiA) verification of excess fissile material released itom the defense programs of the United States and the Russian Federation. Following acceptance of the material using an Attribute Verification System, the IAEA will depend on an Inventory Monitoring System to maintain Continuity of Knowledge of the large inventory of thousands of items. Recovery fiom a total loss of Continuity of Knowledge in such a large storage facility would involve an extremely costly inventory re-verification This paper presents the framework for a Layered and Segmented System Organization that is the basis for a highly reliable IMS with protection-in-depth.

  12. Surface plasmon enhanced organic solar cells with a MoO3 buffer layer.

    PubMed

    Su, Zisheng; Wang, Lidan; Li, Yantao; Zhang, Guang; Zhao, Haifeng; Yang, Haigui; Ma, Yuejia; Chu, Bei; Li, Wenlian

    2013-12-26

    High-efficiency surface plasmon enhanced 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane:C70 small molecular bulk heterojunction organic solar cells with a MoO3 anode buffer layer have been demonstrated. The optimized device based on thermal evaporated Ag nanoparticles (NPs) shows a power conversion efficiency of 5.42%, which is 17% higher than the reference device. The improvement is attributed to both the enhanced conductivity and increased absorption due to the near-field enhancement of the localized surface plasmon resonance of Ag NPs. PMID:24320799

  13. Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Ambade, Swapnil B.; Ambade, Rohan B.; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S.; Mane, Rajaram S.; Lee, Soo-Hyoung

    2016-02-01

    In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM

  14. High-efficiency fluorescent white organic light-emitting diodes using double hole-transporting-layers

    NASA Astrophysics Data System (ADS)

    Jou, Jwo-Huei; Shen, Shih-Ming; Chen, Cheng-Chung; Chung, Yu-Chiao; Wang, Chun-Jan; Hsu, Mao-Feng; Wang, Wei-Ben; Wu, Ming-Hsuan; Yang, Chih-Jie; Liu, Chi-Ping

    2008-04-01

    High-efficiency fluorescent white organic light-emitting diodes (OLED) were fabricated by using double holetransporting- layers (HTLs), poly(3,4-ethylene- dioxythiophene)-poly-(styrenesulfonate) (PEDOT) and N,N'-bis-(1- naphthyl)-N,N'-diphenyl-1,10-biphenyl-4-4'-diamine (NPB). The diodes were composed of a single emissive-layer (EML), with 0.5 wt% red 4-(dicyanomethylene)-2-tbutyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran doped in a mixed-host of 25% trans-1,2-bis(6-(N,N-di-p-tolylamino)-Naphthalene-2-yl)ethene and 75% 1-butyl-9,10-naphthaleneanthracene. The device structure comprised a 125 nm anode layer of indium tin oxide, a 25 nm first HTL of PEDOT, a 0 to 10 nm second HTL of NPB, a 30 nm EML, a 40 nm electron-transporting-layer of 2,2',2"-(1,3,5-benzenetriyl)-tris(1- phenyl-1-H-benzimidazole), a 1 nm electron-injection-layer of lithium fluoride and a 150 nm cathode layer of aluminum. With the addition of a 7.5 nm second HTL (NPB), the resultant power-efficiency at 100 cd/m2, for example, was increased from 11.9 to 18.9 lm/W, an improvement of 59%. The improvement was even more marked at 1,000 cd/m2, i.e. that the power-efficiency was increased from 9.1 to 16.5 lm/W, an improvement of 81%. The marked efficiency improvement may be attributed to a better balance of carrier-injection in the desired emissive zone since the addition of the NPB layer in between the first HTL and the EML may have effectively reduced the injection of excessive holes into the EML due to the relatively high energy-barrier to hole, which was 0.5 eV, at the interface of the two HTLs. The resultant hole-blocking function was plausibly more effective at higher voltage so that comparatively much less holes would be injected into the EML, leading to a much better balanced carrier-injection and consequently a higher efficiency-improvement at the higher brightness.

  15. Hybrid organic inorganic materials: Layered hydroxy double salts intercalated with substituted thiophene monomers

    NASA Astrophysics Data System (ADS)

    Tronto, Jairo; Leroux, Fabrice; Dubois, Marc; Taviot-Gueho, Christine; Valim, João Barros

    2006-05-01

    The present paper describes the synthesis and characterization of Layered Hydroxy Double Salts (HDSs) containing substituted thiophene anions (2-thiophenecarboxylate, 3-thiophenecarboxylate, and 3-thiopheneacetate). The HDSs host was synthesized via hydrothermal method and the organic anions were incorporated between the sheets by anion-exchange reaction. The materials were characterized by powder X-ray diffraction (PXRD), thermal gravimetric (TG) analysis and electron spin resonance (ESR) spectroscopy. For the 2D-hybrid materials, the basal spacing is found to be consistent with the formation of bilayers of the intercalated organic monomers. For the hybrid material formed after intercalation of 3-thiopheneacetate anion, the ESR signals suggest that the monomers connect each other directly forming small oligomers, whereas this process is not occurring for the two other monomers presenting short alkyl chain. The TG analyses show different stages of thermal decomposition between HDSs host and 2D-hybrid materials, underlining the enhanced thermal stability of the hybrid assembly.

  16. Graphene oxide hole transport layers for large area, high efficiency organic solar cells

    SciTech Connect

    Smith, Chris T. G.; Rhodes, Rhys W.; Beliatis, Michail J.; Imalka Jayawardena, K. D. G.; Rozanski, Lynn J.; Mills, Christopher A.; Silva, S. Ravi P.

    2014-08-18

    Graphene oxide (GO) is becoming increasingly popular for organic electronic applications. We present large active area (0.64 cm{sup 2}), solution processable, poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1, 3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:[6,6]-Phenyl C{sub 71} butyric acid methyl ester (PCDTBT:PC{sub 70}BM) organic photovoltaic (OPV) solar cells, incorporating GO hole transport layers (HTL). The power conversion efficiency (PCE) of ∼5% is the highest reported for OPV using this architecture. A comparative study of solution-processable devices has been undertaken to benchmark GO OPV performance with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) HTL devices, confirming the viability of GO devices, with comparable PCEs, suitable as high chemical and thermal stability replacements for PEDOT:PSS in OPV.

  17. Airborne trace organic contaminant removal using thermally regenerable multi-media layered sorbents

    NASA Technical Reports Server (NTRS)

    Atwater, James E.; Holtsnider, John T.

    1991-01-01

    A cyclic two-step process is described which forms the basis for a simple and highly efficient air purification technology. Low molecular weight organic vapors are removed from contaminated airstreams by passage through an optimized sequence of sorbent media layers. The contaminant loaded sorbents are subsequently regenerated by thermal desorption into a low volume inert gas environment. A mixture of airborne organic contaminants consisting of acetone, 2-butanone, ethyl acetate, Freon-113 and methyl chloroform has been quantitatively removed from breathing quality air using this technique. The airborne concentrations of all contaminants have been reduced from initial Spacecraft Maximum Allowable Concentration (SMAC) levels to below the analytical limits of detection. No change in sorption efficiency was observed through multiple cycles of contaminant loading and sorbent regeneration via thermal desorption.

  18. Using white noise to gate organic transistors for dynamic monitoring of cultured cell layers

    PubMed Central

    Rivnay, Jonathan; Leleux, Pierre; Hama, Adel; Ramuz, Marc; Huerta, Miriam; Malliaras, George G.; Owens, Roisin M.

    2015-01-01

    Impedance sensing of biological systems allows for monitoring of cell and tissue properties, including cell-substrate attachment, layer confluence, and the “tightness” of an epithelial tissue. These properties are critical for electrical detection of tissue health and viability in applications such as toxicological screening. Organic transistors based on conducting polymers offer a promising route to efficiently transduce ionic currents to attain high quality impedance spectra, but collection of complete impedance spectra can be time consuming (minutes). By applying uniform white noise at the gate of an organic electrochemical transistor (OECT), and measuring the resulting current noise, we are able to dynamically monitor the impedance and thus integrity of cultured epithelial monolayers. We show that noise sourcing can be used to track rapid monolayer disruption due to compounds which interfere with dynamic polymerization events crucial for maintaining cytoskeletal integrity, and to resolve sub-second alterations to the monolayer integrity. PMID:26112429

  19. Self-Supporting Metal-Organic Layers as Single-Site Solid Catalysts.

    PubMed

    Cao, Lingyun; Lin, Zekai; Peng, Fei; Wang, Weiwei; Huang, Ruiyun; Wang, Cheng; Yan, Jiawei; Liang, Jie; Zhang, Zhiming; Zhang, Teng; Long, Lasheng; Sun, Junliang; Lin, Wenbin

    2016-04-11

    Metal-organic layers (MOLs) represent an emerging class of tunable and functionalizable two-dimensional materials. In this work, the scalable solvothermal synthesis of self-supporting MOLs composed of [Hf6 O4 (OH)4 (HCO2 )6 ] secondary building units (SBUs) and benzene-1,3,5-tribenzoate (BTB) bridging ligands is reported. The MOL structures were directly imaged by TEM and AFM, and doped with 4'-(4-benzoate)-(2,2',2''-terpyridine)-5,5''-dicarboxylate (TPY) before being coordinated with iron centers to afford highly active and reusable single-site solid catalysts for the hydrosilylation of terminal olefins. MOL-based heterogeneous catalysts are free from the diffusional constraints placed on all known porous solid catalysts, including metal-organic frameworks. This work uncovers an entirely new strategy for designing single-site solid catalysts and opens the door to a new class of two-dimensional coordination materials with molecular functionalities. PMID:26954885

  20. Using white noise to gate organic transistors for dynamic monitoring of cultured cell layers

    NASA Astrophysics Data System (ADS)

    Rivnay, Jonathan; Leleux, Pierre; Hama, Adel; Ramuz, Marc; Huerta, Miriam; Malliaras, George G.; Owens, Roisin M.

    2015-06-01

    Impedance sensing of biological systems allows for monitoring of cell and tissue properties, including cell-substrate attachment, layer confluence, and the “tightness” of an epithelial tissue. These properties are critical for electrical detection of tissue health and viability in applications such as toxicological screening. Organic transistors based on conducting polymers offer a promising route to efficiently transduce ionic currents to attain high quality impedance spectra, but collection of complete impedance spectra can be time consuming (minutes). By applying uniform white noise at the gate of an organic electrochemical transistor (OECT), and measuring the resulting current noise, we are able to dynamically monitor the impedance and thus integrity of cultured epithelial monolayers. We show that noise sourcing can be used to track rapid monolayer disruption due to compounds which interfere with dynamic polymerization events crucial for maintaining cytoskeletal integrity, and to resolve sub-second alterations to the monolayer integrity.

  1. Large Magnetoresistance at High Bias Voltage in Double-layer Organic Spin Valves

    NASA Astrophysics Data System (ADS)

    Subedi, R. C.; Liang, S. H.; Geng, R.; Zhang, Q. T.; Lou, L.; Wang, J.; Han, X. F.; Nguyen, T. D.

    We report studies of magnetoresistance (MR) in double-layer organic spin valves (DOSV) using tris (8-hydroxyquinolinato) aluminum (Alq3) spacers. The device exhibits three distinct resistance levels depending on the relative magnetizations of the ferromagnetic electrodes. We observed a much weaker bias voltage dependence of MR in the device compared to that in the conventional organic spin valve (OSV). The MR magnitude reduces by the factor of two at 0.7 V bias voltage in the DOSV compared to 0.02 V in the conventional OSV. Remarkably, the MR magnitude reaches 0.3% at 6 V bias in the DOSVs, the largest MR response ever reported in OSVs at this bias. Our finding may have a significant impact on achieving high efficient bipolar OSVs strictly performed at high voltages. University of Georgia start-up fund, Ministry of Education, Singapore, National Natural Science Foundation of China.

  2. Intramolecular and Intermolecular Interactions in Hybrid Organic-Inorganic Alucone Films Grown by Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Kim, Hyein; Cho, Boram; Lee, Chaeyun; Choi, Sung-Eun; Sung, Myung Mo; Lee, Jin Seok

    2016-07-13

    Investigation of molecular interactions in polymeric films is crucial for understanding and engineering multiscale physical phenomena correlated to device function and performance, but this often involves a compromise between theoretical and experimental data, because of poor film uniformity. Here, we report the intramolecular and intermolecular interactions inside the ultrathin and conformal hybrid organic-inorganic alucone films grown by molecular layer deposition, based on sequential and self-limiting surface reactions. Varying the carbon chain length of organic precursors, which affects their molecular flexibility, caused intramolecular interactions such as double reactions by bending of the molecular backbone, resulting in formation of hole vacancies in the films. Furthermore, intermolecular interactions in alucone polymeric films are dependent on the thermal kinetics of molecules, leading to binding failures and cross-linking at low and high growth temperatures, respectively. We illustrate these key interactions and identify molecular geometries and potential energies by density functional theory calculations. PMID:27314844

  3. Using white noise to gate organic transistors for dynamic monitoring of cultured cell layers.

    PubMed

    Rivnay, Jonathan; Leleux, Pierre; Hama, Adel; Ramuz, Marc; Huerta, Miriam; Malliaras, George G; Owens, Roisin M

    2015-01-01

    Impedance sensing of biological systems allows for monitoring of cell and tissue properties, including cell-substrate attachment, layer confluence, and the "tightness" of an epithelial tissue. These properties are critical for electrical detection of tissue health and viability in applications such as toxicological screening. Organic transistors based on conducting polymers offer a promising route to efficiently transduce ionic currents to attain high quality impedance spectra, but collection of complete impedance spectra can be time consuming (minutes). By applying uniform white noise at the gate of an organic electrochemical transistor (OECT), and measuring the resulting current noise, we are able to dynamically monitor the impedance and thus integrity of cultured epithelial monolayers. We show that noise sourcing can be used to track rapid monolayer disruption due to compounds which interfere with dynamic polymerization events crucial for maintaining cytoskeletal integrity, and to resolve sub-second alterations to the monolayer integrity. PMID:26112429

  4. Ultraviolet Electroluminescence and Blue-Green Phosphorescence using an Organic Diphosphine Oxide Charge Transporting Layer.

    SciTech Connect

    Burrows, Paul E.; Padmaperuma, Asanga B.; Sapochak, Linda S.; Djurovich, Peter I.; Thompson, Mark E.

    2006-05-01

    We report electroluminescence with a peak wavelength at 338 nm from a simple bilayer organic light emitting device (OLED) made using 4,4’-bis(diphenylphosphine oxide) biphenyl (PO1). In an OLED geometry, the material is preferentially electron transporting. Doping the PO1 layer with iridium(III)bis(4,6-(di-fluorophenyl)-pyridinato-N, C2’)picolinate (FIrpic) gives rise to electrophosphorescence with a peak external quantum efficiency of 7.8% at 0.09 mA/cm2 and 5.8% at 13 mA/cm2. The latter current density is obtained at 6.3 V applied forward bias. This represents a new class of wide-bandgap charge transporting organic materials which may prove useful as host materials for blue electrophosphoresent OLEDs.

  5. Novel inorganic host layered double hydroxides intercalated with guest organic inhibitors for anticorrosion applications.

    PubMed

    Poznyak, S K; Tedim, J; Rodrigues, L M; Salak, A N; Zheludkevich, M L; Dick, L F P; Ferreira, M G S

    2009-10-01

    Zn-Al and Mg-Al layered double hydroxides (LDHs) loaded with quinaldate and 2-mercaptobenzothiazolate anions were synthesized via anion-exchange reaction. The resulting compounds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. Spectrophotometric measurements demonstrated that the release of organic anions from these LDHs into the bulk solution is triggered by the presence of chloride anions, evidencing the anion-exchange nature of this process. The anticorrosion capabilities of LDHs loaded with organic inhibitors toward the AA2024 aluminum alloy were analyzed by electrochemical impedance spectroscopy. A significant reduction of the corrosion rate is observed when the LDH nanopigments are present in the corrosive media. The mechanism by which the inhibiting anions can be released from the LDHs underlines the versatility of these environmentally friendly structures and their potential application as nanocontainers in self-healing coatings. PMID:20355873

  6. Amorphous indium-gallium-zinc-oxide as electron transport layer in organic photodetectors

    SciTech Connect

    Arora, H.; Malinowski, P. E. Chasin, A.; Cheyns, D.; Steudel, S.; Schols, S.; Heremans, P.

    2015-04-06

    Amorphous indium-gallium-zinc-oxide (a-IGZO) is demonstrated as an electron transport layer (ETL) in a high-performance organic photodetector (OPD). Dark current in the range of 10 nA/cm{sup 2} at a bias voltage of −2 V and a high photoresponse in the visible spectrum were obtained in inverted OPDs with poly(3-hexylthiophene) and phenyl-C{sub 61}-butyric acid methyl ester active layer. The best results were obtained for the optimum a-IGZO thickness of 7.5 nm with specific detectivity of 3 × 10{sup 12} Jones at the wavelength of 550 nm. The performance of the best OPD devices using a-IGZO was shown to be comparable to state-of-the-art devices based on TiO{sub x} as ETL, with higher rectification achieved in reverse bias. Yield and reproducibility were also enhanced with a-IGZO, facilitating fabrication of large area OPDs. Furthermore, easier integration with IGZO-based readout backplanes can be envisioned, where the channel material can be used as photodiode buffer layer after additional treatment.

  7. The cerebellar Golgi cell and spatiotemporal organization of granular layer activity

    PubMed Central

    D'Angelo, Egidio; Solinas, Sergio; Mapelli, Jonathan; Gandolfi, Daniela; Mapelli, Lisa; Prestori, Francesca

    2013-01-01

    The cerebellar granular layer has been suggested to perform a complex spatiotemporal reconfiguration of incoming mossy fiber signals. Central to this role is the inhibitory action exerted by Golgi cells over granule cells: Golgi cells inhibit granule cells through both feedforward and feedback inhibitory loops and generate a broad lateral inhibition that extends beyond the afferent synaptic field. This characteristic connectivity has recently been investigated in great detail and been correlated with specific functional properties of these neurons. These include theta-frequency pacemaking, network entrainment into coherent oscillations and phase resetting. Important advances have also been made in terms of determining the membrane and synaptic properties of the neuron, and clarifying the mechanisms of activation by input bursts. Moreover, voltage sensitive dye imaging and multi-electrode array (MEA) recordings, combined with mathematical simulations based on realistic computational models, have improved our understanding of the impact of Golgi cell activity on granular layer circuit computations. These investigations have highlighted the critical role of Golgi cells in: generating dense clusters of granule cell activity organized in center-surround structures, implementing combinatorial operations on multiple mossy fiber inputs, regulating transmission gain, and cut-off frequency, controlling spike timing and burst transmission, and determining the sign, intensity and duration of long-term synaptic plasticity at the mossy fiber-granule cell relay. This review considers recent advances in the field, highlighting the functional implications of Golgi cells for granular layer network computation and indicating new challenges for cerebellar research. PMID:23730271

  8. Flexible single-layer ionic organic-inorganic frameworks towards precise nano-size separation.

    PubMed

    Yue, Liang; Wang, Shan; Zhou, Ding; Zhang, Hao; Li, Bao; Wu, Lixin

    2016-01-01

    Consecutive two-dimensional frameworks comprised of molecular or cluster building blocks in large area represent ideal candidates for membranes sieving molecules and nano-objects, but challenges still remain in methodology and practical preparation. Here we exploit a new strategy to build soft single-layer ionic organic-inorganic frameworks via electrostatic interaction without preferential binding direction in water. Upon consideration of steric effect and additional interaction, polyanionic clusters as connection nodes and cationic pseudorotaxanes acting as bridging monomers connect with each other to form a single-layer ionic self-assembled framework with 1.4 nm layer thickness. Such soft supramolecular polymer frameworks possess uniform and adjustable ortho-tetragonal nanoporous structure in pore size of 3.4-4.1 nm and exhibit greatly convenient solution processability. The stable membranes maintaining uniform porous structure demonstrate precisely size-selective separation of semiconductor quantum dots within 0.1 nm of accuracy and may hold promise for practical applications in selective transport, molecular separation and dialysis systems. PMID:26923611

  9. Ultrathin films of organic networks as nanofiltration membranes via solution-based molecular layer deposition.

    PubMed

    Qian, Huidong; Li, Shenghai; Zheng, Jifu; Zhang, Suobo

    2012-12-21

    Ultrathin films of organic networks on various substrates were fabricated through the solution-based molecular layer deposition (MLD) technique. The rigid tetrahedral geometries of polyfunctional amine and acyl chloride involved in the reaction ensure the continuity of the polymerization process. A linear increase in film thickness with respect to cycle number was observed by UV-vis adsorption, ellipsometry, and quartz crystal microbalance. The growth rate per MLD cycle is 1.6 nm, which can be controlled at the single molecular level. For the first time, we develop the MLD method on the top of hydrolyzed PAN substrate, resulting in nanofiltration (NF) membranes. The stepwise growth was monitored via attenuated total reflectance infrared studies. The separation performance of the obtained membrane for various solutes was sensitive to the terminated layers and number of cycles. The rejection of NH(2)-terminated membranes follows the order of CaCl(2) > Na(2)SO(4) > NaCl, while the order for COOH-capped surface is Na(2)SO(4) > CaCl(2) > NaCl. The absolute value of zeta potential for the MLD membranes decreases with the addition of deposition layers. The moderate water flux for the resulting membrane is due to the reduced porosity of the support as well as the low roughness and hydrophilicity of the membrane surface. This bottom-up process provides a promising approach for construction of long-term steady NF membranes with nanoscale dimensions. PMID:23198774

  10. Flexible single-layer ionic organic-inorganic frameworks towards precise nano-size separation

    NASA Astrophysics Data System (ADS)

    Yue, Liang; Wang, Shan; Zhou, Ding; Zhang, Hao; Li, Bao; Wu, Lixin

    2016-02-01

    Consecutive two-dimensional frameworks comprised of molecular or cluster building blocks in large area represent ideal candidates for membranes sieving molecules and nano-objects, but challenges still remain in methodology and practical preparation. Here we exploit a new strategy to build soft single-layer ionic organic-inorganic frameworks via electrostatic interaction without preferential binding direction in water. Upon consideration of steric effect and additional interaction, polyanionic clusters as connection nodes and cationic pseudorotaxanes acting as bridging monomers connect with each other to form a single-layer ionic self-assembled framework with 1.4 nm layer thickness. Such soft supramolecular polymer frameworks possess uniform and adjustable ortho-tetragonal nanoporous structure in pore size of 3.4-4.1 nm and exhibit greatly convenient solution processability. The stable membranes maintaining uniform porous structure demonstrate precisely size-selective separation of semiconductor quantum dots within 0.1 nm of accuracy and may hold promise for practical applications in selective transport, molecular separation and dialysis systems.

  11. Optical spacing effect in organic photovoltaic cells incorporating a dilute acceptor layer

    SciTech Connect

    Menke, S. Matthew; Lindsay, Christopher D.; Holmes, Russell J.

    2014-06-16

    The addition of spacing layers in organic photovoltaic cells (OPVs) can enhance light absorption by optimizing the spatial distribution of the incident optical field in the multilayer structure. We explore the optical spacing effect in OPVs achieved using a diluted electron acceptor layer of C{sub 60}. While optical spacing is often realized by optimizing buffer layer thickness, we find that optical spacing via dilution leads to cells with similar or enhanced photocurrent. This is observed despite a smaller quantity of absorbing molecules, suggesting a more efficient use of absorbed photons. In fact, dilution is found to concentrate optical absorption near the electron donor-acceptor interface, resulting in a marked increase in the exciton diffusion efficiency. Contrasting the use of changes in thickness to engineer optical absorption, the use of dilution does not significantly alter the overall thickness of the OPV. Optical spacing via dilution is shown to be a viable alternative to more traditional optical spacing techniques and may be especially useful in the continued optimization of next-generation, tandem OPVs where it is important to minimize competition for optical absorption between individual sub-cells.

  12. HATCN-based charge recombination layers as effective interconnectors for tandem organic solar cells.

    PubMed

    Wang, Rong-Bin; Wang, Qian-Kun; Xie, Hao-Jun; Xu, Lu-Hai; Duhm, Steffen; Li, Yan-Qing; Tang, Jian-Xin

    2014-09-10

    A comprehensive understanding of the energy-level alignment at the organic heterojunction interfaces is of paramount importance to optimize the performance of organic solar cells (OSCs). Here, the detailed electronic structures of organic interconnectors, consisting of cesium fluoride-doped 4,7-diphenyl-1,10-phenanthroline and hexaazatriphenylene-hexacarbonitrile (HATCN), have been investigated via in situ photoemission spectroscopy, and their impact on the charge recombination process in tandem OSCs has been identified. The experimental determination shows that the HATCN interlayer plays a significant role in the interface energetics with a dramatic decrease in the reverse built-in potential for electrons and holes from stacked subcells, which is beneficial to the charge recombination between HATCN and the adjacent layer. In accordance with the energy-level alignments, the open-circuit voltage of tandem OSC incorporating a HATCN-based interconnector is almost 2 times that of a single-cell OSC, revealing the effectiveness of the HATCN-based interconnectors in tandem organic devices. PMID:25141159

  13. Enhanced catalytic oxidation ability of ternary layered double hydroxides for organic pollutants degradation.

    PubMed

    Fahel, Jean; Kim, Sanghoon; Durand, Pierrick; André, Erwan; Carteret, Cédric

    2016-05-10

    Co(2+) and Cu(2+) substituted MgAl layered double hydroxides with an M(2+)/M(3+) atomic ratio of 2.0 were synthesized by a co-precipitation method and fully characterized using various techniques including powder X-ray diffraction, ICP-AES analysis, FT-IR, DR UV-Vis spectroscopy, N2 adsorption-desorption and transmission electron microscopy. The materials revealed a good crystallinity with no phase impurity and successful substitution of cobalt and copper ions in the framework of binary LDH with the target ratio of metals in the sheet. The adsorption characteristics (kinetic and isotherm) and the catalytic oxidation of organic pollutants, methylene blue (cationic dye) and orange II (anionic) were carried out to investigate a potential use of LDH materials as catalysts. In particular, Co3Cu1Al2 LDH exhibited an excellent catalytic activity towards catalytic dye degradation, especially for orange II with good stability and reusability over several times. Furthermore, this LDH material showed good catalytic performance for several chlorophenol compounds, suggesting its practical application in wastewater treatment. Therefore, layered double hydroxides substituted with Co(2+) and Cu(2+) could be promising candidates in various applications, such as the abatement of organic pollutants. PMID:27097543

  14. Anomalous hole injection deterioration of organic light-emitting diodes with a manganese phthalocyanine layer

    SciTech Connect

    Lee, Hyunbok; Lee, Jeihyun; Yi, Yeonjin; Cho, Sang Wan; Kim, Jeong Won

    2015-01-21

    Metal phthalocyanines (MPcs) are well known as an efficient hole injection layer (HIL) in organic devices. They possess a low ionization energy, and so the low-lying highest occupied molecular orbital (HOMO) gives a small hole injection barrier from an anode in organic light-emitting diodes. However, in this study, we show that the hole injection characteristics of MPc are not only determined by the HOMO position but also significantly affected by the wave function distribution of the HOMO. We show that even with the HOMO level of a manganese phthalocyanine (MnPc) HIL located between the Fermi level of an indium tin oxide anode and the HOMO level of a N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine hole transport layer the device performance with the MnPc HIL is rather deteriorated. This anomalous hole injection deterioration is due to the contracted HOMO wave function, which leads to small intermolecular electronic coupling. The origin of this contraction is the significant contribution of the Mn d-orbital to the MnPc HOMO.

  15. Interface modified thermally stable hole transporting layer for efficient organic light emitting diodes

    SciTech Connect

    Grover, Rakhi; Srivastava, Ritu Dagar, Janardan; Kamalasanan, M. N.; Mehta, D. S.

    2014-08-14

    Electrical transport in thermally stable 2, 7-bis [N, N-bis (4-methoxy-phenyl) amino]-9, 9-spirobifluorene (MeO-Spiro-TPD) thin films has been investigated as a function of temperature and organic layer thickness. ITO/MeO-Spiro-TPD interface was found to be injection limited and has been studied in detail to find barrier height for hole injection. The thickness of tetra-fluoro-tetracyano-quinodimethane thin films were optimized to be used as hole injection buffer layer which resulted in switching of charge transport mechanism from injection limited to space charge limited conduction above a critical thickness of 3 nm. Hole mobility has been measured using transient space charge limited conduction (SCLC), field dependent SCLC, and top contact transistor characteristics. The charge carrier transport in interface modified hole only devices was analysed using Gaussian disorder model. The thermal stability of MeO-Spiro-TPD has been investigated by atomic force microscopy and X-ray diffraction studies. The study indicates a thermally stable and highly efficient hole transport material for application in organic semiconductor based devices.

  16. Distribution and landscape controls of organic layer thickness and carbon within the Alaskan Yukon River Basin

    USGS Publications Warehouse

    Pastick, Neal J.; Rigge, Matthew B.; Wylie, Bruce K.; Jorgenson, M. Torre; Rose, Joshua R.; Johnson, Kristofer D.; Ji, Lei

    2014-01-01

    Understanding of the organic layer thickness (OLT) and organic layer carbon (OLC) stocks in subarctic ecosystems is critical due to their importance in the global carbon cycle. Moreover, post-fire OLT provides an indicator of long-term successional trajectories and permafrost susceptibility to thaw. To these ends, we 1) mapped OLT and associated uncertainty at 30 m resolution in the Yukon River Basin (YRB), Alaska, employing decision tree models linking remotely sensed imagery with field and ancillary data, 2) converted OLT to OLC using a non-linear regression, 3) evaluate landscape controls on OLT and OLC, and 4) quantified the post-fire recovery of OLT and OLC. Areas of shallow (2 = 0.68; OLC: R2 = 0.66), where an average of 16 cm OLT and 5.3 kg/m2 OLC were consumed by fires. Strong predictors of OLT included climate, topography, near-surface permafrost distributions, soil wetness, and spectral information. Our modeling approach enabled us to produce regional maps of OLT and OLC, which will be useful in understanding risks and feedbacks associated with fires and climate feedbacks.

  17. Self-Organized Information Processing in Neuronal Networks: Replacing Layers in Deep Networks by Dynamics

    NASA Astrophysics Data System (ADS)

    Kirst, Christoph

    It is astonishing how the sub-parts of a brain co-act to produce coherent behavior. What are mechanism that coordinate information processing and communication and how can those be changed flexibly in order to cope with variable contexts? Here we show that when information is encoded in the deviations around a collective dynamical reference state of a recurrent network the propagation of these fluctuations is strongly dependent on precisely this underlying reference. Information here 'surfs' on top of the collective dynamics and switching between states enables fast and flexible rerouting of information. This in turn affects local processing and consequently changes in the global reference dynamics that re-regulate the distribution of information. This provides a generic mechanism for self-organized information processing as we demonstrate with an oscillatory Hopfield network that performs contextual pattern recognition. Deep neural networks have proven to be very successful recently. Here we show that generating information channels via collective reference dynamics can effectively compress a deep multi-layer architecture into a single layer making this mechanism a promising candidate for the organization of information processing in biological neuronal networks.

  18. In Situ Analysis of the Growth and Dielectric Properties of Organic Self-Assembled Monolayers: A Way To Tailor Organic Layers for Electronic Applications.

    PubMed

    Markov, Aleksandr; Greben, Kyrylo; Mayer, Dirk; Offenhäusser, Andreas; Wördenweber, Roger

    2016-06-29

    Organic nanoscale science and technology relies on the control of phenomena occurring at the molecular level. This is of particular importance for the self-assembly of molecular monolayers (SAM) that can be used in various applications ranging from organic electronics to bioelectronic applications. However, the understanding of the elementary nanoscopic processes in molecular film growth is still in its infancy. Here, we developed a novel in situ and extremely sensitive detection method for the analysis of the electronic properties of molecular layer during molecular layer deposition. This low-frequency sensor (1 kHz) is employed to analyze the standard vapor deposition process of SAMs of molecules and, subsequently, it is used to optimize the growth process itself. By combining this method with an ex situ determination of the effective thickness of the resulting layers via ellipsometry, we observe a large difference of the permittivity (1 kHz) of the examined aminosilanes in the liquid state (εliquid = 5.5-8.8) and in SAMs (εSAM = 22-52, electric field in the plane of the layer). We ascribe this difference to either the different orientation and order of the molecules, the different density of molecules, or a combination of both effects. Our novel in situ analyses not only allows monitoring and optimizing the deposition of organic layers but also demonstrates the high potential of organic SAMs as organic high-k layers in electronic devices. PMID:27268402

  19. Nanoconfinement of water layers in lamellar structures prepared in the presence and absence of organic solvent.

    PubMed

    De, Dipanwita; Sajjan, Manas; Narayanan, Janaky; Bellare, Jayesh R; Datta, Anindya

    2013-02-21

    An attempt is made to draw a line of comparison between the extent of rigidity of the hydration layers bound to the interfacial region of lamellar structures of Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) in water, in the presence and absence of an organic solvent using POM, SAXS, cryo-TEM, and time-resolved fluorescence spectroscopy. These systems are ternary mixtures of AOT, water, and n-heptane containing lamellar structures in an aqueous layer at higher w(0) values (w(0) = 300 and 150) and a binary solution of 20 and 50% AOT in neat water (w/w). The solvation shells residing at the vicinity of these lamellar structures are monitored using two different coumarin probes (C153 and C500). It is intended to envisage a comparative solvation dynamics study of the restricted aqueous region confined in lamellar structures formed in ternary mixture and binary solution. Though steady state measurements show a similar microenvironment probed by the fluorophores in lamellar structures formed in the two different aqueous phases, temporal evolution of the solvent correlation function C(t) unveils the existence of lamellar structures with different degrees of confinement of water layers in these two systems. A slower relaxation of the restricted aqueous region in lamellar structures of binary solution signifies the presence of more rigid interfacially bound water layers at the lamellar interface than in the ternary mixture having a similar weight percentage of AOT in water. The present investigation concludes that the lamellar structures formed under two different conditions provide a similar hydrophobic environment with different extents of localized water populations at the lamellar interface as manifested by the solvent relaxation time in agreement with SAXS and cryo-TEM images. PMID:23240713

  20. Using atmospheric fallout to date organic horizon layers and quantify metal dynamics during decomposition

    NASA Astrophysics Data System (ADS)

    Kaste, James M.; Bostick, Benjamin C.; Heimsath, Arjun M.; Steinnes, Eiliv; Friedland, Andrew J.

    2011-03-01

    High concentrations of metals in organic matter can inhibit decomposition and limit nutrient availability in ecosystems, but the long-term fate of metals bound to forest litter is poorly understood. Controlled experiments indicate that during the first few years of litter decay, Al, Fe, Pb, and other metals that form stable complexes with organic matter are naturally enriched by several hundred percent as carbon is oxidized. The transformation of fresh litter to humus takes decades, however, such that current datasets describing the accumulation and release of metals in decomposing organic matter are timescale limited. Here we use atmospheric 210Pb to quantify the fate of metals in canopy-derived litter during burial and decay in coniferous forests in New England and Norway where decomposition rates are slow and physical soil mixing is minimal. We measure 210Pb inventories in the O horizon and mineral soil and calculate a 60-630 year timescale for the production of mobile organo-metallic colloids from the decomposition of fresh forest detritus. This production rate is slowest at our highest elevation (˜1000 m) and highest latitude sites (>63°N) where decomposition rates are expected to be low. We calculate soil layer ages by assuming a constant supply of atmospheric 210Pb and find that they are consistent with the distribution of geochemical tracers from weapons fallout, air pollution, and a direct 207Pb application at one site. By quantifying a gradient of organic matter ages with depth in the O horizon, we describe the accumulation and loss of metals in the soil profile as organic matter transforms from fresh litter to humus. While decomposition experiments predict that Al and Fe concentrations increase during the initial few years of decay, we show here that these metals continue to accumulate in humus for decades, and that enrichment occurs at a rate higher than can be explained by quantitative retention during decomposition alone. Acid extractable Al and Fe

  1. Improvement in Mobility and Stability of n-Type Organic Field-Effect Transistors with a Hole Transporting Interfacial Layer

    NASA Astrophysics Data System (ADS)

    Nakayama, Ken-ichi; Ishikawa, Motomi; Yokoyama, Masaaki

    2009-02-01

    Field-effect electron mobility and stability of N,N'-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8H) improved when a hole-transporting layer, used in organic light-emitting diodes, was inserted between the gate insulator and the channel layer. This result suggests that insertion of an electronically active interfacial layer of an organic semiconductor is more effective in eliminating electron traps of the insulator surface compared to conventional surface treatment to obtain an inert surface.

  2. Use of layered double hydroxides and their derivatives as adsorbents for inorganic and organic pollutants

    NASA Astrophysics Data System (ADS)

    You, Youwen

    Contamination of surface and groundwaters by hazardous inorganic and organic pollutants has become an increasing threat to the safety of drinking waters. Cleanup of contaminated surface and groundwaters has, therefore, become a major focus of environmental research. Primary objectives of this dissertation study were to examine the adsorption properties of layered double hydroxides (LDHs) and their derivatives for inorganic and organic contaminants and to identify potential technologies that utilize LDHs and their derivatives for environment remediation. Studies examined the adsorption characteristics of anionic selenium, arsenic and dicamba (3,6 dichloro-2-methoxy benzoic acid) on original LDHs and calcined-LDHs. Adsorption of selenium and arsenic on LDHs was a function of pH. Competing anions in solution strongly affected adsorption of all three contaminants, with divalent anions decreasing adsorption more intensely than monovalent anions. Adsorbed selenium, arsenic and dicamba could be released from LDHs in anion solutions. Adsorption isotherms for selenium and arsenic retention could be fitted to a simple Langmuir equation. Calcination processes significantly increased adsorption capacities of LDHs. Because of adsorption-desorpion characteristics, LDHs could be recycled. X-ray diffraction patterns revealed an increase of d-spacing coupling with adsorption of contaminants, verifying the intercalation of contaminants into layer structure of LDHs. Long chain anionic surfactants intercalated into LDHs modified their surface properties, resulting in organo-LDHs with hydrophobic surface properties. Various organo-LDHs were developed by incorporating different surfactants into LDHs via different synthesis methods. Surfactant intercalation properties were examined and the geometrical arrangements of the intercalated surfactants were characterized. Results revealed that surfactant molecules could adopt various configurations within the LDH interlayer space. Intercalation

  3. Soil surface organic layers in Arctic Alaska: spatial distribution, rates of formation, and microclimatic effects

    USGS Publications Warehouse

    Baughman, Carson A.; Mann, Daniel H.; Verbyla, David L.; Kunz, Michael L.

    2015-01-01

    Organic layers of living and dead vegetation cover the ground surface in many permafrost landscapes and play important roles in ecosystem processes. These soil surface organic layers (SSOLs) store large amounts of carbon and buffer the underlying permafrost and its contained carbon from changes in aboveground climate. Understanding the dynamics of SSOLs is a prerequisite for predicting how permafrost and carbon stocks will respond to warming climate. Here we ask three questions about SSOLs in a representative area of the Arctic Foothills region of northern Alaska: (1) What environmental factors control the thickness of SSOLs and the carbon they store? (2) How long do SSOLs take to develop on newly stabilized point bars? (3) How do SSOLs affect temperature in the underlying ground? Results show that SSOL thickness and distribution correlate with elevation, drainage area, vegetation productivity, and incoming solar radiation. A multiple regression model based on these correlations can simulate spatial distribution of SSOLs and estimate the organic carbon stored there. SSOLs develop within a few decades after a new, sandy, geomorphic surface stabilizes but require 500–700 years to reach steady state thickness. Mature SSOLs lower the growing season temperature and mean annual temperature of the underlying mineral soil by 8 and 3°C, respectively. We suggest that the proximate effects of warming climate on permafrost landscapes now covered by SSOLs will occur indirectly via climate's effects on the frequency, extent, and severity of disturbances like fires and landslides that disrupt the SSOLs and interfere with their protection of the underlying permafrost.

  4. Enhancement of efficiencies for tandem green phosphorescent organic light-emitting devices with a p-type charge generation layer

    SciTech Connect

    Yoo, Byung Soo; Jeon, Young Pyo; Lee, Dae Uk; Kim, Tae Whan

    2014-10-15

    The operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the organic light-emitting device with a molybdenum trioxide layer. The maximum brightness of the tandem green phosphorescent organic light-emitting device at 21.9 V was 26,540 cd/m{sup 2}. The dominant peak of the electroluminescence spectra for the devices was related to the fac-tris(2-phenylpyridine) iridium emission. - Highlights: • Tandem OLEDs with CGL were fabricated to enhance their efficiency. • The operating voltage of the tandem OLED with a HAT-CN layer was improved by 3%. • The efficiency and brightness of the tandem OLED were 13.9 cd/A and 26,540 cd/m{sup 2}. • Efficiency of the OLED with a HAT-CN layer was lower than that with a MoO{sub 3} layer. - Abstract: Tandem green phosphorescent organic light-emitting devices with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile or a molybdenum trioxide charge generation layer were fabricated to enhance their efficiency. Current density–voltage curves showed that the operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the corresponding organic light-emitting device with a molybdenum trioxide layer. The efficiency and the brightness of the tandem green phosphorescent organic light-emitting device were 13.9 cd/A and 26,540 cd/m{sup 2}, respectively. The current efficiency of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was lower by 1.1 times compared to that of the corresponding organic light-emitting device with molybdenum trioxide layer due to the decreased charge generation and transport in the 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer resulting from triplet–triplet exciton annihilation.

  5. Mild oxygen plasma treated PEDOT:PSS as anode buffer layer for vacuum deposited organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhou, Yunfei; Yuan, Yongbo; Lian, Jiarong; Zhang, Jie; Pang, Hongqi; Cao, Lingfang; Zhou, Xiang

    2006-08-01

    The surface morphology of PEDOT:PSS after mild oxygen plasma treatment were investigated by scanning electron microscopy and atomic force microscopy. The nanometer-scale islands on the surface of treated PEDOT:PSS were observed. Vacuum deposited organic light-emitting diodes (OLEDs) with treated PEDOT:PSS as anode buffer layer had been fabricated. The OLEDs with an appropriately treated PEDOT:PSS as anode buffer layer exhibited significantly enhanced lifetime and decreased driving voltage. The results suggest that the appropriate mild oxygen plasma treatment of PEDOT:PSS layers may be useful for the improvement of the interface with the hole transport layer and enhanced device performance.

  6. Improved performance of organic light-emitting devices with plasma treated ITO surface and plasma polymerized methyl methacrylate buffer layer

    NASA Astrophysics Data System (ADS)

    Lim, Jae-Sung; Shin, Paik-Kyun

    2007-02-01

    Transparent indium-tin-oxide (ITO) anode surface was modified using O 3 plasma and organic ultra-thin buffer layers were deposited on the ITO surface using 13.56 MHz rf plasma polymerization technique. A plasma polymerized methyl methacrylate (ppMMA) ultra-thin buffer layer was deposited between the ITO anode and hole transporting layer (HTL). The plasma polymerization of the buffer layer was carried out at a homemade capacitively coupled plasma (CCP) equipment. N, N'-Diphenyl- N, N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) as HTL, Tris(8-hydroxy-quinolinato)aluminum (Alq 3) as both emitting layer (EML)/electron transporting layer (ETL), and aluminum layer as cathode were deposited using thermal evaporation technique. Electroluminescence (EL) efficiency, operating voltage and stability of the organic light-emitting devices (OLEDs) were investigated in order to study the effect of the plasma surface treatment of the ITO anode and role of plasma polymerized methyl methacrylate as an organic ultra-thin buffer layer.

  7. Ordered and ultrathin reduced graphene oxide LB films as hole injection layers for organic light-emitting diode

    PubMed Central

    2014-01-01

    In this paper, we demonstrated the utilization of reduced graphene oxide (RGO) Langmuir-Blodgett (LB) films as high performance hole injection layer in organic light-emitting diode (OLED). By using LB technique, the well-ordered and thickness-controlled RGO sheets are incorporated between the organic active layer and the transparent conducting indium tin oxide (ITO), leading to an increase of recombination between electrons and holes. Due to the dramatic increase of hole carrier injection efficiency in RGO LB layer, the device luminance performance is greatly enhanced comparable to devices fabricated with spin-coating RGO and a commercial conducting polymer PEDOT:PSS as the hole transport layer. Furthermore, our results indicate that RGO LB films could be an excellent alternative to commercial PEDOT:PSS as the effective hole transport and electron blocking layer in light-emitting diode devices. PMID:25298757

  8. Revealing the Buried Metal-Organic Interface: Restructuring of the First Layer by van der Waals Forces.

    PubMed

    Wagner, Margareta; Berkebile, Stephen; Netzer, Falko P; Ramsey, Michael G

    2015-12-22

    With the use of molecular manipulation in a cryogenic scanning tunneling microscope, the structure and rearrangement of sexiphenyl molecules at the buried interface of the organic film with the Cu(110) substrate surface have been revealed. It is shown that a reconstruction of the first monolayer of flat lying molecules occurs due to the van der Waals pressure from subsequent layers. In this rearrangement, additional sexiphenyl molecules are forced into the established complete monolayer and adopt an edge-on configuration. Incorporation of second layer molecules into the first layer is also demonstrated by purposely pushing sexiphenyl molecules with the STM tip. The results indicate that even chemisorbed organic layers at interfaces can be significantly influenced by external stress from van der Waals forces of subsequent layers. PMID:26505912

  9. Ordered and ultrathin reduced graphene oxide LB films as hole injection layers for organic light-emitting diode.

    PubMed

    Yang, Yajie; Yang, Xiaojie; Yang, Wenyao; Li, Shibin; Xu, Jianhua; Jiang, Yadong

    2014-01-01

    In this paper, we demonstrated the utilization of reduced graphene oxide (RGO) Langmuir-Blodgett (LB) films as high performance hole injection layer in organic light-emitting diode (OLED). By using LB technique, the well-ordered and thickness-controlled RGO sheets are incorporated between the organic active layer and the transparent conducting indium tin oxide (ITO), leading to an increase of recombination between electrons and holes. Due to the dramatic increase of hole carrier injection efficiency in RGO LB layer, the device luminance performance is greatly enhanced comparable to devices fabricated with spin-coating RGO and a commercial conducting polymer PEDOT:PSS as the hole transport layer. Furthermore, our results indicate that RGO LB films could be an excellent alternative to commercial PEDOT:PSS as the effective hole transport and electron blocking layer in light-emitting diode devices. PMID:25298757

  10. Thermal transformation of a layered multifunctional network into a metal-organic framework based on a polymeric organic linker.

    PubMed

    Silva, Patrícia; Vieira, Fabiana; Gomes, Ana C; Ananias, Duarte; Fernandes, José A; Bruno, Sofia M; Soares, Rosário; Valente, Anabela A; Rocha, João; Paz, Filipe A Almeida

    2011-09-28

    The preparation of layered [La(H(3)nmp)] as microcrystalline powders from optimized microwave-assisted synthesis or dynamic hydrothermal synthesis (i.e., with constant rotation of the autoclaves) from the reaction of nitrilotris(methylenephosphonic acid) (H(6)nmp) with LaCl(3)·7H(2)O is reported. Thermogravimetry in conjunction with thermodiffractometry showed that the material undergoes a microcrystal-to-microcrystal phase transformation above 300 °C, being transformed into either a three-dimensional or a two-dimensional network (two models are proposed based on dislocation of molecular units) formulated as [La(L)] (where L(3-) = [-(PO(3)CH(2))(2)(NH)(CH(2)PO(2))O(1/2)-](n)(3n-)). The two crystal structures were solved from ab initio methods based on powder X-ray diffraction data in conjunction with structural information derived from (13)C and (31)P solid-state NMR, electron microscopy (SEM and EDS mapping), FT-IR spectroscopy, thermodiffractometry, and photoluminescence studies. It is shown that upon heating the coordinated H(3)nmp(3-) anionic organic ligand undergoes a polymerization (condensation) reaction to form in situ a novel and unprecedented one-dimensional polymeric organic ligand. The lanthanum oxide layers act, thus, simultaneously as insulating and templating two-dimensional scaffolds. A rationalization of the various steps involved in these transformations is provided for the two models. Photoluminescent materials, isotypical with both the as-prepared ([(La(0.95)Eu(0.05))(H(3)nmp)] and [(La(0.95)Tb(0.05))(H(3)nmp)]) and the calcined ([(La(0.95)Eu(0.05))(L)]) compounds and containing stoichiometric amounts of optically active lanthanide centers, have been prepared and their photoluminescent properties studied in detail. The lifetimes of Eu(3+) vary between 2.04 ± 0.01 and 2.31 ± 0.01 ms (considering both ambient and low-temperature studies). [La(H(3)nmp)] is shown to be an effective heterogeneous catalyst in the ring opening of styrene oxide with

  11. Synaptic and cellular organization of layer 1 of the developing rat somatosensory cortex

    PubMed Central

    Muralidhar, Shruti; Wang, Yun; Markram, Henry

    2013-01-01

    Layer 1 of the neocortex is sparsely populated with neurons and heavily innervated by fibers from lower layers and proximal and distal brain regions. Understanding the potential functions of this layer requires a comprehensive understanding of its cellular and synaptic organization. We therefore performed a quantitative study of the microcircuitry of neocortical layer 1 (L1) in the somatosensory cortex in juvenile rats (P13–P16) using multi-neuron patch-clamp and 3D morphology reconstructions. Expert-based subjective classification of the morphologies of the recorded L1 neurons suggest 6 morphological classes: (1) the Neurogliaform cells with dense axonal arborizations (NGC-DA) and with sparse arborizations (NGC-SA), (2) the Horizontal Axon Cell (HAC), (3) those with descending axonal collaterals (DAC), (4) the large axon cell (LAC), and (5) the small axon cell (SAC). Objective, supervised and unsupervised cluster analyses confirmed DAC, HAC, LAC and NGC as distinct morphological classes. The neurons were also classified into 5 electrophysiological types based on the Petilla convention; classical non-adapting (cNAC), burst non-adapting (bNAC), classical adapting (cAC), classical stuttering (cSTUT), and classical irregular spiking (cIR). The most common electrophysiological type of neuron was the cNAC type (40%) and the most common morpho-electrical type was the NGC-DA—cNAC. Paired patch-clamp recordings revealed that the neurons were connected via GABAergic inhibitory synaptic connections with a 7.9% connection probability and via gap junctions with a 5.2% connection probability. Most synaptic connections were mediated by both GABAA and GABAB receptors (62.6%). A smaller fraction of synaptic connections were mediated exclusively by GABAA (15.4%) or GABAB (21.8%) receptors. Morphological 3D reconstruction of synaptic connected pairs of L1 neurons revealed multi-synapse connections with an average of 9 putative synapses per connection. These putative synapses

  12. Safety analysis of exothermic reaction hazards associated with the organic liquid layer in tank 241-C-103

    SciTech Connect

    Postma, A.K.; Bechtold, D.B.; Borsheim, G.L.; Grisby, J.M.; Guthrie, R.L.; Kummerer, M.; Turner, D.A.; Plys, M.G.

    1994-03-01

    Safety hazards associated with the interim storage of a potentially flammable organic liquid in waste Tank C-103 are identified and evaluated. The technical basis for closing the unreviewed safety question (USQ) associated with the floating liquid organic layer in this tank is presented.

  13. Polyethylene/organically-modified layered-silicate nanocomposites with antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Songtipya, P.; Jimenez-Gasco, M. M.; Manias, E.

    2009-03-01

    Despite the very intensive research on polymer nanocomposites, the opportunities for new functionalities possible by nanofillers still remain largely untapped. Here, we present polyethylene/inorganic nanocomposites that exhibit strongly enhanced mechanical performance and, at the same time, also an antimicrobial activity originating from the organo-filler nature. Specifically, PE/organically-modified layered-silicate nanocomposites were prepared via melt-processing, and antimicrobial activity was designed by proper choice of their organic modification. Their antimicrobial activity was measured against three micotoxinogen fungal strains (Penicillium roqueforti and claviforme, and Fusarium graminearum) as model soil-borne plant and food contaminants. Montmorillonite-based organofillers, which only differ in their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the nanocomposites. The comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants.

  14. Layer-by-Layer Assembly of Metal-Organic Frameworks in Macroporous Polymer Monolith and Their Use for Enzyme Immobilization.

    PubMed

    Wen, Liyin; Gao, Aicong; Cao, Yao; Svec, Frantisek; Tan, Tianwei; Lv, Yongqin

    2016-03-01

    New monolithic materials comprising zeolitic imidazolate framework (ZIF-8) located on the pore surface of poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith previously functionalized with N-(3-aminopropyl)-imidazole have been prepared via a layer-by-layer self-assembly strategy. These new ZIF-8@monolith hybrids are used as solid-phase carriers for enzyme immobilization. Their performance is demonstrated with immobilization of a model proteolytic enzyme trypsin. The best of the conjugates enable very efficient digestion of proteins that can be achieved in mere 43 s. PMID:26806691

  15. Dielectric Barrier Discharge Ionization in Characterization of Organic Compounds Separated on Thin-Layer Chromatography Plates

    PubMed Central

    Cegłowski, Michał; Smoluch, Marek; Babij, Michał; Gotszalk, Teodor; Silberring, Jerzy; Schroeder, Grzegorz

    2014-01-01

    A new method for on-spot detection and characterization of organic compounds resolved on thin layer chromatography (TLC) plates has been proposed. This method combines TLC with dielectric barrier discharge ionization (DBDI), which produces stable low-temperature plasma. At first, the compounds were separated on TLC plates and then their mass spectra were directly obtained with no additional sample preparation. To obtain good quality spectra the center of a particular TLC spot was heated from the bottom to increase volatility of the compound. MS/MS analyses were also performed to additionally characterize all analytes. The detection limit of proposed method was estimated to be 100 ng/spot of compound. PMID:25170762

  16. Cobalt-Based Layered Metal-Organic Framework as an Ultrahigh Capacity Supercapacitor Electrode Material.

    PubMed

    Liu, Xiuxiu; Shi, Changdong; Zhai, Changwei; Cheng, Meiling; Liu, Qi; Wang, Guoxiu

    2016-02-24

    Metal-organic frameworks (MOFs) have recently received increasing interest due to their potential application in the energy storage and conversion field. Herein, cobalt-based layered MOF ({[Co(Hmt)(tfbdc)(H2O)2]·(H2O)2}n, Co-LMOF; Hmt = hexamethylenetetramine; H2tfbdc = 2,3,5,6-tetrafluoroterephthalic acid) has been evaluated as an electrode material for supercapacitors. The Co-LMOF electrode exhibits a high specific capacitance and excellent cycling stability. Its maximum specific capacitance is 2474 F g(-1) at a current density of 1 A g(-1), and the specific capacitance retention is about 94.3% after 2000 cycles. The excellent electrochemical property may be ascribed to the intrinsic nature of Co-LMOF, enough space available for the storage and diffusion of the electrolyte, and the particles of nanoscale size. PMID:26829547

  17. Multi-layer imaging of human organs by measurement of laser backscattered radiation.

    PubMed

    Chacko, S; Singh, M

    1999-05-01

    Laser backscattered radiations from tissue phantoms and human forearms are measured by a reflectance imager. Laser radiations are guided by an optical fibre, and the backscattered radiations are collected by three optical fibres in the measurement probe assembly, placed at distances of 2 mm, 4 mm and 6 mm from the input fibre. By placing the measurement probe on the phantom or tissue surface and matching the outline on the computer monitor, the reflectance data from the organ or the phantom are collected. These data, after digitisation, interpolation and filtering, are colour coded and displayed on the computer monitor. Using this imaging procedure, the abnormalities embedded at different depths in the phantoms are located. The structural changes due to colour, composition and blood flow in the multi-layer of human forearms of various subjects are qualitatively shown in reflectance images obtained by this procedure. PMID:10505375

  18. Copper thiocyanate: An attractive hole transport/extraction layer for use in organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Treat, Neil D.; Yaacobi-Gross, Nir; Faber, Hendrik; Perumal, Ajay K.; Bradley, Donal D. C.; Stingelin, Natalie; Anthopoulos, Thomas D.

    2015-07-01

    We report the advantageous properties of the inorganic molecular semiconductor copper(I) thiocyanate (CuSCN) for use as a hole collection/transport layer (HTL) in organic photovoltaic (OPV) cells. CuSCN possesses desirable HTL energy levels [i.e., valence band at -5.35 eV, 0.35 eV deeper than poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)], which produces a 17% increase in power conversion efficiency (PCE) relative to PEDOT:PSS-based devices. In addition, a two-fold increase in shunt resistance for the solar cells measured in dark conditions is achieved. Ultimately, CuSCN enables polymer:fullerene based OPV cells to achieve PCE > 8%. CuSCN continues to offer promise as a chemically stable and straightforward replacement for the commonly used PEDOT:PSS.

  19. Infrared spectroscopy of large scale single layer graphene on self assembled organic monolayer

    SciTech Connect

    Woo Kim, Nak; Youn Kim, Joo; Lee, Chul; Choi, E. J.; Jin Kim, Sang; Hee Hong, Byung

    2014-01-27

    We study the effect of self-assembled monolayer (SAM) organic molecule substrate on large scale single layer graphene using infrared transmission measurement on Graphene/SAM/SiO{sub 2}/Si composite samples. From the Drude weight of the chemically inert CH{sub 3}-SAM, the electron-donating NH{sub 2}-SAM, and the SAM-less graphene, we determine the carrier density doped into graphene by the three sources—the SiO{sub 2} substrate, the gas-adsorption, and the functional group of the SAM's—separately. The SAM-treatment leads to the low carrier density N ∼ 4 × 10{sup 11} cm{sup −2} by blocking the dominant SiO{sub 2}- driven doping. The carrier scattering increases by the SAM-treatment rather than decreases. However, the transport mobility is nevertheless improved due to the reduced carrier doping.

  20. Infrared spectroscopy of large scale single layer graphene on self assembled organic monolayer

    NASA Astrophysics Data System (ADS)

    Woo Kim, Nak; Youn Kim, Joo; Lee, Chul; Jin Kim, Sang; Hee Hong, Byung; Choi, E. J.

    2014-01-01

    We study the effect of self-assembled monolayer (SAM) organic molecule substrate on large scale single layer graphene using infrared transmission measurement on Graphene/SAM/SiO2/Si composite samples. From the Drude weight of the chemically inert CH3-SAM, the electron-donating NH2-SAM, and the SAM-less graphene, we determine the carrier density doped into graphene by the three sources—the SiO2 substrate, the gas-adsorption, and the functional group of the SAM's—separately. The SAM-treatment leads to the low carrier density N ˜ 4 × 1011 cm-2 by blocking the dominant SiO2- driven doping. The carrier scattering increases by the SAM-treatment rather than decreases. However, the transport mobility is nevertheless improved due to the reduced carrier doping.

  1. Copper thiocyanate: An attractive hole transport/extraction layer for use in organic photovoltaic cells

    SciTech Connect

    Treat, Neil D. E-mail: t.anthopoulos@imperial.ac.uk; Stingelin, Natalie; Yaacobi-Gross, Nir; Faber, Hendrik; Perumal, Ajay K.; Bradley, Donal D. C.; Anthopoulos, Thomas D. E-mail: t.anthopoulos@imperial.ac.uk

    2015-07-06

    We report the advantageous properties of the inorganic molecular semiconductor copper(I) thiocyanate (CuSCN) for use as a hole collection/transport layer (HTL) in organic photovoltaic (OPV) cells. CuSCN possesses desirable HTL energy levels [i.e., valence band at −5.35 eV, 0.35 eV deeper than poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)], which produces a 17% increase in power conversion efficiency (PCE) relative to PEDOT:PSS-based devices. In addition, a two-fold increase in shunt resistance for the solar cells measured in dark conditions is achieved. Ultimately, CuSCN enables polymer:fullerene based OPV cells to achieve PCE > 8%. CuSCN continues to offer promise as a chemically stable and straightforward replacement for the commonly used PEDOT:PSS.

  2. Damage/organic free ozonated DI water cleaning on EUVL Ru capping layer

    NASA Astrophysics Data System (ADS)

    Lee, Seung-ho; Kang, Bong-kyun; Kim, Hyuk-min; Kim, Min-soo; Cho, Han-ku; Jeon, Chan-uk; Ko, Hyung-ho; Lee, Han-shin; Ahn, Jin-ho; Park, Jin-Goo

    2010-09-01

    The adaption of EUVL requires the development of new cleaning method for the removal of new contaminant without surface damage. One of the harsh contaminants is the carbon contamination generated during EUV exposure. This highly dense organic contaminant is hardly removed by conventional SPM solution on Ru capped Mo/Si multilayer. The hopeful candidate for this removal is ozonated water (DIO3), which is not only well-known strong oxidizer but also environmentally friendly solution. However, this solution might cause some damage to the Ru capping layer mostly depending on its concentration. For these reasons, DIO3 cleaning solutions, which are generated with various additive gases, were characterized to understand the correlation between DIO3 concentration and damages on 2.5 nm thick ruthenium (Ru) surface. An optimized DIO3 generation method and cleaning condition were developed with reduced surface damage. These phenomena were explained by electrochemical reaction.

  3. Ultra-thin fluoropolymer buffer layer as an anode stabilizer of organic light emitting devices

    NASA Astrophysics Data System (ADS)

    Yang, Nam Chul; Lee, Jaeho; Song, Myung-Won; Ahn, Nari; Kim, Mu-Hyun; Lee, Songtaek; Doo Chin, Byung

    2007-08-01

    We have investigated the effect of thin fluoro-acrylic polymer as an anode stabilizer on the lifetime of an organic light emitting device (OLED). Surface chemical properties of commercial fluoropolymer, FC-722 (Fluorad™ of 3M), on indium-tin oxide (ITO) were characterized by x-ray photoemission spectroscopy. An OLED with 1 nm thick fluoropolymeric film showed identical brightness and efficiency behaviour and improved operational stability compared with the reference device with UV-O3 treated ITO. The improvement in the lifetime was accompanied by the suppression of the voltage increase at the initial stage of constant-current driving, which can be attributed to the action of the FC-722 layer by smoothing the ITO surface. Fluoropolymer coating, therefore, improves the lifetime of the small molecular OLED by the simple and reliable anode-stabilizing process.

  4. Simulation of mixed-host emitting layer based organic light emitting diodes

    SciTech Connect

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Tou, T. Y.; Yap, S. S.

    2015-04-24

    ‘SimOLED’ simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq{sub 3}) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq{sub 3} of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  5. Transition Metal-Oxide Free Perovskite Solar Cells Enabled by a New Organic Charge Transport Layer.

    PubMed

    Chang, Sehoon; Han, Ggoch Ddeul; Weis, Jonathan G; Park, Hyoungwon; Hentz, Olivia; Zhao, Zhibo; Swager, Timothy M; Gradečak, Silvija

    2016-04-01

    Various electron and hole transport layers have been used to develop high-efficiency perovskite solar cells. To achieve low-temperature solution processing of perovskite solar cells, organic n-type materials are employed to replace the metal oxide electron transport layer (ETL). Although PCBM (phenyl-C61-butyric acid methyl ester) has been widely used for this application, its morphological instability in films (i.e., aggregation) is detrimental. Herein, we demonstrate the synthesis of a new fullerene derivative (isobenzofulvene-C60-epoxide, IBF-Ep) that serves as an electron transporting material for methylammonium mixed lead halide-based perovskite (CH3NH3PbI3-xClx) solar cells, both in the normal and inverted device configurations. We demonstrate that IBF-Ep has superior morphological stability compared to the conventional acceptor, PCBM. IBF-Ep provides higher photovoltaic device performance as compared to PCBM (6.9% vs 2.5% in the normal and 9.0% vs 5.3% in the inverted device configuration). Moreover, IBF-Ep devices show superior tolerance to high humidity (90%) in air. By reaching power conversion efficiencies up to 9.0% for the inverted devices with IBF-Ep as the ETL, we demonstrate the potential of this new material as an alternative to metal oxides for perovskite solar cells processed in air. PMID:26947400

  6. Exciton-blocking phosphonic acid-treated anode buffer layers for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Zimmerman, Jeramy D.; Song, Byeongseop; Griffith, Olga; Forrest, Stephen R.

    2013-12-01

    We demonstrate significant improvements in power conversion efficiency of bilayer organic photovoltaics by replacing the exciton-quenching MoO3 anode buffer layer with an exciton-blocking benzylphosphonic acid (BPA)-treated MoO3 or NiO layer. We show that the phosphonic acid treatment creates buffers that block up to 70% of excitons without sacrificing the hole extraction efficiency. Compared to untreated MoO3 anode buffers, BPA-treated NiO buffers exhibit a ˜ 25% increase in the near-infrared spectral response in diphenylanilo functionalized squaraine (DPSQ)/C60-based bilayer devices, increasing the power conversion efficiency under 1 sun AM1.5G simulated solar illumination from 4.8 ± 0.2% to 5.4 ± 0.3%. The efficiency can be further increased to 5.9 ± 0.3% by incorporating a highly conductive exciton blocking bathophenanthroline (BPhen):C60 cathode buffer. We find similar increases in efficiency in two other small-molecule photovoltaic systems, indicating the generality of the phosphonic acid-treated buffer approach to enhance exciton blocking.

  7. Atomically-thin molecular layers for electrode modification of organic transistors.

    PubMed

    Gim, Yuseong; Kang, Boseok; Kim, BongSoo; Kim, Sun-Guk; Lee, Joong-Hee; Cho, Kilwon; Ku, Bon-Cheol; Cho, Jeong Ho

    2015-09-01

    Atomically-thin molecular layers of aryl-functionalized graphene oxides (GOs) were used to modify the surface characteristics of source-drain electrodes to improve the performances of organic field-effect transistor (OFET) devices. The GOs were functionalized with various aryl diazonium salts, including 4-nitroaniline, 4-fluoroaniline, or 4-methoxyaniline, to produce several types of GOs with different surface functional groups (NO2-Ph-GO, F-Ph-GO, or CH3O-Ph-GO, respectively). The deposition of aryl-functionalized GOs or their reduced derivatives onto metal electrode surfaces dramatically enhanced the electrical performances of both p-type and n-type OFETs relative to the performances of OFETs prepared without the GO modification layer. Among the functionalized rGOs, CH3O-Ph-rGO yielded the highest hole mobility of 0.55 cm(2) V(-1) s(-1) and electron mobility of 0.17 cm(2) V(-1) s(-1) in p-type and n-type FETs, respectively. Two governing factors: (1) the work function of the modified electrodes and (2) the crystalline microstructures of the benchmark semiconductors grown on the modified electrode surface were systematically investigated to reveal the origin of the performance improvements. Our simple, inexpensive, and scalable electrode modification technique provides a significant step toward optimizing the device performance by engineering the semiconductor-electrode interfaces in OFETs. PMID:26243510

  8. Band offset of vanadium-doped molybdenum oxide hole transport layer in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Chang, Feng-Kuei; Huang, Yi-Chi; Jeng, Jiann-Shing; Chen, Jen-Sue

    2016-08-01

    Solution-processed vanadium-doped molybdenum oxide films (V)MoOx films with mole ratios of Mo:V = 1:0, 1:0.05, 1:0.2, 1:0.5, 0:1, are fabricated as hole transport layer (HTL) in organic photovoltaics with active layer blend comprising poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The device structure is ITO/(V)MoOx/P3HT:PCBM/ZnO NP/Al, and the working area is 0.16 cm2. The result shows that the device using V0.05MoOx HTL has the best performance, including power conversion efficiency of 2.16%, Voc of 0.6 V, Jsc of 6.93 mA/cm2, and FF of 51.9%. Using ultraviolet photoelectron spectroscopy (UPS), we can define the energy levels of valence band edge and Fermi level of (V)MoOx films. UPS analysis indicates that V0.05MoOx has the smallest energy band offset between its valence band edge to the HOMO of P3HT, which is advantageous for hole transporting from P3HT to ITO anode via the V0.05MoOx HTL. In addition, V0.05MoOx film shows the lowest electrical resistivity among all (V)MoOx films, which is further beneficial for hole transportation.

  9. Characterization and nanoindentation testing of thin ZrO 2 films synthesized using layer-by-layer (LbL) deposited organic templates

    NASA Astrophysics Data System (ADS)

    Zlotnikov, I.; Gotman, I.; Gutmanas, E. Y.

    2008-12-01

    Thin organic LbL (layer-by-layer) films with negatively charged surface were used as templates for biomimetic deposition of ZrO 2 on Si wafers by hydrolysis of Zr(SO 4) 2 solution. The as-deposited ceramic layers were fully amorphous and were composed of the mixture of zirconia and zirconium sulfate. During transmission electron microscopy (TEM) examination, the amorphous ZrO 2 crystallized almost instantaneously to tetragonal (t) ZrO 2 under the electron beam. The ≤110 nm thick as-deposited layers were crack-free and adhered well to the LbL surface. Annealing at 500 °C led to complete crystallization of amorphous ZrO 2 to nanocrystalline t-ZrO 2. Further heating to 900 °C resulted in transformation to monoclinic ZrO 2, complete removal of sulfur and twofold shrinkage of the ceramic layer thickness. Both the nanohardness and elastic modulus of the deposited zirconia layers were significantly improved following the heat treatments.

  10. PbBr-Based Layered Perovskite Organic-Inorganic Superlattice Having Carbazole Chromophore; Hole-Mobility and Quantum Mechanical Calculation.

    PubMed

    Era, Masanao; Yasuda, Takeshi; Mori, Kento; Tomotsu, Norio; Kawano, Naoki; Koshimizu, Masanori; Asai, Keisuke

    2016-04-01

    We have successfully evaluated hole mobility in a spin-coated film of a lead-bromide based layered perovskite having carbazole chromophore-linked ammonium molecules as organic layer by using FET measurement. The values of hole mobility, threshold voltage and on/off ratio at room temperature were evaluated.to.be 1.7 x 10(-6) cm2 V-1 s-1, 27 V and 28 V, respectively. However, the spin-coated films on Si substrates were not so uniform compared with those on fused quartz substrates. To improve the film uniformity, we examined the relationship between substrate temperature during spin-coating and film morphology in the layered perovskite spin-coated films. The mean roughness of the spin-coated films on Si substrates was dependent on the substrate temperature. At 353 K, the mean roughness was minimized and the carrier mobility was enhanced by one order of magnitude; the values of hole mobility and threshold voltage were .estimated to be 3.4 x 10(-5) cm2 V-1 s-1, and 22 V at room temperature in a preliminary FET evaluation, respectively. In addition, we determined a crystal structure of the layered perovskite by X-ray diffraction analysis. To gain a better understanding of the observed hole transports, we conducted quantum mechanical calculations using the obtained crystal structure information. The calculated band structure of the layered organic perovskite showed that the valence band is composed of the organic carbazole layer, which confirms that.the measured hole mobility is mainly derived from the organic part of the layered perovskite. Band and hopping transport mechanisms were discussed by calculating the effective masses and transfer integrals for the 2D periodic system of the organic layer in isolation. PMID:27451598

  11. Influence of active layer and support layer surface structures on organic fouling propensity of thin-film composite forward osmosis membranes.

    PubMed

    Lu, Xinglin; Arias Chavez, Laura H; Romero-Vargas Castrillón, Santiago; Ma, Jun; Elimelech, Menachem

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes. PMID:25564877

  12. Layer-by-layer immobilization of quaternized carboxymethyl chitosan/organic rectorite and alginate onto nanofibrous mats and their antibacterial application.

    PubMed

    Jiang, Linbin; Lu, Yuan; Liu, Xingyun; Tu, Hu; Zhang, Jianwei; Shi, Xiaowen; Deng, Hongbing; Du, Yumin

    2015-05-01

    Quaternized carboxymethyl chitosan (QCM-chitosan) and organic rectorite (OREC) immobilized nanofibrous mats are fabricated via layer-by-layer (LBL) technique in a self-assembly manner. The negatively charged cellulose nanofibrous mats hydrolyzed from electrospun cellulose acetate (CEL) mats are alternately modified with the positively charged QCM-chitosan and OREC intercalated composites and the negatively charged sodium alginate (ALG) via LBL technique. The morphology and antibacterial activity of the resultant mats are studied by changing the number of deposition bilayers, the compositions of dipping solutions and outermost layer. X-ray photoelectron spectroscopy results imply that QCM-chitosan and OREC are coated on cellulose mats. Besides, wide angle X-ray diffraction and small angle X-ray diffraction are applied to investigate the crystalline of the composite mats and the interlayer distance of OREC, respectively. The antibacterial activity of the mats increases with the incorporation of OREC into LBL films. PMID:25659718

  13. Highly efficient tandem organic light-emitting devices utilizing the connecting structure based on n-doped electron-transport layer/HATCN/hole-transport layer.

    PubMed

    Wu, Yi-Lin; Chen, Chien-Yu; Huang, Yi-Hsiang; Lu, Yin-Jui; Chou, Cheng-Hsu; Wu, Chung-Chih

    2014-08-01

    In this work, we conducted studies of tandem organic light-emitting devices (OLEDs) based on the connecting structure consisting of n-doped electron-transport layer (n-ETL)/1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN)/hole-transport layer. We investigated effects of different n-ETL materials and different HATCN thicknesses on characteristics of tandem OLEDs. Results show that the tandem OLEDs with n-BPhen and a 20 nm layer of HATCN in the connecting structure exhibited the best performance. With these, highly efficient and bright green phosphorescent two-emitting-unit tandem OLEDs, with drive voltages significantly lower than twice that of the single-unit benchmark device and current efficiencies higher than twice that of the single-unit benchmark device, were demonstrated. PMID:25090347

  14. Layer-by-layer assembly of luminescent ultrathin films by Mg-Al-Eu LDHs nanosheets and organic ligand with high transparency

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjun; Li, Yanlin; Fan, Hongxian

    2016-01-01

    We fabricated a kind of luminescent ordered multilayer transparent ultrathin films (OMTFs) based on inorganic rare earth doped layered double hydroxides (Mg-Al-Eu LDHs) nanosheets and the organic ligand 2-thenoyltrifluoroacetone (TTA) via layer-by-layer assembly method. At the same time, Polyvinyl Alcohol (PVA) aqueous solution was used as intermediate linkers. UV-visible absorption spectroscopy, X-ray diffraction, fluorescence spectroscopy and scanning electron microscopy were introduced to investigate the structure and properties of these films. Surprisingly, the uniformity and the fluorescence emission intensity of OMTFs which utilized polyvinyl Alcohol (PVA) as intermediate linkers are significantly enhanced compared with that of OMTFs without PVA. Herein, it was found that the fluorescence emission intensity of this kind of ultrathin film with PVA displays a monotonic increase as the number of deposition cycles increasing, and further the films which are highly transparent, uniform and ultrathin have potential applications in the optical display devices.

  15. Improving quality of textile wastewater with organic materials as multi soil layering

    NASA Astrophysics Data System (ADS)

    Supriyadi; Widijanto, H.; Pranoto; Dewi, AK

    2016-02-01

    On agricultural land, fresh water is needed especially for irrigation. Alternative ways to fulfill needs of fresh water is by utilizing wastewater from industry. Wastewater that produced in the industry in Surakarta is over flowing especially textile wastewater. Wastewater that produced from industry has many pollutants that affected decreasing fresh water quality for irrigation. Multi Soil Layering (MSL) is one of method that utilize the soil ability as main media by increasing its function of soil structure to purify wastewater, so it does not contaminate the environment and reusable. This research was purposed to know affectivity of organic materials (such as rice straw, baggase, sawdust, coconut fibre, and corncob) and dosage (5%, 10% and 25%) in MSL, also get alternative purification ways with easy and cheaper price as natural adsorbent. This study using field and laboratory experiment. The result shows that MSL can be an alternative method of purification of wastewater. The appropriate composition of organic materials that can be used as adsorbent is MSL with wood sawdust 10% dosage because it can increase pH, decrease the number of Cr, ammonia, and phosphate but less effective to decrease BOD and COD.

  16. Laser-induced microstructuring of two-dimensional layered inorganic-organic perovskites.

    PubMed

    Kanaujia, Pawan K; Vijaya Prakash, G

    2016-04-14

    Non-contact bi-directional micropatterning of two-dimensional (2D) layered inorganic-organic (IO) perovskite [(R-NH3)2PbI4, R = organic moiety] thin films by direct laser writing (DLW) has been reported. These 2D materials are in the form of natural multiple quantum well (MQW) structures and show excitonic luminescence at room temperature because of quantum and dielectric confinement effects. Systematic optical and structural analyses of these laser processed hybrid systems provide an insight into laser-matter interaction and a pathway to develop technology to define complex 2D material based devices with new functionalities. These laser-matter interaction studies reveal several concurrent processes: single photon absorption, material ablation, melting and agglomeration of nanostructures and chemical/physical modifications. This study also provides an insight into chemical and optical changes in laser processed 2D perovskites which subsequently can be recovered by chemical processing. Apart from controllable feature sizes, the prolonged laser exposure results in material agglomeration in the form of nano-pillars at the laser track boundaries. Low-cost micro/nano-scaffolding of IO perovskites may have several important advantages in scalable optoelectronic devices, the realisation of luminescent photonic architectures (photonic crystals and waveguides), and light harvesting elements for IO LEDs and solar cells. PMID:26996747

  17. Soil Surface Organic Layers in Alaska's Arctic Foothills: Development, Distribution and Microclimatic Feedbacks

    NASA Astrophysics Data System (ADS)

    Baughman, C. A.; Mann, D. H.; Verbyla, D.; Valentine, D.; Kunz, M. L.; Heiser, P. A.

    2013-12-01

    Accumulated organic matter at the ground surface plays an important role in arctic ecosystems. These soil surface organic layers (SSOLs) influence temperature, moisture, and chemistry in the underlying mineral soil and, on a global basis, comprise enormous stores of labile carbon. Understanding the dynamics of SSOLs is prerequisite to modeling the responses of arctic ecosystem processes to climate changes. Here, we ask three questions regarding SSOLs in the Arctic Foothills in northern Alaska: 1) What environmental factors control their spatial distribution? 2) How long do they take to form? 3) What is the relationship between SSOL thickness and mineral soil temperature through the growing season? The best topographically-controlled predictors of SSOL thickness and spatial distribution are duration of sunlight during the growing-season, upslope drainage area, slope gradient, and elevation. SSOLs begin to form within several decades following disturbance but require 500-700 years to reach equilibrium states. Once formed, mature SSOLs lower peak growing-season temperature and mean annual temperature in the underlying mineral horizon by 8° and 3° C respectively, which reduces available growing degree days within the upper mineral soil by nearly 80%. How ongoing climate change in northern Alaska will affect the region's SSOLs is an open and potentially crucial question.

  18. Tailoring of energy levels in lead chloride based layered perovskites and energy transfer between the organic and inorganic planes

    NASA Astrophysics Data System (ADS)

    Braun, M.; Tuffentsammer, W.; Wachtel, H.; Wolf, H. C.

    1999-04-01

    Excitonic inter-layer energy transfer is proved in a system consisting of bimolecular layers of organic dyes (benzyl, naphthyl, or anthryl) in lead chloride perovskites. By a systematic variation of the dye molecules we place the inorganic exciton band of lead chloride energetically beneath, above or between the singlet and triplet levels of the dye. Therefore we observe emission from that exciton band, the molecular singlet or triplet level due to energy transfer between the inorganic and organic layers. In the case of the layered perovskite (C 6H 5-CH 2-NH 3) 2PbCl 4 we succeeded in energetically matching the inorganic exciton band with the molecular triplet level.

  19. Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers

    PubMed Central

    Nakanotani, Hajime; Furukawa, Taro; Morimoto, Kei; Adachi, Chihaya

    2016-01-01

    Understanding exciton behavior in organic semiconductor molecules is crucial for the development of organic semiconductor-based excitonic devices such as organic light-emitting diodes and organic solar cells, and the tightly bound electron-hole pair forming an exciton is normally assumed to be localized on an organic semiconducting molecule. We report the observation of long-range coupling of electron-hole pairs in spatially separated electron-donating and electron-accepting molecules across a 10-nanometers-thick spacer layer. We found that the exciton energy can be tuned over 100 megaelectron volts and the fraction of delayed fluorescence can be increased by adjusting the spacer-layer thickness. Furthermore, increasing the spacer-layer thickness produced an organic light-emitting diode with an electroluminescence efficiency nearly eight times higher than that of a device without a spacer layer. Our results demonstrate the first example of a long-range coupled charge-transfer state between electron-donating and electron-accepting molecules in a working device. PMID:26933691

  20. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    PubMed

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere. PMID:27483916

  1. Influence of PEDOT:PSS on the effectiveness of barrier layers prepared by atomic layer deposition in organic light emitting diodes

    SciTech Connect

    Wegler, Barbara; Schmidt, Oliver; Hensel, Bernhard

    2015-01-15

    Organic light emitting diodes (OLEDs) are well suited for energy saving lighting applications, especially when thinking about highly flexible and large area devices. In order to avoid the degradation of the organic components by water and oxygen, OLEDs need to be encapsulated, e.g., by a thin sheet of glass. As the device is then no longer flexible, alternative coatings are required. Atomic layer deposition (ALD) is a very promising approach in this respect. The authors studied OLEDs that were encapsulated by 100 nm Al{sub 2}O{sub 3} deposited by ALD. The authors show that this coating effectively protects the active surface area of the OLEDs from humidity. However, secondary degradation processes still occur at sharp edges of the OLED stack where the extremely thin encapsulation layer does not provide perfect coverage. Particularly, the swelling of poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate), which is a popular choice for the planarization of the bottom electrode and at the same time acts as a hole injection layer, affects the effectiveness of the encapsulation layer.

  2. Storm runoff generation at a steep pre-alpine hillslope - transmissivity feedback or organic layer interflow?

    NASA Astrophysics Data System (ADS)

    Schneider, Philipp; Pool, Sandra; Strouhal, Ludek; Seibert, Jan

    2015-04-01

    This study investigated storm runoff generation processes of a pre-alpine hillslope prone to slide. The experimental pasture plot is located in the northern front range of the Swiss Alps on a 30° steep hillslope. A gleysol overlies weathered marlstone and conglomerate of subalpine molasse. We conducted sprinkling experiments on a subplot with variable rainfall intensities. During both experiments fluorescein line-tracer injections into the topsoil, and sodium chloride (NaCl) injections into the sprinkling water were used to monitor flow velocities in the soil. The observed flow velocities for fluorescein in the soil were 1.2 and 1.4 × 10-3 m s-1. The NaCl breakthrough occurred almost simultaneously in all monitored discharge levels (0.05, 0.25 and 1.0 m depth), indicating a high infiltration capacity and efficient lateral drainage of the soil. These initial observations suggested 'transmissivity feedback' (a form of subsurface stormflow described in Nordic catchments by Allan Rhode in 1987) as the dominant storm runoff generation process. However, excavation of dye-stained soil horizons from a brilliant blue tracer experiment completely changed our perceptions of the prevailing storm flow paths and its runoff generation mechanisms. The results highlighted the dominance of 'organic layer interflow', a form of shallow subsurface stormflow at the hillslope. The dye stained the entire topsoil horizon, vertical soil fractures, and macropores (mostly worm burrows) up to 0.5 m depth. Lateral drainage in the subsoil horizons or at the soil-bedrock interface was not observed; drainage was limited to the organic topsoil. The subsoil with its low permeability acted locally as a soil percolation and bedrock exfiltration barrier, producing significant lateral drainage in the organic topsoil and pronounced pore water pressure changes in the bedrock. Reference Rohde, A.: The origin of streamwater traced by Oxygen-18, 260 pp., Uppsala University., 1987.

  3. Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites with excellent decolorization performance

    SciTech Connect

    Zhou, Junli; Yu, Lin; Sun, Ming; Ye, Fei; Lan, Bang; Diao, Guiqiang; He, Jun

    2013-02-15

    Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled in the presence of CTAB, and subsequently pillared with Keggin ions. The obtained CTAB-Al-MO with the basal spacing of 1.59 nm could be stable at 300 Degree-Sign C for 2 h and also possesses high total pore volumes (0.41 cm Superscript-Three g{sup -1}) and high specific BET surface area (161 m{sup 2} g{sup -1}), which is nine times larger than that of the pristine (19 m{sup 2} g{sup -1}). Possible formation process for the highly thermal stable CTAB-Al-MO is proposed here. The decolorization experiments of methyl orange showed that the obtained CTAB-Al-MO exhibit excellent performance in wastewater treatment and the decolorization rate could reach 95% within 5 min. - Graphical Abstract: Well-ordered organic-inorganic hybrid LMO nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled by CTAB, and subsequently pillared with Keggin ions. Highlights: Black-Right-Pointing-Pointer A two-step synthesis method was used to prepare the CTAB-Al-MO. Black-Right-Pointing-Pointer The CTAB-Al-MO has the large basal spacing and high specific BET surface area. Black-Right-Pointing-Pointer The thermal stability of the well-ordered CTAB-Al-MO could obviously improve. Black-Right-Pointing-Pointer The CTAB-Al-MO exhibits excellent oxidation and absorption ability to remove organic pollutants.

  4. Water soluble poly(1-vinyl-1,2,4-triazole) as novel dielectric layer for organic field effect transistors

    PubMed Central

    Abbas, Mamatimin; Cakmak, Gulbeden; Tekin, Nalan; Kara, Ali; Guney, Hasan Yuksel; Arici, Elif; Sariciftci, Niyazi Serdar

    2011-01-01

    Water soluble poly(1-vinyl-1,2,4-triazole) (PVT) as a novel dielectric layer for organic field effect transistor is studied. Dielectric spectroscopy characterization reveals it has low leakage current and rather high breakdown voltage. Both n-channel and p-channel organic field effect transistors are fabricated using pentacene and fullerene as active layers. Both devices show device performances with lack of hysteresis, very low threshold voltages and high on/off ratios. Excellent film formation property is utilized to make AlOx and thin PVT bilayer in order to decrease the operating voltage of the devices. All solution processed ambipolar device is fabricated with simple spin coating steps using poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH–PPV) end capped with polyhedral oligomeric silsesquioxanes (POSS) as active layer. Our investigations show that PVT can be a very promising dielectric for organic field effect transistors. PMID:23794963

  5. Barrier performance optimization of atomic layer deposited diffusion barriers for organic light emitting diodes using x-ray reflectivity investigations

    SciTech Connect

    Singh, Aarti Schröder, Uwe; Klumbies, Hannes; Müller-Meskamp, Lars; Leo, Karl; Geidel, Marion; Knaut, Martin; Hoßbach, Christoph; Albert, Matthias; Mikolajick, Thomas

    2013-12-02

    The importance of O{sub 3} pulse duration for encapsulation of organic light emitting diodes (OLEDs) with ultra thin inorganic atomic layer deposited Al{sub 2}O{sub 3} layers is demonstrated for deposition temperatures of 50 °C. X-ray reflectivity (XRR) measurements show that O{sub 3} pulse durations longer than 15 s produce dense and thin Al{sub 2}O{sub 3} layers. Correspondingly, black spot growth is not observed in OLEDs encapsulated with such layers during 91 days of aging under ambient conditions. This implies that XRR can be used as a tool for process optimization of OLED encapsulation layers leading to devices with long lifetimes.

  6. Investigation of hole injection enhancement by MoO{sub 3} buffer layer in organic light emitting diodes

    SciTech Connect

    Haitao, Xu; Xiang, Zhou

    2013-12-28

    An MoO{sub 3} buffer layer prepared by thermal evaporation as hole injection layer was investigated in organic light emitting diodes. The MoO{sub 3} film inserted between the anode and hole transport layer decreased the operating voltage and enhanced power efficiency. Introduction of 1 nm MoO{sub 3} film, which was found to be the optimum layer thickness, resulted in 45% increase in efficiency compared with traditional ITO anode. Results from atomic force microscopy and photoemission spectroscopy showed that smooth surface morphology and suitable energy level alignment of ITO/MoO{sub 3} interface facilitated hole injection and transport. The hole injection and transport mechanism at the ITO/MoO{sub 3} interface in thin and thick buffer layers were analyzed.

  7. Inner plexiform layer of jack mackerel retina: participation of amacrine and ganglion cells in its spatial organization.

    PubMed

    Podugolnikova, T A

    1985-01-01

    In the jack mackerel retina (Trachurus mediterraneus ponticus) the inner plexiform layer demonstrates a very high degree of differentiation and contains not less than 25 sublayers. Investigation with Golgi method revealed many varieties of neurons, which are responsible for the structural organization of the inner plexiform layer. There are 8 types of bipolar cells, 24 types of amacrine cells and 7 types of ganglion cells with layered processes. The branching levels of the processes of these neurons were determined. Several varieties of neurons are described for the first time. PMID:3832609

  8. Efficient white phosphorescent organic light-emitting diodes consisting of orange ultrathin and blue mixed host emission layers

    NASA Astrophysics Data System (ADS)

    Sheng, Ren; Zuo, Liangmei; Xue, Kaiwen; Duan, Yu; Chen, Ping; Cheng, Gang; Zhao, Yi

    2016-08-01

    We have successfully demonstrated highly efficient white phosphorescent organic light-emitting diodes (OLEDs) by inserting an ultrathin non-doped orange layer within blue mixed host emission layer. The key feature of the novel device is the employment of blue mixed host and orange ultrathin layers, resulting in an extended recombination region and more balanced charge carrier. The maximum efficiencies of 33.8 lm W‑1 and 32.2 cd A‑1 are obtained. Moreover, the resulting white device achieves a slight efficiency roll-off and a high luminance at low operating voltage. Our versatile concept suggests a promising simple method to achieve high performance white OLEDs.

  9. Atomically-thin molecular layers for electrode modification of organic transistors

    NASA Astrophysics Data System (ADS)

    Gim, Yuseong; Kang, Boseok; Kim, Bongsoo; Kim, Sun-Guk; Lee, Joong-Hee; Cho, Kilwon; Ku, Bon-Cheol; Cho, Jeong Ho

    2015-08-01

    Atomically-thin molecular layers of aryl-functionalized graphene oxides (GOs) were used to modify the surface characteristics of source-drain electrodes to improve the performances of organic field-effect transistor (OFET) devices. The GOs were functionalized with various aryl diazonium salts, including 4-nitroaniline, 4-fluoroaniline, or 4-methoxyaniline, to produce several types of GOs with different surface functional groups (NO2-Ph-GO, F-Ph-GO, or CH3O-Ph-GO, respectively). The deposition of aryl-functionalized GOs or their reduced derivatives onto metal electrode surfaces dramatically enhanced the electrical performances of both p-type and n-type OFETs relative to the performances of OFETs prepared without the GO modification layer. Among the functionalized rGOs, CH3O-Ph-rGO yielded the highest hole mobility of 0.55 cm2 V-1 s-1 and electron mobility of 0.17 cm2 V-1 s-1 in p-type and n-type FETs, respectively. Two governing factors: (1) the work function of the modified electrodes and (2) the crystalline microstructures of the benchmark semiconductors grown on the modified electrode surface were systematically investigated to reveal the origin of the performance improvements. Our simple, inexpensive, and scalable electrode modification technique provides a significant step toward optimizing the device performance by engineering the semiconductor-electrode interfaces in OFETs.Atomically-thin molecular layers of aryl-functionalized graphene oxides (GOs) were used to modify the surface characteristics of source-drain electrodes to improve the performances of organic field-effect transistor (OFET) devices. The GOs were functionalized with various aryl diazonium salts, including 4-nitroaniline, 4-fluoroaniline, or 4-methoxyaniline, to produce several types of GOs with different surface functional groups (NO2-Ph-GO, F-Ph-GO, or CH3O-Ph-GO, respectively). The deposition of aryl-functionalized GOs or their reduced derivatives onto metal electrode surfaces dramatically

  10. Self-organization of local magnetoplasma structures in the upper layers of the solar convection zone

    SciTech Connect

    Chumak, O. V.

    2013-08-15

    Self-organization and evolution of magnetoplasma structures in the upper layers of the solar convection zone are discussed as a process of diffuse aggregation of magnetic flux tubes. Equations describing the tube motion under the action of magnetic interaction forces, hydrodynamic forces, and random forces are written explicitly. The process of aggregation of magnetic flux tubes into magnetic flux clusters of different shapes and dimensions is simulated numerically. The obtained structures are compared with the observed morphological types of sunspot groups. The quantitative comparison with the observational data was performed by comparing the fractal dimensions of the photospheric magnetic structures observed in solar active regions with those of structures obtained in the numerical experiment. The model has the following free parameters: the numbers of magnetic flux tubes with opposite polarities on the considered area element (Nn and Ns), the average radius of the cross section of the magnetic flux tube (a), its effective length (l), the twist factor of the tube field (k), and the absolute value of the average velocity of chaotic tube displacements (d). Variations in these parameters in physically reasonable limits leads to the formation of structures (tube clusters of different morphological types) having different fractal dimensions. Using the NOAA 10488 active region, which appeared and developed into a complicated configuration near the central meridian, as an example, it is shown that good quantitative agreement between the fractal dimensions is achieved at the following parameters of the model: Nn = Ns = 250 ± 50; a = 150 ± 50 km; l ∼ 5000 km, and d = 80 ± 10 m/s. These results do not contradict the observational data and theoretical estimates obtained in the framework of the Parker “spaghetti” model and provide new information on the physical processes resulting in the origin and evolution of local magnetic plasma structures in the near

  11. Dithiapyrannylidenes as efficient hole collection interfacial layers in organic solar cells.

    PubMed

    Berny, Stéphane; Tortech, Ludovic; Véber, Michelle; Fichou, Denis

    2010-11-01

    One inherent limitation to the efficiency of photovoltaic solar cells based on polymer/fullerene bulk heterojunctions (BHJs) is the accumulation of positive charges at the anodic interface. The unsymmetrical charge collection of holes and electrons dramatically decreases the short-circuit current. Interfacial layers (IFLs) such as poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) have no effect on the unbalanced electron/hole transport across the BHJ. We report here on the use of dithiapyrannylidenes (DITPY), a new class of planar quinoid compounds, as efficient hole-transporting/electron-blocking layers in organic solar cells based on poly(3-hexylthiophene)/[6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM) BHJs. Inserting a 15-nm-thick IFL of 4,4'-bis(diphenyl-2,6-thiapyrannylidene) (DITPY-Ph(4)) between the indium-tin oxide electrode and the P3HT:PCBM BHJ prevents detrimental space-charge effects and favors recombination-limited currents. Current-sensing atomic force microscopy reveals a drastic increase of the hole-carrying pathways in DITPY-Ph(4) compared to PEDOT:PSS. In ambient conditions, photovoltaic cells using DITPY-Ph(4) exhibit an 8% increase in the current density, although the conversion efficiency remains slightly lower compared to PEDOT:PSS-based devices. Finally, we present a detailed analysis of the photocurrent generation, showing that DITPY-Ph(4) IFLs induce a transition from unproductive space-charge-limited currents to recombination-limited currents. PMID:21028838

  12. Self-organization of local magnetoplasma structures in the upper layers of the solar convection zone

    NASA Astrophysics Data System (ADS)

    Chumak, O. V.

    2013-08-01

    Self-organization and evolution of magnetoplasma structures in the upper layers of the solar convection zone are discussed as a process of diffuse aggregation of magnetic flux tubes. Equations describing the tube motion under the action of magnetic interaction forces, hydrodynamic forces, and random forces are written explicitly. The process of aggregation of magnetic flux tubes into magnetic flux clusters of different shapes and dimensions is simulated numerically. The obtained structures are compared with the observed morphological types of sunspot groups. The quantitative comparison with the observational data was performed by comparing the fractal dimensions of the photospheric magnetic structures observed in solar active regions with those of structures obtained in the numerical experiment. The model has the following free parameters: the numbers of magnetic flux tubes with opposite polarities on the considered area element ( Nn and Ns), the average radius of the cross section of the magnetic flux tube ( a), its effective length ( l), the twist factor of the tube field ( k), and the absolute value of the average velocity of chaotic tube displacements ( d). Variations in these parameters in physically reasonable limits leads to the formation of structures (tube clusters of different morphological types) having different fractal dimensions. Using the NOAA 10488 active region, which appeared and developed into a complicated configuration near the central meridian, as an example, it is shown that good quantitative agreement between the fractal dimensions is achieved at the following parameters of the model: Nn = Ns = 250 ± 50; a = 150 ± 50 km; l ˜ 5000 km, and d = 80 ± 10 m/s. These results do not contradict the observational data and theoretical estimates obtained in the framework of the Parker "spaghetti" model and provide new information on the physical processes resulting in the origin and evolution of local magnetic plasma structures in the near

  13. Highly enhanced phosphorescent organic light-emitting diodes with cesium fluoride doped electron injection layer

    NASA Astrophysics Data System (ADS)

    Han, Jongseok; Kwon, Yongwon; Sohn, Jiho; Lee, Changhee

    2015-09-01

    We systematically investigate doping effect of cesium fluoride (CsF) on the device performance of organic light-emitting diodes (OLEDs). CsF can be used as a stable n-type dopant due to its low chemical reactivity and simple deposition process. We have observed that CsF could be employed as an effective n-type dopant in thin films of 3,3'-[5'- [3-(3-Pyridinyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bispyridine (TmPyPB) through experimental studies of optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS) with different doping concentration. In addition, we measured bulk resistance using impedance spectroscopy in an electron-only devices (EODs) with CsF-doped TmPyPB. As the doping ratio of the CsF increases, the current densities of EOD increase and the bulk resistances of the CsF-doped layer decrease. Owing to high electrical property of CsF-doped TmPyPB in EIL, green phosphorescent OLEDs showed significantly lower voltage and considerably enhanced efficiency. The device with 30 vol% CsF-doped TmPyPB showed power efficiency of 28.1 lm/W at 1000 cd/m2, whereas the device with pristine TmPyPB exhibited 13.8 lm/W. From these results, CsF-doped TmPyPB as EIL can reduce bulk resistance of EIL and improve the electron-injection and transport properties of electron-transport layer. Therefore, we can utilize CsF as an efficient n-type dopant in EIL of OLEDs.

  14. Acidic precipitation-induced chemical changes in subalpine fir forest organic soil layers

    SciTech Connect

    Hanson, D.W.

    1980-01-01

    The effects of acid precipitation and heavy metal deposition on the surface organic layer of conifer forest soils of New England and Canada were studied. Trends in concentrations of elements across the regional precipitation pH gradient were analyzed. Leaching of Mn, and Ca from subalpine fir forest soil litter increased as precipitation acidity increased. The order of relative susceptibility to increased leaching due to increased precipitation acidity is Mn > Ca > Mg greater than or equal to K greater than or equal to Zn. Sodium and Cd possibly show leaching patterns similar to those of Mg, K, and Zn. Iron and Pb concentrations increased as precipitation acidity increased. The Fe and Pb concentration gradients are partially caused by relative enrichment of Fe and Pb in litter as more mobile cations and compounds are leached. Relative enrichment was greatest at sites receiving precipitation of greater acidity. A large part of the Pb concentration gradient in litter is due to an atmospheric Pb deposition gradient which parallels the regional precipitation-pH gradient. The order of relative accumulation is Pb > Fe. Lead concentrations were highest in soil L and F layers, indicating that Pb accumulation is a recent, continuing phenomenon. Soil litter showed a pH gradient across the sampling transect. Litter generally increased in acidity as precipitation acidity increased. Increased soil litter acidity and increased cation leaching are related; both are caused by acidic precipitation. Cluster analysis of soil litter chemistry data ordered the mountain sites, with one exception, according to their position along the regional precipitation-pH gradient. This implies that precipitation-pH, and associated heavy metal deposition, control soil litter chemistry in subalpine fir forests. 113 references. (MDF)

  15. Layer-by-Layer Assemblies in Nanoporous Templates: Nano-Organized Design and Applications of Soft Nanotechnology

    PubMed Central

    Azzaroni, Omar; Lau, K.H. Aaron

    2011-01-01

    The synergistic combination of layer-by-layer (LbL) assembly and nanoporous membrane templating has greatly facilitated the creation of complex and functional nanotubular structures. The approach takes advantage of both the new properties conferred by assembling diverse LbL building blocks and the tight dimensional control offered by nanotemplating to enable new functionalities that arise from the highly anisotropic “one-dimensional” LbL-nanotube format. In this review, we aim to convey the key developments and provide a current snap-shot of such templated LbL nanoarchitectures. We survey recent developments that have enabled the assembly of polymers, biomolecules and inorganic nanoparticles “à la carte”, via electrostatic, covalent and specific (bio)recognition interactions. We also discuss the emerging mechanistic understanding of the LbL assembly process within the nanopore environment. Finally, we present a diverse range of LbL nanotube “devices” to illustrate the versatility of the nanotemplated LbL toolbox for generating functional soft nanotechnology. PMID:22216060

  16. Growth of lanthanum manganate buffer layers for coated conductors via a metal-organic decomposition process

    NASA Astrophysics Data System (ADS)

    Venkataraman, Kartik

    LaMnO3 (LMO) was identified as a possible buffer material for YBa2Cu3O7-x conductors due to its diffusion barrier properties and close lattice match with YBa2Cu 3O7-x. Growth of LMO films via a metal-organic decomposition (MOD) process on Ni, Ni-5at.%W (Ni-5W), and single crystal SrTiO3 substrates was investigated. Phase-pure LMO was grown via MOD on Ni and SrTiO 3 substrates at temperatures and oxygen pressures within a thermodynamic "process window" wherein LMO, Ni, Ni-5W, and SrTiO3 are all stable components. LMO could not be grown on Ni-5W in the "process window" because tungsten diffused from the substrate into the overlying film, where it reacted to form La and Mn tungstates. The kinetics of tungstate formation and crystallization of phase-pure LMO from the La and Mn acetate precursors are competitive in the temperature range explored (850--1100°C). Temperatures <850°C might mitigate tungsten diffusion from the substrate to the film sufficiently to obviate tungstate formation, but LMO films deposited via MOD require temperatures ≥850°C for nucleation and grain growth. Using a Y2O3 seed layer on Ni-5W to block tungsten from diffusing into the LMO film was explored; however, Y2O3 reacts with tungsten in the "process window" at 850--1100°C. Tungsten diffusion into Y2O3 can be blocked if epitaxial, crack-free NiWO4 and NiO layers are formed at the interface between Ni-5W and Y2O3. NiWO 4 only grows epitaxially if the overlying NiO and buffer layers are thick enough to mechanically suppress (011)-oriented NiWO4 grain growth. This is not the case when a bare 75 nm-thick Y2O3 film on Ni-5W is processed at 850°C. These studies show that the Ni-5W substrate must be at a low temperature to prevent tungsten diffusion, whereas the LMO precursor film must be at elevated temperature to crystallize. An excimer laser-assisted MOD process was used where a Y2O 3-coated Ni-5W substrate was held at 500°C in air and the pulsed laser photo-thermally heated the Y2O3 and LMO

  17. Organic-geochemical investigations on soil layers affected by theTohoku-oki tsunami (March 2011)

    NASA Astrophysics Data System (ADS)

    Reicherter, Klaus; Schwarzbauer, Jan; Jaffe, Bruce; Szczucinski, Witold

    2014-05-01

    Geochemical investigations on tsunami deposits, in particular palaeotsunamites, have mainly focused on inorganic indicators that have been used to distinguish between terrestrial and marine matter in sedimentary archives. Observable tsunami deposits may also be characterised by organic-geochemical parameters reflecting the mixture and unexpected transport of marine and terrestrial matter. The application of organic substances with indicative properties has so far not been used, although the approach of using specific indicators to determine prehistoric, historic and recent processes and impacts (so-called biomarker and anthropogenic marker approach) already exists. In particular, for recent tsunami deposit the analysis of anthropogenic or even xenobiotic compounds as indicators for assessing the impact of tsunamis has been neglected so far. The Tohoku-oki tsunami in March 2011 showed the huge threat that tsunamis, and subsequent flooding of coastal lowlands, pose to society. The mainly sandy deposits of this mega-tsunami reach more than 4.5 km inland as there were run-up heights of ca. 10 m (wave height). The destruction of infrastructure by wave action and flooding is accompanied by the release of environmental pollutants (e.g. fuels, fats, tarmac, plastics, heavy metals, etc.) contaminating the coastal areas and ocean. To characterize this event in the sedimentary deposits, we analyzed several soil archives from the Bay of Sendai area. Soil layers representing the tsunami deposits have been contrasted with unaffected pre-tsunami samples by means of organic-geochemical analyses based on GC/MS. Natural compounds and their diagenetic transformation products have been tested as marker compounds for monitoring this recent tsunami. The relative composition of fatty acids, n-alkanes, sesquiterpenes and further substances pointed to significant variations before and after the tsunami event. Additionally, anthropogenic marker compounds (such as soil derived pesticides

  18. Charge transport in organic multi-layer devices under electric and optical fields

    NASA Astrophysics Data System (ADS)

    Park, June Hyoung

    2007-12-01

    Charge transport in small organic molecules and conjugated conducting polymers under electric or optical fields is studied by using field effect transistors and photo-voltaic cells with multiple thin layers. With these devices, current under electric field, photo-current under optical field, and luminescence of optical materials are measured to characterize organic and polymeric materials. For electric transport studies, poly(3,4-ethylenedioxythiophene) doped by polystyrenesulfonic acid is used, which is conductive with conductivity of approximately 25 S/cm. Despite their high conductance, field effect transistors based on the films are successfully built and characterized by monitoring modulations of drain current by gate voltage and IV characteristic curves. Due to very thin insulating layers of poly(vinylphenol), the transistors are relative fast under small gate voltage variation although heavy ions are involved in charge transport. In IV characteristic curves, saturation effects can be observed. Analysis using conventional field effect transistor model indicates high mobility of charge carriers, 10 cm2/V·sec, which is not consistent with the mobility of the conducting polymer. It is proposed that the effect of a small density of ions injected via polymer dielectric upon application of gate voltage and the ion compensation of key hopping sites accounts for the operation of the field effect transistors. For the studies of transport under optical field, photovoltaic cells with 3 different dendrons, which are efficient to harvest photo-excited electrons, are used. These dendrons consist of two electron-donors (tetraphenylporphyrin) and one electron-accepter (naphthalenediimide). Steady-state fluorescence measurements show that inter-molecular interaction is dominant in solid dendron film, although intra-molecular interaction is still present. Intra-molecular interaction is suggested by different fluorescence lifetimes between solutions of donor and dendrons. This

  19. Advances in Plexcore active layer technology systems for organic photovoltaics: roof-top and accelerated lifetime analysis of high performance organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Laird, Darin W.; Vaidya, Swanand; Li, Sergey; Mathai, Mathew; Woodworth, Brian; Sheina, Elena; Williams, Shawn; Hammond, Troy

    2007-09-01

    We report NREL-certified efficiencies and initial lifetime data for organic photovoltaic (OPV) cells based on Plexcore PV photoactive layer and Plexcore HTL-OPV hole transport layer technology. Plexcore PV-F3, a photoactive layer OPV ink, was certified in a single-layer OPV cell at the National Renewable Energy Laboratory (NREL) at 5.4%, which represents the highest official mark for a single-layer organic solar cell. We have fabricated and measured P3HT:PCBM solar cells with a peak efficiency of 4.4% and typical efficiencies of 3 - 4% (internal, NREL-calibrated measurement) with P3HT manufactured at Plextronics by the Grignard Metathesis (GRIM) method. Outdoor and accelerated lifetime testing of these devices is reported. Both Plexcore PV-F3 and P3HT:PCBM-based OPV cells exhibit >750 hours of outdoor roof-top, non-accelerated lifetime with less than 8% loss in initial efficiency for both active layer systems when exposed continuously to the climate of Western Pennsylvania. These devices are continuously being tested to date. Accelerated testing using a high-intensity (1000W) metal-halide lamp affords shorter lifetimes; however, the true acceleration factor is still to be determined.

  20. Secondary organic aerosol formation of relevance to the marine boundary layer

    NASA Astrophysics Data System (ADS)

    Cai, Xuyi

    The chlorine atom (Cl) is a potential oxidant of volatile organic compounds (VOCs) in the atmosphere and is hypothesized to lead to secondary organic aerosol (SOA) formation in coastal areas. The purpose of this dissertation is to test this hypothesis and quantify the SOA formation potentials of some representative biogenic and anthropogenic hydrocarbons when oxidized by Cl in laboratory chamber experiments. The chosen model compounds for biogenic and anthropogenic hydrocarbons in this study are three monoterpenes (alpha-pinene, beta-pinene, and d-limonene) and two aromatics (m-xylene and toluene), respectively. Results indicate that the oxidation of these monoterpenes and aromatics generates significant amounts of aerosol. The SOA yields of alpha-pinene, beta-pinene, and d-limonene obtained in this study are comparable to those when they are oxidized by ozone, by nitrate radical, and in photooxidation scenarios. For aerosol mass up to 30.0 mug m-3, their yields reach approximately 0.20, 0.20, and 0.30, respectively. The SOA yields for m-xylene and toluene are found to be in the range of 0.035 to 0.12 for aerosol concentrations up to 19 mug m-3. For d-limonene and toluene, data indicate two yield curves that depend on the initial concentration ratios of Cl precursor to hydrocarbon hydrocarbon. Zero-dimensional calculations based on these yields show that SOA formation from the five model compounds when oxidized by Cl in the marine boundary layer could be a significant source of SOA in the early morning. In addition, the mechanistic reaction pathways for Cl oxidation of alpha-pinene, beta-pinene, d-limonene, and toluene with Cl have been developed within the framework of the Caltech Atmospheric Chemistry Mechanisms (CACM). Output from the developed mechanisms is combined with an absorptive partitioning model to predict precursor decay curves and time-dependent SOA concentrations in experiments. Model calculations are able to match (in general within general +/- 50

  1. Toward a single-layer two-dimensional honeycomb supramolecular organic framework in water.

    PubMed

    Zhang, Kang-Da; Tian, Jia; Hanifi, David; Zhang, Yuebiao; Sue, Andrew Chi-Hau; Zhou, Tian-You; Zhang, Lei; Zhao, Xin; Liu, Yi; Li, Zhan-Ting

    2013-11-27

    The self-assembly of well-defined 2D supramolecular polymers in solution has been a challenge in supramolecular chemistry. We have designed and synthesized a rigid stacking-forbidden 1,3,5-triphenylbenzene compound that bears three 4,4'-bipyridin-1-ium (BP) units on the peripheral benzene rings. Three hydrophilic bis(2-hydroxyethyl)carbamoyl groups are introduced to the central benzene ring to suppress 1D stacking of the triangular backbone and to ensure solubility in water. Mixing the triangular preorganized molecule with cucurbit[8]uril (CB[8]) in a 2:3 molar ratio in water leads to the formation of the first solution-phase single-layer 2D supramolecular organic framework, which is stabilized by the strong complexation of CB[8] with two BP units of adjacent molecules. The periodic honeycomb 2D framework has been characterized by various (1)H NMR spectroscopy, dynamic light scattering, X-ray diffraction and scattering, scanning probe and electron microscope techniques and by comparing with the self-assembled structures of the control systems. PMID:24079461

  2. Highly efficient low color temperature organic LED using blend carrier modulation layer

    NASA Astrophysics Data System (ADS)

    Hsieh, Yao-Ching; Chen, Szu-Hao; Shen, Shih-Ming; Wang, Ching-Chiun; Chen, Chien-Chih; Jou, Jwo-Huei

    2012-10-01

    Color temperature (CT) of light has great effect on human physiology and psychology, and low CT light, minimizing melatonin suppression and decreasing the risk of breast, colorectal, and prostate cancer. We demonstrates the incorporation of a blend carrier modulation interlayer (CML) between emissive layers to improve the device performance of low CT organic light emitting diodes, which exhibits an external quantum efficiency of 22.7% and 36 lm W-1 (54 cd A-1) with 1880 K at 100 cd m-2, or 20.8% and 29 lm W-1 (50 cd A-1) with 1940 K at 1000 cd m-2. The result shows a CT much lower than that of incandescent bulbs, which is 2500 K with 15 lmW-1 efficiency, and even as low as that of candles, which is 2000 K with 0.1 lmW-1. The high efficiency of the proposed device may be attributed to its CML, which helps effectively distribute the entering carriers into the available recombination zones.

  3. Physico-chemical properties of organically modified silicates' sol-gel layers for optical fibre sensors

    NASA Astrophysics Data System (ADS)

    Chodkowska, Eliza; Rayss, Jan

    2006-10-01

    The paper concerns the investigation of modified silica gel materials applied in optical fibre sensors. These materials are products of a sol-gel process in which three kinds of alkoxysilanes undergo hydrolysis and condensation and may play a role of the matrices containing transducer's molecules in the active layer of the sensor. In the experiment presented below three different compositions comprising tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PhTES) were used. The alkoxysilanes underwent hydrolysis and condensation and the obtained gels were investigated in order to determine their texture, strucuture, composition and chemical properties as far as the dependence of those characteristics on the hydrolysis time and the molar ratio of the ingredients in the initial sols. The methods employed in the experiment were: Atomic Force Microscopy (AFM) which delivered vital information about the gels' textures, contact angles' and surface charge's measurements serving to estimate chemical properties of the gels' surfaces, Nuclear Magnetic Resonance (NMR) which helped to evaluate the hydrolysis' rate and porosimetric measurements enabling a determination of BET surface area and average diametres of the pores. The results may occur important for improving the construction of optical fibre sensors in which organically modified silicates (ORMOSILs)-TEOS layes are used.

  4. Self-Doping, O2-Stable, n-Type Interfacial Layer for Organic Electronics

    SciTech Connect

    Reilly, T. H. III; Hains, A. W.; Chen, H. Y.; Gregg, B. A.

    2012-04-01

    Solid films of a water-soluble dicationic perylene diimide salt, perylene bis(2-ethyltrimethylammonium hydroxide imide), Petma{sup +}OH{sup -}, are strongly doped n-type by dehydration and reversibly de-doped by hydration. The hydrated films consist almost entirely of the neutral perylene diimide, PDI, while the dehydrated films contain {approx}50% PDI anions. The conductivity increases by five orders of magnitude upon dehydration, probably limited by film roughness, while the work function decreases by 0.74 V, consistent with an n-type doping density increase of {approx}12 orders of magnitude. Remarkably, the PDI anions are stable in dry air up to 120 C. The work function of the doped film, {phi} (3.96 V vs. vacuum), is unusually negative for an O{sub 2}-stable contact. Petma{sup +} OH{sup -} is also characterized as an interfacial layer, IFL, in two different types of organic photovoltaic cells. Results are comparable to state of the art cesium carbonate IFLs, but may improve if film morphology can be better controlled. The films are stable and reversible over many months in air and light. The mechanism of this unusual self-doping process may involve the change in relative potentials of the ions in the film caused by their deshielding and compaction as water is removed, leading to charge transfer when dry.

  5. Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

    SciTech Connect

    Liu, Guohong; Liu, Yong; Li, Baojun; Zhou, Xiang

    2015-06-07

    We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphthyl]-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takes parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.

  6. Electron transport mechanism of bathocuproine exciton blocking layer in organic photovoltaics.

    PubMed

    Lee, Jeihyun; Park, Soohyung; Lee, Younjoo; Kim, Hyein; Shin, Dongguen; Jeong, Junkyeong; Jeong, Kwangho; Cho, Sang Wan; Lee, Hyunbok; Yi, Yeonjin

    2016-02-21

    Efficient exciton management is a key issue to improve the power conversion efficiency of organic photovoltaics (OPVs). It is well known that the insertion of an exciton blocking layer (ExBL) having a large band gap promotes the efficient dissociation of photogenerated excitons at the donor-acceptor interface. However, the large band gap induces an energy barrier which disrupts the charge transport. Therefore, building an adequate strategy based on the knowledge of the true charge transport mechanism is necessary. In this study, the true electron transport mechanism of a bathocuproine (BCP) ExBL in OPVs is comprehensively investigated by in situ ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, density functional theory calculation, and impedance spectroscopy. The chemical interaction between deposited Al and BCP induces new states within the band gap of BCP, so that electrons can transport through these new energy levels. Localized trap states are also formed upon the Al-BCP interaction. The activation energy of these traps is estimated with temperature-dependent conductance measurements to be 0.20 eV. The Al-BCP interaction induces both transport and trap levels in the energy gap of BCP and their interplay results in the electron transport observed. PMID:26821701

  7. Iodine oxide in the global marine boundary layer: inorganic versus organic sources

    NASA Astrophysics Data System (ADS)

    Prados-Roman, Cristina; Cuevas, Carlos; Mahajan, Anoop; Fernandez, Rafael; Saiz-Lopez, Alfonso

    2014-05-01

    In the last decades iodine has been object of increasing interest in atmospheric chemistry due to its link to the oxidizing capacity of the atmosphere, the NOx and HOx partitioning and the formation of ultra-fine particles. Recently laboratory and numerous fieldwork efforts have been carried out trying to assess the sources and sinks of reactive iodine in the open marine environment. Within the framework of the Malaspina expedition, in 2010-2011 the Spanish research vessel Hesperides circumnavigated the world aiming at investigating the biogeochemistry, physical oceanography and microbiological biodiversity of the oceans from a multidisciplinary approach. During that 7-months campaign throughout the Atlantic, Indian and Pacific oceans, a MAX-DOAS system was deployed, along with a surface ozone instrument, in order to monitor the geographical distribution of relevant reactive iodine compounds such IO. Complementing this extensive dataset with results from previous works in the Eastern Pacific Ocean, we show not only the ubiquity of iodine oxide in the open marine boundary layer (MBL) ranging between 0.3-1 pptv levels, but also provide what is- to our knowledge- the most comprehensive global map of the of IO and O3 distribution in the subpolar MBL. Ultimately, by means of a photochemical model, we will address the contribution of inorganic and organic iodine sources to the measured levels of IO.

  8. "Supersaturated" self-assembled charge-selective interfacial layers for organic solar cells.

    PubMed

    Song, Charles Kiseok; Luck, Kyle A; Zhou, Nanjia; Zeng, Li; Heitzer, Henry M; Manley, Eric F; Goldman, Samuel; Chen, Lin X; Ratner, Mark A; Bedzyk, Michael J; Chang, Robert P H; Hersam, Mark C; Marks, Tobin J

    2014-12-24

    To achieve densely packed charge-selective organosilane-based interfacial layers (IFLs) on the tin-doped indium oxide (ITO) anodes of organic photovoltaic (OPV) cells, a series of Ar2N-(CH2)n-SiCl3 precursors with Ar = 3,4-difluorophenyl, n = 3, 6, 10, and 18, was synthesized, characterized, and chemisorbed on OPV anodes to serve as IFLs. To minimize lateral nonbonded -NAr2···Ar2N- repulsions which likely limit IFL packing densities in the resulting self-assembled monolayers (SAMs), precursor mixtures having both small and large n values are simultaneously deposited. These "heterogeneous" SAMs are characterized by a battery of techniques: contact angle measurements, X-ray reflectivity, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), cyclic voltammetry, and DFT computation. It is found that the headgroup densities of these "supersaturated" heterogeneous SAMs (SHSAMs) are enhanced by as much as 17% versus their homogeneous counterparts. Supersaturation significantly modifies the IFL properties including the work function (as much as 16%) and areal dipole moment (as much as 49%). Bulk-heterojunction OPV devices are fabricated with these SHSAMs: ITO/IFL/poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][2-[[(2-ethylhexyl)oxy]carbonyl]-3-fluorothieno[3,4-b]thiophenediyl

  9. Composite organic-inorganic butterfly scales: production of photonic structures with atomic layer deposition.

    PubMed

    Gaillot, Davy P; Deparis, Olivier; Welch, Victoria; Wagner, Brent K; Vigneron, Jean Pol; Summers, Christopher J

    2008-09-01

    Recent advances in the photonics and optics industries have produced great demand for ever more sophisticated optical devices, such as photonic crystals. However, photonic crystals are notoriously difficult to manufacture. Increasingly, therefore, researchers have turned towards naturally occurring photonic structures for inspiration and a wide variety of elaborate techniques have been attempted to copy and harness biological processes to manufacture artificial photonic structures. Here, we describe a simple, direct process for producing an artificial photonic device by using a naturally occurring structure from the wings of the butterfly Papilio blumei as a template and low-temperature atomic layer deposition of TiO2 to create a faithful cast of the structure. The optical properties of the organic-inorganic diffraction structures produced are assessed by normal-incidence specular reflectance and found to be well described by multilayer computation method using a two-dimensional photonic crystal model. Depending on the structural integrity of the initially sealed scale, it was found possible not only to replicate the outer but also the inner and more complex surfaces of the structure, each resulting in distinct multicolor optical behavior as revealed by experimental and theoretical data. In this paper, we also explore tailoring the process to design composite skeleton architectures with desired optical properties and integrated multifunctional (mechanical, thermal, optical, fluidic) properties. PMID:18851080

  10. Modeling the impacts of organic layer depth on forest stand recovery from disturbance in the North American boreal forest

    NASA Astrophysics Data System (ADS)

    Trugman, A. T.; Medvigy, D.; Fenton, N.; Bergeron, Y.

    2014-12-01

    The boreal forest contains over 30 percent of Earth's terrestrial carbon, stored mainly as organic matter in soils. Warming temperatures have decreased the fire return interval at many locations, potentially opening more boreal forest space to early-successional deciduous species. However, previous observational studies have shown that the residual forest organic layer depth after a fire can be directly related to fire severity and that this organic layer depth plays a critical role in determining post-fire secondary succession in the North American boreal forest. In this study, we use a numerical model constrained by field data to evaluate: (1) the extent to which the organic layer inhibits deciduous seedling establishment; (2) whether differences in seedling establishment after mild and severe burns affect mature forest structure and composition on decadal to century time scales. Our modeling experiments were carried out with the Ecosystem Demography model version 2 (ED2) terrestrial biosphere model. ED2 is designed to explicitly track the growth and mortality of individual trees, which compete for light, water, and nutrients using an open nitrogen cycle. Our simulations feature parameterizations for aspen and black spruce species-types as well as a new dynamic soil organic layer module with species-specific litter decay rates. The updated boreal forest model is validated using several datasets across the North American boreal forest that range from daily carbon and energy fluxes to multi-century basal area chronosequences including: (1) sub-daily to monthly eddy covariance measurements taken in Delta Junction, Alaska and Manitoba, Canada; (2) decade-long forest inventory data from the Cooperative Alaska Forest Inventory taken throughout the Alaskan boreal forest; and (3) multi-century basal area chronosequences measured in Manitoba and Quebec. We then use the model to identify the controls that the soil organic layer exerts on secondary succession between aspen

  11. Atomic/molecular layer deposition: a direct gas-phase route to crystalline metal-organic framework thin films.

    PubMed

    Ahvenniemi, E; Karppinen, M

    2016-01-21

    Atomic/molecular layer deposition offers us an elegant way of fabricating crystalline copper(ii)terephthalate metal-organic framework (MOF) thin films on various substrate surfaces. The films are grown from two gaseous precursors with a digital atomic/molecular level control for the film thickness under relatively mild conditions in a simple and fast one-step process. PMID:26612265

  12. Broadband absorption enhancement in organic solar cells with an antenna layer through surface-plasmon mediated energy transfer

    NASA Astrophysics Data System (ADS)

    Jin, Yu; Feng, Jing; Zhang, Xu-Lin; Xu, Ming; Chen, Qi-Dai; Wu, Zhi-Jun; Sun, Hong-Bo

    2015-06-01

    We demonstrated a strategy to realize broadband enhanced absorption in the top-incident inverted organic solar cells (OSCs) by employing an external antenna layer on top of the periodic corrugated metallic anode. Surface-plasmon polaritons (SPPs) are excited on the opposite interfaces of the periodic corrugated metallic anode, which mediate the energy transfer from the antenna layer to the active layer through the anode. The absorption of the OSCs is significantly broadened and enhanced by tuning the SPP resonance to coincide with both the emission of the antenna and the absorption of the active material. The power conversion efficiency exhibits an enhancement of 16% compared to that of the OSCs without the antenna layer.

  13. Effect of Ti seed layers on structure of self-organized epitaxial face-centered-cubic-Ag(001) oriented nanodots

    SciTech Connect

    Kamiko, M.; Nose, K.; Suenaga, R.; Kyuno, K.; Koo, J.-W.; Ha, J.-G.

    2013-12-28

    The influence of Ti seed layers on the structure of self-organized Ag nanodots, obtained with a Ti seed-layer-assisted thermal agglomeration method, has been investigated. The samples were grown on MgO(001) single crystal substrates by RF magnetron sputter deposition. The samples were deposited at room temperature and post-annealed at 350 °C for 4 h while maintaining the chamber vacuum conditions. The results of atomic force microscopy (AFM) observations indicated that the insertion of the Ti seed layer (0.6–5.0 nm) between the MgO substrate and Ag layer promotes the agglomeration process, forming the nanodot array. Comparisons between the AFM images revealed that the size of the Ag nanodots was increased with an increase in the Ti seed layer thickness. The atomic concentration of the film surface was confirmed by X-ray photoelectron spectroscopy (XPS). The XPS result suggested that the nanodot surface mainly consisted of Ag. Moreover, X-ray diffraction results proved that the initial deposition of the Ti seed layer (0.6–5.0 nm) onto MgO(001) prior to the Ag deposition yielded high-quality fcc-Ag(001) oriented epitaxial nanodots. The optical absorbance spectra of the fabricated Ag nanodots with various Ti seed layer thicknesses were obtained in the visible light range.

  14. Improvement of on/off ratio in organic field-effect transistor with carrier generation layer using oblique deposition

    NASA Astrophysics Data System (ADS)

    Tamura, Hidetsugu; Minagawa, Masahiro; Baba, Akira; Shinbo, Kazunari; Kato, Keizo; Kaneko, Futao

    2016-02-01

    Improvement of the on/off ratio in carrier-generation type organic field-effect transistors with pentacene and MoO3 layers was attempted using oblique deposition. A MoO3 layer was formed only between the gold (Au) source and the drain electrodes, and devices with a MoO3 layer evaporated under various deposition angles were fabricated. A formation of a MoO3-free area is expected adjacent to the source or drain electrode by the oblique deposition. The off-current in the device decreased and the on/off ratio was increased with increasing deposition angle, and we achieved a fabricating device with a MoO3 layer having high on/off ratio, almost the same as that of the device without the MoO3 layer. From those results, we deduced that charge-transfer (CT) complexes at the pentacene/MoO3 interface formed a high-conductive path for the off-current, and the off-current was reduced by the formation of a highly-resistive MoO3-free area between electrodes. Therefore, controlling the CT complex layer formation by patterning the MoO3 layer can reduce the amount of off-current and improve the on/off ratio.

  15. Ordered conducting polymer multilayer films and its application for hole injection layers in organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Xu, Jianhua; Yang, Yajie; Yu, Junsheng; Jiang, Yadong

    2009-01-01

    We reported a controlled architecture growth of layer-ordered multilayer film of poly(3,4-ethylene dioxythiophene) (PEDOT) via a modified Langmuir-Blodgett (LB) method. An in situ polymerization of 3,4-ethylene dioxythiophene (EDOT) monomer in multilayer LB film occurred for the formation of ordered conducting polymer embedded multilayer film. The well-distribution of conducting polymer particles was characterized by secondary-ion mass spectrometry (SIMS). The conducting film consisting of ordered PEDOT ultrathin layers was investigated as a hole injection layer for organic light-emitting diodes (OLEDs). The results showed that, compared to conventional spin-coating PEDOT film and electrostatic self-assembly (ESA) film, the improved performance of OLEDs was obtained after using ordered PEDOT LB film as hole injection layer. It also indicated that well-ordered structure of hole injection layer was attributed to the improvement of OLED performance, leading to the increase of charged carrier mobility in hole injection layer and the recombination rate of electrons and holes in the electroluminescent layer.

  16. Study of Electrical Conduction Mechanism of Organic Double-Layer Diode Using Electric Field Induced Optical Second Harmonic Generation Measurement.

    PubMed

    Nishi, Shohei; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2016-04-01

    By using electric field induced optical second harmonic generation (EFISHG) and current voltage (I-V) measurements, we studied the electrical transport mechanism of organic double-layer diodes with a structure of Au/N, N'-di-[(1-naphthyl)-N, N'-diphenyl]-(1,1'-biphenyl)-4,4'-diamine (a-NPD)/poly(methyl methacrylate) (PMMA)/indium zinc oxide (IZO). Here the α-NPD is a carrier transport layer and the PMMA is an electrical insulating layer. The current level was very low, but the I-V characteristics showed a rectifying behavior. The EFISHG measurement selectively and directly probed the electric field across the α-NPD layer, and showed that the electric field across the a-NPD layer is completely relaxed owing to the charge accumulation at the a-NPD/PMMA interface in the region V > 0, whereas the carrier accumulation was not significant in the region V < 0. On the basis of these experimental results, we proposed a model of the rectification. Further, by coupling the I-V characteristics with the EFISHG measurement, the I-V characteristics of the diodes were well converted into the current-electric field (I-E) characteristics of the α-NPD layer and the PMMA layer. The I-E characteristics suggested the Schottky-type conduction governs the carrier transport. We conclude that the I-V measurement coupled with the EFISHG measurement is very useful to study carrier transport mechanism of the organic double-layer diodes. PMID:27451633

  17. Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific

    NASA Astrophysics Data System (ADS)

    Omori, Yuko; Hama, Takeo; Ishii, Masao; Saito, Shu

    2010-06-01

    Spatial and temporal distributions of marine humic-like fluorescent dissolved organic matter (FDOMM) were determined in the subtropical western North Pacific to evaluate the controlling factors of FDOMM behaviors. The observations were conducted at 4 stations (15-30°N) along 137°E in a subtropical area between January 2006 and April 2007. The florescence intensity of FDOMM was low (0.14-0.25 quinine sulfate units (QSU)) in the surface layer probably due to photodegradation, and increased with depth (0.90-1.10 QSU at 1000 m), irrespective of season and station. In the surface layer, the thickness of the water mass with low fluorescence intensity (<0.3 QSU) showed the seasonal change by being deeper in winter and shallower in summer, depending on the mixed layer depth (MLD). The average fluorescence intensity within the mixed layer also varied seasonally at midlatitudes; the intensity in summer was 40.8-53.8% of that in winter. Since the MLD was very much shallower in summer than in winter, FDOMM in the mixed layer would be kept within a shallow depth during the summer where intensive photodegradation could occur. The concentration of total organic carbon (TOC) was at its maximum at the water surface and decreased with depth, being adverse to FDOMM. Thus, the ratio of fluorescence intensity to TOC concentration was lowest (0.002-0.003) in surface water, which implies that FDOMM is not quantitatively important to the dissolved organic carbon pool. However, considering the possible difference in the stabilities of FDOMM against photochemical and microbial degradation, it is conceivable that photobleached FDOMM is one of the important organic groups constituting marine dissolved organic matter.

  18. Electronic structure of a dual-layered organic charge transfer salt

    NASA Astrophysics Data System (ADS)

    Jeschke, Harald; Altmeyer, Michaela; Valenti, Roser

    2015-03-01

    We examine the electronic properties of polymorphs of (BEDT-TTF)2Ag(CF3)4(TCE) (1,1,2-trichloroethane) within density functional theory (DFT). While a phase with low superconducting transition temperature Tc = 2 . 6 K exhibits a κ packing motif, two high Tc phases are layered structures consisting of α' and κ packed layers. We determine the electronic structures and discuss the influence of the insulating α' layer on the conducting κ layer. We find that the stripes of high and low charge in the α' layer correspond to a stripe pattern of hopping parameters in the κ layer. This finding is the basis for studying the effect of the different underlying Hamiltonians on the superconducting properties. Research funded within DFG Transregio 49.

  19. Highly Photoactive Titanyl Phthalocyanine Polymorphs as Textured Donor Layers in Organic Solar Cells

    SciTech Connect

    Placencia, Diogenes; Wang, Weining; Gantz, Jeremy; Jenkins, Judith L.; Armstrong, Neal R.

    2011-09-29

    We present a comparison of the photovoltaic activity of organic solar cells (OPVs) based on vacuum-deposited and solvent-annealed titanyl phthalocyanine (TiOPc) donor layers with C₆₀ as the electron acceptor, where the TiOPc donor layer exists in three different polymorphic forms: TiOPc included the “as-deposited” form, with a Q-band absorbance spectrum reminiscent of the phase I polymorph, and films subjected to solvent annealing which systematically increased the fraction of either the phase II (α-phase) or the phase III (γ-TiOPc) polymorphs. As-deposited TiOPc/C₆₀ heterojunctions showed open-circuit photopotentials (V{sub OC}) of ca. 0.65 V, with estimated AM 1.5G efficiencies of ca. 1.4%. Partial conversion of these thin films to their phase II or phase III polymorphs significantly enhanced the short-circuit photocurrent (J{sub SC}), as a result of (i) texturing of the TiOPc layers (ca. 100 nm length scales) and (ii) enhancements in near-IR absorptivity/photoelectrical activity. All TiOPc/C₆₀ heterojunctions, characterized by UV–photoelectron spectroscopy (UPS), showed that estimated E{sub HOMO}{sup Pc} – E{sub LUMO}{sup C60} energy differences, which set the upper limit for VOC, are nearly identical for each TiOPc polymorph. Incident and absorbed photon current efficiency measurements (IPCE, APCE) are consistent with previous studies that showed a majority of the photoactivity in these higher order polymorphs deriving from excitonic states created at λ{sub max} ≈ 680 and 844 nm for both the phase II and the phase III polymorphs. The near-IR absorbance features (844 nm) in these Pc polymorphs are believed to have substantial charge-transfer (CT) character, leading to enhanced probabilities for photoinduced electron transfer (PIET). APCE measurements of TiOPc/C₆₀ OPVs, however, show that higher photocurrent yields per absorbed photon arise from the higher energy (680 nm) excitonic state. When C₇₀ is used as the electron acceptor

  20. Stitching 2D polymeric layers into flexible interpenetrated metal-organic frameworks within single crystals.

    PubMed

    Zhang, Zi-Xuan; Ding, Ni-Ni; Zhang, Wen-Hua; Chen, Jin-Xiang; Young, David J; Hor, T S Andy

    2014-04-25

    A 2D coordination polymer prepared with bulky diethylformamide solvates exhibits channels which allow dipyridyl bridging ligands to diffuse into the crystal lattice. The absorbed dipyridyls thread through the pores of one layer and substitute the surface diethylformamide molecules on the neighboring layers to stitch alternate layers to form flexible interpenetrated metal-orgaic frameworks. The threading process also results in exchange of the bulky diethylformamide solvates for aqua to minimize congestion and, more strikingly, forces the slippage of two-dimensional layers, while still maintaining crystallinity. PMID:24692130

  1. Rare earth and zinc layered hydroxide salts intercalated with the 2-aminobenzoate anion as organic luminescent sensitizer

    SciTech Connect

    Cursino, Ana Cristina Trindade; Rives, Vicente; Trujillano, Raquel

    2015-10-15

    Rare earth (RE = Eu, Y and Tb) and zinc layered hydroxide salts intercalated with nitrate anions were synthesized, followed by exchange with 2-aminobenzoate. The UV absorption ability was improved after intercalation/grafting in relation to that shown by the parent material. - Highlights: • Rare earth (RE = Eu, Y and Tb) and zinc layered hydroxide were synthesized. • Intercalated nitrate anions were exchanged by 2-aminobenzoate. • In all the 2-aminobenzoate containing compounds, the grafting reaction was detected. • The UV absorption ability was improved after the exchange reactions. • Rare earth hydroxide salts are potential matrixes to produce luminescent materials. - Abstract: Rare earth (RE = Eu, Y and Tb) and zinc layered hydroxide salts intercalated with nitrate anions were synthesized, followed by exchange with 2-aminobenzoate. The obtained compounds were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and ultraviolet visible (UV–vis) spectroscopies, fluorescence measurements and thermal analysis (TGA/DTA). The results from FTIR spectroscopy suggest a direct coordination of 2-aminobenzoate to the metal cations of the inorganic layered structure. The organic derivative products from the intercalation reactions absorb a broader range of UV-light in relation to that shown by the parent material; the photoluminescence measurements present a strong violet, blue and green luminescence under UV-light excitation for layered compounds with, Zn, Y and Tb, respectively. Rare earth hydroxide salts (RE-LHS) are potential alternative matrices for the immobilization of organic species to produce luminescent materials.

  2. Highly efficient, solution processed electrofluorescent small molecule white organic light-emitting diodes with a hybrid electron injection layer.

    PubMed

    Jiang, Zhixiong; Zhong, Zhiming; Xue, Shanfeng; Zhou, Yan; Meng, Yanhong; Hu, Zhanhao; Ai, Na; Wang, Jianbin; Wang, Lei; Peng, Junbiao; Ma, Yuguang; Pei, Jian; Wang, Jian; Cao, Yong

    2014-06-11

    Highly efficient, solution-processed, and all fluorescent white organic light-emitting diodes (WOLEDs) based on fluorescent small molecules have been achieved by incorporating a low-conductivity hole injection layer and an inorganic-organic hybrid electron injection layer. The light-emission layer is created by doping a fluorescent π-conjugated blue dendrimer host (the zeroth generation dendrimer, G0) with a yellow-emitting fluorescent dopant oligo(paraphenylenevinylene) derivative CN-DPASDB with a doping ratio of 100:0.15 (G0:CN-DPASDB) by weight. To suppress excessive holes, the high-conductivity hole injection layer (PEDOT:PSS AI 4083) is replaced by the low-conductivity PEDOT:PSS CH 8000. To facilitate the electron injection, a hybrid electron injection layer is introduced by doping a methanol/water-soluble conjugated polymer poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFNR2) with solution-processed cesium fluoride (CsF). The device achieves a maximum luminous efficiency of 17.0 cd A(-1) and a peak power efficiency of 15.6 lm W(-1) at (0.32, 0.37) with a color rendering index of 64. PMID:24840940

  3. Enhancement of current injection in organic light emitting diodes with sputter treated molybdenum oxides as hole injection layers

    NASA Astrophysics Data System (ADS)

    Wang, Po-Sheng; Wu, I.-Wen; Tseng, Wei-Hsuan; Chen, Mei-Hsin; Wu, Chih-I.

    2011-04-01

    The enhancement of current density and luminance in organic light emitting diodes is achieved by treating molybdenum oxide (MoO3) hole-injection-layers with slight argon ion sputtering. The sputter treated MoO3 layers provide improvement in current injection efficiency, resulting in better current density which is about ten times higher than that of the reference devices. Photoemission spectroscopy shows that molybdenum in MoO3 is reduced to lower oxidation states after sputter treatment due to the removal of oxygen. As a result, gap states are formed to enhance metallic characteristics of the sputter treated MoO3 surface and facilitate better hole injection efficiency.

  4. Synthesis, structure and photoluminescent behavior of a novel pillar-layered {Zn3}-based metal-organic framework

    NASA Astrophysics Data System (ADS)

    Song, Xue-Zhi; Mu, Wen-Sheng; Han, Bing-Yan; Yan, Yang

    2016-09-01

    A novel 3D metal-organic framework (MOF) {[Zn3(bpdc)3 (p-4-bpmb)](DMF)2}n ( 1) (H2bpdc=biphenyl-4,4‧-dicarboxylic acid; p-4-bpmb=1,4-bis(pyridine-4-ylmethoxy)benzene) has been solvothermally synthesized and structurally characterized. Compound 1 exhibits a 3D pillar-layered framework based on the trinuclear {Zn3} building blocks, consisting of Zn-dicarboxylate layers and bipyridyl-derivative pillars. Furthermore, it features three-fold interpenetrating 8-connected hex-type topology. In addition, its thermal stability and luminescent property have also been investigated.

  5. High efficient white organic light-emitting diodes with single emissive layer using phosphorescent red, green, and blue dopants

    NASA Astrophysics Data System (ADS)

    Kim, You-Hyun; Wai Cheah, Kok; Young Kim, Woo

    2013-07-01

    Phosphorescent white organic light-emitting diodes (PHWOLEDs) with single emissive layer were fabricated by co-doping phosphorescent blue, green, and red emitters with different concentrations. WOLEDs using Ir(piq)3 and Ir(ppy)3 as red and green dopants along with 8% of Firpic as blue dopant with host materials of 4CzPBP in the emissive layer were compared under various doping ratio between Ir(piq)3 and Ir(ppy)3. Triplet-triplet Dexter energy transfer in single emissive PHWOLEDs including three primary colors was saturated from higher triplet energy levels to lower triplet energy levels directly.

  6. Effects of Link Annotations on Search Performance in Layered and Unlayered Hierarchically Organized Information Spaces.

    ERIC Educational Resources Information Center

    Fraser, Landon; Locatis, Craig

    2001-01-01

    Investigated the effects of link annotations on high school user search performance in Web hypertext environments having deep (layered) and shallow link structures. Results confirmed previous research that shallow link structures are better than deep (layered) link structures, and also showed that annotations had virtually no effect on search…

  7. High reliable and stable organic field-effect transistor nonvolatile memory with a poly(4-vinyl phenol) charge trapping layer based on a pn-heterojunction active layer

    NASA Astrophysics Data System (ADS)

    Xiang, Lanyi; Ying, Jun; Han, Jinhua; Zhang, Letian; Wang, Wei

    2016-04-01

    In this letter, we demonstrate a high reliable and stable organic field-effect transistor (OFET) based nonvolatile memory (NVM) with a polymer poly(4-vinyl phenol) (PVP) as the charge trapping layer. In the unipolar OFETs, the inreversible shifts of the turn-on voltage (Von) and severe degradation of the memory window (ΔVon) at programming (P) and erasing (E) voltages, respectively, block their application in NVMs. The obstacle is overcome by using a pn-heterojunction as the active layer in the OFET memory, which supplied a holes and electrons accumulating channel at the supplied P and E voltages, respectively. Both holes and electrons transferring from the channels to PVP layer and overwriting the trapped charges with an opposite polarity result in the reliable bidirectional shifts of Von at P and E voltages, respectively. The heterojunction OFET exhibits excellent nonvolatile memory characteristics, with a large ΔVon of 8.5 V, desired reading (R) voltage at 0 V, reliable P/R/E/R dynamic endurance over 100 cycles and a long retention time over 10 years.

  8. Noncontact Temperature Measurements of Organic Layers in an Organic Light-Emitting Diode Using Wavenumber-Temperature Relations of Raman Bands

    NASA Astrophysics Data System (ADS)

    Sugiyama, Takuro; Furukawa, Yukio

    2008-05-01

    We have measured the temperatures of the organic layers in operating organic light-emitting diodes (OLEDs) by Raman spectroscopy. The wavenumbers of the Raman bands due to N,N'-di-naphthaleyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD) and copper phthalocyanine (CuPc) have been measured as a function of temperature in the range of 25-191 °C. The observed positions of strong bands around 1607 cm-1 (NPD) and 1531 cm-1 (CuPc) shifted downward linearly with increasing temperature in the ranges lower than 92 and 191 °C, respectively. We have determined the temperatures of the NPD and CuPc layers in an operating OLED from the wavenumber-temperature relations of these bands.

  9. Multifunctional colloids with optical, magnetic, and superhydrophobic properties derived from nucleophilic substitution-induced layer-by-layer assembly in organic media.

    PubMed

    Yoon, Miseon; Kim, Younghoon; Cho, Jinhan

    2011-07-26

    We demonstrate the successful preparation of multifunctional silica colloids by coating with 2-bromo-2-methylpropionic acid (BMPA)-stabilized quantum dots (BMPA-QDs) and BMPA-stabilized iron oxide particles (BMPA-Fe(3)O(4)), along with amine-functionalized poly(amidoamine) (PAMA) dendrimers, using layer-by-layer (LbL) assembly based on a nucleophilic substitution (NS) reaction between the bromo and amine groups in organic media. The QDs and Fe(3)O(4) nanoparticles used in this study were directly synthesized in a nonpolar solvent (chloroform or toluene), and the oleic acid stabilizers were exchanged with BMPA in the same solvent to minimize chemical and physical damage to the nanoparticles. The direct adsorption of nanoparticles via an NS reaction in organic solvent significantly increased the packing density of the nanoparticles in the lateral dimensions because electrostatic repulsion between neighboring nanoparticles was absent. The multifunctional colloids densely coated with nanoparticles showed excellent characteristics (i.e., superparamagnetism, photoluminescence, and magneto-optical tuning properties) with long-term stability in nonpolar solvents. Furthermore, deposition of the nanocomposite colloids onto flat substrates, followed by coating with a low-surface-energy fluoroalkylsilane polymer, produced a densely packed rugged surface morphology in the colloidal films that displayed superhydrophobic properties with water contact angles greater than 150°. PMID:21688776

  10. Implications of fire-mediated changes in larch forest structure on leaf litter inputs, organic layer accumulation, and permafrost dynamics

    NASA Astrophysics Data System (ADS)

    Ganzlin, P.; Alexander, H. D.; Petronio, B.; Natali, S.; Davydov, S.

    2012-12-01

    The boreal forest is an expansive biome and stores the majority of the world's above and belowground carbon stocks. These forests are very vulnerable to changes in global climate. As climate warms and dries, boreal forest ecosystems are expected to experience greater fire activity. An increase in fire activity will likely lead to greater consumption of the soil organic layer (SOL), the thick layer of undecomposed mosses and other plant materials lying above the mineral soil. Because the SOL serves as a natural barrier to seed germination, a reduction in SOL depth could increase tree seedling establishment during post-fire succession. This could ultimately lead to stands of greater density, with potentially cascading effects on belowground carbon dynamics due to density-driven changes in understory microenvironment and leaf litter inputs, especially in forests dominated by deciduous species. In permafrost-affected regions, organic soil materials - especially mosses - are important insulators of permafrost and the high content of thermally protected carbon it contains. In order to assess the importance of fire-mediated changes in stand density on permafrost dynamics, we surveyed forests of Cajander Larch (Larix cajander) surrounding the Northeast Science Station in far northeastern Siberia. Two sets of low and high-density stands were selected to establish a natural density gradient in these forests. In each stand we evaluated stand density effects on aboveground biomass, leaf litter inputs, moss abundance, organic layer depth, and permafrost thaw depth. Here we show that the low-density larch stands had significantly higher moss abundance, green moss depth, and organic layer depth. The insulating organic layer was nearly 25% shallower in high-density stands, which was accompanied by a nearly 50% increase in depth of seasonal permafrost thaw. In addition to density, stand biomass and landscape position may also be very important factors in determining litter inputs

  11. Numerical simulation of top-emitting organic light-emitting diodes with electron and hole blocking layers

    NASA Astrophysics Data System (ADS)

    Chang, Shu-Hsuan; Yang, Cheng-Hong

    2007-09-01

    The few reported high-contrast organic light-emitting diodes (OLEDs) all deal with bottom-emitting OLEDs and may not be readily adapted for top-emitting OLEDs (TOLEDs), which have a few technical merits over bottom-emitting devices for high-performance active-matrix OLED displays (AMOLEDs). The thin-film transistors on the back-plane of an AM substrate reduce the aperture ratio of a pixel that decreases the display brightness. A TOLED, which can provide a more flexible pixel design on an opaque AM substrate, represents a promising technique for achieving a high aperture-ratio AMOLED. In this work, the characteristics of TOLEDs with α-NPD and LiF blocking layers are numerically investigated with the APSYS simulation program. The α-NPD layer is used as an electron blocking layer, while the LiF layer is used as a hole blocking layer. The TOLED structure used in this study is based on a real device fabricated in lab by Yang et al. (Appl. Phys. Lett. 87, 143507, 2005). The simulation results indicate that when the TOLED device is with either α-NPD or LiF blocking layer, the luminance efficiency and radiative recombination rate at the same drive voltage can be markedly improved. The TOLED with α-NPD blocking layer has the best performance when the position of light emission is located at the anti-node of the standing wave due to micro-cavity effect. The TOLED with LiF blocking layer has improved performance because the LUMO of Alq 3 can be lowered by band bending, which leads to better carrier balance and thus increased radiative recombination rate.

  12. Outer organic layer and internal repair mechanism protects pteropod Limacina helicina from ocean acidification

    NASA Astrophysics Data System (ADS)

    Peck, Victoria L.; Tarling, Geraint A.; Manno, Clara; Harper, Elizabeth M.; Tynan, Eithne

    2016-05-01

    Scarred shells of polar pteropod Limacina helicina collected from the Greenland Sea in June 2012 reveal a history of damage, most likely failed predation, in earlier life stages. Evidence of shell fracture and subsequent re-growth is commonly observed in specimens recovered from the sub-Arctic and further afield. However, at one site within sea-ice on the Greenland shelf, shells that had been subject to mechanical damage were also found to exhibit considerable dissolution. It was evident that shell dissolution was localised to areas where the organic, periostracal sheet that covers the outer shell had been damaged at some earlier stage during the animal's life. Where the periostracum remained intact, the shell appeared pristine with no sign of dissolution. Specimens which appeared to be pristine following collection were incubated for four days. Scarring of shells that received periostracal damage during collection only became evident in specimens that were incubated in waters undersaturated with respect to aragonite, ΩAr≤1. While the waters from which the damaged specimens were collected at the Greenland Sea sea-ice margin were not ΩAr≤1, the water column did exhibit the lowest ΩAr values observed in the Greenland and Barents Seas, and was likely to have approached ΩAr≤1 during the winter months. We demonstrate that L. helicina shells are only susceptible to dissolution where both the periostracum has been breached and the aragonite beneath the breach is exposed to waters of ΩAr≤1. Exposure of multiple layers of aragonite in areas of deep dissolution indicate that, as with many molluscs, L. helicina is able to patch up dissolution damage to the shell by secreting additional aragonite internally and maintain their shell. We conclude that, unless breached, the periostracum provides an effective shield for pteropod shells against dissolution in waters ΩAr≤1, and when dissolution does occur the animal has an effective means of self-repair. We suggest

  13. A low-temperature processed environment-friendly full-organic carrier collection layer for polymer solar cells

    SciTech Connect

    Shi, Ai-Li; Li, Yan-Qing E-mail: zhangdd@suda.edu.cn Jiang, Xiao-Chen; Ma, Zhong-Sheng; Wang, Qian-Kun; Guo, Zhen-Yu; Zhang, Dan-Dan E-mail: zhangdd@suda.edu.cn Lee, Shuit-Tong; Tang, Jian-Xin E-mail: zhangdd@suda.edu.cn

    2014-08-04

    We constructed a concept of the full-organic carrier collection layer (CCL) used for polymer solar cells. The CCL is composed of dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile as hole collection layer (HCL) and chlorine-free solvents (formic acid (FA)) processed 4,7-Diphenyl-1,10-phenanthroline (Bphen) as electron collection layer, exhibiting good solubility, and environmental protection. The FA based device shows ideal power conversion efficiency (3.75%), which is higher than that of control device (3.6%). Besides, the HCL shows a different mechanism in hole extraction by functioning as a charge recombination zone for electrons injected from anode and holes extracted from the donor materials.

  14. Moisture exposure to different layers in organic light-emitting diodes and the effect on electroluminescence characteristics

    SciTech Connect

    Liao, L. S.; Tang, C. W.

    2008-08-15

    Moisture effect on electroluminescence characteristics, including current density versus voltage, luminance versus voltage, luminous efficiency versus current density, dark spot formation, and operational stability of organic light-emitting diodes, has been systematically investigated by exposing each layer of the devices to moisture at room temperature. Moisture has a different effect on each of the interfaces or surfaces, and the influence increases as exposure time increases. There is a slight effect on the electroluminescence characteristics after the anode surface has been exposed to moisture. However, severe luminance decrease, dark spot formation, and operational stability degradation take place after the light-emitting layer or the electron-transporting layer is exposed to moisture. It is also demonstrated that the effect of moisture can be substantially reduced if the exposure to moisture is in a dark environment.

  15. A low-temperature processed environment-friendly full-organic carrier collection layer for polymer solar cells

    NASA Astrophysics Data System (ADS)

    Shi, Ai-Li; Li, Yan-Qing; Jiang, Xiao-Chen; Ma, Zhong-Sheng; Wang, Qian-Kun; Guo, Zhen-Yu; Zhang, Dan-Dan; Lee, Shuit-Tong; Tang, Jian-Xin

    2014-08-01

    We constructed a concept of the full-organic carrier collection layer (CCL) used for polymer solar cells. The CCL is composed of dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile as hole collection layer (HCL) and chlorine-free solvents (formic acid (FA)) processed 4,7-Diphenyl-1,10-phenanthroline (Bphen) as electron collection layer, exhibiting good solubility, and environmental protection. The FA based device shows ideal power conversion efficiency (3.75%), which is higher than that of control device (3.6%). Besides, the HCL shows a different mechanism in hole extraction by functioning as a charge recombination zone for electrons injected from anode and holes extracted from the donor materials.

  16. Improved color stability of white organic light-emitting diodes without interlayer between red, orange and blue emission layers

    NASA Astrophysics Data System (ADS)

    Xue, Kaiwen; Chen, Ping; Duan, Yu; Sheng, Ren; Han, Guangguang; Zhao, Yi

    2016-03-01

    We demonstrated color stability improved white phosphorescent organic light-emitting diodes (WOLEDs) based on red, orange and blue emission layers. Iridium(III) Bis(3,5-diflouro)-2-(2-pyridyl)phenyl-(2-carboxypyridyl) was doped into red emission layer (R-EML) and orange emission layer (O-EML) to lower the electrons injection barrier and facilitate the ambipolar charge carriers balance. Consequently, the recombination region was extended to the R-EML and O-EML, leading to the excellently stable spectra and the reduction of triplet-triplet annihilation. Then the resulting device with a negligible Commission International de L'Eclairage coordinates shift of (0.003, 0.007) within a wide luminance range as well as a high color rendering index of 90 was gained, which was comparable to the profit caused by the conventional method of introducing the interlayer. And the emission mechanism of the WOLEDs was also discussed.

  17. Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean margin benthic nepheloid layer

    SciTech Connect

    Guo, L. Santschi, P.H.

    2000-02-01

    Average {sup 14}C ages of dissolved organic carbon (DOC) in the ocean are 3--6,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC), which is chemically very similar to that of bulk DOC, can be effectively isolated from seawater using cross-flow ultrafiltration, it can hold clues to sources and pathways of DOC turnover in the ocean. Radiocarbon measurements on COC in the water column and benthic nepheloid layer (BNL) from two continental margin areas (the Middle Atlantic Bight and the Gulf of Mexico) and controlled laboratory experiments were carried out to study sources of old DOC in the ocean margin areas. Vertical distributions of suspended particulate matter (SPM), particulate organic carbon (POC), nitrogen (PON), and DOC in the water column and bottom waters near the sediment-water interface all demonstrate a well developed benthic nepheloid layer in both ocean margin areas. COC from the BNL was much older than COC from the overlying water column. These results, together with strong concentration gradients of SPM, POC, PON, and DOC, suggest a sedimentary source for organic carbon species and possibly for old COC as well in BNL waters. This is confirmed by the results from controlled laboratory experiments. The heterogeneity of {Delta}{sup 14}C signatures in bulk SOC thus points to a preferential release of old organic components from sediment resuspension, which can be the transport mechanism of the old benthic COC observed in ocean margin areas. Old COC from continental margin nepheloid layers may thus be a potential source of old DOC to the deep ocean.

  18. Organic solar cells with graphene electrodes and vapor printed poly(3,4-ethylenedioxythiophene) as the hole transporting layers.

    PubMed

    Park, Hyesung; Howden, Rachel M; Barr, Miles C; Bulović, Vladimir; Gleason, Karen; Kong, Jing

    2012-07-24

    For the successful integration of graphene as a transparent conducting electrode in organic solar cells, proper energy level alignment at the interface between the graphene and the adjacent organic layer is critical. The role of a hole transporting layer (HTL) thus becomes more significant due to the generally lower work function of graphene compared to ITO. A commonly used HTL material with ITO anodes is poly(3,4-ethylenedioxythiophene) (PEDOT) with poly(styrenesulfonate) (PSS) as the solid-state dopant. However, graphene's hydrophobic surface renders uniform coverage of PEDOT:PSS (aqueous solution) by spin-casting very challenging. Here, we introduce a novel, yet simple, vapor printing method for creating patterned HTL PEDOT layers directly onto the graphene surface. Vapor printing represents the implementation of shadow masking in combination with oxidative chemical vapor deposition (oCVD). The oCVD method was developed for the formation of blanket (i.e., unpatterened) layers of pure PEDOT (i.e., no PSS) with systematically variable work function. In the unmasked regions, vapor printing produces complete, uniform, smooth layers of pure PEDOT over graphene. Graphene electrodes were synthesized under low-pressure chemical vapor deposition (LPCVD) using a copper catalyst. The use of another electron donor material, tetraphenyldibenzoperiflanthene, instead of copper phthalocyanine in the organic solar cells also improves the power conversion efficiency. With the vapor printed HTL, the devices using graphene electrodes yield comparable performances to the ITO reference devices (η(p,LPCVD) = 3.01%, and η(p,ITO) = 3.20%). PMID:22724887

  19. Chemically Compatible Sacrificial Layer-Assisted Lift-Off Patterning Method for Fabrication of Organic Light-Emitting Displays

    NASA Astrophysics Data System (ADS)

    Choi, Wonsuk; Kim, Min-Hoi; Lee, Sin-Doo

    2011-08-01

    We developed a generic platform to pattern combinatorial functional layers composed of different classes of organic materials using a repetitive lift-off method based on a chemically compatible sacrificial layer (SL) for organic light-emitting diodes (OLEDs). The essential features come from the chemically compatible SL of a fluorous-polymer that can be generated by laser-inscription or transfer-printing. The precise registration of lateral patterns of different materials was achieved on a single substrate through a series of SL-assisted lift-off processes. The chemical compatibility of the SL and the stability of the light-emitting characteristics were shown in a fluorous-solvent treated monochrome OLEDs.

  20. Controlled surface oxidation of multi-layered graphene anode to increase hole injection efficiency in organic electronic devices

    NASA Astrophysics Data System (ADS)

    Han, Tae-Hee; Kwon, Sung-Joo; Seo, Hong-Kyu; Lee, Tae-Woo

    2016-03-01

    Ultraviolet ozone (UVO) surface treatment of graphene changes its sp2-hybridized carbons to sp3-bonded carbons, and introduces oxygen-containing components. Oxidized graphene has a finite energy band gap, so UVO modification of the surface of a four-layered graphene anode increases its surface ionization potential up to ∼5.2 eV and improves the hole injection efficiency (η) in organic electronic devices by reducing the energy barrier between the graphene anode and overlying organic layers. By controlling the conditions of the UVO treatment, the electrical properties of the graphene can be tuned to improve η. This controlled surface modification of the graphene will provide a way to achieve efficient and stable flexible displays and solid-state lighting.

  1. Polyethylenimine Interfacial Layers in Inverted Organic Photovoltaic Devices: Effects of Ethoxylation and Molecular Weight on Efficiency and Temporal Stability.

    PubMed

    Courtright, Brett A E; Jenekhe, Samson A

    2015-12-01

    We report a comparative study of polyethylenimine (PEI) and ethoxylated-polyethylenimine (PEIE) cathode buffer layers in high performance inverted organic photovoltaic devices. The work function of the indium-tin oxide (ITO)/zinc oxide (ZnO) cathode was reduced substantially (Δφ = 0.73-1.09 eV) as the molecular weight of PEI was varied from 800 g mol(-1) to 750 000 g mol(-1) compared with the observed much smaller reduction when using a PEIE thin film (Δφ = 0.56 eV). The reference inverted polymer solar cells based on the small band gap polymer PBDTT-FTTE (ITO/ZnO/PBDTT-FTTE:PC70BM/MoO3/Ag), without a cathode buffer layer, had an average power conversion efficiency (PCE) of 6.06 ± 0.22%. Incorporation of a PEIE cathode buffer layer in the same PBDTT-FTTE:PC70BM blend devices gave an enhanced performance with a PCE of 7.37 ± 0.53%. In contrast, an even greater photovoltaic efficiency with a PCE of 8.22 ± 0.10% was obtained in similar PBDTT-FTTE:PC70BM blend solar cells containing a PEI cathode buffer layer. The temporal stability of the inverted polymer solar cells was found to increase with increasing molecular weight of the cathode buffer layer. The results show that PEI is superior to PEIE as a cathode buffer layer in high performance organic photovoltaic devices and that the highest molecular weight PEI interlayer provides the highest temporal stability. PMID:26550983

  2. The preparation of a Eu3+-doped ZnO bi-functional layer and its application in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wu, Na; Luo, Qun; Qiao, Xvsheng; Ma, Chang-Qi

    2015-12-01

    Recently, spectra conversion has been used to minimize energy loss in photovoltaic devices. In this work, we explore the development of a novel Eu3+-doped ZnO bi-functional layer for use in organic solar cells. The bi-functional layer acts as both a spectra conversion and an electron transporting layer. Compared to conventional spectra conversion layers, it has a simpler device structure, is easier to fabricate, and has a wider spectrum-sensitized region. A series of Eu3+-doped ZnO nanocrystals were synthesized using the simple solution route. X-ray powder diffraction patterns (XRD), transmission electron microscopy (TEM), and UV-visible absorbance spectra were used to characterize the obtained ZnO nanocrystals. The results reveal that the size and bandgap of ZnO nanocrystals can be controlled through regulation of the doping concentration of Eu3+ ions. The energy transfer of ZnO → Eu3+ is observed by photoluminescence (PL) spectra. At a bandgap excitation of around 300-400 nm, a typical emission band from the Eu3+ is obtained. By employing the Eu3+- doped ZnO nanocrystals as a buffer layer in a P3HT:PC61BM bulk heterojunction device, the obtained performance is similar to the undoped ZnO device, indicating that the electrical properties of ZnO are not affected by Eu3+ doping. Due to the down-conversion energy transfer between ZnO and Eu3+, the external quantum efficiency of the ZnO:Eu3+ device at 300-400 nm is higher than that of the pure ZnO device, which subsequently leads to an increase in short circuit current density (J SC). This work proves that it is possible to improve the solar spectrum response in the ultraviolet region of organic solar cells effectively by incorporating the bi-functional layer.

  3. Critical CuI buffer layer surface density for organic molecular crystal orientation change

    SciTech Connect

    Ahn, Kwangseok; Kim, Jong Beom; Lee, Dong Ryeol; Kim, Hyo Jung; Lee, Hyun Hwi

    2015-01-21

    We have determined the critical surface density of the CuI buffer layer inserted to change the preferred orientation of copper phthalocyanine (CuPc) crystals grown on the buffer layer. X-ray reflectivity measurements were performed to obtain the density profiles of the buffer layers and out-of-plane and 2D grazing-incidence X-ray diffraction measurements were performed to determine the preferred orientations of the molecular crystals. Remarkably, it was found that the preferred orientation of the CuPc film is completely changed from edge-on (1 0 0) to face-on (1 1 −2) by a CuI buffer layer with a very low surface density, so low that a large proportion of the substrate surface is bare.

  4. Surface-Engineered Graphene Quantum Dots Incorporated into Polymer Layers for High Performance Organic Photovoltaics

    PubMed Central

    Kim, Jung Kyu; Kim, Sang Jin; Park, Myung Jin; Bae, Sukang; Cho, Sung-Pyo; Du, Qing Guo; Wang, Dong Hwan; Park, Jong Hyeok; Hong, Byung Hee

    2015-01-01

    Graphene quantum dots (GQDs), a newly emerging 0-dimensional graphene based material, have been widely exploited in optoelectronic devices due to their tunable optical and electronic properties depending on their functional groups. Moreover, the dispersibility of GQDs in common solvents depending on hydrophobicity or hydrophilicity can be controlled by chemical functionalization, which is particularly important for homogeneous incorporation into various polymer layers. Here we report that a surface-engineered GQD-incorporated polymer photovoltaic device shows enhanced power conversion efficiency (PCE), where the oxygen-related functionalization of GQDs enabled good dispersity in a PEDOT:PSS hole extraction layer, leading to significantly improved short circuit current density (Jsc) value. To maximize the PCE of the device, hydrophobic GQDs that are hydrothermally reduced (rGQD) were additionally incorporated in a bulk-heterojunction layer, which is found to promote a synergistic effect with the GQD-incorporated hole extraction layer. PMID:26392211

  5. Crystal Organic Light-Emitting Diodes with Perfectly Oriented Non-Doped Pt-Based Emitting Layer.

    PubMed

    Kim, Kwon-Hyeon; Liao, Jia-Ling; Lee, Si Woo; Sim, Bomi; Moon, Chang-Ki; Lee, Gene-Hsiang; Kim, Hyo Jung; Chi, Yun; Kim, Jang-Joo

    2016-04-01

    Organic light-emitting diodes with external quantum efficiency of 38.8% are realized using a Pt-based thin-film emitting layer with photoluminescence quantum yield of 96% and transition dipole ratio of 93%. The emitting dipole orientation of the thin films fabricated using Pt complexes is investigated and the structural relationship between X-ray structural analysis and the structures in thin films are discussed based on quantum chemical calculations. PMID:26833629

  6. Few-Layer MoS2-Organic Thin-Film Hybrid Complementary Inverter Pixel Fabricated on a Glass Substrate.

    PubMed

    Lee, Hee Sung; Shin, Jae Min; Jeon, Pyo Jin; Lee, Junyeong; Kim, Jin Sung; Hwang, Hyun Chul; Park, Eunyoung; Yoon, Woojin; Ju, Sang-Yong; Im, Seongil

    2015-05-13

    Few-layer MoS2-organic thin-film hybrid complementary inverters demonstrate a great deal of device performance with a decent voltage gain of ≈12, a few hundred pW power consumption, and 480 Hz switching speed. As fabricated on glass, this hybrid CMOS inverter operates as a light-detecting pixel as well, using a thin MoS2 channel. PMID:25641643

  7. 'Maximum' entropy production in self-organized plasma boundary layer: A thermodynamic discussion about turbulent heat transport

    SciTech Connect

    Yoshida, Z.; Mahajan, S. M.

    2008-03-15

    A thermodynamic model of a plasma boundary layer, characterized by enhanced temperature contrasts and ''maximum entropy production,'' is proposed. The system shows bifurcation if the heat flux entering through the inner boundary exceeds a critical value. The state with a larger temperature contrast (larger entropy production) sustains a self-organized flow. An inverse cascade of energy is proposed as the underlying physical mechanism for the realization of such a heat engine.

  8. Manipulating the dipole layer of polar organic molecules on metal surfaces via different charge-transfer channels

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Wang, Chin-Yung; Pi, Tun-Wen; Ishii, Hisao; Tang, S.-J.

    The key properties of organic films such as energy level alignment (ELA), work functions, and injection barriers are closely linked to this dipole layer. Using angle resolved photoemission spectroscopy (ARPES), we systemically investigate the coverage-dependent work functions and spectra line shapes of occupied molecular orbital states of a polar molecule, chloroaluminium phthalocyanine (ClAlPc), grown on Ag(111) to show that the orientations of the first ClAlPc layer can be manipulated via the molecule deposition rate and post annealing, causing ELA at organic-metal interface to differ for about 0.3 eV between Cl-up and Cl-down configuration. Moreover, by comparing the experimental results with the calculations based on both gas-phase model and realistic model of ClAlPc on Ag(111) , we evidence that the different orientations of ClAlPc dipole layers lead to different charge-transfer channels between ClAlPc and Ag, a key factor that controls the ELA at organic-metal interface.

  9. Efficiency enhancement of solution-processed inverted organic solar cells with a carbon-nanotube-doped active layer

    NASA Astrophysics Data System (ADS)

    Lin, Wen-Kai; Su, Shui-Hsiang; Yeh, Meng-Cheng; Huang, Yang-Chan; Yokoyama, Meiso

    2016-01-01

    Solution-processed titanium-doped ZnO (TZO) is synthesized by the sol-gel method to be the electron-transporting layer (ETL) in an inverted organic solar cell (IOSC). Carbon nanotubes (CNTs) are doped into an active layer of poly(3-hexylthiophene):[6,6]-phenyl C 61 butyric acid methyl ester (P3HT:PCBM). The addition of CNTs in the P3HT:PCBM composite increases the conjugation length of P3HT:PCBM:CNTs, which simultaneously enhances the capacity of the composite to absorb solar energy radiation. Vanadium oxide (V2O5) was spin-coated onto the active layer to be a hole-transporting layer (HTL). The power conversion efficiency (PCE) results indicate that the V2O5 nanobelt structure possesses better phase separation and provides a more efficient surface area for the P3HT:PCBM:CNT active layer to increase photocurrent. The optimized IOSCs exhibited an open circuit voltage (Voc), a short-circuit current density (Jsc), a fill factor (FF), and a PCE of 0.55 V, 6.50 mA/cm2, 58.34%, and 2.20%, respectively, under simulated AM1.5G illumination of 100 mW/cm2.

  10. Unpinning the Open-Circuit Voltage in Organic Solar Cells through Tuning Ternary Blend Active Layer Morphology

    NASA Astrophysics Data System (ADS)

    Khlyabich, Petr; Thompson, Barry; Loo, Yueh-Lin

    2015-03-01

    The use of ternary, as opposed to binary, blends having complementary absorption in active layers of organic bulk heterojunction solar cells is a simple approach to increase overall light absorption. While the open-circuit voltage (Voc) of such solar cells have generally been shown to be pinned by the smallest energy level difference between the donor and acceptor constituents, there have been materials systems, that when incorporated into active layers of solar cells, exhibit composition dependent and tunable Voc. Herein, we demonstrate that this Voc tunability in ternary blend solar cells is correlated with the morphology of the active layer. Chemical compatibility between the constituents in the blend, as probed by grazing-incidence X-ray diffraction (GIXD) measurements, affords Voc tuning. The constituents need not ``co-crystallize'' limited miscibility between the constituents in the active layers of solar cells affords Voc tunability. Poor physical interactions between the constituent domains within the active layers, on the other hand, result in devices that exhibit an invariant Voc that is pinned by the smallest energy level difference between the donor(s) and the acceptor(s). Our morphological studies thus support the proposed alloying model that was put forth originally.

  11. Influence of Dopant Concentration on Electroluminescent Performance of Organic White-Light-Emitting Device with Double-Emissive-Layered Structure

    NASA Astrophysics Data System (ADS)

    Wu, Xiao-Ming; Hua, Yu-Lin; Yin, Shou-Gen; Zhang, Li-Juan; Wang, Yu; Hou, Qing-Chuan; Zhang, Jun-Mei

    2008-01-01

    A novel phosphorescent organic white-light-emitting device (WOLED) with configuration of ITO/NPB/CBP:TBPe:rubrene/Zn(BTZ)2:Ir(piq)2(acac)/Zn(BTZ)2/Mg:Ag is fabricated successfully, where the phosphorescent dye bis (1-(phenyl)isoquinoline) iridium (III) acetylanetonate (Ir(piq)2(acac)) doped into bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2) (greenish-blue emitting material with electron transport character) as the red emitting layer, and fluorescent dye 2,5,8,11-tetra-tertbutylperylene (TBPe) and 5,6,11,12-tetraphenyl-naphthacene (rubrene) together doped into 4,4'-N,N'-dicarbazole-biphenyl (CBP) (ambipolar conductivity material) as the blue-orange emitting layer, respectively. The two emitting layers are sandwiched between the hole-transport layer N,N'-biphenyl-N, N'-bis (1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) and electron-transport layer (Zn(BTZ)2). The optimum device turns on at the driving voltage of 4.5 V. A maximum external quantum efficiency of 1.53% and brightness 15000 cd/m2 are presented. The best point of the Commission Internationale de l'Eclairage (CIE) coordinates locates at (0.335, 0.338) at about 13 V. Moreover, we also discuss how to achieve the bright pure white light through optimizing the doping concentration of each dye from the viewpoint of energy transfer process.

  12. Organic/inorganic hybrid pn-junction between copper phthalocyanine and CdSe quantum dot layers as solar cells

    NASA Astrophysics Data System (ADS)

    Saha, Sudip K.; Guchhait, Asim; Pal, Amlan J.

    2012-08-01

    We have introduced an organic/inorganic hybrid pn-junction for solar cell applications. Layers of II-VI quantum dots and a metal-phthalocyanine in sequence have been used as n- and p-type materials, respectively, to form a junction. The film of quantum dots has been formed through a layer-by-layer process by replacing the long-chain ligands of the nanoparticles in each ultrathin layer or a monolayer with short-chain ones so that interparticle distance becomes small leading to a decrease in resistance of the quantum dot layer. With indium tin oxide and Au as electrodes, we have formed an inverted sandwiched structure. These electrodes formed ohmic contacts with the neighboring materials. From the current-voltage characteristics of the hybrid heterostructure, we have inferred formation of a depletion region at the pn-junction that played a key role in charge separation and correspondingly a photocurrent in the external circuit. For comparison, we have also formed and characterized Schottky devices based on components of the pn-junction keeping the electrode combination same. From capacitance-voltage characteristics, we have observed that the depletion region of the hybrid pn-junction was much wider as compared to that in Schottky devices based on components of the junction.

  13. AFM, ellipsometry, XPS and TEM on ultra-thin oxide/polymer nanocomposite layers in organic thin film transistors.

    PubMed

    Fian, A; Haase, A; Stadlober, B; Jakopic, G; Matsko, N B; Grogger, W; Leising, G

    2008-03-01

    Here we report on the fabrication and characterization of ultra-thin nanocomposite layers used as gate dielectric in low-voltage and high-performance flexible organic thin film transistors (oTFTs). Reactive sputtered zirconia layers were deposited with low thermal exposure of the substrate and the resulting porous oxide films with high leakage currents were spin-coated with an additional layer of poly-alpha-methylstyrene (P alphaMS). After this treatment a strong improvement of the oTFT performance could be observed; leakage currents could be eliminated almost completely. In ellipsometric studies a higher refractive index of the ZrO(2)/P alphaMS layers compared to the "as sputtered" zirconia films could be detected without a significant enhancement of the film thickness. Atomic force microscopy (AFM) measurements of the surface topography clearly showed a surface smoothing after the P alphaMS coating. Further studies with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) also indicated that the polymer definitely did not form an extra layer. The polymer chains rather (self-)assemble in the nano-scaled interspaces of the porous oxide film giving an oxide-polymer "nanocomposite" with a high oxide filling grade resulting in high dielectric constants larger than 15. The dielectric strength of more than 1 MV cm(-1) is in good accordance with the polymer-filled interspaces. PMID:17952415

  14. Driving voltage reduction in white organic light-emitting devices from selectively doping in ambipolar blue-emitting layer

    NASA Astrophysics Data System (ADS)

    Hsiao, Chih-Hung; Lin, Chi-Feng; Lee, Jiun-Haw

    2007-11-01

    White organic light-emitting devices (OLEDs) consisting of ambipolar 9,10-bis(2'-naphthyl) anthracene (ADN) as a host of blue-emitting layer (EML) were investigated. A thin codoped layer of yellow 5,6,11,12-Tetraphenylnaphthacene (rubrene) served as a probe for detecting the position of maximum recombination rate in the 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) doped-ADN EML. Due to the energy barrier and bipolar carrier transport, the maximum recombination rate was found to be close to but not exactly at the interface of the hole-transporting layer and the EML. With appropriate tuning in the thickness, position, and dopant concentrations of the codoped layer (rubrene:DPAVBi:ADN) in the EML, the device driving voltage decreased by 21.7%, nearly 2 V in reduction, due to the increased recombination current from the faster exciton relaxation induced by the yellow dopants. Among the advantages of introducing the codoped layer over conventional single-doped layers are the elimination of the trapping effect to avoid increasing the device driving voltage, the alleviation of the dependence of the recombination zone on the applied voltage for improving color stability, and the utilization of excitons in a more efficient way to enhance device efficiency. Without using any electrically conductive layers such as the p-i-n structure, we were able to successfully generate 112 cd/m2 at 4 V from our white OLED simply by engineering the structure of the EML.

  15. Structural transformation and photoluminescence behavior during calcination of the layered europium-doped yttrium hydroxide intercalate with organic-sensitizer

    SciTech Connect

    Sun, Yahong; Pan, Guohua; Gu, Qingyang; Li, Xinxin; Sun, Genban; Ma, Shulan; Yang, Xiaojing

    2013-11-15

    Graphical abstract: Calcination of organic sensitizer intercalated layered europium-doped yttrium hydroxide displayed tunable luminescent performance dependent on calcined temperatures. The 200 °C-calcined sample revealed an optimal fluorescence behavior with respect to TA-LYH:Eu composite and the as-transformed oxide. - Highlights: • We report the calcinations process of organic/LYH:Eu nanocomposite materials. • We study structural transformation and fluorescence behavior of the calcined samples. • Calcined samples displayed tunable luminescent performance dependent on temperatures. • The optimal fluorescence was found in 200 °C-calcined sample. • This material can provide valuable guide for developing tunable luminescent materials. - Abstract: We report, for the first time, structural transformation and photoluminescence behavior by calcination of layered europium-doped yttrium hydroxide (LYH:Eu) intercalate with organic sensitizer terephthalate (TA). The calcined samples displayed tunable luminescent performance dependent on calcined temperatures. Calcination under low temperatures (200 and 300 °C) retained layered structure, while high temperatures (>400 °C) yielded oxide phase. The optimal fluorescence occurred in 200 °C-calcination, possibly resulting from an optimal arrangement of TA. Above 200 °C, the luminescence intensity was first weakened and then enhanced, due to gradual departure of TA and following occurrence of oxide phase. The energy transfer presented an intrinsic transition from TA-to-Eu{sup 3+} in the organic intercalate to O{sup 2−}-to-Eu{sup 3+} charge transfer in as-transformed oxide. The predominant luminescence property of the hybrid material can provide valuable guide for developing tunable luminescent materials, especially flexible materials resulting from the containing organic component.

  16. Enhanced Breakdown Reliability and Spatial Uniformity of Atomic Layer Deposited High-k Gate Dielectrics on Graphene via Organic Seeding Layers

    NASA Astrophysics Data System (ADS)

    Sangwan, Vinod; Jariwala, Deep; Filippone, Stephen; Karmel, Hunter; Johns, James; Alaboson, Justice; Marks, Tobin; Lauhon, Lincoln; Hersam, Mark

    2013-03-01

    Ultra-thin high- κ top-gate dielectrics are essential for high-speed graphene-based nanoelectronic circuits. Motivated by the need for high reliability and spatial uniformity, we report here the first statistical analysis of the breakdown characteristics of dielectrics grown on graphene. Based on these measurements, a rational approach is devised that simultaneously optimizes the gate capacitance and the key parameters of large-area uniformity and dielectric strength. In particular, vertically heterogeneous oxide stacks grown via atomic-layer deposition (ALD) seeded by a molecularly thin perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) organic monolayer result in improved reliability (Weibull shape parameter β > 25) compared to the control dielectric directly grown on graphene without PTCDA (β < 1). The optimized sample also showed a large breakdown strength (Weibull scale parameter, EBD > 7 MV/cm) that is comparable to that of the control dielectric grown on Si substrates.

  17. Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion.

    PubMed

    Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2009-03-01

    To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements. PMID:20355986

  18. Metal-organic coordination-enabled layer-by-layer self-assembly to prepare hybrid microcapsules for efficient enzyme immobilization.

    PubMed

    Wang, Xiaoli; Jiang, Zhongyi; Shi, Jiafu; Liang, Yanpeng; Zhang, Chunhong; Wu, Hong

    2012-07-25

    A novel layer-by-layer self-assembly approach enabled by metal-organic coordination was developed to prepare polymer-inorganic hybrid microcapsules. Alginate was first activated via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) coupling chemistry, and subsequently reacted with dopamine. Afterward, the dopamine modified alginate (Alg-DA) and titanium(IV) bis(ammonium lactato) dihydroxide (Ti(IV)) were alternatively deposited onto CaCO3 templates. The coordination reaction between the catechol groups of Alg-DA and the Ti(IV) allowed the alternative assembly to form a series of multilayers. After removing the templates, the alginate-titanium hybrid microcapsules were obtained. The high mechanical stability of hybrid microcapsules was demonstrated by osmotic pressure experiment. Furthermore, the hybrid microcapsules displayed superior thermal stability due to Ti(IV) coordination. Catalase (CAT) was used as model enzyme, either encapsulated inside or covalently attached on the surface of the resultant microcapsules. No CAT leakage from the microcapsules was detected after incubation for 48 h. The encapsulated CAT, with a loading capacity of 450-500 mg g(-1) microcapsules, exhibited desirable long-term storage stability, whereas the covalently attached CAT, with a loading capacity of 100-150 mg g(-1) microcapsules, showed desirable operational stability. PMID:22724538

  19. Flexible n-type thermoelectric materials by organic intercalation of layered transition metal dichalcogenide TiS2.

    PubMed

    Wan, Chunlei; Gu, Xiaokun; Dang, Feng; Itoh, Tomohiro; Wang, Yifeng; Sasaki, Hitoshi; Kondo, Mami; Koga, Kenji; Yabuki, Kazuhisa; Snyder, G Jeffrey; Yang, Ronggui; Koumoto, Kunihito

    2015-06-01

    Organic semiconductors are attracting increasing interest as flexible thermoelectric materials owing to material abundance, easy processing and low thermal conductivity. Although progress in p-type polymers and composites has been reported, their n-type counterpart has fallen behind owing to difficulties in n-type doping of organic semiconductors. Here, we present an approach to synthesize n-type flexible thermoelectric materials through a facile electrochemical intercalation method, fabricating a hybrid superlattice of alternating inorganic TiS2 monolayers and organic cations. Electrons were externally injected into the inorganic layers and then stabilized by organic cations, providing n-type carriers for current and energy transport. An electrical conductivity of 790 S cm(-1) and a power factor of 0.45 mW m(-1) K(-2) were obtained for a hybrid superlattice of TiS2/[(hexylammonium)x(H2O)y(DMSO)z], with an in-plane lattice thermal conductivity of 0.12 ± 0.03 W m(-1) K(-1), which is two orders of magnitude smaller than the thermal conductivities of the single-layer and bulk TiS2. High power factor and low thermal conductivity contributed to a thermoelectric figure of merit, ZT, of 0.28 at 373 K, which might find application in wearable electronics. PMID:25849369

  20. Non-cellulosic polysaccharides help to reveal the history of thick organic surface layers on calcareous Alpine soils

    NASA Astrophysics Data System (ADS)

    Prietzel, Jörg; Spielvogel, Sandra

    2015-04-01

    We investigated the potential of non-cellulosic polysaccharides (NCP) as biomarkers to identify the plant types that dominate present and past litter input into organic surface covers on calcareous Alpine soils and to reveal historic vegetation changes. At two sites in the Alps, NCP monomers were quantified in different organs of site-dominating plants, the Oa horizon of four Folic Leptosols, and different sections of thick organic surface layers of four Folic Histosols on calcareous bedrock. The dominating plant types at our study sites differ markedly in their NCP composition and (galactose + mannose)/(arabinose + xylose) [GM/AX] ratio (grasses and sedges: 0.2; dicots Fagus and Vaccinium: 0.2-0.6; conifers Abies, Picea, Pinus: 0.7-2.4; mosses: 5). For all except one soil, the NCP signature of the uppermost Oa horizon reflects the present vegetation. For all Histosol O horizons, NCP signatures indicate a dominance of conifer litter throughout their development (up to 1,500 years). Different NCP and GM/AX depth profiles reflect specific patterns of O layer genesis. From those results we conclude that NCP and GM/AX depth profiles in organic surface covers of soils provide important information about dominating litter sources in the past and can be valuable tools to reveal historic vegetation and/ or land use changes.

  1. Seeding atomic layer deposition of high-k dielectrics on epitaxial graphene with organic self-assembled monolayers.

    PubMed

    Alaboson, Justice M P; Wang, Qing Hua; Emery, Jonathan D; Lipson, Albert L; Bedzyk, Michael J; Elam, Jeffrey W; Pellin, Michael J; Hersam, Mark C

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO(2) and Al(2)O(3) on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al(2)O(3) and 10 nm HfO(2) dielectric stack show high capacitance values of ∼700 nF/cm(2) and low leakage currents of ∼5 × 10(-9) A/cm(2) at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics. PMID:21553842

  2. Investigation of Nonvolatile Memory Effect of Organic Thin-Film Transistors with Triple Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Yu, Hsin-Chieh; Chen, Ying-Chih; Huang, Chun-Yuan; Su, Yan-Kuin

    2012-03-01

    Pentacene thin-film transistor (TFT) memory using poly(2-hydroxyethyl methacrylate) (PHEMA)-based polymer dielectric layers has been developed. The electric performance and memory behaviors of memory TFTs can be significantly improved by using triple polymer dielectric layers consisting of PHEMA/poly(methyl methacrylate) (PMMA)/PHEMA. This can be attributed to the improvement of the channel/dielectric interface. This memory effect is due to the charge storage of the dipolar group or molecules in the dielectric. The devices exhibit a wide memory window (ΔVth, >20 V), switchable channel current, and long retention time.

  3. Evaluating Mechanisms of Dihydroxylation by Thin-Layer Chromatography: A Microscale Experiment for Organic Chemistry

    ERIC Educational Resources Information Center

    Burlingham, Benjamin T.; Rettig, Joseph C.

    2008-01-01

    A microscale experiment is presented in which cyclohexene is dihydroxylated under three sets of conditions: epoxidation-hydrolysis, permanganate oxidation, and the Woodward dihydroxylation. The products of the reactions are determined by the use of thin-layer chromatography. Teams of students are presented with proposed mechanisms for each…

  4. Formation of Organic Thin Films of Nonlinear Optical Materials by Molecular Layer Epitaxy

    NASA Astrophysics Data System (ADS)

    Burtman, V.; Kopylova, T. N.; Van Der Boom, M.; Gadirov, R. M.; Tel'minov, E. N.; Nikonov, S. Yu.; Nikonova, E. N.

    2016-03-01

    Conditions are described under which films of [(aminophenyl)azo]pyridine are formed by molecular layer epitaxy, and their optical absorption and x-ray photoelectron spectra are investigated. The nonlinear properties of such structures are described with the help of measurements of the intensity of second harmonic generation as a function of the angle of incidence.

  5. Thermal conductivity of giant mono- to few-layered CVD graphene supported on an organic substrate.

    PubMed

    Liu, Jing; Wang, Tianyu; Xu, Shen; Yuan, Pengyu; Xu, Xu; Wang, Xinwei

    2016-05-21

    The thermal conductivity (k) of supported graphene is a critical property that reflects the graphene-substrate interaction, graphene structure quality, and is needed for thermal design of a graphene device. Yet the related k measurement has never been a trivial work and very few studies are reported to date, only at the μm level. In this work, for the first time, the k of giant chemical vapor decomposition (CVD) graphene supported on poly(methyl methacrylate) (PMMA) is characterized using our transient electro-thermal technique based on a differential concept. Our graphene size is ∼mm, far above the samples studied in the past. This giant graphene measurement eliminates the thermal contact resistance problems and edge phonon scattering encountered in μm-scale graphene k measurement. Such mm-scale measurement is critical for device/system-level thermal design since it reflects the effect of abundant grains in graphene. The k of 1.33-layered, 1.53-layered, 2.74-layered and 5.2-layered supported graphene is measured as 365 W m(-1) K(-1), 359 W m(-1) K(-1), 273 W m(-1) K(-1) and 33.5 W m(-1) K(-1), respectively. These values are significantly lower than the k of supported graphene on SiO2, and are about one order of magnitude lower than the k of suspended graphene. We speculate that the abundant C atoms in the PMMA promote more ready energy and momentum exchange with the supported graphene, and give rise to more phonon scattering than the SiO2 substrate. This leads to a lower k of CVD graphene on PMMA than that on SiO2. We attribute the existence of disorder in the sp(2) domain, graphene oxide (GO) and stratification in the 5.2-layered graphene to its more k reduction. The Raman linewidth (G peak) of the 5.2-layered graphene is also twice larger than that of the other three kinds of graphene, indicating the much more phonon scattering and shorter phonon lifetime in it. Also the electrical conductivity of the 5.2-layered graphene is about one-fifth of that for the

  6. Thermal conductivity of giant mono- to few-layered CVD graphene supported on an organic substrate

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wang, Tianyu; Xu, Shen; Yuan, Pengyu; Xu, Xu; Wang, Xinwei

    2016-05-01

    The thermal conductivity (k) of supported graphene is a critical property that reflects the graphene-substrate interaction, graphene structure quality, and is needed for thermal design of a graphene device. Yet the related k measurement has never been a trivial work and very few studies are reported to date, only at the μm level. In this work, for the first time, the k of giant chemical vapor decomposition (CVD) graphene supported on poly(methyl methacrylate) (PMMA) is characterized using our transient electro-thermal technique based on a differential concept. Our graphene size is ~mm, far above the samples studied in the past. This giant graphene measurement eliminates the thermal contact resistance problems and edge phonon scattering encountered in μm-scale graphene k measurement. Such mm-scale measurement is critical for device/system-level thermal design since it reflects the effect of abundant grains in graphene. The k of 1.33-layered, 1.53-layered, 2.74-layered and 5.2-layered supported graphene is measured as 365 W m-1 K-1, 359 W m-1 K-1, 273 W m-1 K-1 and 33.5 W m-1 K-1, respectively. These values are significantly lower than the k of supported graphene on SiO2, and are about one order of magnitude lower than the k of suspended graphene. We speculate that the abundant C atoms in the PMMA promote more ready energy and momentum exchange with the supported graphene, and give rise to more phonon scattering than the SiO2 substrate. This leads to a lower k of CVD graphene on PMMA than that on SiO2. We attribute the existence of disorder in the sp2 domain, graphene oxide (GO) and stratification in the 5.2-layered graphene to its more k reduction. The Raman linewidth (G peak) of the 5.2-layered graphene is also twice larger than that of the other three kinds of graphene, indicating the much more phonon scattering and shorter phonon lifetime in it. Also the electrical conductivity of the 5.2-layered graphene is about one-fifth of that for the other three. This

  7. InAsSb/InPSb Strained-Layer Superlattice Growth Using Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Biefeld, R.M.; Kurtz, S.R.; Phillips, J.D.

    1999-08-09

    The authors report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InPSb as well as mid-infrared optically pumped lasers grown using a high speed rotating disk-reactor (RDR). The devices contain AlAsSb cladding layers and strained, type I, InAsSb/InPSb active regions. By changing the layer thickness and composition of InAsSb/InPSb SLSs, they have prepared structures with low temperature (< 20 K) photoluminescence wavelengths ranging from 3.4 to 4.8 {micro}m. They find a variation in bandgap of 0.272 to 0.324 eV for layer thicknesses of 9.0 to 18.2 nm. From these data they have estimated a valence band offset for the InAsSb/InPSb interface of about 400 meV. The optical properties of the superlattices revealed an anomalous low energy transition that can be assigned to an antimony rich interfacial layer in the superlattice. An InAsSb/InPSb SLS, laser was grown on an InAs substrate with AlAs{sub 0.16}Sb{sub 0.84} cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80 through 200 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T{sub 0} = 72 K, from 80 to 200 K.

  8. Comparative Study of MIL-96(Al) as Continuous Metal-Organic Frameworks Layer and Mixed-Matrix Membrane.

    PubMed

    Knebel, Alexander; Friebe, Sebastian; Bigall, Nadja Carola; Benzaqui, Marvin; Serre, Christian; Caro, Jürgen

    2016-03-23

    MIL-96(Al) layers were prepared as supported metal-organic frameworks membrane via reactive seeding using the α-alumina support as the Al source for the formation of the MIL-96(Al) seeds. Depending on the solvent mixture employed during seed formation, two different crystal morphologies, with different orientation of the transport-active channels, have been formed. This crystal orientation and habit is predefined by the seed crystals and is kept in the subsequent growth of the seeds to continuous layers. In the gas separation of an equimolar H2/CO2 mixture, the hydrogen permeability of the two supported MIL-96(Al) layers was found to be highly dependent on the crystal morphology and the accompanied channel orientation in the layer. In addition to the neat supported MIL-96(Al) membrane layers, mixed-matrix membranes (MMMs, 10 wt % filler loading) as a composite of MIL-96(Al) particles as filler in a continuous Matrimid polymer phase have been prepared. Five particle sizes of MIL-96(Al) between 3.2 μm and 55 nm were synthesized. In the preparation of the MIL-96(Al)/Matrimid MMM (10 wt % filler loading), the following preparation problems have been identified: The bigger micrometer-sized MIL-96(Al) crystals show a trend toward sedimentation during casting of the MMM, whereas for nanoparticles aggregation and recrystallization to micrometer-sized MIL-96(Al) crystals has been observed. Because of these preparation problems for MMM, the neat supported MIL-96(Al) layers show a relatively high H2/CO2 selectivity (≈9) and a hydrogen permeance approximately 2 magnitudes higher than that of the best MMM. PMID:26886432

  9. Sum-Frequency Generation Spectroscopy for Studying Organic Layers at Water-Air Interfaces: Microlayer Monitoring and Surface Reactivity

    NASA Astrophysics Data System (ADS)

    Laß, Kristian; Kleber, Joscha; Bange, Hermann; Friedrichs, Gernot

    2015-04-01

    The sea surface microlayer, according to commonly accepted terminology, comprises the topmost millimetre of the oceanic water column. It is often enriched with organic matter and is directly influenced by sunlight exposure and gas exchange with the atmosphere, hence making it a place for active biochemistry and photochemistry as well as for heterogeneous reactions. In addition, surface active material either is formed or accumulates directly at the air-water interface and gives rise to very thin layers, sometimes down to monomolecular thickness. This "sea surface nanolayer" determines the viscoelastic properties of the seawater surface and thus may impact the turbulent air-sea gas exchange rates. To this effect, this small scale layer presumably plays an important role for large scale changes of atmospheric trace gas concentrations (e.g., by modulating the ocean carbon sink characteristics) with possible implications for coupled climate models. To date, detailed knowledge about the composition, structure, and reactivity of the sea surface nanolayer is still scarce. Due to its small vertical dimension and the small amount of material, this surfactant layer is very difficult to separate and analyse. A way out is the application of second-order nonlinear optical methods, which make a direct surface-specific and background-free detection of this interfacial layer possible. In recent years, we have introduced the use of vibrational sum frequency generation (VSFG) spectroscopy to gain insight into natural and artificial organic monolayers at the air-water interface. In this contribution, the application of VSFG spectroscopy for the analysis of the sea surface nanolayer will be illustrated. Resulting spectra are interpreted in terms of layer composition and surfactant classes, in particular with respect to carbohydrate-containing molecules such as glycolipids. The partitioning of the detected surfactants into soluble and non-soluble ("wet" and "dry") surfactants will be

  10. Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.

    PubMed

    Lemaire, Paul C; Zhao, Junjie; Williams, Philip S; Walls, Howard J; Shepherd, Sarah D; Losego, Mark D; Peterson, Gregory W; Parsons, Gregory N

    2016-04-13

    Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth. PMID:26999431

  11. Detection of organic colorants in historical painting layers using UV laser ablation surface-enhanced Raman microspectroscopy.

    PubMed

    Cesaratto, Anna; Leona, Marco; Lombardi, John R; Comelli, Daniela; Nevin, Austin; Londero, Pablo

    2014-12-22

    Surface-enhanced Raman spectroscopy (SERS) has been increasingly used in the study of works of art to identify organic pigments and dyes in paintings, which (depending on the material) are difficult or not possible to detect by other current methods. The application of SERS to the study of paintings has been limited, however, by the lack of a sampling approach with sufficient sensitivity and spatial resolution. We show that ultraviolet laser ablation (LA) sampling coupled with SERS detection can be successfully used to study paint layers. LA-SERS permitted the isolation of signals from colorants in individual thin paint layers in sample cross-sections, avoiding contamination from adjacent layers. These results expand the range of analytical applications of SERS demonstrating how the technique can be used to sensitively detect minor organic components in complex matrices. While this is fundamental for the study of cultural heritage, it is also relevant in other fields such as forensic analysis, food science, and pharmacology. PMID:25353694

  12. Interface investigation of the alcohol-/water-soluble conjugated polymer PFN as cathode interfacial layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shu; Wang, Rui; Ying Mao, Hong; He, Zhicai; Wu, Hongbin; Chen, Wei; Cao, Yong

    2013-09-01

    In this work, in situ ultraviolet photoelectron spectroscopy measurements were used to investigate the working mechanism of an alcohol-/water-soluble conjugated polymer poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode interfacial layer in organic solar cells from the view of interfacial energy level alignment. Fullerene (C60) was chosen as the model acceptor material in contact with PFN as well as two other cathode interfacial layers ZnO and TiO2 in the configuration of an inverted solar cell structure. Significant charge transfer between PFN modified ITO (indium tin oxide) electrode and C60 is observed due to the low work function of PFN. This results in the Fermi level of the substrate pinned very close to the lowest unoccupied molecular orbital of C60 as well as an additional electric field at the cathode/acceptor interface. Both of them facilitate the electron extraction from the acceptor C60 to the ITO cathode, as confirmed by the electrical measurements of the electron-only devices with PFN modification. The better electron extraction originated from the Fermi level pinning and the additional interface electric field are believed to contribute to the efficiency enhancement of the inverted organic solar cells employing PFN as cathode interfacial layer.

  13. A Light Scattering Layer for Internal Light Extraction of Organic Light-Emitting Diodes Based on Silver Nanowires.

    PubMed

    Lee, Keunsoo; Shin, Jin-Wook; Park, Jun-Hwan; Lee, Jonghee; Joo, Chul Woong; Lee, Jeong-Ik; Cho, Doo-Hee; Lim, Jong Tae; Oh, Min-Cheol; Ju, Byeong-Kwon; Moon, Jaehyun

    2016-07-13

    We propose and fabricate a random light scattering layer for light extraction in organic light-emitting diodes (OLEDs) with silver nanodots, which were obtained by melting silver nanowires. The OLED with the light scattering layer as an internal light extraction structure was enhanced by 49.1% for the integrated external quantum efficiency (EQE). When a wrinkle structure is simultaneously used for an external light extraction structure, the total enhancement of the integrated EQE was 65.3%. The EQE is maximized to 65.3% at a current level of 2.0 mA/cm(2). By applying an internal light scattering layer and wrinkle structure to an OLED, the variance in the emission spectra was negligible over a broad viewing angle. Power mode analyses with finite difference time domain (FDTD) simulations revealed that the use of a scattering layer effectively reduced the waveguiding mode while introducing non-negligible absorption. Our method offers an effective yet simple approach to achieve both efficiency enhancement and spectral stability for a wide range of OLED applications. PMID:27314500

  14. White top-emitting organic light-emitting diodes with solution-processed nano-particle scattering layers

    SciTech Connect

    Schaefer, Tim; Schwab, Tobias; Lenk, Simone; Gather, Malte C.

    2015-12-07

    A random scattering approach to enhance light extraction in white top-emitting organic light-emitting diodes (OLEDs) is reported. Through solution processing from fluorinated solvents, a nano-particle scattering layer (NPSL) can be deposited directly on top of small molecule OLEDs without affecting their electrical performance. The scattering length for light inside the NPSL is determined from transmission measurements and found to be in agreement with Mie scattering theory. Furthermore, the dependence of the light outcoupling enhancement on electron transport layer thickness is studied. Depending on the electron transport layer thickness, the NPSL enhances the external quantum efficiency of the investigated white OLEDs by between 1.5 and 2.3-fold. For a device structure that has been optimized prior to application of the NPSL, the maximum external quantum efficiency is improved from 4.7% to 7.4% (1.6-fold improvement). In addition, the scattering layer strongly reduces the undesired shift in emission color with viewing angle.

  15. UV-ozone-treated ultra-thin NaF film as anode buffer layer on organic light emitting devices.

    PubMed

    Chen, Yu-Cheng; Kao, Po-Ching; Chu, Sheng-Yuan

    2010-06-21

    An ultra-thin NaF film was thermally deposited between ITO and NPB as the buffer layer and then treated with the ultraviolet (UV) ozone, in the fabrication of organic light emitting diodes (ITO/NaF/NPB/Alq(3)/LiF/Al) to study its effect on hole-injection properties. The treatment drastically transforms the role of NaF film from hole-blocking to hole-injecting. This transformation is elucidated using hole-only devices, energy band measurement, surface energy, surface polarity, and X-ray photoelectron spectra. With the optimal thickness (3 nm) of the UV-ozone-treated NaF layer, the device performance is significantly improved, with a turn-on voltage, maximum luminance, and maximum current efficiency of 2.5 V, 15700 cd/m(2), and 4.9 cd/A, respectively. Results show that NaF film is not only a hole-blocking layer, but also a promising hole-injecting layer after UV-ozone treatment. PMID:20588585

  16. Charge generation layers for all-solution processed organic tandem light emitting diodes with regular device architecture

    NASA Astrophysics Data System (ADS)

    Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Colsmann, Alexander

    2015-10-01

    We present multi-photon OLEDs where enhanced light emission was achieved by stacking two OLEDs utilizing a regular device architecture (top cathode) and an intermediate charge carrier generation layer (CGL) for monolithic device interconnection. With respect to future printing processes for organic optoelectronic devices, all functional layers were deposited from solution. The CGL comprises a low-work function zinc oxide layer that was applied from solution under ambient conditions and at moderate processing temperatures and a high-work function interlayer that was realized from various solution processable precursor-based metal oxides, like molybdenum-, vanadium- and tungsten-oxide. Since every injected electron-hole pair generates two photons, the luminance and the current efficiency of the tandem OLED at a given device current are doubled while the power efficiency remains constant. At a given luminance, the lower operating current in the tandem device reduces electrical stress and improves the device life-time. ToF-SIMS, TEM/FIB and EDX analyses provided evidence of a distinct layer sequence without intermixing upon solution deposition.

  17. Optical properties of three-layer metal-organic nanoparticles with a molecular J-aggregate shell

    SciTech Connect

    Lebedev, V S; Medvedev, A S

    2013-11-30

    This paper examines the optical properties of two types of spherical three-component nanoparticles: (1) particles comprising a metallic core, outer organic dye J-aggregate shell and passive intermediate layer and (2) metallic nanoshells having an insulator or semiconductor core and coated with a molecular J-aggregate layer. The two types of nanoparticles are shown to differ significantly in the behaviour of electromagnetic fields and photoabsorption spectra. As a result of additional possibilities to control the magnitude and nature of the coupling between Frenkel excitons and localised surface plasmons in these systems, the spectral properties of the three-layer particles have radically new inherent features in comparison with earlier studied metal/J-aggregate bilayer particles. In the case of J-aggregate-coated metallic nanoshells, particular attention is paid to the strong plasmon – exciton coupling regime, which takes place when the plasmon resonance frequency of the nanoshell approaches the centre frequency of the J-band of the dye forming the outer layer of the particle. (optics of nanoparticles)

  18. Dynamics of dissolved organic matter in fjord ecosystems: Contributions of terrestrial dissolved organic matter in the deep layer

    NASA Astrophysics Data System (ADS)

    Yamashita, Youhei; McCallister, S. Leigh; Koch, Boris P.; Gonsior, Michael; Jaffé, Rudolf

    2015-06-01

    Annually, rivers and inland water systems deliver a significant amount of terrestrial organic matter (OM) to the adjacent coastal ocean in both particulate and dissolved forms; however, the metabolic and biogeochemical transformations of OM during its seaward transport remains one of the least understood components of the global carbon cycle. This transfer of terrestrial carbon to marine ecosystems is crucial in maintaining trophic dynamics in coastal areas and critical in global carbon cycling. Although coastal regions have been proposed as important sinks for exported terrestrial materials, most of the global carbon cycling data, have not included fjords in their budgets. Here we present distributional patterns on the quantity and quality of dissolved OM in Fiordland National Park, New Zealand. Specifically, we describe carbon dynamics under diverse environmental settings based on dissolved organic carbon (DOC) depth profiles, oxygen concentrations, optical properties (fluorescence) and stable carbon isotopes. We illustrate a distinct change in the character of DOC in deep waters compared to surface and mid-depth waters. Our results suggest that, both, microbial reworking of terrestrially derived plant detritus and subsequent desorption of DOC from its particulate counterpart (as verified in a desorption experiment) are the main sources of the humic-like enriched DOC in the deep basins of the studied fjords. While it has been suggested that short transit times and protection of OM by mineral sorption may ultimately result in significant terrestrial carbon burial and preservation in fjords, our data suggests the existence of an additional source of terrestrial OM in the form of DOC generated in deep, fjord water.

  19. Structural organization of DMPC lipid layers on chemically micropatterned self-assembled monolayers as biomimetic systems.

    PubMed

    Brechling, A; Pohl, M; Kleineberg, U; Heinzmann, U

    2004-08-26

    The growth structure of DMPC lipid layers on hydrophobic and hydrophilic alkylsilane-based self-assembled monolayers adsorbed on silicon has been investigated by means of X-ray reflectometry and atomic force microscopy. Hydrophilic modification of hydrophobically terminated ODS-SAMs has been achieved by dose-controlled irradiation with DUV light. While island formation of small DMPC bilayer islands is observed on hydrophobic SAM surfaces, closed layers of DMPC monolayers are formed on hydrophilic SAM surfaces. Furthermore, DMPC adsorption on chemically micropatterned substrates with alternating hydrophobic/hydrophilic surface properties has been studied by imaging ellipsometry and photoemission microscopy. Indication for at least partial bridging of hydrophobic areas by an adsorbed DMPC monolayer has been found. PMID:15288947

  20. Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers

    NASA Astrophysics Data System (ADS)

    Peng, Ying; Yaacobi-Gross, Nir; Perumal, Ajay K.; Faber, Hendrik A.; Vourlias, George; Patsalas, Panos A.; Bradley, Donal D. C.; He, Zhiqun; Anthopoulos, Thomas D.

    2015-06-01

    We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ˜5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE >3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices.

  1. Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers

    SciTech Connect

    Peng, Ying; Yaacobi-Gross, Nir; Perumal, Ajay K.; Faber, Hendrik A.; Bradley, Donal D. C.; Anthopoulos, Thomas D. E-mail: t.anthopoulos@imperial.ac.uk; Vourlias, George; Patsalas, Panos A.; He, Zhiqun E-mail: t.anthopoulos@imperial.ac.uk

    2015-06-15

    We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ∼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE >3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices.

  2. An extremely low-index photonic crystal layer for enhanced light extraction from organic light-emitting diodes.

    PubMed

    Shim, Yong Sub; Hwang, Ju Hyun; Park, Cheol Hwee; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2016-02-21

    This paper reports organic light-emitting diodes (OLEDs) with improved light extraction fabricated by embedding an extremely low-index photonic crystal (LIPC) layer. The LIPC layer increases the optical efficiency through the reduced wave-guide mode between the substrate and anode both by increased light resonance and by a strengthened diffraction effect from an extremely low-refractive-index medium, specifically a line structure composed of a vacuum gap. As a result, the current efficiency and power efficiency of the LIPC-OLEDs are 1.51 and 1.93 times higher, respectively, than the reference device at 1000 cd m(-2). Because most of the light extraction is significant, especially in the forward direction, at the specific wavelengths satisfying the Bragg's diffraction equation, it is possible to calculate the anomalous spectrum of the LIPC-OLED through the finite-difference time domain (FDTD) method. PMID:26822966

  3. Low driving voltage and high stability organic light-emitting diodes with rhenium oxide-doped hole transporting layer

    NASA Astrophysics Data System (ADS)

    Leem, Dong-Seok; Park, Hyung-Dol; Kang, Jae-Wook; Lee, Jae-Hyun; Kim, Ji Whan; Kim, Jang-Joo

    2007-07-01

    The authors report a promising metal oxide-doped hole transporting layer (HTL) of rhenium oxide (ReO3)-doped N ,N'-diphenyl-N ,N'-bis (1,1'-biphenyl)-4,4'-diamine (NPB). The tris(8-hydroxyquinoline) aluminum-based organic light-emitting diodes with ReO3-doped NPB HTL exhibit driving voltage of 5.2-5.4V and power efficiency of 2.2-2.3lm/W at 20mA/cm2, which is significantly improved compared to those (7.1V and 2.0lm/W, respectively) obtained from the devices with undoped NPB. Furthermore, the device with ReO3-doped NPB layer reveals the prolonged lifetime than that with undoped NPB. Details of ReO3 doping effects are described based on the UV-Vis absorption spectra and characteristics of hole-only devices.

  4. Optically monitored spray coating system for the controlled deposition of the photoactive layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Vak, Doojin; van Embden, Joel; Wong, Wallace W. H.; Watkins, Scott

    2015-01-01

    A spray deposition process equipped with an in situ optical thickness monitoring system has been developed to fabricate the photoactive layer of solar cells. Film thickness is monitored by a photodiode-LED couple after each deposition cycle. Using optimized conditions, the thickness of the spray deposited photoactive films can be tuned to increase linearly with the number of deposition cycles over a wide range of deposition conditions. After instrument calibration, optimization of the active layer thickness can be accomplished by simply setting the desired absorbance of the film. The simple process outlined here may be used for the rapid optimization of thin film photovoltaic devices. As proof of this, we fabricate a poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester as well as a P3HT and indene-C60 bis-adduct organic solar cells, which achieve a champion power conversion efficiency of 4.2%.

  5. Development of a silver/polymer nanocomposite interconnection layer for organic tandem solar cells

    NASA Astrophysics Data System (ADS)

    Torabi, Naeimeh; Behjat, Abbas; Shahpari, Mahboobeh; Edalati, Shadi

    2015-01-01

    Interconnecting layers (ICL) play an important role in regulating the performance of tandem devices. We report the design of a solution-processed ICL that consists of a silver/polymer nanocomposite deposited on the top of a TiO2 layer. This nanocomposite contains modified poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid (PEDOT:PSS), and silver nanoparticles (Ag NPs) synthesized by the chemical reduction of silver nitrate in the presence of PEDOT:PSS. Formation of Ag NPs was confirmed by monitoring the plasmon absorption peak characteristics in the UV-visible spectrum of the synthesized nanocomposite. Transmission electron microscopy analysis indicated the presence of spherical silver NPs in a polymer matrix with a mean size of around 20 nm. The sheet resistance of PEDOT:PSS was found to be 2474±35 Ω/sq. It was changed to 445±28 Ω/sq after solvent modification and decreased to 53.31±3.59 Ω/sq after synthesizing silver NPs in the polymer medium. Meanwhile, the transparency of the nanocomposite film deposited on TiO2 was 89.6%, which is considered appropriate for an interconnecting electrode. We demonstrated that by incorporating a silver/polymer nanocomposite as a hole-transporting layer in contact with TiO2 as an electron-transporting layer, the ohmic behavior of ICL is enhanced with respect to pristine PEDOT:PSS. P3HT:PCBM-based tandem solar cells based on this solution-processed intermediate electrode represent significantly increased open-circuit voltage (Voc), reaching close to the sum of the single cells. By incorporating the nanocomposite in the tandem structure, a Voc of 1.1 V was obtained. This value was almost the sum of the Voc of two single cells, which was 1.18 V.

  6. Synthesis of Organized Layered Carbon by Self-Templating of Dithiooxamide.

    PubMed

    Xu, Jingsan; Zhu, Jixin; Yang, Xiaofei; Cao, Shaowen; Yu, Jiaguo; Shalom, Menny; Antonietti, Markus

    2016-08-01

    An unusual small molecule, dithiooxamide is used to produce nanostructured carbon via direct pyrolysis. The carbon shows a unique 2D-layer assembled structure and is in situ dual-heteroatom (N and S)-doped, meanwhile having relatively high surface area. These carbon materials can be further decorated with inorganic parts via a precomplexing approach. The functionalized carbon and the hybrid nanomaterials demonstrate remarkable performance for lithium-ion storage. PMID:27187106

  7. CVD graphene as interfacial layer to engineer the organic donor-acceptor heterojunction interface properties.

    PubMed

    Zhong, Shu; Zhong, Jian Qiang; Mao, Hong Ying; Wang, Rui; Wang, Yu; Qi, Dong Chen; Loh, Kian Ping; Wee, Andrew Thye Shen; Chen, Zhi Kuan; Chen, Wei

    2012-06-27

    We demonstrate the use of chemical-vapor-deposited (CVD) graphene as an effective indium-tin-oxide (ITO) electrode surface modifier to engineer the organic donor-acceptor heterojunction interface properties in an inverted organic solar cell device configuration. As revealed by in situ near-edge X-ray adsorption fine structure measurement, the organic donor-acceptor heterojunction, comprising copper-hexadecafluoro-phthalocyanine (F16CuPc) and copper phthalocyanine (CuPc), undergoes an obvious orientation transition from a standing configuration (molecular π-plane nearly perpendicular to the substrate surface) on the bare ITO electrode to a less standing configuration with the molecular π-plane stacking adopting a large projection along the direction perpendicular to the electrode surface on the CVD graphene-modified ITO electrode. Such templated less-standing configuration of the organic heterojunction could significantly enhance the efficiency of charge transport along the direction perpendicular to the electrode surface in the planar heterojunction-based devices. Compared with the typical standing organic-organic heterojunction on the bare ITO electrode, our in situ ultraviolet photoelectron spectroscopy experiments reveal that the heterojunction on the CVD graphene modified ITO electrode possesses better aligned energy levels with respective electrodes, hence facilitating effective charge collection. PMID:22662875

  8. Rapid recovery of polycrystalline silicon from kerf loss slurry using double-layer organic solvent sedimentation method

    NASA Astrophysics Data System (ADS)

    Xing, Peng-fei; Guo, Jing; Zhuang, Yan-xin; Li, Feng; Tu, Gan-feng

    2013-10-01

    The rapid development of photovoltaic (PV) industries has led to a shortage of silicon feedstock. However, more than 40% silicon goes into slurry wastes due to the kerf loss in the wafer slicing process. To effectively recycle polycrystalline silicon from the kerf loss slurry, an innovative double-layer organic solvent sedimentation process was presented in the paper. The sedimentation velocities of Si and SiC particles in some organic solvents were investigated. Considering the polarity, viscosity, and density of solvents, the chloroepoxy propane and carbon tetrachloride were selected to separate Si and SiC particles. It is found that Si and SiC particles in the slurry waste can be successfully separated by the double-layer organic solvent sedimentation method, which can greatly reduce the sedimentation time and improve the purity of obtained Si-rich and SiC-rich powders. The obtained Si-rich powders consist of 95.04% Si, and the cast Si ingot has 99.06% Si.

  9. Numerical simulations of the role of a ferroelectric polymer interfacial layer in organic solar cells.

    PubMed

    Liu, Bo; Xu, Feng; Zhang, Xinghua; Yan, Dadong; Lu, Dan

    2016-02-21

    A Pauli master equation method is adopted for the simulation of polymer bulk heterojunction (BHJ) solar cells with vinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) films as interfacial layers. According to previous reports, using highly crystalline P(VDF-TrFE) films as interfacial layers can highly enhance the efficiency of polymer BHJ solar cells, and possible mechanisms for the enhancement by two different groups were given as the dipole induced permanent internal electric field or simply the electrode improvement which implied that the origin is the barrier lowering effect. The correlation between the appearance of S-shaped current density-voltage (J-V) characteristics and the energy barrier is studied first, and then further results indicate that the previous electrode improvement model provides a consistent explanation for the origin of performance enhancement due to the insertion of polarized P(VDF-TrFE) interfacial layers. Moreover, the phenomenon of an increase of the internal electric field observed before can be attributed to better contact conditions which help reduce the bimolecular recombination rate. Comparatively speaking, the electrode improvement model can give a more rational explanation for the origin of performance enhancement experimentally found. In contrast, the dipole induced permanent internal electric field model was not complete enough. PMID:26822850

  10. An extremely low-index photonic crystal layer for enhanced light extraction from organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Shim, Yong Sub; Hwang, Ju Hyun; Park, Cheol Hwee; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2016-02-01

    This paper reports organic light-emitting diodes (OLEDs) with improved light extraction fabricated by embedding an extremely low-index photonic crystal (LIPC) layer. The LIPC layer increases the optical efficiency through the reduced wave-guide mode between the substrate and anode both by increased light resonance and by a strengthened diffraction effect from an extremely low-refractive-index medium, specifically a line structure composed of a vacuum gap. As a result, the current efficiency and power efficiency of the LIPC-OLEDs are 1.51 and 1.93 times higher, respectively, than the reference device at 1000 cd m-2. Because most of the light extraction is significant, especially in the forward direction, at the specific wavelengths satisfying the Bragg's diffraction equation, it is possible to calculate the anomalous spectrum of the LIPC-OLED through the finite-difference time domain (FDTD) method.This paper reports organic light-emitting diodes (OLEDs) with improved light extraction fabricated by embedding an extremely low-index photonic crystal (LIPC) layer. The LIPC layer increases the optical efficiency through the reduced wave-guide mode between the substrate and anode both by increased light resonance and by a strengthened diffraction effect from an extremely low-refractive-index medium, specifically a line structure composed of a vacuum gap. As a result, the current efficiency and power efficiency of the LIPC-OLEDs are 1.51 and 1.93 times higher, respectively, than the reference device at 1000 cd m-2. Because most of the light extraction is significant, especially in the forward direction, at the specific wavelengths satisfying the Bragg's diffraction equation, it is possible to calculate the anomalous spectrum of the LIPC-OLED through the finite-difference time domain (FDTD) method. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07312j

  11. Resolving Organized Aerosol Structures (Rolls and Layers) with Airborne Fast Mobility Particle Sizer (FMPS) During MILAGRO/INTEX Campaign

    NASA Astrophysics Data System (ADS)

    Kapustin, V.; Clarke, A.; Zhou, J.; Howell, S.; Shinozuka, Y.; Brekhovskikh, V.; McNaughton, C.

    2007-12-01

    The Hawaii Group for Environmental Aerosol Research [http://www.soest.hawaii.edu/HIGEAR] deployed a wide range of aerosol instrumentation aboard the C-130 and the NASA DC-8 as part of MILAGRO/INTEX. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering-f(RH), and the role of condensed species in changing the absorption properties of black carbon (BC) and inferred properties of organic carbon (OC). These measurements included size distributions from about 7 nm up to about 10,000 nm and their volatility at 150, 300 and 400 C; size selected response to heating (volatility) to resolve the state of mixing of the aerosol; continuous measurements of the light scattering and absorption at 3 wavelengths; measurements of the f(RH). We also flew the first airborne deployment of the new Fast Mobility Particle Sizer (FMPS, TSI Inc.) that provided information on rapid (1Hz) size variations in the Aitken mode. This revealed small scale structure of the aerosol and allowed us to examine size distributions varying over space and time associated with mixing processes previously unresolved etc. Rapid measurements during profiles also revealed variations in size over shallow layers. Other dynamic processes included rapid size distribution measurements within orographically induced aerosol layers and size distribution evolution of the nanoparticles formed by nucleation (C-130 flights 5, 6 and 9). Evidence for fluctuations induced by underlying changes in topography was also detected. These measurements also frequently revealed the aerosol variability in the presence of boundary layer rolls aligned along the wind in the Marine Boundary Layer (Gulf region) both with and without visible cloud streets (DC-8 flight 4 and C-130 flight 7). This organized convection over 1-2 km scales influences the mixing processes (entrainment, RH

  12. Organic functionalization of the germanium(100)- 2 x 1 semiconductor interface: Reaction chemistry, selective attachment strategies, and molecular layer deposition

    NASA Astrophysics Data System (ADS)

    Filler, Michael Aaron

    The explosive advancement in microelectronics technology and overall trend toward molecular devices, coupled with the tailorability inherent in organic molecules, have sparked interest in combined inorganic/organic systems. As a result, the attachment of organic molecules to the (100)-2x1 reconstructed, group IV semiconductor surfaces of silicon and germanium has received considerable attention in recent years. The well characterized surface structure and range of attachment configurations possible for the direct, covalent organic functionalization of semiconductor surfaces may uniquely enable the construction of the organic/semiconductor interface with molecular level precision and control. To develop a fundamental understanding of the chemical principles that govern reactions of carbonyl-containing compounds on these surfaces, carboxylic acids, acyl halides, tertiary amides, and formaldehyde were experimentally and theoretically investigated on Ge(100)-2x1 under ultrahigh vacuum conditions. We found that initial dative bond formation is a common motif observed for these compounds and subsequent surface reaction often leads to products which are analogous to those reported on clean transition metal surfaces. The observation of charge transfer, bidentate surface structures, as well as a catalytic coupling reaction suggests that the semi-metallic character of, and moderate strength bonds formed with, germanium substantially influence the reactivity of this surface. The controlled deposition of nanoscale organic films with precisely tailored properties and useful functionalities will likely be required for molecular devices, and layer-by-layer reaction of multifunctional molecules appears to be a promising synthetic strategy with which to achieve these layers. An essential prerequisite to this type of deposition is the selective attachment of multifunctional compounds at the semiconductor interface, with retention of at least one reactive moiety. Our studies of

  13. Effect of tunneling layers on the performances of floating-gate based organic thin-film transistor nonvolatile memories

    SciTech Connect

    Wang, Wei Han, Jinhua; Ying, Jun; Xiang, Lanyi; Xie, Wenfa

    2014-09-22

    Two types of floating-gate based organic thin-film transistor nonvolatile memories (FG-OTFT-NVMs) were demonstrated, with poly(methyl methacrylate co glycidyl methacrylate) (P(MMA-GMA)) and tetratetracontane (TTC) as the tunneling layer, respectively. Their device performances were measured and compared. In the memory with a P(MMA-GMA) tunneling layer, typical unipolar hole transport was obtained with a relatively small mobility of 0.16 cm{sup 2}/V s. The unidirectional shift of turn-on voltage (V{sub on}) due to only holes trapped/detrapped in/from the floating gate resulted in a small memory window of 12.5 V at programming/erasing voltages (V{sub P}/V{sub E}) of ±100 V and a nonzero reading voltage. Benefited from the well-ordered molecule orientation and the trap-free surface of TTC layer, a considerably high hole mobility of 1.7 cm{sup 2}/V s and a visible feature of electrons accumulated in channel and trapped in floating-gate were achieved in the memory with a TTC tunneling layer. High hole mobility resulted in a high on current and a large memory on/off ratio of 600 at the V{sub P}/V{sub E} of ±100 V. Both holes and electrons were injected into floating-gate and overwritten each other, which resulted in a bidirectional V{sub on} shift. As a result, an enlarged memory window of 28.6 V at the V{sub P}/V{sub E} of ±100 V and a zero reading voltage were achieved. Based on our results, a strategy is proposed to optimize FG-OTFT-NVMs by choosing a right tunneling layer to improve the majority carrier mobility and realize ambipolar carriers injecting and trapping in the floating-gate.

  14. Low temperature aqueous electrodeposited TiO(x) thin films as electron extraction layer for efficient inverted organic solar cells.

    PubMed

    Wong, Kim Hai; Mason, Chad William; Devaraj, Sappani; Ouyang, Jianyong; Balaya, Palani

    2014-02-26

    Organic solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester were fabricated with electrodeposited TiOx electron extraction layers 5-180 nm thick. Electrodeposition under ambient conditions is an attractive, facile and viable approach to prepare metal oxide interfacial layers. The TiOx films obtained displayed a linear relationship between thickness and deposition time when fabricated under ambient conditions using an aqueous air stable peroxotitanium precursor. The precursor solution was prepared from titanium isopropoxide using a chelate process, which allowed water to be used as solvent due to considerably decreased sensitivity of the precursor solution towards hydrolysis. Highly conformal TiOx films, typically observed with vacuum deposition techniques, were obtained on the indium tin oxide substrate upon electrogeneration of OH(-) ions using H2O2 additive. Conversely, significantly rougher films with spherical growths were obtained using NO3(-) additives. Low temperature annealing at 200 °C in air was found to greatly improve purity and O stoichiometry of the TiOx films, enabling efficient devices incorporating the electrodeposited TiOx to be made. Using MoOx as the hole extraction layer, the maximum power conversion efficiency obtained was 3.8% (Voc = 610 mV; Jsc = 10.6 mA/cm(2); FF = 59%) under simulated 100 mW/cm(2) (AM1.5G) solar irradiation, whereas an efficiency of 3.4% was achieved with fully solution processed interfacial layers comprising the electrodeposited TiOx films and a surfactant-modified PEDOT:PSS hole extraction layer. PMID:24484299

  15. Ternary Blend Composed of Two Organic Donors and One Acceptor for Active Layer of High-Performance Organic Solar Cells.

    PubMed

    Lee, Jong Won; Choi, Yoon Suk; Ahn, Hyungju; Jo, Won Ho

    2016-05-01

    Ternary blends composed of two donor absorbers with complementary absorptions provide an opportunity to enhance the short-circuit current and thus the power conversion efficiency (PCE) of organic solar cells. In addition to complementary absorption of two donors, ternary blends may exhibit favorable morphology for high-performance solar cells when one chooses properly the donor pair. For this purpose, we develop a ternary blend with two donors (diketopyrrolopyrrole-based polymer (PTDPP2T) and small molecule ((TDPP)2Ph)) and one acceptor (PC71BM). The solar cell made of a ternary blend with 10 wt % (TDPP)2Ph exhibits higher PCE of 7.49% as compared with the solar cells with binary blends, PTDPP2T:PC71BM (6.58%) and (TDPP)2Ph:PC71BM (3.21%). The higher PCE of the ternary blend solar cell is attributed mainly to complementary absorption of two donors. However, a further increase in (TDPP)2Ph content in the ternary blend (>10 wt %) decreases the PCE. The ternary blend with 10 wt % (TDPP)2Ph exhibits well-developed morphology with narrow-sized fibrils while the blend with 15 wt % (TDPP)2Ph shows phase separation with large-sized domains, demonstrating that the phase morphology and compatibility of ternary blend are important factors to achieve a high-performance solar cell made of ternary blends. PMID:27067461

  16. Methyl blue dyed polyethylene oxide films: Optical and electrochemical characterization and application as a single layer organic device

    NASA Astrophysics Data System (ADS)

    Kamath, Archana; Raghu, S.; Devendrappa, H.

    2016-01-01

    A single layer organic device employing methyl blue (MB) dyed polyethylene oxide (PEO) film has been fabricated and studied. The cyclic voltammetry was used to estimate the redox potential and energy band diagram of the device. The polymer film with highest concentration of the dye in PEO (PMB2%) possessing highest conductivity exhibited energy band gap of 2.62 eV with HOMO and LUMO values of 5.34 and 2.72 eV respectively. Based on cyclic voltammetry data, the electron affinity, ionization potential and energy band diagram of the device are discussed.

  17. Morphology of bipolar cells and their participation in spatial organization of the inner plexiform layer of jack mackerel retina.

    PubMed

    Podugolnikova, T A

    1985-01-01

    Morphology of bipolar cells in the jack mackerel retina [Trachurus mediterraneus ponticus (Aleev)] was investigated by the Golgi method. Eight types of bipolar cells are described. It is the first time that cells with an unbranched main dendrite are found in fish retina. It is shown that the inner plexiform layer of the jack mackerel retina contains regular lattices, located at 5 levels and conserted in a characteristic way with the cone mosaic. These lattices are formed by swellings of bipolar cell axons. It is shown that only bipolar cells with small dendritic aborizations (less than or equal to 14 micron dia) take part in this organization. PMID:3832608

  18. MoO3 as combined hole injection layer and tapered spacer in combinatorial multicolor microcavity organic light emitting diodes

    SciTech Connect

    Liu, R.; Xu, Chun; Biswas, Rana; Shinar, Joseph; Shinar, Ruth

    2011-09-01

    Multicolor microcavity ({mu}C) organic light-emitting diode (OLED) arrays were fabricated simply by controlling the hole injection and spacer MoO{sub 3} layer thickness. The normal emission was tunable from {approx}490 to 640 nm and can be further expanded. A compact, integrated spectrometer with two-dimensional combinatorial arrays of {mu}C OLEDs was realized. The MoO{sub 3} yields more efficient and stable devices, revealing a new breakdown mechanism. The pixel current density reaches {approx}4 A/cm{sup 2} and a maximal normal brightness {approx}140 000 Cd/m{sup 2}, which improves photoluminescence-based sensing and absorption measurements.

  19. Blue organic light-emitting devices with an oxadiazole-containing emitting layer exhibiting excited state intramolecular proton transfer

    NASA Astrophysics Data System (ADS)

    Ma, Dongge; Liang, Fushun; Wang, Lixiang; Lee, S. T.; Hung, L. S.

    2002-05-01

    We report a blue organic light-emitting device having an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), that exhibits excited state intramolecular proton transfer (ESIPT). The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/ m2. Electroluminescence spectra revealed a dominating peak at 450 nm and two additional peaks at 480 and 515 nm with a full width at half maximum of 50 nm. Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

  20. Substrate Orientation Effect in the On-Surface Synthesis of Tetrathiafulvalene-Integrated Single-Layer Covalent Organic Frameworks.

    PubMed

    Dong, Wei-long; Wang, Lin; Ding, Hui-min; Zhao, Lu; Wang, Dong; Wang, Cheng; Wan, Li-Jun

    2015-11-01

    The on-surface reactions of tetrathiafulvalene equipped with four benzaldehyde groups (4ATTF) and ditopic diamine molecules are investigated. 4ATTF tends to form large-scale-ordered rhombus structures when reacted with p-phenylenediamine (PPDA). A longer ditopic diamine molecule, 1,1'-biphenyl-4,4'-diamine dihydrochloride (BPDA), causes the domain size of the regular rhombus structure to decrease and triangular and irregular rhombus structures to appear upon reaction with 4ATTF. However, in the rhombus structures formed by different-length ditopic diamine molecules, the single-layer covalent organic frameworks on the graphite surface preferentially orient in alignment with the underlying HOPG substrate lattice. PMID:26467436

  1. Airborne measurements of organic bromine compounds in the Pacific tropical tropopause layer

    PubMed Central

    Navarro, Maria A.; Atlas, Elliot L.; Saiz-Lopez, Alfonso; Rodriguez-Lloveras, Xavier; Kinnison, Douglas E.; Lamarque, Jean-Francois; Tilmes, Simone; Filus, Michal; Harris, Neil R. P.; Meneguz, Elena; Ashfold, Matthew J.; Manning, Alistair J.; Cuevas, Carlos A.; Schauffler, Sue M.; Donets, Valeria

    2015-01-01

    Very short-lived brominated substances (VSLBr) are an important source of stratospheric bromine, an effective ozone destruction catalyst. However, the accurate estimation of the organic and inorganic partitioning of bromine and the input to the stratosphere remains uncertain. Here, we report near-tropopause measurements of organic brominated substances found over the tropical Pacific during the NASA Airborne Tropical Tropopause Experiment campaigns. We combine aircraft observations and a chemistry−climate model to quantify the total bromine loading injected to the stratosphere. Surprisingly, despite differences in vertical transport between the Eastern and Western Pacific, VSLBr (organic + inorganic) contribute approximately similar amounts of bromine [∼6 (4−9) parts per thousand] to the stratospheric input at the tropical tropopause. These levels of bromine cause substantial ozone depletion in the lower stratosphere, and any increases in future abundances (e.g., as a result of aquaculture) will lead to larger depletions. PMID:26504212

  2. Airborne measurements of organic bromine compounds in the Pacific tropical tropopause layer.

    PubMed

    Navarro, Maria A; Atlas, Elliot L; Saiz-Lopez, Alfonso; Rodriguez-Lloveras, Xavier; Kinnison, Douglas E; Lamarque, Jean-Francois; Tilmes, Simone; Filus, Michal; Harris, Neil R P; Meneguz, Elena; Ashfold, Matthew J; Manning, Alistair J; Cuevas, Carlos A; Schauffler, Sue M; Donets, Valeria

    2015-11-10

    Very short-lived brominated substances (VSLBr) are an important source of stratospheric bromine, an effective ozone destruction catalyst. However, the accurate estimation of the organic and inorganic partitioning of bromine and the input to the stratosphere remains uncertain. Here, we report near-tropopause measurements of organic brominated substances found over the tropical Pacific during the NASA Airborne Tropical Tropopause Experiment campaigns. We combine aircraft observations and a chemistry-climate model to quantify the total bromine loading injected to the stratosphere. Surprisingly, despite differences in vertical transport between the Eastern and Western Pacific, VSLBr (organic + inorganic) contribute approximately similar amounts of bromine [∼6 (4-9) parts per trillion] [corrected] to the stratospheric input at the tropical tropopause. These levels of bromine cause substantial ozone depletion in the lower stratosphere, and any increases in future abundances (e.g., as a result of aquaculture) will lead to larger depletions. PMID:26504212

  3. Conductive conjugated polyelectrolyte as hole-transporting layer for organic bulk heterojunction solar cells.

    PubMed

    Zhou, Huiqiong; Zhang, Yuan; Mai, Cheng-Kang; Collins, Samuel D; Nguyen, Thuc-Quyen; Bazan, Guillermo C; Heeger, Alan J

    2014-02-01

    Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as the hole-transporting layer (HTL) in bulk heterojunction (BHJ) solar cells, however, its anisotropic electrical conduction and intrinsic acidic nature generally limit the device performance. Here we demonstrate the application of a water/alcohol soluble CPE (CPE-K) as HTLs in BHJ solar cells, achieving a PCE up to 8.2%. The more superior and uniform vertical electrical conductivity found in CPE-K reduces the series resistance and provides efficient hole extraction. PMID:24170587

  4. A preliminary investigation of large-scale organized motions in a supersonic turbulent boundary layer on a curved surface

    NASA Technical Reports Server (NTRS)

    Donovan, J. F.; Smits, A. J.

    1987-01-01

    An experimental investigation concentrating on the change in the large-scale organized motions of a supersonic turbulent boundary layer subjected to a short region of concave surface curvature is presented. Two flows were studied, a relatively weak and a relatively strong perturbation. In both flows the freestream Mach number was 2.89 and the Reynolds number based on momentum thickness was 81,900. Hot-wire anemometry and schlieren photography provided the principle tools for this investigation. Hot-wire data were analyzed using spectral and correlation methods and conditional sampling techniques. Changes in structure angle and results of conditionally sampled velocity signals are discussed. The strong perturbation is found to increase the structure angle, and in both flows the length scales of the organized motions are altered.

  5. Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure

    PubMed Central

    2014-01-01

    This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d’Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm). PMID:25328506

  6. Synthesis, structure, and electrochemical properties of nano-layered organic-inorganic perovskites containing Fe(CN)6 3- layers and its application for detection of DNA hybridization

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Liu, Hanxing; Lin, Zhidong; Cao, Minghe; Yu, Zhiyong; Hao, Hua; Guo, Linlin

    2009-07-01

    Steady organic-inorganic perovskite hybrids with [H22-AMP]3/2Fe(CN)6, [H23-AMP]3/2Fe(CN)6 and [H24- AMP]3/2Fe(CN)6 (AMP = aminomethylpyridine) were formed in the air. Each structure shows an unusual layered organic-inorganic structural type. The hybrids enveloped in paraffin, respectively, to prepare hybrid paste electrode (HPE) (HPE-2 with [H22-AMP]3/2Fe(CN)6, HPE-3 with [H23-AMP]3/2Fe(CN)6, HPE-4 with [H24-AMP]3/2Fe(CN)6). Three hybrids in HPEs showed good electrochemical characteristics. The sequence of redox activity is [H24- AMP]3/2Fe(CN)6 > [H22-AMP]3/2Fe(CN)6 > [H23-AMP]3/2Fe(CN)6 and that of electrocatalytical characteristics is [H23- AMP]3/2Fe(CN)6 > [H22-AMP]3/2Fe(CN)6 > [H24-AMP]3/2 Fe(CN)6. Three hybrids have been employed to investigate the interaction between DNA and three hybrids. The results indicate that between [H23-AMP]3/2Fe(CN)6 and DNA is useful and [H23-AMP]3/2Fe(CN)6 can detect the hybridization of DNA. And the interaction between [H22-AMP]3/2Fe(CN)6 and DNA and between [H24-AMP]3/2Fe(CN)6 and DNA is slender. Three HPEs display remarkable electrochemical sensitivity and stability. The variation coefficients (RSD) of repeatedly successive and interval assays are less than 2.5%. The chemical and physical stability of three hybrids is satisfactory.

  7. A solution-doped small molecule hole transport layer for efficient ITO-free organic solar cells (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Bormann, Ludwig; Selzer, Franz; Leo, Karl; Mueller-Meskamp, Lars

    2015-10-01

    Indium-tin-oxide-free (ITO-free) organic solar cells are an important, emerging research field because ITO transparent electrodes are a bottleneck for cheap large area devices on flexible substrates. Among highly conductive PEDOT:PSS and metal grids, percolation networks made of silver nanowires (AgNW) with a diameter in the nanoscale show a huge potential due to easy processing (e.g. spray coating), high aspect ratios and excellent electrical and optical properties like 15 Ohm/sq with a transmission of 83.5 % including the substrate. However, the inherent surface roughness of the AgNW film impedes the implementation as bottom electrode in organic devices, especially fully vacuum deposited ones, where often shunts are obtained. Here, we report about the solution processing of a small molecule hole transport layer (s-HTL) comprising N,N'-((Diphenyl-N,N'-bis)9,9,-dimethyl-fluoren-2-yl)-benzidine (BF-DPB, host material) and the proprietary NDP9 (p-dopant) deposited from tetrahydrofuran (THF) as non-halogenated, "green" solvent. We show, that the doping process already takes place in solution and that conductivities, achieved with this process at high doping efficiencies (4 * 10^-4 S/cm at 10 wt% doping concentration), are comparable to thermal co-evaporation of BF-DPB:NDP9 under high vacuum, which is the proven deposition method for doped small molecule films. Applying this s-HTL to AgNW films leads to well smoothened electrodes, ready for application in organic devices. Vacuum-deposited organic p-i-n solar cells with DCV2-5T-Me(3:3):C60 as active layer show a power conversion efficiency of 4.4% and 3.7% on AgNW electrode with 35nm and 90 nm wire diameter, compared to 4.1% on ITO with the s-HTL.

  8. Fundamental studies of molecular depth profiling using organic delta layers as model systems

    PubMed Central

    Lu, C.; Wucher, A.; Winograd, N.

    2012-01-01

    Alternating Langmuir–Blodgett multilayers of barium arachidate (AA) and barium dimyristoyl phosphatidate (DMPA) were used to elucidate the factors that control depth resolution in molecular depth profiling experiments. More specifically, thin (4.4 nm) layers of DMPA were embedded in relatively thick (~50 nm) multilayer stacks of AA, resulting in a well-defined delta-layer model system closely resembling a biological membrane. This system was subjected to a three-dimensional imaging depth profile analysis using a focused buckminsterfullerene (C60) cluster ion beam. The depth response function measured in these experiments exhibits similar features as those determined in inorganic depth profiling: namely, an asymmetric shape with quasi-exponential leading and trailing edges and a central Gaussian peak. The magnitude of the corresponding characteristic rise and decay lengths is found to be 5 and 16 nm, respectively, while the total half width of the response function characterizing the apparent depth resolution was about 29 nm. Ion-induced mixing is proposed to be largely responsible for the broadening, rather than topography, as determined by atomic force microscopy. PMID:24347743

  9. Novel building units with bimetallic rings in inorganic/organic hybrid chains and layers

    SciTech Connect

    Mahenthirarajah, Thushitha; Li Yang; Lightfoot, Philip

    2009-11-15

    Hydrothermal synthesis has produced three new compounds constructed from novel building units containing vanadium-oxide (or oxyfluoride) subunits linked together via covalently bound cationic copper complexes. Each new compound exhibits novel structural features: [Cu(dipa)][VOF{sub 4}] (1) incorporates a corner-sharing octahedral vanadium(IV) oxyfluoride chain decorated by copper-(2,2'-dipyridyl amine) complexes which form intra-chain bridges. Within a similar reactant system [Cu(dipa)]{sub 2}[V{sub 6}O{sub 17}] (2) is produced, the structure of which exhibits edge-sharing trigonal bipyramidal vanadium(V) 'ladder-like' double chains which are bridged into layers by tetrahedral pyrovanadate dimers together with the copper-(2,2'-dipyridyl amine) complexes. [Cu(py){sub 4}]{sub 2}[V{sub 4}O{sub 12}] (3), is a 2-D structure featuring exclusively tetrahedral vanadium(V) in four-membered ring building blocks, linked through octahedral copper-pyridine complexes to form two crystallographically different bimetallic layers. - Graphical abstract: Hydrothermal synthesis is used to prepare hybrid mixed metal oxides and oxyfluorides with novel extended connectivities

  10. Multi-pulse LIBDE of fused silica at different thicknesses of the organic absorber layer

    NASA Astrophysics Data System (ADS)

    Pan, Yunxiang; Ehrhardt, Martin; Lorenz, Pierre; Han, Bing; Hopp, Bela; Vass, Csaba; Ni, Xiaowu; Zimmer, Klaus

    2015-12-01

    Laser-induced etching techniques feature several unique characteristics that enable ultraprecise machining of transparent materials. However, LIBDE (laser-induced back side dry etching) and LIBWE (laser-induced back side wet etching) are preferentially studied due to experimental feasibilities either using a very thin or a bulk absorber at the rear side of the transparent material. This study aims to fill the gap by examining the thickness dependence of the absorbing material. Multi-pulse-LIBDE (MP-LIBDE) of fused silica using different thick photoresist absorber layers (dL = 0.2-11.7 μm) was performed with a KrF excimer laser (λ = 248 nm, tp ≈ 20 ns). The influence of several experimental parameters, such as laser fluence, pulse number, film thickness, on the ablation morphology and the etching rate were investigated. Especially at moderate fluences (F = 0.7-1.5 J/cm2) MP-LIBDE and LIBWE show several similar process characteristics such as the etching rate dependence on the laser fluence and the pulse number with a typical etching rate of approx. 12 nm at 1 J/cm2. However, the specific etching rate values depend on the absorber layer thickness, for instance. The morphology of the etched surface is smooth with a roughness of below 5 nm rms. Further, the modification of the surface has been observed and will be discussed in relation to the multi-pulse laser etching mechanism.

  11. Na₂B₁₀O₁₇·H₂en: a three-dimensional open-framework layered borate co-templated by inorganic cations and organic amines.

    PubMed

    Wang, Jun-Hua; Wei, Qi; Cheng, Jian-Wen; He, Huan; Yang, Bai-Feng; Yang, Guo-Yu

    2015-03-25

    A layered borate Na2B10O17·H2en (1, en = ethylenediamine) with three-dimensional microporosity within the layers has been synthesized under solvothermal conditions by using organic amines and inorganic cations as the templates. Its framework displays a unique 5-connected net constructed by B5O11 cluster and emits blue luminescence. PMID:25711166

  12. Roles of Energy/Charge Cascades and Intermixed Layers at Donor/Acceptor Interfaces in Organic Solar Cells

    PubMed Central

    Nakano, Kyohei; Suzuki, Kaori; Chen, Yujiao; Tajima, Keisuke

    2016-01-01

    The secret to the success of mixed bulk heterojunctions (BHJs) in yielding highly efficient organic solar cells (OSCs) could reside in the molecular structures at their donor/acceptor (D/A) interfaces. In this study, we aimed to determine the effects of energy and charge cascade structures at the interfaces by using well-defined planar heterojunctions (PHJs) as a model system. The results showed that (1) the charge cascade structure enhanced VOC because it shuts down the recombination pathway through charge transfer (CT) state with a low energy, (2) the charge cascade layer having a wider energy gap than the bulk material decreased JSC because the diffusion of the excitons from the bulk to D/A interface was blocked; the energy of the cascade layers must be appropriately arranged for both the charges and the excitons, and (3) molecular intermixing in the cascade layer opened the recombination path through the low-energy CT state and decreased VOC. Based on these findings, we propose improved structures for D/A interfaces in BHJs. PMID:27404948

  13. Roles of Energy/Charge Cascades and Intermixed Layers at Donor/Acceptor Interfaces in Organic Solar Cells

    NASA Astrophysics Data System (ADS)

    Nakano, Kyohei; Suzuki, Kaori; Chen, Yujiao; Tajima, Keisuke

    2016-07-01

    The secret to the success of mixed bulk heterojunctions (BHJs) in yielding highly efficient organic solar cells (OSCs) could reside in the molecular structures at their donor/acceptor (D/A) interfaces. In this study, we aimed to determine the effects of energy and charge cascade structures at the interfaces by using well-defined planar heterojunctions (PHJs) as a model system. The results showed that (1) the charge cascade structure enhanced VOC because it shuts down the recombination pathway through charge transfer (CT) state with a low energy, (2) the charge cascade layer having a wider energy gap than the bulk material decreased JSC because the diffusion of the excitons from the bulk to D/A interface was blocked; the energy of the cascade layers must be appropriately arranged for both the charges and the excitons, and (3) molecular intermixing in the cascade layer opened the recombination path through the low-energy CT state and decreased VOC. Based on these findings, we propose improved structures for D/A interfaces in BHJs.

  14. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tsukanov, A. A.; Psakhie, S. G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered.

  15. Highly efficient organic light emitting diodes formed by solution processed red emitters with evaporated blue common layer structure

    NASA Astrophysics Data System (ADS)

    Cho, Ye Ram; Kim, Hyung Suk; Yu, Young-Jun; Suh, Min Chul

    2015-10-01

    We prepared highly-efficient solution-processed red phosphorescent organic light emitting diodes (PHOLEDs) with a blue common layer structure that can reasonably confine the triplet excitons inside of the red emission layer (EML) with the assistance of a bipolar exciton blocking layer. The red PHOLEDs containing EML with a 7 : 3 ratio of 11-(4,6-diphenyl-[1,3,5]triazin-2-yl)-12-phenyl-11,12-dihydro-11,12-diaza-indeno[2,1-a]fluorene (n-type host, NH) : 4-(3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene (p-type host, PH) doped with 5% Iridium(III) bis(2-(3,5-dimethylphenyl)quinolinato-N,C2’)tetramethylheptadionate (Red Dopant, RD) produced the highest current and power efficiencies at 23.4 cd/A and 13.6 lm/W, with a 19% external quantum efficiency at 1000 cd/m2. To the best of our knowledge, such efficiency was the best among those that have been obtained from solution-processed small molecular red PHOLEDs. In addition, the host molecules utilized in this study have no flexible spacers, such as an alkyl chain, which normally deteriorate the stability of the device.

  16. Highly efficient organic light emitting diodes formed by solution processed red emitters with evaporated blue common layer structure

    PubMed Central

    Cho, Ye Ram; Kim, Hyung Suk; Yu, Young-Jun; Suh, Min Chul

    2015-01-01

    We prepared highly-efficient solution-processed red phosphorescent organic light emitting diodes (PHOLEDs) with a blue common layer structure that can reasonably confine the triplet excitons inside of the red emission layer (EML) with the assistance of a bipolar exciton blocking layer. The red PHOLEDs containing EML with a 7 : 3 ratio of 11-(4,6-diphenyl-[1,3,5]triazin-2-yl)-12-phenyl-11,12-dihydro-11,12-diaza-indeno[2,1-a]fluorene (n-type host, NH) : 4-(3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene (p-type host, PH) doped with 5% Iridium(III) bis(2-(3,5-dimethylphenyl)quinolinato-N,C2’)tetramethylheptadionate (Red Dopant, RD) produced the highest current and power efficiencies at 23.4 cd/A and 13.6 lm/W, with a 19% external quantum efficiency at 1000 cd/m2. To the best of our knowledge, such efficiency was the best among those that have been obtained from solution-processed small molecular red PHOLEDs. In addition, the host molecules utilized in this study have no flexible spacers, such as an alkyl chain, which normally deteriorate the stability of the device. PMID:26514274

  17. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    PubMed Central

    Tsukanov, A.A.; Psakhie, S.G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered. PMID:26817816

  18. Study of Sequential Dexter Energy Transfer in High Efficient Phosphorescent White Organic Light-Emitting Diodes with Single Emissive Layer

    NASA Astrophysics Data System (ADS)

    Kim, Jin Wook; You, Seung Il; Kim, Nam Ho; Yoon, Ju-An; Cheah, Kok Wai; Zhu, Fu Rong; Kim, Woo Young

    2014-11-01

    In this study, we report our effort to realize high performance single emissive layer three color white phosphorescent organic light emitting diodes (PHOLEDs) through sequential Dexter energy transfer of blue, green and red dopants. The PHOLEDs had a structure of; ITO(1500 Å)/NPB(700 Å)/mCP:Firpic-x%:Ir(ppy)3-0.5%:Ir(piq)3-y%(300 Å)/TPBi(300 Å)/Liq(20 Å)/Al(1200 Å). The dopant concentrations of FIrpic, Ir(ppy)3 and Ir(piq)3 were adjusted and optimized to facilitate the preferred energy transfer processes attaining both the best luminous efficiency and CIE color coordinates. The presence of a deep trapping center for charge carriers in the emissive layer was confirmed by the observed red shift in electroluminescent spectra. White PHOLEDs, with phosphorescent dopant concentrations of FIrpic-8.0%:Ir(ppy)3-0.5%:Ir(piq)3-0.5% in the mCP host of the single emissive layer, had a maximum luminescence of 37,810 cd/m2 at 11 V and a luminous efficiency of 48.10 cd/A at 5 V with CIE color coordinates of (0.35, 0.41).

  19. Highly efficient organic light emitting diodes formed by solution processed red emitters with evaporated blue common layer structure.

    PubMed

    Cho, Ye Ram; Kim, Hyung Suk; Yu, Young-Jun; Suh, Min Chul

    2015-01-01

    We prepared highly-efficient solution-processed red phosphorescent organic light emitting diodes (PHOLEDs) with a blue common layer structure that can reasonably confine the triplet excitons inside of the red emission layer (EML) with the assistance of a bipolar exciton blocking layer. The red PHOLEDs containing EML with a 7 : 3 ratio of 11-(4,6-diphenyl-[1,3,5]triazin-2-yl)-12-phenyl-11,12-dihydro-11,12-diaza-indeno[2,1-a]fluorene (n-type host, NH) : 4-(3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene (p-type host, PH) doped with 5% Iridium(III) bis(2-(3,5-dimethylphenyl)quinolinato-N,C2')tetramethylheptadionate (Red Dopant, RD) produced the highest current and power efficiencies at 23.4 cd/A and 13.6 lm/W, with a 19% external quantum efficiency at 1000 cd/m(2). To the best of our knowledge, such efficiency was the best among those that have been obtained from solution-processed small molecular red PHOLEDs. In addition, the host molecules utilized in this study have no flexible spacers, such as an alkyl chain, which normally deteriorate the stability of the device. PMID:26514274

  20. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study.

    PubMed

    Tsukanov, A A; Psakhie, S G

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered. PMID:26817816

  1. Effect of two yellow delta-emitting layers on device performance of phosphorescent white organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Zhao, Juan; Yu, Junsheng; Wang, Xiao; Zhang, Lei

    2013-03-01

    Phosphorescent white organic light-emitting devices (WOLEDs) with a structure of ITO/TAPC/δ-EML1/mCP:FIrpic/δ-EML2/Bphen/Mg:Ag were fabricated, wherein two ultrathin and host-free emitting layers (EMLs) were formed by using yellow bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate) [(tbt)2Ir(acac)] and referred to as delta-EMLs (δ-EML1 and δ-EML2). By adjusting the thicknesses of δ-EMLs, a maximum current efficiency of 27.6 cd/A, an external quantum efficiency (EQE) of 10%, together with low efficiency roll-off at high luminance were achieved. The results showed that δ-EML1 played a dominant role on charge carrier trapping, while δ-EML2 had major impact on yellow light emission, which were highly sensitive to the location of δ-EMLs. Furthermore, by introducing 5-nm Au as anode modifying layer, high device efficiency was maintained along with excellent color stability of warm white emission, displaying color coordinates of (0.38, 0.42) and color temperature of 4348 K at a luminance of 7000 cd/m2. Importantly, explanation and analysis for the influence of both ultrathin δ-EMLs and anode modifying layer on device performance were proposed.

  2. Roles of Energy/Charge Cascades and Intermixed Layers at Donor/Acceptor Interfaces in Organic Solar Cells.

    PubMed

    Nakano, Kyohei; Suzuki, Kaori; Chen, Yujiao; Tajima, Keisuke

    2016-01-01

    The secret to the success of mixed bulk heterojunctions (BHJs) in yielding highly efficient organic solar cells (OSCs) could reside in the molecular structures at their donor/acceptor (D/A) interfaces. In this study, we aimed to determine the effects of energy and charge cascade structures at the interfaces by using well-defined planar heterojunctions (PHJs) as a model system. The results showed that (1) the charge cascade structure enhanced VOC because it shuts down the recombination pathway through charge transfer (CT) state with a low energy, (2) the charge cascade layer having a wider energy gap than the bulk material decreased JSC because the diffusion of the excitons from the bulk to D/A interface was blocked; the energy of the cascade layers must be appropriately arranged for both the charges and the excitons, and (3) molecular intermixing in the cascade layer opened the recombination path through the low-energy CT state and decreased VOC. Based on these findings, we propose improved structures for D/A interfaces in BHJs. PMID:27404948

  3. Effect of fluorine plasma treatment with chemically reduced graphene oxide thin films as hole transport layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Youn-Yeol; Kang, Byung Hyun; Lee, Yang Doo; Lee, Sang Bin; Ju, Byeong-Kwon

    2013-12-01

    The inorganic materials such as V2O5, MoO3 and WO3 were investigated to replace PEDOT:PSS as hole transport layer (HTL) in organic electronic devices such as organic solar cells (OSCs) and organic lighting emission diodes. However, these methods require vacuum techniques that are long time process and complex. Here, we report about plasma treatment with SF6 and CF4 using reactive ion etching on reduced graphene oxide (rGO) thin films that are obtained using an eco-friendly method with vitamin C. The plasma treated rGO thin films have dipoles since they consist of covalent bonds with fluorine on the surface of rGO. This means it is possible to increase the electrostatic potential energy than bare rGO. Increased potential energy on the surface of rGO films is worth applying organic electronic devices as HTL such as OSCs. Consequently, the power conversion efficiency of OSCs increased more than the rGO films without plasma treatment.

  4. Controllable Threshold Voltage in Organic Complementary Logic Circuits with an Electron-Trapping Polymer and Photoactive Gate Dielectric Layer.

    PubMed

    Dao, Toan Thanh; Sakai, Heisuke; Nguyen, Hai Thanh; Ohkubo, Kei; Fukuzumi, Shunichi; Murata, Hideyuki

    2016-07-20

    We present controllable and reliable complementary organic transistor circuits on a PET substrate using a photoactive dielectric layer of 6-[4'-(N,N-diphenylamino)phenyl]-3-ethoxycarbonylcoumarin (DPA-CM) doped into poly(methyl methacrylate) (PMMA) and an electron-trapping layer of poly(perfluoroalkenyl vinyl ether) (Cytop). Cu was used for a source/drain electrode in both the p-channel and n-channel transistors. The threshold voltage of the transistors and the inverting voltage of the circuits were reversibly controlled over a wide range under a program voltage of less than 10 V and under UV light irradiation. At a program voltage of -2 V, the inverting voltage of the circuits was tuned to be at nearly half of the supply voltage of the circuit. Consequently, an excellent balance between the high and low noise margins (NM) was produced (64% of NMH and 68% of NML), resulting in maximum noise immunity. Furthermore, the programmed circuits showed high stability, such as a retention time of over 10(5) s for the inverter switching voltage. Our findings bring about a flexible, simple way to obtain robust, high-performance organic circuits using a controllable complementary transistor inverter. PMID:27348479

  5. Effect of dye concentrations in blended-layer white organic light-emitting devices based on phosphorescent dyes

    NASA Astrophysics Data System (ADS)

    Pearson, C.; Cadd, D. H.; Petty, M. C.; Hua, Y. L.

    2009-09-01

    The electronic and optoelectronic behavior of white organic light-emitting devices (OLEDs) based on blue (FIrpic) and red [Ir(piq)2(acac)] phosphorescent dyes doped into the same layer of a polyvinylcarbazole (PVK) host are reported. The conductivity of all the OLEDs studied appeared to be dominated by space-charge injection effects, exhibiting a current I versus voltage V dependence of the form I ∝Vn, with n ≈7 at applied voltages at which electroluminescence was observed. Systematic studies of the current versus voltage and light-emitting behavior of the OLEDs have identified different excitation processes for the two dyes. It is suggested that electroluminescence from the FIrpic molecules originates by direct transfer of the exciton energy from the PVK to the dye molecules, while the process of light emission from the Ir(piq)2(acac) molecules involves carrier trapping. The efficiency of the devices can be tuned, to some extent, by varying the thickness of the organic film. Luminous efficiencies and luminous power efficiencies of 8 cd A-1 and 3 lm W-1 were measured for these blended-layer OLEDs, with Commission Internationale de l'Eclairage coordinates of 0.35, 0.35.

  6. Pressure-assisted fabrication of organic light emitting diodes with MoO{sub 3} hole-injection layer materials

    SciTech Connect

    Du, J.; Anye, V. C.; Vodah, E. O.; Tong, T.; Zebaze Kana, M. G.; Soboyejo, W. O.

    2014-06-21

    In this study, pressures of ∼5 to ∼8 MPa were applied to organic light emitting diodes containing either evaporated molybdenum trioxide (MoO{sub 3}) or spin-coated poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) hole-injection layers (HILs). The threshold voltages for both devices were reduced by about half, after the application of pressure. Furthermore, in an effort to understand the effects of pressure treatment, finite element simulations were used to study the evolution of surface contact between the HIL and emissive layer (EML) under pressure. The blister area due to interfacial impurities was also calculated. This was shown to reduce by about half, when the applied pressures were between ∼5 and 8 MPa. The finite element simulations used Young's modulus measurements of MoO{sub 3} that were measured using the nanoindentation technique. They also incorporated measurements of the adhesion energy between the HIL and EML (measured by force microscopy during atomic force microscopy). Within a fracture mechanics framework, the implications of the results are then discussed for the pressure-assisted fabrication of robust organic electronic devices.

  7. Thickness dependence of the MoO3 blocking layers on ZnO nanorod-inverted organic photovoltaic devices

    PubMed Central

    Wang, Mingjun; Li, Yuan; Huang, Huihui; Peterson, Eric D.; Nie, Wanyi; Zhou, Wei; Zeng, Wei; Huang, Wenxiao; Fang, Guojia; Sun, Nanhai; Zhao, Xingzhong; Carroll, David L.

    2011-01-01

    Organic solar cells based on vertically aligned zinc oxide nanorod arrays (ZNR) in an inverted structure of indium tin oxide (ITO)∕ZNR∕poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester(P3HT:PCBM)∕MoO3∕aluminum(Al) were studied. We found that the optimum MoO3 layer thickness condition of 20 nm, the MoO3 can effectively decrease the probability of bimolecular recombination either at the Al interface or within the active layer itself. For this optimum condition we get a power conversion efficiency of 2.15%, a short-circuit current density of 9.02 mA∕cm2, an open-circuit voltage of 0.55V, and a fill factor of 0.44 under 100 mW∕cm2 irradiation. Our investigations also show that the highly crystallized ZNR can create short and continuous pathways for electron transport and increase the contact area between the ZNR and the organic materials. PMID:21464889

  8. Comparative Strength and Dendritic Organization of Thalamocortical and Corticocortical Synapses onto Excitatory Layer 4 Neurons

    PubMed Central

    Schoonover, Carl E.; Tapia, Juan-Carlos; Schilling, Verena C.; Wimmer, Verena; Blazeski, Richard; Zhang, Wanying; Mason, Carol A.

    2014-01-01

    Thalamus is a potent driver of cortical activity even though cortical synapses onto excitatory layer 4 neurons outnumber thalamic synapses 10 to 1. Previous in vitro studies have proposed that thalamocortical (TC) synapses are stronger than corticocortical (CC) synapses. Here, we investigated possible anatomical and physiological differences between these inputs in the rat in vivo. We developed a high-throughput light microscopy method, validated by electron microscopy, to completely map the locations of synapses across an entire dendritic tree. This demonstrated that TC synapses are slightly more proximal to the soma than CC synapses, but detailed compartmental modeling predicted that dendritic filtering does not appreciably favor one synaptic class over another. Measurements of synaptic strength in intact animals confirmed that both TC and CC synapses are weak and approximately equivalent. We conclude that thalamic effectiveness does not rely on enhanced TC strength, but rather on coincident activation of converging inputs. PMID:24828630

  9. Dry Etching of Organic Low Dielectric Constant Film without Etch Stop Layer

    NASA Astrophysics Data System (ADS)

    Mizumura, Michinobu; Fukuyama, Ryouji; Oomoto, Yutaka

    2002-04-01

    We investigated the trade-off between the increase of etch rate and the control of subtrenching in H2/N2 etching of a SiLK film (SiLK is a trademark of The Dow Chemical Company) without an etch stop layer for a Cu/low-k dual damascene structure. Based on our results, it is clear that the re-incident distribution of the reaction product influenced the mechanism of subtrenching strongly. As H etchant had the ability to remove the reaction product efficiently, we have successfully obtained good etching performance (an average etch rate of 128 nm/min, no subtrenching, and an etch rate uniformity of 8.9% within a 200 mm wafer) using an H2 high-flow-rate process in order to increase the amount of H etchant.

  10. Highly fluorescent colloids based on rhodamine 6G, modified layered silicate, and organic solvent.

    PubMed

    Bujdák, Juraj; Iyi, Nobuo

    2012-12-15

    Synthetic layered silicate saponite was modified with dodecyltrimethylammonium (C12), octadecyltrimethylammonium (C18), and dioctadecyldimethylammonium (2C18) cations for use as sorbents of the laser dye, rhodamine 6G (R6G). Via solvent exchange, transparent colloids in xylene were prepared and investigated using absorption and fluorescence spectroscopies. Molecular aggregation and partial quenching of the fluorescence were observed for the colloids based on 2C18 cations. Maximal fluorescence yields were observed for the colloids with C12 and C18 cations. Transparent gels without an apparent loss of luminescent efficiency could be prepared by concentrating the colloids. These highly fluorescent colloids and gels represent new types of materials with interesting optical properties. PMID:22995248

  11. Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

    PubMed

    Rao, Arun D; Karalatti, Suresh; Thomas, Tiju; Ramamurthy, Praveen C

    2014-10-01

    Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer. PMID:25238197

  12. Highly efficient blue organic light-emitting diodes using quantum well-like multiple emissive layer structure

    NASA Astrophysics Data System (ADS)

    Yoon, Ju-An; Kim, You-Hyun; Kim, Nam Ho; Yoo, Seung Il; Lee, Sang Youn; Zhu, Fu Rong; Kim, Woo Young

    2014-04-01

    In this study, the properties of blue organic light-emitting diodes (OLEDs), employing quantum well-like structure (QWS) that includes four different blue emissive materials of 4,4'-bis(2,2'-diphenylyinyl)-1,1'-biphenyl (DPVBi), 9,10-di(naphth-2-yl)anthracene (ADN), 2-( N, N-diphenyl-amino)-6-[4-( N, N-diphenyl amine)styryl]naphthalene (DPASN), and bis(2-methyl-8-quinolinolate)-4-(phenyl phenolato) aluminum (BAlq), were investigated. Conventional QWS blue OLEDs composed of multiple emissive layers and charge blocking layer with lower highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy level, and devices with triple emissive layers for more significant hole-electron recombination and a wider region for exciton generation were designed. The properties of triple emissive layered blue OLEDs with the structure of indium tin oxide (ITO) / N, N'-diphenyl- N, N'-bis(1-naphthyl-phenyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) (700 Ǻ)/X (100 Ǻ)/BAlq (100 Ǻ)/X (100 Ǻ)/4,7-diphenyl-1,10-phenanthroline (Bphen) (300 Ǻ)/lithium quinolate (Liq) (20 Ǻ)/aluminum (Al) (1,200 Ǻ) (X = DPVBi, ADN, DPASN) were examined. HOMO-LUMO energy levels of DPVBi, ADN, DPASN, and BAlq are 2.8 to 5.9, 2.6 to 5.6, 2.3 to 5.2, and 2.9 to 5.9 eV, respectively. The OLEDs with DPASN/BAlq/DPASN QWS with maximum luminous efficiency of 5.32 cd/A was achieved at 3.5 V.

  13. Controlling charge balance and exciton recombination by bipolar host in single-layer organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Qiao, Xianfeng; Tao, Youtian; Wang, Qiang; Ma, Dongge; Yang, Chuluo; Wang, Lixiang; Qin, Jingui; Wang, Fosong

    2010-08-01

    Highly efficient single-layer organic light-emitting diodes with reduced efficiency roll-off are demonstrated by using a bipolar host material of 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) doped with iridium complexes as the emissive layer. For example, the green single-layer device, employing fac-tris(2-phenylpyridine)iridium Ir(ppy)3 as dopant, shows a peak current efficiency of 45.57 cd A-1, corresponding to external quantum efficiency (EQE) of 12.42%, and still exhibits efficiencies of 45.26 cd A-1 and 40.42 cd A-1 at luminance of 1000 and 10 000 cd m-2, respectively. In addition, the yellow and red single-layer devices, with bis(2-(9,9- diethyl-9H-fluoren-2-yl)-1-phenyl-1H-benzoimidazol-N ,C3)iridium(acetylacetonate) (fbi)2Ir(acac) and bis(1-phenylisoquinolinolato-C2,N)iridium(acetylacetonate) (piq)2Ir(acac) as emitter, also show high EQE of 7.04% and 7.28%, respectively. The transport properties of o-CzOXD film are well investigated by current-voltage measurement, from which both hole and electron mobility are determined. It is found that the o-CzOXD shows appealing bipolar transport character, which is favor for the balanced charge distribution in the whole doped zone. More importantly, the multifunctional role of hole trapping and electron transporting of the iridium complex in o-CzOXD further balances the charge carriers and broadens the recombination zone. As a result, the recombination of electrons and holes is significantly improved and the triplet-triplet annihilation and triplet-polaron quenching processes are effectively suppressed, eventually leading to the high efficiency as well as the reduced efficiency roll-off.

  14. Highly efficient blue organic light-emitting diodes using quantum well-like multiple emissive layer structure

    PubMed Central

    2014-01-01

    In this study, the properties of blue organic light-emitting diodes (OLEDs), employing quantum well-like structure (QWS) that includes four different blue emissive materials of 4,4′-bis(2,2′-diphenylyinyl)-1,1′-biphenyl (DPVBi), 9,10-di(naphth-2-yl)anthracene (ADN), 2-(N,N-diphenyl-amino)-6-[4-(N,N-diphenyl amine)styryl]naphthalene (DPASN), and bis(2-methyl-8-quinolinolate)-4-(phenyl phenolato) aluminum (BAlq), were investigated. Conventional QWS blue OLEDs composed of multiple emissive layers and charge blocking layer with lower highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy level, and devices with triple emissive layers for more significant hole-electron recombination and a wider region for exciton generation were designed. The properties of triple emissive layered blue OLEDs with the structure of indium tin oxide (ITO) /N,N′-diphenyl-N,N′-bis(1-naphthyl-phenyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) (700 Ǻ)/X (100 Ǻ)/BAlq (100 Ǻ)/X (100 Ǻ)/4,7-diphenyl-1,10-phenanthroline (Bphen) (300 Ǻ)/lithium quinolate (Liq) (20 Ǻ)/aluminum (Al) (1,200 Ǻ) (X = DPVBi, ADN, DPASN) were examined. HOMO-LUMO energy levels of DPVBi, ADN, DPASN, and BAlq are 2.8 to 5.9, 2.6 to 5.6, 2.3 to 5.2, and 2.9 to 5.9 eV, respectively. The OLEDs with DPASN/BAlq/DPASN QWS with maximum luminous efficiency of 5.32 cd/A was achieved at 3.5 V. PMID:24940170

  15. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction

    NASA Astrophysics Data System (ADS)

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A.; Casanova, Fèlix; van der Zant, Herre S. J.; Castellanos-Gomez, Andres; Hueso, Luis E.

    2015-09-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials

  16. Optically readout write once read many memory with single active organic layer

    NASA Astrophysics Data System (ADS)

    Nguyen, Viet Cuong; Lee, Pooi See

    2016-01-01

    An optically readable write once read many memory (WORM) in Ag/Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH PPV)/ITO is demonstrated in this work. Utilising characteristics of the organic light emitting diode structure of Ag/MEH PPV/ITO and electrochemical metallization of Ag, a WORM with light emitting capability can be realised. The simple fabrication process and multifunction capability of the device can be useful for future wearable optoelectronics and photomemory applications, where fast and parallel readout can be achieved by photons.

  17. Contribution of dissolved organic matter to submicron water-soluble organic aerosols in the marine boundary layer over the eastern equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Miyazaki, Yuzo; Coburn, Sean; Ono, Kaori; Ho, David T.; Pierce, R. Bradley; Kawamura, Kimitaka; Volkamer, Rainer

    2016-06-01

    Stable carbon isotopic compositions of water-soluble organic carbon (WSOC) and organic molecular markers were measured to investigate the relative contributions of the sea surface sources to the water-soluble fraction of submicron organic aerosols collected over the eastern equatorial Pacific during the Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOCs (TORERO)/KA-12-01 cruise. On average, the water-soluble organic fraction of the total carbon (TC) mass in submicron aerosols was ˜ 30-35 % in the oceans with the low chlorophyll a (Chl a) concentrations, whereas it was ˜ 60 % in the high-Chl a regions. The average stable carbon isotope ratio of WSOC (δ13CWSOC) was -19.8 ± 2.0 ‰, which was systematically higher than that of TC (δ13CTC) (-21.8 ± 1.4 ‰). We found that in the oceans with both high and low Chl a concentrations the δ13CWSOC was close to the typical values of δ13C for dissolved organic carbon (DOC), ranging from -22 to -20 ‰ in surface seawater of the tropical Pacific Ocean. This suggests an enrichment of marine biological products in WSOC aerosols in the study region regardless of the oceanic area. In particular, enhanced levels of WSOC and biogenic organic marker compounds together with high values of WSOC / TC ( ˜ 60 %) and δ13CWSOC were observed over upwelling areas and phytoplankton blooms, which was attributed to planktonic tissues being more enriched in δ13C. The δ13C analysis estimated that, on average, marine sources contribute ˜ 90 ± 25 % of the aerosol carbon, indicating the predominance of marine-derived carbon in the submicron WSOC. This conclusion is supported by Lagrangian trajectory analysis, which suggests that the majority of the sampling points on the ship had been exposed to marine boundary layer (MBL) air for more than 80 % of the time during the previous 7 days. The combined analysis of the δ13C and monosaccharides, such as glucose and fructose, demonstrated that DOC concentration was

  18. The role of fluids in rock layering development: a pressure solution self-organized process revealed by laboratory experiments

    NASA Astrophysics Data System (ADS)

    Gratier, Jean-Pierre; Noiriel, Catherine; Renard, Francois

    2015-04-01

    Natural deformation of rocks is often associated with stress-driven differentiation processes leading to irreversible transformations of their microstructures. The development mechanisms of such processes during diagenesis, tectonic, metamorphism or fault differentiation are poorly known as they are difficult to reproduce experimentally due to the very slow kinetics of stress-driven chemical processes. Here, we show that experimental compaction with development of differentiated layering, similar to what happens in natural deformation, can be obtained by indenter techniques in laboratory conditions. Samples of plaster mixed with clay and of diatomite loosely interbedded with volcanic dust were loaded in presence of their saturated aqueous solutions during several months at 40°C and 150°C, respectively. High-resolution X-ray microtomography and scanning electron microscopy observations show that the layering development is a pressure solution self-organized process. Stress-driven dissolution of the soluble minerals (either gypsum or silica) is initiated in the areas initially richer in insoluble minerals (clays or volcanic dust) because the kinetics of diffusive mass transfer along the soluble/insoluble mineral interfaces is much faster than along the healed boundaries of the soluble minerals. The passive concentration of insoluble minerals amplifies the localization of dissolution along some layers oriented perpendicular to the maximum compressive stress. Conversely, in the areas with initial low content in insoluble minerals and clustered soluble minerals, dissolution is slower. Consequently, these areas are less deformed, they host the re-deposition of the soluble species and they act as rigid objects that concentrate the dissolution near their boundaries thus amplifying the differentiation. A crucial parameter required for self-organized process of pressure solution is the presence of a fluid that is a good solvent of at least some of the rock-forming minerals

  19. Synthesis and functionalization of gold nanorods for probing plasmonic enhancement mechanisms in organic photovoltaic active layers

    NASA Astrophysics Data System (ADS)

    Wadams, Robert Christopher

    DNA nanotechnology is one of the most flourishing interdisciplinary research fields. Through the features of programmability and predictability, DNA nanostructures can be designed to self-assemble into a variety of periodic or aperiodic patterns of different shapes and length scales, and more importantly, they can be used as scaffolds for organizing other nanoparticles, proteins and chemical groups. By leveraging these molecules, DNA nanostructures can be used to direct the organization of complex bio-inspired materials that may serve as smart drug delivery systems and in vitro or in vivo bio-molecular computing and diagnostic devices. In this dissertation I describe a systematic study of the thermodynamic properties of complex DNA nanostructures, including 2D and 3D DNA origami, in order to understand their assembly, stability and functionality and inform future design endeavors. It is conceivable that a more thorough understanding of DNA self-assembly can be used to guide the structural design process and optimize the conditions for assembly, manipulation, and functionalization, thus benefiting both upstream design and downstream applications. As a biocompatible nanoscale motif, the successful integration, stabilization and separation of DNA nanostructures from cells/cell lysate suggests its potential to serve as a diagnostic platform at the cellular level. Here, DNA origami was used to capture and identify multiple T cell receptor mRNA species from single cells within a mixed cell population. This demonstrates the potential of DNA nanostructure as an ideal nano scale tool for biological applications.

  20. High-performance hybrid buffer layer using 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile/molybdenum oxide in inverted top-emitting organic light-emitting diodes.

    PubMed

    Park, Cheol Hwee; Lee, Hyun Jun; Hwang, Ju Hyun; Kim, Kyu Nyun; Shim, Yong Sub; Jung, Sun-Gyu; Park, Chan Hyuk; Park, Young Wook; Ju, Byeong-Kwon

    2015-03-25

    A high-performance 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN)/molybdenum oxide (MoO3) hybrid buffer layer with high hole-injection efficiency and superior plasma resistance under the sputtering process was developed. The HATCN enhances the hole-injection efficiency, and the MoO3 effectively protects the underlying organic layers from plasma damage during deposition by sputtering. This improves the characteristics of inverted top-emitting organic light-emitting diodes using a top transparent conductive oxide electrode. The device using the hybrid buffer layer showed the highest electroluminescence characteristics among devices with other buffer layers. The high hole-injection efficiency of HATCN was shown by the J-F curve of hole-only devices, and the plasma protection performance of MoO3 was shown by atomic force microscope surface morphology images of the buffer layer film after O2 plasma treatment. PMID:25761363

  1. Polyethyleneimine as a novel desorbent for anionic organic dyes on layered double hydroxide surface.

    PubMed

    Wang, Siming; Li, Zenghe; Lu, Chao

    2015-11-15

    Polyethyleneimine (PEI) is a positively charged polymer with hydrogen-bonding sites and hydrophobic chains. Therefore, it has been clearly established as an efficient adsorbent by means of these native properties in the literatures. However, there is apparently no good reason to disregard the use of PEI as a desired desorbent. Herein, using methyl orange as a model anionic dye, we investigated the desorption performances of PEI toward anionic dyes adsorbed on the surface of CO3-layered double hydroxides (LDHs) in a wide range of pH values. The experiment results showed that the positively charged PEI had very strong desorption capacity for anionic dyes at low pH values (<9.5) through electrostatic attraction between PEI and methyl orange because of the high degree of protonation of PEI. At high pH values (>9.5), PEI existed as neutral molecule, it could desorb methyl orange via hydrogen bonding between the amino groups of it and sulfonate group of methyl orange; simultaneously, the anion-exchange process occurred between abundant hydroxyl anions and anionic methyl orange. The adsorption capacity of the used LDH adsorbent was about 80% after five cycles of adsorption-desorption-regeneration, which was much higher than that conducted by 0.1M NaOH solution. These findings suggested that PEI could be regarded as a promising desorbent for enriching anionic dyes in wastewater and regenerating LDHs through surface adsorption-desorption cycles. PMID:26255712

  2. Optimization of UV absorptivity of layered double hydroxide by intercalating organic UV-absorbent molecules.

    PubMed

    Mohsin, Sumaiyah Megat Nabil; Hussein, Mohd Zobir; Sarijo, Siti Halimah; Fakurazi, Sharida; Arulselvan, Palanisamy; Taufiq-Yap, Yun Hin

    2014-08-01

    Intercalation of Zn/Al layered double hydroxide (LDH) with benzophenone 9 (B9), a strong ultraviolet (UV) absorber, had been carried out by two different routes; co-precipitation and ion exchange method. Powder X-ray diffraction (PXRD) patterns of co-precipitated (ZB9C) and ion exchanged product (ZB91) showed basal spacing of 15.9 angstrom and 16.6 angstrom, respectively, as a result of the intercalation of B9 anions into the lamellae spaces of LDH. Intercalation was further confirmed by Fourier transform infrared spectra (FTIR), carbon, hydrogen, nitrogen and sulfur (CHNS) and thermogravimetric and differential thermogravimetric (TGA/DTG) studies. UV-vis absorption properties of the nanocomposite was investigated with diffuse reflectance UV-visible spectrometer and showed broader UV absorption range. Furthermore, stability of sunscreen molecules in LDH interlayer space was tested in deionized water, artificial sea water and skin pH condition to show slow deintercalation and high retention in host. Cytotoxicity study of the synthesized nanocomposites on human dermal fibroblast (HDF) cells shows no significant cytotoxicity after 24 h exposure for test concentrations up to 25 microg/mL. PMID:25016649

  3. Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

    NASA Astrophysics Data System (ADS)

    Brown, S. S.; Dubé, W. P.; Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; Warneke, C.; de Gouw, J. A.; Washenfelder, R. A.; Atlas, E.; Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Schwarz, J. P.; Spackman, R.; Trainer, M.; Parrish, D. D.; Fehshenfeld, F. C.; Ravishankara, A. R.

    2013-11-01

    Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter category serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100-400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2-2.7 ppbv h-1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1 ppbv h-1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Some profiles may have been influenced by biomass burning sources as well, making quantitative attribution of organic aerosol sources difficult. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m-3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m-3.

  4. Solution-processed high-LUMO-level polymers in n-type organic field-effect transistors: a comparative study as a semiconducting layer, dielectric layer, or charge injection layer

    NASA Astrophysics Data System (ADS)

    Liu, Chuan; Xu, Yong; Liu, Xuying; Minari, Takeo; Sirringhaus, Henning; Noh, Yong-Young

    2015-04-01

    In solution-processed organic field-effect transistors (OFETs), the polymers with high level of lowest unoccupied molecular orbitals (LUMOs, > -3.5 eV) are especially susceptible to electron-trapping that causes low electron mobility and strong instability in successive operation. However, the role of high-LUMO-level polymers could be different depending on their locations relative to the semiconductor/insulator interface, or could even possibly benefit the device in some cases. We constructed unconventional polymer heterojunction n-type OFETs to control the location of the same polymer with a high LUMO level, to be in, under, or above the accumulation channel. We found that although the devices with the polymer in the channel suffer from dramatic instability, the same polymer causes much less instability when it acts as a dielectric modification layer or charge injection layer. Especially, it may even improve the device performance in the latter case. This result helps to improve our understanding of the electron-trapping and explore the value of these polymers in OFETs.

  5. Measuring the Thickness and Potential Profiles of the Space-Charge Layer at Organic/Organic Interfaces under Illumination and in the Dark by Scanning Kelvin Probe Microscopy.

    PubMed

    Rojas, Geoffrey A; Wu, Yanfei; Haugstad, Greg; Frisbie, C Daniel

    2016-03-01

    Scanning Kelvin probe microscopy was used to measure band-bending at the model donor/acceptor heterojunction poly(3-hexylthiophene) (P3HT)/fullerene (C60). Specifically, we measured the variation in the surface potential of C60 films with increasing thicknesses grown on P3HT to produce a surface potential profile normal to the substrate both in the dark and under illumination. The results confirm a space-charge carrier region with a thickness of 10 nm, consistent with previous observations. We discuss the possibility that the domain size in bulk heterojunction organic solar cells, which is comparable to the space-charge layer thickness, is actually partly responsible for less than expected electron/hole recombination rates. PMID:26890658

  6. Synthesized layered inorganic-organic magnesium organosilicate containing a disulfide moiety as a promising sorbent for cations removal.

    PubMed

    Moscofian, Andrea S O; Airoldi, Claudio

    2008-12-15

    A new-layered inorganic-organic magnesium organosilicate was synthesized through a single step template sol-gel route under mild conditions, using a new alkoxysilane, containing a 2-aminophenyldisulfide molecule. Elemental analysis data based on the nitrogen atom showed an incorporation of 1.97mmol of organic pendant groups for each gram of the hybrid formed. The X-ray diffraction patterns demonstrated that this nanocompound exhibited lamellar structure, in agreement with that found for natural inorganic silicates. Infrared spectroscopy and nuclear magnetic resonance for the (29)Si nucleus in the solid state are in agreement with the success of the proposed synthetic method. The presence of nitrogen and sulfur basic centers attached to the pendant groups inside the lamellar structure is used as basic centers to coordinate cations from aqueous solution at the solid/liquid interface. The isotherms were fitted to Langmuir and Freundlich models. The maxima adsorption capacities for copper, lead and cadmium, calculated from Langmuir model, were 3.28, 1.42 and 0.35mmol g(-1), respectively. These values are comparable to other adsorbing nanomaterials. This behavior suggested that this new inorganic-organic hybrid could be employed as a promising adsorbent for cation removal from polluted systems. PMID:18395976

  7. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications. PMID:26335856

  8. Temperature and exposure dependence of hybrid organic-inorganic layer formation by sequential vapor infiltration into polymer fibers.

    PubMed

    Akyildiz, Halil I; Padbury, Richard P; Parsons, Gregory N; Jur, Jesse S

    2012-11-01

    The characteristic processing behavior for growth of a conformal nanoscale hybrid organic-inorganic modification to polyamide 6 (PA6) by sequential vapor infiltration (SVI) is demonstrated. The SVI process is a materials growth technique by which exposure of organometallic vapors to a polymeric material promotes the formation of a hybrid organic-inorganic modification at the near surface region of the polymer. This work investigates the SVI exposure temperature and cycling times of sequential exposures of trimethylaluminum (TMA) on PA6 fiber mats. The result of TMA exposure is the preferential subsurface organic-inorganic growth by diffusion into the polymer and reaction with the carbonyl in PA6. Mass gain, infrared spectroscopy, and transmission electron microscopy analysis indicate enhanced materials growth and uniformity at lower processing temperatures. The inverse relationship between mass gain and exposure temperature is explained by the formation of a hybrid layer that prevents the diffusion of TMA into the polymer to react with the PA6 upon subsequent exposure cycles. As few as 10 SVI exposure cycles are observed to saturate the growth, yielding a modified thickness of ∼75 nm and mass increase of ∼14 wt %. Removal of the inherent PA6 moisture content reduces the mass gain by ∼4 wt % at low temperature exposures. The ability to understand the characteristic growth process is critical for the development of the hybrid materials fabrication and modification techniques. PMID:23050951

  9. Hole-selective and impedance characteristics of an aqueous solution-processable MoO3 layer for solution-processable organic semiconducting devices

    NASA Astrophysics Data System (ADS)

    Moon, Byung Seuk; Lee, Soo-Hyoung; Huh, Yoon Ho; Park, Byoungchoo

    2015-02-01

    We herein report an investigation of aqueous solution-processable molybdenum-oxide (MoO3) hole-selective layers fabricated for solution-processable organic semiconducting devices. A homogeneous MoO3 layer was successfully deposited via spin-coating using aqueous solutions of ammonium heptamolybdate as a MoO3 precursor. The use of the solution-processable MoO3 layer as a hole-injecting layer (HIL) on an indium-tin-oxide (ITO) anode in solution-processable organic light-emitting diodes (OLEDs) resulted in excellent device performance in terms of the brightness (maximum brightness of 37,000 cd m-2) and the efficiency (peak efficiency of 25.2 cd A-1), comparable to or better than those of a reference OLED with a conventional poly(ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS) HIL. Such good device performance is attributed to the water-processable MoO3 hole-selective layers, which allowed the formation of a high-quality film and provided good matching of the energy levels between adjacent layers with improved hole-injecting properties, impedance characteristics, and stability. Furthermore, polymer solar cells (PSCs) with a MoO3 layer used as a hole-collecting layer (HCL) showed improved power conversion efficiency (3.81%), which was higher than that obtained using the PEDOT:PSS HCL. These results clearly indicate the benefits of using a water-processable MoO3 layer, which effectively acts as a hole-selective layer on an ITO anode and provides good hole-injection/collection, electron-blocking and energy-level-matching properties, and improved stability. They, therefore, offer considerable promise as an alternative to a conventional PEDOT:PSS layer in the production of high-performance solution-processable organic semiconducting devices.

  10. One-step synthesis of layered yttrium hydroxides in immiscible liquid-liquid systems: Intercalation of sterically-bulky hydrophobic organic anions and doping of europium ions

    NASA Astrophysics Data System (ADS)

    Watanabe, Mebae; Fujihara, Shinobu

    2014-02-01

    Inorganic-organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid-liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu3+ ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect.

  11. MoO3 as a Cathode Buffer Layer Material for the Improvement of Planar pn-Heterojunction Organic Solar Cell Performance

    NASA Astrophysics Data System (ADS)

    Kageyama, Hiroshi; Kajii, Hirotake; Ohmori, Yutaka; Shirota, Yasuhiko

    2011-03-01

    The use of MoO3 as a cathode buffer layer inserted between LiF and Al improved the power conversion efficiency (PCE) of planar pn-heterojunction organic solar cells (OSCs) by reducing exciton quenching at the interface between the n-type organic active layer and the electrode. The cell using an amorphous molecular material, tris[4-(5-phenylthiophen-2-yl)phenyl]amine, as a p-type organic semiconductor, C70 as an n-type organic semiconductor and MoO3 as a cathode buffer layer exhibited a PCE of 3.3% under AM1.5G illumination (100 mW cm-2), which is of the highest level among those for planar pn-heterojunction OSCs using amorphous molecular materials as donor materials.

  12. The role of the organic layer for phosphorus nutrition of young beech trees (Fagus sylvatica L.) at two sites differing in soil Phosphorus availability

    NASA Astrophysics Data System (ADS)

    Hauenstein, Simon

    2016-04-01

    Simon Hauenstein1, Thomas Pütz2, and Yvonne Oelmann1, 1 Geoecology, Department of Geosciences, University of Tübingen, Tübingen, Germany 2 Agrosphere (IBG-3), Forschungszentrum Jülich, Jülich, Germany The accumulation of an organic layer in forests is linked to the ratio between litterfall rates and decomposition rates with decomposition rates being decelerated due to acidification and associated nutrient depletion with proceeding ecosystem development. Nevertheless, the nutrient pool in the organic layer might still represent an important source for Phosphorus (P) nutrition of forests on nutrient-poor soils. Our objective was to assess the importance of the organic layer to P nutrition of young beech trees at two sites differing in soil P availability. We established a mesocosm experiment including plants and soil from a Phosphorus depleted forest site on a Haplic Podzol in Lüss and a Phosphorus rich forest site on a Eutric Cambisol in Bad Brückenau either with or without the organic layer. After 1 year under outdoor conditions, we applied 33P to the pots. After 0h, 24h, 48h, 96h, 192h, 528h we destructively harvested the young beech trees (separated into leaves, branches, stems) and sampled the organic layer and mineral soil of the pots. In each soil horizon we measured concentrations of resin-extractable P, plant available P fractions and total P. We extracted the xylem sap of the whole 2-year-old trees by means of scholander pressure bomb. 33P activity was measured for every compartment in soil and plant. The applied 33P was recovered mainly in the organic layer in Lüss, whereas it was evenly distributed among organic and mineral horizons in pots of Bad Brückenau soil. Comparing pots with and without an organic layer, the specific 33P activity differed by 323% between pots with and without an organic layer present in the Lüss soil. For both sites, the presence of the organic layer increased 33P activity in xylem sap compared to the treatment without

  13. Improvement in the performance of inverted organic solar cell using electric field assisted spray deposited ZnO layer

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Neha; Swami, Sanjay Kumar; Dutta, Viresh

    2015-06-01

    ZnO film was deposited using spray technique. The application of electric field (applying a DC voltage = 700V to the nozzle) during spray deposition provide compact nanostructured film of ZnO as compared to agglomerated ZnO film deposited using spray process. The ZnO film deposited after applying DC voltage during spray process showed good crystallinity as well as transmittance in the visible range. Use of this crystalline, compact layer of ZnO in inverted organic solar cell (ITO/ZnO/P3HT: PCBM/Ag) provide improved efficiency of 2.8% with JSC of 14.0 mA/cm2, VOC of 0.55V and FF of 36%. Thus the process remove the need of any post deposition treatment to improve the film quality as well as solar cell performance.

  14. Ex situ and in situ characterization of patterned photoreactive thin organic surface layers using friction force microscopy

    PubMed Central

    Shen, Quan; Edler, Matthias; Griesser, Thomas; Knall, Astrid-Caroline; Trimmel, Gregor; Kern, Wolfgang; Teichert, Christian

    2014-01-01

    Photolithographic methods allow an easy lateral top-down patterning and tuning of surface properties with photoreactive molecules and polymers. Employing friction force microscopy (FFM), we present here different FFM-based methods that enable the characterization of several photoreactive thin organic surface layers. First, three ex situ methods have been evaluated for the identification of irradiated and non-irradiated zones on the same organosilane sample by irradiation through different types of masks. These approaches are further extended to a time dependent ex situ FFM measurement, which allows to study the irradiation time dependent evolution of the resulting friction forces by sequential irradiation through differently sized masks in crossed geometry. Finally, a newly designed in situ FFM measurement, which uses a commercial bar-shaped cantilever itself as a noncontact shadow mask, enables the determination of time dependent effects on the surface modification during the photoreaction. SCANNING 36:590–598, 2014. PMID:25183629

  15. Effect of Hole Mobility Through Emissive Layer on Temporal Stability of Blue Organic Light-Emitting Diodes

    SciTech Connect

    Culligan, S.W.; Chen, A.C.-A.; Wallace, J.U.; Klubek, K.P.; Tang, C.W.; Chen, S.H.

    2006-07-13

    Light-emitting conjugated oligomers comprising anthracene, naphthalene, and fluorene units have been synthesized to investigate three configurations of blue organic light-emitting diodes (OLEDs) that are designed to identify the origins of device instablilty. The transient OLED technique is employed to measure hole mobilities, which are found to be 3.1 x 10^-4, 8.9 x 10^-5, and 3.6 x 10^-5 cm^2V^-1s^-1 for three different blue-light-emitting model compounds with varying fluorene content. A higher hole mobility through the emissive layer results in a wider recombination zone, which, in turn, is responsible for a longer device lifetime and a lower drive voltage at the expense of luminance yield.

  16. Process for depositing thin film layers onto surfaces modified with organic functional groups and products formed thereby

    DOEpatents

    Tarasevich, B.J.; Rieke, P.C.

    1998-06-02

    A method is provided for producing a thin film product, comprising a first step in which an underlying substrate of a first material is provided. The underlying substrate includes a plurality of unmodified sites. The underlying substrate is then chemically modified wherein a plurality of organic functional groups are attached to a plurality of the unmodified sites. The arrangement and type of the functional group used can be selected for the purpose of controlling particular properties of the second material deposited. A thin film layer of at least one second material is then deposited onto the chemically modified underlying substrate. This can be accomplished by connecting the thin film to the underlying substrate by binding the thin film to the functional groups. 5 figs.

  17. Process for depositing thin film layers onto surfaces modified with organic functional groups and products formed thereby

    DOEpatents

    Tarasevich, Barbara J.; Rieke, Peter C.

    1998-01-01

    A method is provided for producing a thin film product, comprising a first step in which an underlying substrate of a first material is provided. The underlying substrate includes a plurality of unmodified sites. The underlying substrate is then chemically modified wherein a plurality of organic functional groups are attached to a plurality of the unmodified sites. The arrangement and type of the functional group used can be selected for the purpose of controlling particular properties of the second material deposited. A thin film layer of at least one second material is then deposited onto the chemically modified underlying substrate. This can be accomplished by connecting the thin film to the underlying substrate by binding the thin film to the functional groups.

  18. Promotion of low-humidity proton conduction by controlling hydrophilicity in layered metal-organic frameworks.

    PubMed

    Sadakiyo, Masaaki; Okawa, Hisashi; Shigematsu, Akihito; Ohba, Masaaki; Yamada, Teppei; Kitagawa, Hiroshi

    2012-03-28

    We controlled the hydrophilicity of metal-organic frameworks (MOFs) to achieve high proton conductivity and high adsorption of water under low humidity conditions, by employing novel class of MOFs, {NR(3)(CH(2)COOH)}[MCr(ox)(3)]·nH(2)O (abbreviated as R-MCr, where R = Me (methyl), Et (ethyl), or Bu (n-butyl), and M = Mn or Fe): Me-FeCr, Et-MnCr, Bu-MnCr, and Bu-FeCr. The cationic components have a carboxyl group that functions as the proton carrier. The hydrophilicity of the cationic ions was tuned by the NR(3) residue to decrease with increasing bulkiness of the residue: {NMe(3)(CH(2)COOH)}(+) > {NEt(3)(CH(2)COOH)}(+) > {NBu(3)(CH(2)COOH)}(+). The proton conduction of the MOFs increased with increasing hydrophilicity of the cationic ions. The most hydrophilic sample, Me-FeCr, adsorbed a large number of water molecules and showed a high proton conductivity of ~10(-4) S cm(-1), even at a low humidity of 65% relative humidity (RH), at ambient temperature. Notably, this is the highest conductivity among the previously reported proton-conducting MOFs that operate under low RH conditions. PMID:22409393

  19. Electronic, structural, and substrate effect properties of single-layer covalent organic frameworks

    SciTech Connect

    Liang, Liangbo; Zhu, Pan; Meunier, Vincent

    2015-05-14

    Recently synthesized two-dimensional covalent organic frameworks (COFs) exhibit high surface area, large pore size, and unique structural architectures, making them promising materials for various energy applications. Here, a total of nine COFs structures, including two deposited on a hexagonal boron nitride substrate, are investigated using density functional theory, quasi-particle many-body theory within the GW approximation, and an image charge model. The structures considered belong to two major families (thiophene-based COF-n (T-COF-n) and tetrakis (4-aminophenyl) porphyrin-x (TAPP-x)) differing from the presence of B—O or C=N linkers. While T-COF-n structures are shown to constitute planar networks, TAPP-x systems can display non-negligible corrugation due to the out-of-plane rotation of phenyl rings. We find that the electronic properties do not differ significantly when altering the chain molecules within each family. Many-body effects are shown to lead to large band-gap increase while the presence of the substrate yields appreciable reductions of the gaps, due to substrate polarization effects.

  20. Electronic, structural, and substrate effect properties of single-layer covalent organic frameworks.

    PubMed

    Liang, Liangbo; Zhu, Pan; Meunier, Vincent

    2015-05-14

    Recently synthesized two-dimensional covalent organic frameworks (COFs) exhibit high surface area, large pore size, and unique structural architectures, making them promising materials for various energy applications. Here, a total of nine COFs structures, including two deposited on a hexagonal boron nitride substrate, are investigated using density functional theory, quasi-particle many-body theory within the GW approximation, and an image charge model. The structures considered belong to two major families (thiophene-based COF-n (T-COF-n) and tetrakis (4-aminophenyl) porphyrin-x (TAPP-x)) differing from the presence of B-O or C=N linkers. While T-COF-n structures are shown to constitute planar networks, TAPP-x systems can display non-negligible corrugation due to the out-of-plane rotation of phenyl rings. We find that the electronic properties do not differ significantly when altering the chain molecules within each family. Many-body effects are shown to lead to large band-gap increase while the presence of the substrate yields appreciable reductions of the gaps, due to substrate polarization effects. PMID:25978906

  1. Electronic, structural, and substrate effect properties of single-layer covalent organic frameworks

    NASA Astrophysics Data System (ADS)

    Liang, Liangbo; Zhu, Pan; Meunier, Vincent

    2015-05-01

    Recently synthesized two-dimensional covalent organic frameworks (COFs) exhibit high surface area, large pore size, and unique structural architectures, making them promising materials for various energy applications. Here, a total of nine COFs structures, including two deposited on a hexagonal boron nitride substrate, are investigated using density functional theory, quasi-particle many-body theory within the GW approximation, and an image charge model. The structures considered belong to two major families (thiophene-based COF-n (T-COF-n) and tetrakis (4-aminophenyl) porphyrin-x (TAPP-x)) differing from the presence of B—O or C=N linkers. While T-COF-n structures are shown to constitute planar networks, TAPP-x systems can display non-negligible corrugation due to the out-of-plane rotation of phenyl rings. We find that the electronic properties do not differ significantly when altering the chain molecules within each family. Many-body effects are shown to lead to large band-gap increase while the presence of the substrate yields appreciable reductions of the gaps, due to substrate polarization effects.

  2. Room-temperature, solution-processable organic electron extraction layer for high-performance planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Jong H.; Chueh, Chu-Chen; Williams, Spencer T.; Jen, Alex K.-Y.

    2015-10-01

    In this work, we describe a room-temperature, solution-processable organic electron extraction layer (EEL) for high-performance planar heterojunction perovskite solar cells (PHJ PVSCs). This EEL is composed of a bilayered fulleropyrrolidinium iodide (FPI)-polyethyleneimine (PEIE) and PC61BM, which yields a promising power conversion efficiency (PCE) of 15.7% with insignificant hysteresis. We reveal that PC61BM can serve as a surface modifier of FPI-PEIE to simultaneously facilitate the crystallization of perovskite and the charge extraction at FPI-PEIE/CH3NH3PbI3 interface. Furthermore, the FPI-PEIE can also tune the work function of ITO and dope PC61BM to promote the efficient electron transport between ITO and PC61BM. Based on the advantages of room-temperature processability and decent electrical property of FPI-PEIE/PC61BM EEL, a high-performance flexible PVSC with a PCE ~10% is eventually demonstrated. This study shows the potential of low-temperature processed organic EEL to replace transition metal oxide-based interlayers for highly printing compatible PVSCs with high-performance.In this work, we describe a room-temperature, solution-processable organic electron extraction layer (EEL) for high-performance planar heterojunction perovskite solar cells (PHJ PVSCs). This EEL is composed of a bilayered fulleropyrrolidinium iodide (FPI)-polyethyleneimine (PEIE) and PC61BM, which yields a promising power conversion efficiency (PCE) of 15.7% with insignificant hysteresis. We reveal that PC61BM can serve as a surface modifier of FPI-PEIE to simultaneously facilitate the crystallization of perovskite and the charge extraction at FPI-PEIE/CH3NH3PbI3 interface. Furthermore, the FPI-PEIE can also tune the work function of ITO and dope PC61BM to promote the efficient electron transport between ITO and PC61BM. Based on the advantages of room-temperature processability and decent electrical property of FPI-PEIE/PC61BM EEL, a high-performance flexible PVSC with a PCE ~10% is

  3. Laboratory measurements of nitric oxide release from forest soil with a thick organic layer under different understory types

    NASA Astrophysics Data System (ADS)

    Bargsten, A.; Falge, E.; Huwe, B.; Meixner, F. X.

    2010-01-01

    Nitric oxide (NO) plays an important role in the photochemistry of the troposphere. NO from soil contributes up to 40% to the global budget of atmospheric NO. Soil NO emissions are primarily caused by biological activity (nitrification and denitrification), that occurs in the uppermost centimetres of the soil, a soil region often characterized by high contents of organic material. Most studies of NO emission potentials to date have investigated mineral soil layers. In our study we sampled soil organic matter under different understories (moss, grass, spruce and blueberries) in a humid mountainous Norway spruce forest plantation in the Fichtelgebirge (Germany). We performed laboratory incubation and fumigation experiments using a customized chamber technique to determine the response of net potential NO flux to physical and chemical soil conditions (water content and temperature, bulk density, particle density, pH, C/N ratio, organic C, soil ammonium, soil nitrate). Net potential NO fluxes (in terms of mass of N) from soils of different understories ranged from 1.7-9.8 ng m-2 s-1 (grass and moss), 55.4-59.3 ng m-2 s-1 (spruce), and 43.7-114.6 ng m-2 s-1 (blueberry) at optimum water content and a soil temperature of 10°C. The water content for optimum net potential NO flux ranged between 0.76 and 0.8 gravimetric soil moisture for moss, between 1.0 and 1.1 for grass, 1.1 and 1.2 for spruce, and 1.3 and 1.9 for blueberries. Effects of soil physical and chemical characteristics on net potential NO flux were statistically significant (0.01 probability level) only for NH4+. Therefore, the effects of biogenic factors like understory type, amount of roots, and degree of mycorrhization on soil biogenic NO emission are discussed; they have the potential to explain the observed different of net potential NO fluxes. Quantification of NO emissions from the upmost soil layer is therefore an important step to quantify soil NO emissions in ecosystems with substantial organic soil

  4. Reducing the variability in performance of organic solar cells containing vacuum deposited MoOx extraction layers

    NASA Astrophysics Data System (ADS)

    Williams, Graeme; Aziz, Hany

    2014-10-01

    Reproducibility in efficiency and lifetime of organic solar cells (OSCs) remains a major concern, especially with the development of more complex and modern multi-layer device architectures. In this work, OSCs are studied for their efficiency and photo-stability as a function of the quality of their thermally evaporated MoOx hole extraction layer (HEL). To this end, the characteristics of the MoOx film are demonstrated to change with repeat evaporation runs from the same source material. These variations have strong effects on polymer OSCs (p-OSCs), with an effective halving of the power conversion efficiency after only three MoO3 evaporation runs. In contrast, vacuum deposited small molecule OSCs (sm-OSCs) appear to be unaffected by the history of the MoO3 source material. sm- OSCs are instead shown to be prone to large changes in efficiency as a function of the delay time in between deposition of the MoOx HEL and subsequent photo-active materials. Increased delay time between these deposition steps is also demonstrated to decrease the sm-OSC photo-stability. The results thus emphasize subtleties in materials deposition processes that can play a significant role in obtaining reproducible and scientifically relevant data.

  5. Impact of light on organic solar cells: evolution of the chemical structure, morphology, and photophysical properties of the active layer

    NASA Astrophysics Data System (ADS)

    Rivaton, Agnès; Chambon, Sylvain; Manceau, Matthieu; Gardette, Jean-Luc; Firon, Muriel; Lemaître, Noëlla; Guillerez, Stéphane; Cros, Stéphane

    2008-04-01

    Organic photovoltaic represents an emerging technology thanks to its ability to give flexible, light weight and large-area devices, with low production cost by simple solution process or printing technologies. But these devices are known to exhibit low resistance to the combined action of sunlight, oxygen and water. This paper is focused on the behaviour of the active layer of the devices under illumination in the presence and absence of oxygen. The monitoring of the evolution of the chemical structure of MDMO-PPV submitted to accelerated artificial ageing permitted the elucidation of the mechanisms by which the polymer degrades. Extrapolation of the data to natural ageing suggested that, if well protected from oxygen (encapsulation), MDMO-PPV:PCBM based active layer is photochemically stable for several years in use conditions. In addition the charge transfer between the two materials was observed to remain efficient under exposure. The study of P3HT:PCBM blends allowed to point out the Achilles heel of P3HT towards the impact of light. In addition, P3HT:PCBM blends were shown to be much more stable under illumination than MDMO:PCBM blends. Preliminary results devoted to the AFM monitoring of the morphological modifications of P3HT:PCBM blends under the impact of light are also reported.

  6. Improving the layer morphology of solution-processed perylene diimide organic solar cells with the use of a polymeric interlayer

    NASA Astrophysics Data System (ADS)

    Singh, Ranbir; Mróz, Marta M.; Di Fonzo, Fabio; Cabanillas-Gonzalez, Juan; Marchi, Enrico; Bergamini, Giacomo; Müllen, Klaus; Jacob, Josemon; Keivanidis, Panagiotis E.

    2013-10-01

    Herein we demonstrate a method to improve the power conversion efficiency (PCE) parameter of organic photovoltaic (OPV) devices based on the electron acceptor N,N'-bis(1- ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) blended with the electron donor poly(indenofluorene)-aryloctyl (PIF-Aryl). The device parameters of the short-circuit current, open-circuit voltage and fill factor are found increased after the insertion of a thin poly [9, 9-dioctylfluorene-co-N- [4-(3-methylpropyl)]-diphenylamine] (TFB) photoactive interlayer between the hole-collecting electrode and the photoactive layer of the device. Unlike to most of the cases where interlayers serve as charge extractors, in our system the polymeric interlayer serves as a morphology modifying agent that drives the PDI component to segregate better at the interface with the device cathode; that is at the carrier-collecting electrode interface, which is not in physical contact with the interlayer. The processes of energy/charge transfer of the TFB excitons to/with the PIF-Aryl:PDI top-layer are also addressed. Charge transfer reactions dominate at the TFB/PIF-Aryl:PDI interface but no significant contribution in the photocurrent generation is seen in the photoaction spectra of the bilayer device.

  7. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells.

    PubMed

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-01-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells. PMID:27453530

  8. Highly Efficient White Organic Light-Emitting Diodes with Ultrathin Emissive Layers and a Spacer-Free Structure

    NASA Astrophysics Data System (ADS)

    Wu, Shengfan; Li, Sihua; Sun, Qi; Huang, Chenchao; Fung, Man-Keung

    2016-05-01

    Ultrathin emissive layers (UEMLs) of phosphorescent materials with a layer thickness of less than 0.3 nm were introduced for high-efficiency organic light-emitting diodes (OLEDs). All the UEMLs for white OLEDs can be prepared without the use of interlayers or spacers. Compared with devices fabricated with interlayers inserted in-between the UEMLs, our spacer-free structure not only significantly improves device efficiency, but also simplifies the fabrication process, thus it has a great potential in lowering the cost of OLED panels. In addition, its spacer-free structure decreases the number of interfaces which often introduce unnecessary energy barriers in these devices. In the present work, UEMLs of red, green and blue-emitting phosphorescent materials and yellow and blue phosphorescent emitters are utilized for the demonstration of spacer-free white OLEDs. Upon optimization of the device structure, we demonstrated spacer-free and simple-structured white-emitting OLEDs with a good device performance. The current and power efficiencies of our white-emitting devices are as high as 56.0 cd/A and 55.5 lm/W, respectively. These efficiencies are the highest ever reported for OLEDs fabricated with the UEML approach.

  9. Shubnikov-de Haas Effect and Angular-Dependent Magnetoresistance in Layered Organic Conductor β''-(ET)(TCNQ)

    NASA Astrophysics Data System (ADS)

    Yasuzuka, Syuma; Uji, Shinya; Konoike, Takako; Terashima, Taichi; Graf, David; Choi, Eun Sang; Brooks, James S.; Yamamoto, Hiroshi M.; Kato, Reizo

    2016-08-01

    This paper reports the experimental results of the Shubnikov-de Haas (SdH) effect and angular-dependent magnetoresistance oscillation (AMRO) for the organic conductor β''-(ET)(TCNQ). We observed several two dimensional (2D) SdH frequencies, whose cross-sectional areas of the Fermi surfaces (FSs) correspond to only a few percent of the first Brillouin zone. Such small 2D FSs are not predicted by band-structure calculations, suggesting that these FS pockets are created by an imperfect nesting of FSs at low temperatures. It is found that the AMRO consists of a long-period oscillation and a short-period one. The long-period oscillation is associated with the Yamaji oscillation corresponding to the α orbit, whose shape and area are consistent with previous magneto-optical measurement. The short-period oscillation is not caused by peaks instead but dips. The dip structure is discussed in terms of the AMRO of a quasi-2D electron system with a periodic potential caused by the possible density-wave related to the ET layers or the 4kF charge-density-wave associated with the TCNQ layers.

  10. Highly Efficient White Organic Light-Emitting Diodes with Ultrathin Emissive Layers and a Spacer-Free Structure

    PubMed Central

    Wu, Shengfan; Li, Sihua; Sun, Qi; Huang, Chenchao; Fung, Man-Keung

    2016-01-01

    Ultrathin emissive layers (UEMLs) of phosphorescent materials with a layer thickness of less than 0.3 nm were introduced for high-efficiency organic light-emitting diodes (OLEDs). All the UEMLs for white OLEDs can be prepared without the use of interlayers or spacers. Compared with devices fabricated with interlayers inserted in-between the UEMLs, our spacer-free structure not only significantly improves device efficiency, but also simplifies the fabrication process, thus it has a great potential in lowering the cost of OLED panels. In addition, its spacer-free structure decreases the number of interfaces which often introduce unnecessary energy barriers in these devices. In the present work, UEMLs of red, green and blue-emitting phosphorescent materials and yellow and blue phosphorescent emitters are utilized for the demonstration of spacer-free white OLEDs. Upon optimization of the device structure, we demonstrated spacer-free and simple-structured white-emitting OLEDs with a good device performance. The current and power efficiencies of our white-emitting devices are as high as 56.0 cd/A and 55.5 lm/W, respectively. These efficiencies are the highest ever reported for OLEDs fabricated with the UEML approach. PMID:27170543

  11. The effect of a charge control layer on the electroluminescent characteristic of blue and white organic light-emitting diodes.

    PubMed

    Lee, Dong Hyung; Lee, Seok Jae; Koo, Ja-Ryong; Lee, Ho Won; Shin, Hyun Su; Lee, Song Eun; Kim, Woo Young; Lee, Kum Hee; Yoon, Seung Soo; Kim, Young Kwan

    2014-08-01

    We investigated blue fluorescent organic light-emitting diode (OLED) with a charge control layer (CCL) to produce high efficiency and improve the half-decay lifetime. Three types of devices (device A, B, and C) were fabricated following the number of CCLs within the emitting layer (EML), maintaining the thickness of whole EML. The CCL and host material, 2-methyl-9,10-di(2-naphthyl)anthracene, which has a bipolar property, was able to control the carrier movement with ease inside the EML. Device B demonstrated a maximum luminous efficiency (LE) and external quantum efficiency (EQE) of 9.19 cd/A and 5.78%, respectively. It also showed that the enhancement of the half-decay lifetime, measured at an initial luminance of 1,000 cd/m2, was 1.5 times longer than that of the conventional structure. A hybrid white OLED (WOLED) was also fabricated using a phosphorescent red emitter, bis(2-phenylquinoline)-acetylacetonate iridium III doped in 4,4'-N,N'-dicarbazolyl-biphenyl. The property of the hybrid WOLED with CCL showed a maximum LE and an EQE of 13.46 cd/A and 8.32%, respectively. It also showed white emission with Commission International de L'Éclairage coordinates of (x = 0.41, y = 0.33) at 10 V. PMID:25936005

  12. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells

    PubMed Central

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-01-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells. PMID:27453530

  13. Mg-Al and Zn-Fe layered double hydroxides used for organic species storage and controlled release.

    PubMed

    Seftel, E M; Cool, P; Lutic, D

    2013-12-01

    Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400°C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic-mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn3Fe sample obtained by ionic exchange for 6h with Phe solution. A delivery test in PBS of pH=7.4 showed the release of the Phe in several steps up to 25 h indicating different host-guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer. PMID:24094226

  14. Highly Efficient White Organic Light-Emitting Diodes with Ultrathin Emissive Layers and a Spacer-Free Structure.

    PubMed

    Wu, Shengfan; Li, Sihua; Sun, Qi; Huang, Chenchao; Fung, Man-Keung

    2016-01-01

    Ultrathin emissive layers (UEMLs) of phosphorescent materials with a layer thickness of less than 0.3 nm were introduced for high-efficiency organic light-emitting diodes (OLEDs). All the UEMLs for white OLEDs can be prepared without the use of interlayers or spacers. Compared with devices fabricated with interlayers inserted in-between the UEMLs, our spacer-free structure not only significantly improves device efficiency, but also simplifies the fabrication process, thus it has a great potential in lowering the cost of OLED panels. In addition, its spacer-free structure decreases the number of interfaces which often introduce unnecessary energy barriers in these devices. In the present work, UEMLs of red, green and blue-emitting phosphorescent materials and yellow and blue phosphorescent emitters are utilized for the demonstration of spacer-free white OLEDs. Upon optimization of the device structure, we demonstrated spacer-free and simple-structured white-emitting OLEDs with a good device performance. The current and power efficiencies of our white-emitting devices are as high as 56.0 cd/A and 55.5 lm/W, respectively. These efficiencies are the highest ever reported for OLEDs fabricated with the UEML approach. PMID:27170543

  15. Organized bacterial assemblies in manganese nodules: evidence for a role of S-layers in metal deposition

    NASA Astrophysics Data System (ADS)

    Wang, Xiaohong; Schröder, Heinz C.; Schloßmacher, Ute; Müller, Werner E. G.

    2009-04-01

    Polymetallic/ferro-manganese nodules (Mn-nodules) reach sizes of up to 10 cm in diameter and are abundantly found on the seabed. To date, the origin of Mn-nodules remains unclear, and both abiogenic and biogenic origins have been proposed. In search of evidence for a contribution of microbial processes to the formation of Mn-nodules, we analyzed those spherical nodules which contain a concentrically banded texture in their interior. The Mn-nodules were collected at a depth of 5,152 m from the Clarion-Clipperton Zone. Our high-resolution scanning electron microscopy analyses reveal first published evidence that endolithic microorganisms exist and are arranged in a highly organized manner on plane mineral surfaces within the nodules. These microorganisms are adorned on their surfaces with S-layers, which are indicative for bacteria. Moreover, the data suggest that these S-layers are the crystallization seeds for the mineralization process. We conclude that the mineral material of the Mn-nodule has a biogenic origin, and hope that these data will contribute to the development of biotechnological approaches to concentrate metals from seawater using bacteria in bioreactors.

  16. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells

    NASA Astrophysics Data System (ADS)

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-07-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells.

  17. Low-temperature gas-barrier films by atomic layer deposition for encapsulating organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Tseng, Ming-Hung; Yu, Hui-Huan; Chou, Kun-Yi; Jou, Jwo-Huei; Lin, Kung-Liang; Wang, Chin-Chiun; Tsai, Feng-Yu

    2016-07-01

    Dependences of gas-barrier performance on the deposition temperature of atomic-layer-deposited (ALD) Al2O3, HfO2, and ZnO films were studied to establish low-temperature ALD processes for encapsulating organic light-emitting diodes (OLEDs). By identifying and controlling the key factors, i.e. using H2O2 as an oxidant, laminating Al2O3 with HfO2 or ZnO layers into AHO or AZO nanolaminates, and extending purge steps, OLED-acceptable gas-barrier performance (water vapor transmission rates ∼ 10‑6 g m‑2 d‑1) was achieved for the first time at a low deposition temperature of 50 °C in a thermal ALD mode. The compatibility of the low-temperature ALD process with OLEDs was confirmed by applying the process to encapsulate different types of OLED devices, which were degradation-free upon encapsulation and showed adequate lifetime during accelerated aging tests (pixel shrinkage <5% after 240 h at 60 °C/90% RH).

  18. Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

    NASA Astrophysics Data System (ADS)

    Brown, S. S.; Dubé, W. P.; Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; Warneke, C.; de Gouw, J. A.; Washenfelder, R. A.; Atlas, E.; Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Schwarz, J. P.; Spackman, R.; Trainer, M.; Parrish, D. D.; Fehshenfeld, F. C.; Ravishankara, A. R.

    2013-05-01

    Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100-400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2-2.7ppbv h-1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1ppbv h-1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m-3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m-3.

  19. Decomposition of old organic matter as a result of deeper active layers in a snow depth manipulation experiment.

    PubMed

    Nowinski, Nicole S; Taneva, Lina; Trumbore, Susan E; Welker, Jeffrey M

    2010-07-01

    A snow addition experiment in moist acidic tussock tundra at Toolik Lake, Alaska, increased winter snow depths 2-3 m, and resulted in a doubling of the summer active layer depth. We used radiocarbon (Delta(14)C) to (1) determine the age of C respired in the deep soils under control and deepened active layer conditions (deep snow drifts), and (2) to determine the impact of increased snow and permafrost thawing on surface CO(2) efflux by partitioning respiration into autotrophic and heterotrophic components. Delta(14)C signatures of surface respiration were higher in the deep snow areas, reflecting a decrease in the proportion of autotrophic respiration. The radiocarbon age of soil pore CO(2) sampled near the maximum mid-July thaw depth was approximately 1,000 years in deep snow treatment plots (45-55 cm thaw depth), while CO(2) from the ambient snow areas was approximately 100 years old (30-cm thaw depth). Heterotrophic respiration Delta(14)C signatures from incubations were similar between the two snow depths for the organic horizon and were extremely variable in the mineral horizon, resulting in no significant differences between treatments in either month. Radiocarbon ages of heterotrophically respired C ranged from <50 to 235 years BP in July mineral soil samples and from 1,525 to 8,300 years BP in August samples, suggesting that old soil C in permafrost soils may be metabolized upon thawing. In the surface fluxes, this old C signal is obscured by the organic horizon fluxes, which are significantly higher. Our results indicate that, as permafrost in tussock tundra ecosystems of arctic Alaska thaws, carbon buried up to several thousands of years ago will become an active component of the carbon cycle, potentially accelerating the rise of CO(2) in the atmosphere. PMID:20084398

  20. Spatial variability of organic layer thickness and carbon stocks in mature boreal forest stands--implications and suggestions for sampling designs.

    PubMed

    Kristensen, Terje; Ohlson, Mikael; Bolstad, Paul; Nagy, Zoltan

    2015-08-01

    Accurate field measurements from inventories across fine spatial scales are critical to improve sampling designs and to increase the precision of forest C cycling modeling. By studying soils undisturbed from active forest management, this paper gives a unique insight in the naturally occurring variability of organic layer C and provides valuable references against which subsequent and future sampling schemes can be evaluated. We found that the organic layer C stocks displayed great short-range variability with spatial autocorrelation distances ranging from 0.86 up to 2.85 m. When spatial autocorrelations are known, we show that a minimum of 20 inventory samples separated by ∼5 m is needed to determine the organic layer C stock with a precision of ±0.5 kg C m(-2). Our data also demonstrates a strong relationship between the organic layer C stock and horizon thickness (R (2) ranging from 0.58 to 0.82). This relationship suggests that relatively inexpensive measurements of horizon thickness can supplement soil C sampling, by reducing the number of soil samples collected, or to enhance the spatial resolution of organic layer C mapping. PMID:26205281

  1. [Soil organic carbon mineralization of Black Locust forest in the deep soil layer of the hilly region of the Loess Plateau, China].

    PubMed

    Ma, Xin-Xin; Xu, Ming-Xiang; Yang, Kai

    2012-11-01

    The deep soil layer (below 100 cm) stores considerable soil organic carbon (SOC). We can reveal its stability and provide the basis for certification of the deep soil carbon sinks by studying the SOC mineralization in the deep soil layer. With the shallow soil layer (0-100 cm) as control, the SOC mineralization under the condition (temperature 15 degrees C, the soil water content 8%) of Black Locust forest in the deep soil layer (100-400 cm) of the hilly region of the Loess Plateau was studied. The results showed that: (1) There was a downward trend in the total SOC mineralization with the increase of soil depth. The total SOC mineralization in the sub-deep soil (100-200 cm) and deep soil (200-400 cm) were equivalent to approximately 88.1% and 67.8% of that in the shallow layer (0-100 cm). (2) Throughout the carbon mineralization process, the same as the shallow soil, the sub-deep and deep soil can be divided into 3 stages. In the rapid decomposition phase, the ratio of the mineralization or organic carbon to the total mineralization in the sub-deep and deep layer (0-10 d) was approximately 50% of that in the shallow layer (0-17 d). In the slow decomposition phase, the ratio of organic carbon mineralization to total mineralization in the sub-deep, deep layer (11-45 d) was 150% of that in the shallow layer (18-45 d). There was no significant difference in this ratio among these three layers (46-62 d) in the relatively stable stage. (3) There was no significant difference (P > 0.05) in the mineralization rate of SOC among the shallow, sub-deep, deep layers. The stability of SOC in the deep soil layer (100-400 cm) was similar to that in the shallow soil layer and the SOC in the deep soil layer was also involved in the global carbon cycle. The change of SOC in the deep soil layer should be taken into account when estimating the effects of soil carbon sequestration in the Hilly Region of the Loess Plateau, China. PMID:23323422

  2. One-step synthesis of layered yttrium hydroxides in immiscible liquid–liquid systems: Intercalation of sterically-bulky hydrophobic organic anions and doping of europium ions

    SciTech Connect

    Watanabe, Mebae; Fujihara, Shinobu

    2014-02-15

    Inorganic–organic layered rare-earth compounds were synthesized on the basis of a biphasic liquid–liquid system in one pot. Layered yttrium hydroxides (LYHs) were chosen as a host material for the intercalation of hydrophobic organic guest anions such as benzoate, sebacate, or laurate. In a typical synthesis, an organic phase dissolving carboxylic acid was placed in contact with an equal amount of an aqueous phase dissolving yttrium nitrate n-hydrate and urea. At elevated temperatures up to 80 °C, urea was hydrolyzed to release hydroxyl anions which were used to form yttrium hydroxide layers. LYHs were then precipitated with the intercalation of carboxylate anions delivered from the organic phase under the distribution law. The structure and the morphology of the LYHs could be modulated by the intercalated anions. Doped with Eu{sup 3+} ions, the LYHs exhibited red photoluminescence which was enhanced by the intercalated anions due to the antenna effect. - Graphical abstract: The Eu{sup 3+}-doped layered yttrium hydroxide exhibits intense red photoluminescence after intercalation of benzoate ions. Display Omitted - Highlights: • Immiscible biphasic liquid systems were introduced to synthesize layered yttrium hydroxides. • The temperature of the biphasic systems does not exceed 80 °C in one step of the synthesis. • Hydrophobic organic anions were intercalated between the hydroxide layers in one pot. • Structure and morphology of the hydroxides were modulated by changing the kind of organic anions. • Eu{sup 3+}-doping led to red luminescence from the hydroxides in association with the intercalated organic anions.

  3. Quantitative resonant soft x-ray reflectivity of ultrathin anisotropic organic layers: Simulation and experiment of PTCDA on Au.

    PubMed

    Capelli, R; Mahne, N; Koshmak, K; Giglia, A; Doyle, B P; Mukherjee, S; Nannarone, S; Pasquali, L

    2016-07-14

    Resonant soft X-ray reflectivity at the carbon K edge, with linearly polarized light, was used to derive quantitative information of film morphology, molecular arrangement, and electronic orbital anisotropies of an ultrathin 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) film on Au(111). The experimental spectra were simulated by computing the propagation of the electromagnetic field in a trilayer system (vacuum/PTCDA/Au), where the organic film was treated as an anisotropic medium. Optical constants were derived from the calculated (through density functional theory) absorption cross sections of the single molecule along the three principal molecular axes. These were used to construct the dielectric tensor of the film, assuming the molecules to be lying flat with respect to the substrate and with a herringbone arrangement parallel to the substrate plane. Resonant soft X-ray reflectivity proved to be extremely sensitive to film thickness, down to the single molecular layer. The best agreement between simulation and experiment was found for a film of 1.6 nm, with flat laying configuration of the molecules. The high sensitivity to experimental geometries in terms of beam incidence and light polarization was also clarified through simulations. The optical anisotropies of the organic film were experimentally determined and through the comparison with calculations, it was possible to relate them to the orbital symmetry of the empty electronic states. PMID:27421398

  4. Quantitative resonant soft x-ray reflectivity of ultrathin anisotropic organic layers: Simulation and experiment of PTCDA on Au

    NASA Astrophysics Data System (ADS)

    Capelli, R.; Mahne, N.; Koshmak, K.; Giglia, A.; Doyle, B. P.; Mukherjee, S.; Nannarone, S.; Pasquali, L.

    2016-07-01

    Resonant soft X-ray reflectivity at the carbon K edge, with linearly polarized light, was used to derive quantitative information of film morphology, molecular arrangement, and electronic orbital anisotropies of an ultrathin 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) film on Au(111). The experimental spectra were simulated by computing the propagation of the electromagnetic field in a trilayer system (vacuum/PTCDA/Au), where the organic film was treated as an anisotropic medium. Optical constants were derived from the calculated (through density functional theory) absorption cross sections of the single molecule along the three principal molecular axes. These were used to construct the dielectric tensor of the film, assuming the molecules to be lying flat with respect to the substrate and with a herringbone arrangement parallel to the substrate plane. Resonant soft X-ray reflectivity proved to be extremely sensitive to film thickness, down to the single molecular layer. The best agreement between simulation and experiment was found for a film of 1.6 nm, with flat laying configuration of the molecules. The high sensitivity to experimental geometries in terms of beam incidence and light polarization was also clarified through simulations. The optical anisotropies of the organic film were experimentally determined and through the comparison with calculations, it was possible to relate them to the orbital symmetry of the empty electronic states.

  5. Strong coupling of exciton and photon modes in photonic crystal infiltrated with organic-inorganic layered perovskite

    NASA Astrophysics Data System (ADS)

    Sumioka, Kazuhiro; Nagahama, Hiroyuki; Tsutsui, Tetsuo

    2001-03-01

    Large vacuum Rabi-splitting, the evidence of strong coupling of photon and exciton modes, was observed at room temperature in an ordered array of silica microspheres infiltrated with organic-inorganic layered perovskite. By natural sedimentation of a colloidal suspension of monodispersed silica microspheres with a diameter of 256 nm, three-dimensional ordered array of silica microspheres (silica opal) were prepared. Into an air space of the silica opal, organic-inorganic perovskite, bis-(phenethylammonium) tetraiodoplumbate (PAPI), which exhibits intense exciton absorption at 2.40 eV, was infiltrated. The silica opal infiltrated with PAPI (23% of air space was filled) exhibited a stop band at 2.13 eV, when observed at a normal direction to the sample surface. By changing the observation angle, the coupling of the stop band at around 2.1-2.4 eV and the exciton band at 2.40 eV due to PAPI was attained. From angle-tuning measurements of reflection spectra, a vacuum Rabi-splitting of 240 meV was evaluated.

  6. 5 V driving organic non-volatile memory transistors with poly(vinyl alcohol) gate insulator and poly(3-hexylthiophene) channel layers

    NASA Astrophysics Data System (ADS)

    Nam, Sungho; Seo, Jooyeok; Kim, Hwajeong; Kim, Youngkyoo

    2015-10-01

    Organic non-volatile memory devices were fabricated by employing organic field-effect transistors (OFETs) with poly(vinyl alcohol) (PVA) and poly(3-hexylthiophene) as a gate insulating layer and a channel layer, respectively. The 10-nm-thick nickel layers were inserted for better charge injection between the channel layer and the top source/drain electrodes. The fabricated PVA-OFET memory devices could be operated at low voltages (≤5 V) and showed pronounced hysteresis characteristics in the transfer curves, even though very small hysteresis was measured from the output curves. The degree of hysteresis was considerably dependent on the ratio of channel width (W) to channel length (L). The PVA-OFET memory device with the smaller W/L ratio (25) exhibited better retention characteristics upon 700 cycles of writing-reading-erasing-reading operations, which was assigned to the stability of charged states in devices.

  7. Charge transport dependent high open circuit voltage tandem organic photovoltaic cells with low temperature deposited HATCN-based charge recombination layers.

    PubMed

    Wei, Huai-Xin; Zu, Feng-Shuo; Li, Yan-Qing; Chen, Wen-Cheng; Yuan, Yi; Tang, Jian-Xin; Fung, Man-Keung; Lee, Chun-Sing; Noh, Yong-Young

    2016-02-01

    Mechanisms of charge transport between the interconnector and its neighboring layers in tandem organic photovoltaic cells have been systematically investigated by studying electronic properties of the involving interfaces with photoelectron spectroscopies and performance of the corresponding devices. The results show that charge recombination occurs at HATCN and its neighboring hole transport layers which can be deposited at low temperature. The hole transport layer plays an equal role to the interconnector itself. These insights provide guidance for the identification of new materials and the device architecture for high performance devices. PMID:26775613

  8. A novel facile synthesis and characterization of heterostructures composed of carbon nanotubes and few-layer molybdenum disulfide sheets containing organic interlayers

    NASA Astrophysics Data System (ADS)

    Lenenko, Natalia D.; Zaikovskii, Vladimir I.; Golub, Alexandre S.

    2014-12-01

    A novel convenient room-temperature method for surface covering of carbon nanotubes (CNTs) with few-layer MoS2 shell was developed. For this purpose, liquid-phase single-layer dispersions of molybdenum disulfide produced by chemical exfoliation of its compound with lithium, LiMoS2, were applied. As evidenced by XRD and TEM studies, the dispersed MoS2 layers readily attach to the outer CNT surface and tend to envelop it. Measuring the interlayer distances in the vicinity of the MoS2-CNT interface showed, that deposited particles typically contain 1-3 (rarely, up to 10) MoS2 layers, which are in close contact with graphitic CNT walls. Similar deposition performed in the presence of cationic polymers containing polydiallyldimethylammonium units was found to lead to incorporation of polymer molecules in the sulfide shell of CNT in the form of 0.5 nm thick organic interlayers between the layers of MoS2. The same sequence of the layers of MoS2 and the polymer is also realized in the absence of CNT due to self-organization of the components. The method presented in this work has a great potential for designing other nanohybrid structures with participation of layered metal sulfides.

  9. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-01

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells. PMID:24452695

  10. Layer-by-Layer Deposition of Organic-Inorganic Hybrid Multilayer on Microporous Polyethylene Separator to Enhance the Electrochemical Performance of Lithium-Ion Battery.

    PubMed

    Xu, Wuxia; Wang, Zhuyi; Shi, Liyi; Ma, Ying; Yuan, Shuai; Sun, Lining; Zhao, Yin; Zhang, Meihong; Zhu, Jiefang

    2015-09-23

    A simple layer-by-layer (LbL) self-assembly process of poly(acrylic acid) (PAA) and ZrO2 was applied to construct functional ultrathin multilayers on polyethylene (PE) separators without sacrificing the excellent porous structure of separators. Such PAA/ZrO2 LbL-modified PE separators possess good electrolyte wettability, excellent electrolyte uptake, high ionic conductivity and large Li(+) transference number. More importantly, the top layer of LbL self-assembly would affect the dissociation of electrolyte and the formation of solid electrolyte interphase (SEI) layer in half-cells. Compared with the pristine and (PAA/ZrO2)1PAA-modified PE separators, (PAA/ZrO2)3-modified PE separator shows a larger Li(+) transference number (0.6) and a faster tendency to form a stable SEI layer, endowing half-cells with excellent capacity retention at high C-rates and superior cycling performance. These fascinating characteristics will provide the LbL self-assembly with a promising method to improve the surface property of PE separators for high performance lithium-ion batteries. PMID:26336109

  11. Influence of a compost layer on the attenuation of 28 selected organic micropollutants under realistic soil aquifer treatment conditions: insights from a large scale column experiment.

    PubMed

    Schaffer, Mario; Kröger, Kerrin Franziska; Nödler, Karsten; Ayora, Carlos; Carrera, Jesús; Hernández, Marta; Licha, Tobias

    2015-05-01

    Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in column experiments using two large scale column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption. PMID:25723339

  12. Decomposition of old organic matter as a result of deeper active layers in a snow depth manipulation experiment

    PubMed Central

    Taneva, Lina; Trumbore, Susan E.; Welker, Jeffrey M.

    2010-01-01

    A snow addition experiment in moist acidic tussock tundra at Toolik Lake, Alaska, increased winter snow depths 2–3 m, and resulted in a doubling of the summer active layer depth. We used radiocarbon (∆14C) to (1) determine the age of C respired in the deep soils under control and deepened active layer conditions (deep snow drifts), and (2) to determine the impact of increased snow and permafrost thawing on surface CO2 efflux by partitioning respiration into autotrophic and heterotrophic components. ∆14C signatures of surface respiration were higher in the deep snow areas, reflecting a decrease in the proportion of autotrophic respiration. The radiocarbon age of soil pore CO2 sampled near the maximum mid-July thaw depth was approximately 1,000 years in deep snow treatment plots (45–55 cm thaw depth), while CO2 from the ambient snow areas was ~100 years old (30-cm thaw depth). Heterotrophic respiration ∆14C signatures from incubations were similar between the two snow depths for the organic horizon and were extremely variable in the mineral horizon, resulting in no significant differences between treatments in either month. Radiocarbon ages of heterotrophically respired C ranged from <50 to 235 years BP in July mineral soil samples and from 1,525 to 8,300 years BP in August samples, suggesting that old soil C in permafrost soils may be metabolized upon thawing. In the surface fluxes, this old C signal is obscured by the organic horizon fluxes, which are significantly higher. Our results indicate that, as permafrost in tussock tundra ecosystems of arctic Alaska thaws, carbon buried up to several thousands of years ago will become an active component of the carbon cycle, potentially accelerating the rise of CO2 in the atmosphere. Electronic supplementary material The online version of this article (doi:10.1007/s00442-009-1556-x) contains supplementary material, which is available to authorized users. PMID:20084398

  13. A novel porous anionic metal-organic framework with pillared double-layer structure for selective adsorption of dyes

    NASA Astrophysics Data System (ADS)

    Sheng, Shu-Nan; Han, Yi; Wang, Bin; Zhao, Cui; Yang, Fan; Zhao, Min-Jian; Xie, Ya-Bo; Li, Jian-Rong

    2016-01-01

    A novel porous anionic metal-organic framework, (Me2NH2)2[Zn2L1.5bpy]·2DMF (BUT-201; H4L=4,8-disulfonaphthalene-2,6-dicarboxylic acid; bpy=4,4-bipyridine; DMF=N,N-dimethylformamide), with pillared double-layer structure has been synthesized through the reaction of a sulfonated carboxylic acid ligand and Zn(NO3)2·6H2O with 4,4-bipyridine as a co-ligand. It is found that BUT-201 can rapidly adsorb cationic dyes with a smaller size such as Methylene Blue (MB) and Acriflavine Hydrochloride (AH) by substitution of guest (CH3)2NH2+, but has no adsorption towards the cationic dyes with a lager size such as Methylene Violet (MV), the anionic dyes like C. I. Acid Yellow 1 (AY1) and neutral dyes like C. I. Solvent Yellow 7 (SY7), respectively. The results show that the adsorption behavior of BUT-201 relates not only to the charge but also to the size/shape of dyes. Furthermore, the adsorbed dyes can be gradually released in the methanol solution of LiNO3.

  14. Influence of surface chemistry on the structural organization of monomolecular protein layers adsorbed to functionalized aqueous interfaces.

    PubMed Central

    Lösche, M; Piepenstock, M; Diederich, A; Grünewald, T; Kjaer, K; Vaknin, D

    1993-01-01

    The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both in subphase water molecules and in the alkyl chains of the lipid surface monolayer, was utilized to determine the interface structure on the molecular length scale. In all cases studied, the protein forms monomolecular layers underneath the interface with thickness values of approximately 40 A. A systematic dependence of the structural properties of such self-assembled SA monolayers on the surface chemistry was observed: the lateral protein density depends on the length of the spacer connecting the biotin moiety and its hydrophobic anchor. The hydration of the lipid head groups in the protein-bound state depends on the dipole moment density at the interface. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 11 FIGURE 12 FIGURE A1 PMID:8298041

  15. Positional isomerism-driven two 3D pillar-layered metal-organic frameworks: Syntheses, topological structures and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Sun, Yayong; Zhao, Siwei; Ma, Haoran; Han, Yi; Liu, Kang; Wang, Lei

    2016-06-01

    Two novel three-dimensional (3D) pillar-layered metal-organic frameworks (MOFs), namely [Zn2(μ2-OH)(boaba)(1,4-bmimb)]n (1) and {[Zn5K2(μ2-H2O)2(boaba)4(1,2-bmimb)2(H2O)2]·H2O}n (2), were prepared by hydrothermal reactions (H3boaba=3,5-bis-oxyacetate-benzoic acid; 1,4-bmimb=1,4-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene; 1,2-bmimb =1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene). Notably, 1 exhibits a (3,5)-connected binodal (63)(69·8)-gra net with binuclear [Zn2(μ2-OH)(COO)]2+ clusters, while 2 shows a novel (4,4,5,9)-connected 4-nodal net constructed from the unique Zn(II)-K(I) heterometal rod-like substructures. The results indicate that the disposition of the 2-methylimidazolyl groups of bis(imidazole) ligands have a significant effect on structural diversity. Moreover, the photoluminescence properties of 1 and 2 have been investigated.

  16. Highly efficient blue organic light-emitting diodes using dual emissive layers with host-dopant system

    NASA Astrophysics Data System (ADS)

    Lee, Bo Mi; Yu, Hyeong Hwa; Kim, You Hyun; Kim, Nam Ho; Yoon, Ju An; Mascher, Peter; Kim, Woo Young

    2012-10-01

    In this study, we fabricated highly efficient blue organic light-emitting diodes by designing different emitting layer structures with fluorescent host and dopant materials of 4,4-bis(2,2-diphenylyinyl)-1,10-biphenyl (DPVBi) and 9,10- bis(2-naphthyl) anthracene (ADN) as host materials and 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'biphenyl (BCzVBi) as a dopant material to demonstrate electrical and optical improvements. Best enhancement in luminance and luminous efficiency were achieved by a quantum well structure and energy transfer between host and dopant materials in device F as of 8668cd/m2 at 8V and 5.16 Cd/A at 103.20 mA/cm2 respectively. Among the blue OLED devices doped by BCzVBi, device B emits the deepest blue emission with Commission Internationale de l'É clairage (CIExy) coordinates of (0.157, 0.117) at 8V.

  17. Ideal p-n Diode Current Equation for Organic Heterojunction using a Buffer Layer: Derivation and Numerical Study

    NASA Astrophysics Data System (ADS)

    Kim, SeongMin; Ha, Jaewook; Kim, Jin-Baek

    2016-04-01

    The equation of p-n diode current-voltage (J-V) of an organic heterojunction (HJ) including a hole and electron buffer layer is derived, and its characteristics are numerically simulated based on a polaron-pair model Giebink et al. (Forrest, Phys. Rev. B 82; 1-12, 2010). In particular, the correlation between a fraction of the potential drop for an electron/hole buffer ( δ e - b / δ h - b ) and for a donor (D)/acceptor (A) ( δ D / δ A ) is numerically investigated for J-V curves. As a result, the lowest diode current (DC) is obtained for the condition of δ e - b + δ A ≅ 0 or δ D + δ h - b ≅ 1. It is suggested that it is important to characterize the lowest DC curve for the state of D/A blending with a condition of a fraction of the potential drop ( δ e - b / δ h - b ). Under these circumstances, the transport of holes ( h +) from a DC source at the reverse bias is effectively limited.

  18. Influences of Alq3 as electron extraction layer instead of Ca on the photo-stability of organic solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyong; Tian, Miaomiao; Wang, Ning

    2014-03-01

    Calcium (Ca) is not a desirable candidate as electron extraction layer (EEL) for long-term stability organic photovoltaics (OPVs) on account of its nature of active metal. In this paper, we has selected thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as donor and acceptor, respectively, and the device architecture is Glass/ITO/poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS)/PTB7:PC71BM/EEL/Aluminum. For comparison, tris (8-hydroxyquinoline) aluminum (Alq3) and Ca were used as EEL to reveal their influence on the performance [power conversion efficiency (PCE), short-circuit current density (JSC), open-circuit voltage (VOC) and fill factor (FF)] of the OPVs. As a result, PCE of the device with Ca as EEL rapidly reduced over 60% after three days due to the poor stability of Ca. The device with Alq3 as EEL shows favorable stability owing to the PCE moderate declined less than 30% after one month. Furthermore, PCE of the device with Alq3 as EEL was fully comparable to that with Ca as EEL. Our results indicate that Alq3 is an alternative candidate for high-performance and long-term photo-stability OPVs.

  19. Efficiency improvements in single-heterojunction organic photovoltaic cells by insertion of wide-bandgap electron-blocking layers

    NASA Astrophysics Data System (ADS)

    Ho, Chiu-Sheng; Lee, Ching-Sung; Hsu, Wei-Chou; Lin, Cheng-Yung; Lai, Ying-Nan; Wang, Ching-Wu

    2012-10-01

    This letter reports efficiency improvements in single-heterojunction organic photovoltaic (OPV) cells exploiting different wide-bandgap electron-blocking layer (EBL) materials of N,N,NO',N' tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), Tris(phenypyrazole)iridium (Ir(ppz)3), or 4,4,4"-tris-(3-methylphenylphenylamino)triphenylamine (m-MTDATA), respectively. The OPV structure consists of an indium-tin-oxide (ITO) anode, 4 nm m-MTDATA, 30 nm copper phthalocyanine (CuPc), 40 nm fullerene (C60), 10 nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and a 100 nm Al cathode. Optimum device performances by insertion the EBL of m-MTDATA have been achieved, including short-circuit current density (JSC) of 7.26 mA/cm2, open-circuit voltage (VOC) of 0.5 V, fill-factor (FF) of 43%, and power conversion efficiency (PCE) of 1.56% at an illumination intensity of 100 mW/cm2.

  20. Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes.

    PubMed

    Park, Hyesung; Brown, Patrick R; Bulović, Vladimir; Kong, Jing

    2012-01-11

    In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications. PMID:22107487

  1. Enhanced hole injection in phosphorescent organic light-emitting diodes by thermally evaporating a thin indium trichloride layer.

    PubMed

    Gao, Chun-Hong; Cai, Shi-Duan; Gu, Wei; Zhou, Dong-Ying; Wang, Zhao-Kui; Liao, Liang-Sheng

    2012-10-24

    An ultrathin layer of indium trichloride (InCl(3)) is thermally evaporated on the indium tin oxide (ITO) anode to enhance the hole injection in simplified phosphorescent organic light-emitting diodes (PHOLEDs). Comparing with the device with ultraviolet (UV)-ozone treatment, the device modified by InCl(3) exhibits a maximum current efficiency of 82.2 cd/A measured at about 2000 cd/cm(2) and 36% improvement in power efficiency measured at 20 mA/cm(2). More importantly, more than three times improvement in half lifetime estimated at an initial luminance of 1000 cd/cm(2) is achieved. The investigations using ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and the bias- and temperature-dependent current density-voltage characteristics in the related hole-dominated devices have revealed that the improved device performance is mainly attributed to the enhanced hole injection resulting from the lowered hole injection barrier height in the InCl(3)-modified devices. PMID:23003119

  2. Influence of UV and visible laser light on the structure and composition of layered organic - inorganic zinc and copper nanocomposites

    SciTech Connect

    Borodina, T I; Val'yano, G E; Gololobova, O A; Karpukhin, Vyacheslav T; Malikov, Mikhail M; Strikanov, D A

    2013-06-30

    The effect of UV and visible laser light on the structure and composition of layered organic-inorganic nanocomposites of transition metals, zinc [zinc hydroxide/dodecyl sulfate, Zn(OH){sub 2}DS] and copper [copper hydroxide/dodecyl sulfate, Cu{sub 2}(OH){sub 3}DS], has been experimentally investigated. Nanocomposites have been synthesised by laser ablation of targets from the aforementioned materials in aqueous solutions of a surfactant: sodium dodecyl sulfate (SDS). The absorption and Raman spectra of the thus obtained colloids are analysed. The structural composition and morphology of the solid phase isolated from the colloids are determined using X-ray diffraction, atomic-force microscopy, and scanning electron microscopy. It is shown that exposure of nanocomposites to UV and visible laser light with intensities in the range of 5 Multiplication-Sign 10{sup 5}-10{sup 7} W cm{sup -2} or higher leads to their fragmentation and change in their composition. (optical nanostructures)

  3. Evaluation of the water and organic liquids extraction efficiency of Spirulina maxima dyes using thermostated micro thin-layer chromatography.

    PubMed

    Zarzycki, Paweł K; Zarzycka, Magdalena B

    2008-01-01

    Thermostated micro thin-layer chromatography was applied for separation and quantification studies of Spirulina maxima dyes isolated from pharmaceutical formulation by a simple one-step liquid extraction. The isolation process was performed using a number of liquids, including water; 10 mM water solutions of native alpha-, beta-, and gamma-cyclodextrin and their hydroxypropyl derivatives; and a number of common organic liquids characterized by different polarity, namely, methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, acetone, tetrahydrofuran, dichloromethane, toluene, and n-hexane. Chromatographic studies were performed on RP18W plates working inside a small thermostated horizontal chamber allowing a development distance of 45 mm. Using a mobile phase consisting of acetone-n-hexane (30 + 70, v/v) and 40 degrees C separation temperature, plate peak capacity of at least 15 spots/lane and developing time <5 min were obtained. Validation data indicated that under such conditions, with an office scanner used for chromatogram digitalization, spot quantification could be accurately performed within an analyte mass range of 2 factors. The raw quantitative data obtained from microchromatograms acquired under visible light conditions were explored using cluster analysis and principal components analysis. Chemometric investigations revealed that the best extraction liquids for isolation of dye mixtures from Spirulina samples were methanol, ethanol, tetrahydrofuran, and dichloromethane. Moreover, it was found that the liquids' parachor values could be used for estimation of the dye extraction efficiency from complex samples. PMID:18980141

  4. Enhanced luminous efficiency and brightness using DNA electron blocking layers in bio-organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Hagen, Joshua A.

    The biopolymer deoxyribonucleic acid (DNA) has been extracted from salmon (saDNA) and used successfully as an electron blocking layer (EBL) in multiple structures of Organic Light Emitting Diodes (OLED). Water soluble saDNA was complexed with a cationic surfactant hexadecytrimethylammonium chloride (CTMA) which makes the resulting DNA-CTMA molecule water insoluble, and soluble in common organic media such as alcohols. Solutions of DNA-CTMA and butanol make uniform thin films from 20nm to 5 microns in thickness by varying spin coating parameters and molecular weight. The optical properties of DNA-CTMA thin films include high transparency and low optical loss for applications at wavelengths above 400nm. The DNA-CTMA films have an electrical resistivity on the order of 107 O*cm. All of these properties combined made DNA-CTMA a candidate as an EBL in OLEDs, and this resulting device was termed a Bio-organic Light Emitting Diode (BioLED). Enhanced electroluminescent efficiency has been demonstrated in both green and blue emitting BioLEDs. The resulting green and blue BioLEDs showed a maximum luminous efficiency of 8.2 and 0.8 cd/A, respectively. The DNA based BioLEDs were as much as 10x more efficient and 30x brighter than their OLED counterparts. The enhancement in performance is due to the electron blocking action with the 0.9 eV (lowest unoccupied molecular orbital) value, allows hole injection to proceed with a 5.6eV (highest occupied molecular orbital) value. DNA-CTMA has also been successfully deposited in thin film form via molecular beam deposition (MBD). The growth was achieved at 160°C at vacuum levels of 10-5 Torr at a deposition rate of 0.8A/s. MBD grown DNA-CTMA thin films were highly uniform, optically transparent, and adhere to silicon, quartz and glass substrates more strongly than spin coated films. The material deposited was verified as DNA-CTMA through optical absorption, energy dispersive X-ray analysis, and using a DNA indicating fluorescent dye

  5. Laboratory measurements of nitric oxide release from forest soil with a thick organic layer under different understory types

    NASA Astrophysics Data System (ADS)

    Bargsten, A.; Falge, E.; Pritsch, K.; Huwe, B.; Meixner, F. X.

    2010-05-01

    Nitric oxide (NO) plays an important role in the photochemistry of the troposphere. NO from soil contributes up to 40% to the global budget of atmospheric NO. Soil NO emissions are primarily caused by biological activity (nitrification and denitrification), that occurs in the uppermost centimeter of the soil, a soil region often characterized by high contents of organic material. Most studies of NO emission potentials to date have investigated mineral soil layers. In our study we sampled soil organic matter under different understories (moss, grass, spruce and blueberries) in a humid mountainous Norway spruce forest plantation in the Fichtelgebirge (Germany). We performed laboratory incubation and flushing experiments using a customized chamber technique to determine the response of net potential NO flux to physical and chemical soil conditions (water content and temperature, bulk density, particle density, pH, C/N ratio, organic C, soil ammonium, soil nitrate). Net potential NO fluxes (in terms of mass of N) from soil samples taken under different understories ranged from 1.7-9.8 ng m-2 s-1 (soil sampled under grass and moss cover), 55.4-59.3 ng m-2 s-1 (soil sampled under spruce cover), and 43.7-114.6 ng m-2 s-1 (soil sampled under blueberry cover) at optimum water content and a soil temperature of 10 °C. The water content for optimum net potential NO flux ranged between 0.76 and 0.8 gravimetric soil moisture for moss covered soils, between 1.0 and 1.1 for grass covered soils, 1.1 and 1.2 for spruce covered soils, and 1.3 and 1.9 for blueberry covered soils. Effects of soil physical and chemical characteristics on net potential NO flux were statistically significant (0.01 probability level) only for NH4+. Therefore, as an alternative explanation for the differences in soil biogenic NO emission we consider more biological factors like understory vegetation type, amount of roots, and degree of mycorrhization; they have the potential to explain the observed

  6. Perovskite-organic hybrid tandem solar cells using a nanostructured perovskite layer as the light window and a PFN/doped-MoO3/MoO3 multilayer as the interconnecting layer

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Lu, Shunmian; Zhu, Lu; Li, Xinchen; Choy, Wallace C. H.

    2016-02-01

    In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL.In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL. Electronic supplementary information (ESI) available. See DOI: 10

  7. Al2O3/TiO2 nanolaminate thin film encapsulation for organic thin film transistors via plasma-enhanced atomic layer deposition.

    PubMed

    Kim, Lae Ho; Kim, Kyunghun; Park, Seonuk; Jeong, Yong Jin; Kim, Haekyoung; Chung, Dae Sung; Kim, Se Hyun; Park, Chan Eon

    2014-05-14

    Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al2O3 films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al2O3 films are significantly corroded by water. In this study, we examined the deformation of PEALD Al2O3 films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al2O3/TiO2 nanolamination (NL) technique. Our Al2O3/TiO2 NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated. PMID:24712401

  8. Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit

    NASA Astrophysics Data System (ADS)

    Rodenhausen, K. B.; Kasputis, T.; Pannier, A. K.; Gerasimov, J. Y.; Lai, R. Y.; Solinsky, M.; Tiwald, T. E.; Wang, H.; Sarkar, A.; Hofmann, T.; Ianno, N.; Schubert, M.

    2011-10-01

    Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing.

  9. Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit.

    PubMed

    Rodenhausen, K B; Kasputis, T; Pannier, A K; Gerasimov, J Y; Lai, R Y; Solinsky, M; Tiwald, T E; Wang, H; Sarkar, A; Hofmann, T; Ianno, N; Schubert, M

    2011-10-01

    Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing. PMID:22047284

  10. Illumination angle and layer thickness influence on the photo current generation in organic solar cells: A combined simulative and experimental study

    SciTech Connect

    Mescher, Jan Mertens, Adrian; Egel, Amos; Kettlitz, Siegfried W.; Colsmann, Alexander; Lemmer, Uli

    2015-07-15

    In most future organic photovoltaic applications, such as fixed roof installations, facade or clothing integration, the solar cells will face the sun under varying angles. By a combined simulative and experimental study, we investigate the mutual interdependencies of the angle of light incidence, the absorber layer thickness and the photon harvesting efficiency within a typical organic photovoltaic device. For thin absorber layers, we find a steady decrease of the effective photocurrent towards increasing angles. For 90-140 nm thick absorber layers, however, we observe an effective photocurrent enhancement, exhibiting a maximum yield at angles of incidence of about 50°. Both effects mainly originate from the angle-dependent spatial broadening of the optical interference pattern inside the solar cell and a shift of the absorption maximum away from the metal electrode.

  11. Luminance Mechanisms of White Organic Light-Emitting Devices Fabricated Utilizing a Charge Generation Layer with a Light-Emitting Function.

    PubMed

    Kim, K H; Jeon, Y P; Choo, D C; Kim, T W

    2015-07-01

    The luminance mechanisms of the white organic light-emitting devices (WOLEDs) with a charge generation layer (CGL) consisting of a tungsten oxide layer and a 5,6,11,12-tetraphenyltetracene (rubrene) doped N,N',-bis-(1-naphthyl)-N,N'-diphenyl1-1'-biphenyl-4,4'-diamine (NPB) layer were investigated. Current densities and luminances of the WOLEDs increased with increasing a rubrene doping concentration because the formation of excitons in the rubrene-doped NPB layer increased due to the more exciton trapping in rubrene molecules and the delay of the electron injection due to the insertion of the litium qunolate layer. The yellow light emitted from the rubrene-doped NPB layer in the CGL combined with the blue light from the main emitting layer of the WOLEDs, resulting in the emission of the white light. The ratio between the yellow and the blue color peak intensities of the electroluminescence spectra for the WOLEDs was controlled by the rubrene doping concentration. The Commission Internationale de l'Eclairage coordinates of the fabricated WOLED were (0.31, 0.42) at 740.7 cd/m2, indicative of white emission color. PMID:26373110

  12. Crystallinity and interface of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile thin films between organic and transparent conductive oxide layers

    NASA Astrophysics Data System (ADS)

    Lee, Hyun Hwi; Lee, Jeong-Hwan; Kim, Jang-Joo; Kim, Hyo Jung

    2015-05-01

    The crystallinity, preferential ordering, and interfacial stability of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HATCN) thin films interconnected with organic/inorganic multilayers have been investigated. In the region close to the organic-organic interface, HATCN formed a low crystalline order with a substantial amorphous phase. As film growth continued, HATCN stacked to the high crystalline ordered phase. After the sputtering deposition of the indium zinc oxide (IZO) layer on top, the volume fraction of the preferentially ordered region of HATCN increased without any structural deterioration. In addition, the HATCN surface was kept quite stable by preserving the sharp interface between the HATCN and sputtering-deposited IZO layers.

  13. The incorporation of an organic soil layer in the Noah-MP land surface model and its evaluation over a boreal aspen forest

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Li, Yanping; Chen, Fei; Barr, Alan; Barlage, Michael; Wan, Bingcheng

    2016-07-01

    A thick top layer of organic matter is a dominant feature in boreal forests and can impact land-atmosphere interactions. In this study, the multi-parameterization version of the Noah land surface model (Noah-MP) was used to investigate the impact of incorporating a forest-floor organic soil layer on the simulated surface energy and water cycle components at the BERMS Old Aspen site (OAS) field station in central Saskatchewan, Canada. Compared to a simulation without an organic soil parameterization (CTL), the Noah-MP simulation with an organic soil (OGN) improved Noah-MP-simulated soil temperature profiles and soil moisture at 40-100 cm, especially the phase and amplitude (Seasonal cycle) of soil temperature below 10 cm. OGN also enhanced the simulation of sensible and latent heat fluxes in spring, especially in wet years, which is mostly related to the timing of spring soil thaw and warming. Simulated top-layer soil moisture is better in OGN than that in CTL. The effects of including an organic soil layer on soil temperature are not uniform throughout the soil depth and are more prominent in summer. For drought years, the OGN simulation substantially modified the partitioning of water between direct soil evaporation and vegetation transpiration. For wet years, the OGN-simulated latent heat fluxes are similar to CTL except for the spring season when OGN produced less evaporation, which was closer to observations. Including organic soil produced more subsurface runoff and resulted in much higher runoff throughout the freezing periods in wet years.

  14. Al-TiO₂ composite-modified single-layer graphene as an efficient transparent cathode for organic solar cells.

    PubMed

    Zhang, Di; Xie, Fengxian; Lin, Peng; Choy, Wallace C H

    2013-02-26

    While there are challenges in tuning the properties of graphene (surface wettability, work function alignment, and carrier transport) for realizing an efficient graphene cathode in organic solar cells (OSCs), we propose and demonstrate using an Al-TiO₂ composite to modify single-layer graphene as an efficient cathode for OSCs. To unveil the contributions of the composite in addressing the aforementioned challenges, the evaporated aluminum nanoclusters in the composite benefit the graphene cathode by simultaneously achieving two roles of improving its surface wettability for subsequent TiO₂ deposition and reducing its work function to offer better energy alignment. To address challenges related to charge transport, solution-processed TiO₂ with excellent electron transport can offer charge extraction enhancement to the graphene cathode, which is essential to efficient devices. However, it is a well-known issue for methods such as spin-coating to produce uniform films on the initially hydrophobic graphene, even with improved wettability. The undesirable morphology of TiO₂ by such methods considerably inhibits its effectiveness in enhancing charge extraction. We propose a self-assembly method to deposit the solution-processed TiO₂ on the Al-covered graphene for forming the Al-TiO₂ composite. Compared with spin-coating, the self-assembly method is found to achieve more uniform coating on the graphene surface, with highly controllable thickness. Consequently, the graphene cathode modified with the Al-TiO₂ composite in inverted OSCs gives rise to enhanced power conversion efficiency of 2.58%, which is 2-fold of the previously best reported efficiency (1.27%) for graphene cathode OSCs, reaching ∼75% performance of control devices using indium tin oxide. PMID:23327464

  15. Response of soil organic layer characteristics to different amounts of logging residue in a Scots pine thinning stand

    NASA Astrophysics Data System (ADS)

    Smolander, Aino; Kitunen, Veikko; Tamminen, Pekka; Kukkola, Mikko

    2010-05-01

    Since there is an increasing demand for production of bioenergy, forest management using logging residue from both clear-cutting and thinning stands is becoming more common. Therefore there is a need of information how this whole-tree harvest, as compared to the traditional stem-only harvest, changes forest soil characteristics in long-term. The aim of this study was to investigate the effects of logging residue removal on soil microbial processes related to C and N cycling and on two major groups of plant secondary compounds, phenolic compounds and terpenes. These two groups of compounds were of interest since logging residue contains the highest proportion of most of these compounds. In addition, certain phenolic compounds and terpenes have been shown to regulate N transformations in forests soils. The study site was a young Scots pine stand in central Finland. It was thinned and four different amounts of logging residue, consisting of needles and tree branches, were distributed around a tree: 0, 40, 80 and 120 kg of fresh logging residue on a circle (diameter 2.5 m) around a tree. Samples were taken from the organic layer (F+H) four years after the treatment. Two highest amounts of logging residue increased both C and net N mineralization and glucose-induced respiration, but the amount of logging residue did not affect microbial biomass C or N. There were not any large differences between the treatments in the concentrations of mono, sesqui-, di- or triterpenes, although some terpenes showed an increase with the highest amount of residues. Amount of logging residue did not clearly affect the concentrations of volatile monoterpenes in soil atmosphere.

  16. Understanding gate adsorption behaviour of CO2 on elastic layer-structured metal-organic framework-11.

    PubMed

    Hiraide, Shotaro; Tanaka, Hideki; Miyahara, Minoru T

    2016-03-14

    We demonstrate that CO2 gate adsorption behaviour of elastic layer-structured metal-organic framework-11 (ELM-11: [Cu(BF4)2(4,4'-bipyridine)2]), which is a family of soft porous crystals (SPCs), can be described by a thermodynamic model by free energy analysis with the aid of an adsorption experiment and a molecular simulation. The structures of ELM-11 (closed structure) at 273 K after its evacuation and CO2-encapsulated ELM-11 (open structure) at 195-298 K were determined by the Rietveld analysis using in situ synchrotron X-ray powder diffraction data. We then performed grand canonical Monte Carlo (GCMC) simulations for CO2 adsorption on the open host framework structures of ELM-11 from the Rietveld analysis. The temperature dependence of the Helmholtz free energy change of host ΔF(host) from the closed structure to the open structure was obtained by the free energy analysis using the GCMC data. We show that there is a linear correlation between ΔF(host) and temperature, and thus, the internal energy and entropy changes of host, ΔU(host) and ΔS(host), respectively, can be obtained. The obtained ΔU(host) value is in good agreement with that obtained from the quantum chemical calculations using the closed and open host framework structures, which demonstrates that the thermodynamic model for gate adsorption is highly appropriate. Moreover, our result suggests that the gate adsorption pressure depends on not only the guest-host interaction and the internal energy change of host, but also the entropy change of host, which should be one of the key factors for the tailored synthesis of SPCs. PMID:26498489

  17. Adsorption mechanism of ester phosphate on baryum titanate in organic medium. Preliminary results on the structure of the adsorbed layer

    NASA Astrophysics Data System (ADS)

    Le Bars, N.; Tinet, D.; Faugère, A. M.; van Damme, H.; Levitz, P.

    1991-05-01

    The purpose of this work is to evidence the adsorption mechanism and the structure of commercial phosphate ester surfactant stabilized BaTiO3 in organic suspension, and to relate these characteristics to rheological behaviour. Binders and plasticizers are omitted to reduce the number of system components. Firstly adsorption isotherm were determined by inductively coupled argon plasma technique and interpretated based on transmission electron microscopy and ^{31}P nuclear magnetic resonance studies. Preliminary rheological measurements were then performed and related to suspension structure. Structure of the adsorption layer is critically discussed. L'objectif de cette étude est la compréhension du mécanisme d'adsorption d'agents dispersants phosphatés dans des suspensions organiques de BaTiO3, ainsi que la caractérisation de la structure, et du comportement rhéologique de ces suspensions. Liants et plastifiants ne sont pas utilisés, afin de réduire le nombre de composants dans le système. Dans un premier temps, l'isotherme d'adsorption est établie par dosage en émission plasma, puis interprétée sur la base de résultats de Microscopie Eloctronique à Transmission, et de spectroscopie par Résonance Magnétique Nucléaire du ^{31}P. Des mesures rhéologiques préliminaires sont effectuées pour caractériser la structure des suspensions.

  18. Perovskite-organic hybrid tandem solar cells using a nanostructured perovskite layer as the light window and a PFN/doped-MoO3/MoO3 multilayer as the interconnecting layer.

    PubMed

    Liu, Jian; Lu, Shunmian; Zhu, Lu; Li, Xinchen; Choy, Wallace C H

    2016-02-14

    In this study, we present a two-terminal perovskite (PVSK)-organic hybrid tandem solar cell with a nanostructured PVSK as the light window and a PFN/doped MoO3/MoO3 structure as the interconnecting layer (ICL). In this tandem structure, the PVSK layer is specially designed with a nanostructured surface morphology; thus the PCBM could be filled-up for forming intimately contacted interface with PVSK layers. This design could not only efficiently increase the device performance, it could also greatly remove the hysteresis of PVSK solar cells. The study indicates that doped MoO3 as the step layer plays a key role in protecting the underlying layer against multi-solution processes and aids in the efficient recombination of electrons and holes generated from the sub-cells. The hybrid tandem solar cell could achieve a high VOC of 1.58 V, which is the sum of those in the two sub-cells, and a high FF of 0.68, indicating the effectiveness of the multilayer ICL. PMID:26809656

  19. Effects of matrix layer composition on the structural and optical properties of self-organized InGaN quantum dots

    NASA Astrophysics Data System (ADS)

    Li, Z. C.; Liu, J. P.; Feng, M. X.; Zhou, K.; Zhang, S. M.; Wang, H.; Li, D. Y.; Zhang, L. Q.; Sun, Q.; Jiang, D. S.; Wang, H. B.; Yang, H.

    2013-09-01

    Self-organized InGaN quantum dots (QDs) with emission wavelength from green to red range have been grown on GaN templated c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The effects of matrix layer composition on the structural and optical properties of InGaN QDs have been investigated. A continued growth of QDs is observed during the growth of In0.1Ga0.9N matrix layer, which results in an increase of the QDs' size. By using In0.1Ga0.9N matrix layer instead of GaN one, the annealing induced blue-shift in emission energy of the InGaN QDs can be suppressed. After the growth of top GaN cap layer, a larger red-shift caused by the quantum confined Stark effect is observed in the sample with In0.1Ga0.9N matrix layer. Employing this method, InGaN QD sample emitting at 615 nm with an internal quantum efficiency of 24.3% has been grown. The significance of this method is that it allows a higher growth temperature of InGaN QDs with emission wavelength in the green range to improve the crystalline quality, which is beneficial to enhance the efficiency of green InGaN QD light-emitting-diodes and laser diodes.

  20. Numerical model for a watering plan to wash out organic matter from the municipal solid waste incinerator bottom ash layer in closed system disposal facilities.

    PubMed

    Ishii, Kazuei; Furuichi, Toru; Tanikawa, Noboru

    2009-02-01

    Bottom ash from municipal solid waste incineration (MSWI) is a main type of waste that is landfilled in Japan. The long-term elution of organic matter from the MSWI bottom ash layers is a concern because maintenance and operational costs of leachate treatment facilities are high. In closed system disposal facilities (CSDFs), which have a roof to prevent rainfall from infiltrating into the waste layers, water must be supplied artificially and its quantity can be controlled. However, the quantity of water needed and how to apply it (the intensity, period and frequency) have not been clearly defined. In order to discuss an effective watering plan, this study proposes a new washout model to clarify a fundamental mechanism of total organic carbon (TOC) elution behavior from MSWI bottom ash layers. The washout model considers three phases: solid, immobile water and mobile water. The parameters, including two mass transfer coefficients of the solid-immobile water phases and immobile-mobile water phases, were determined by one-dimensional column experiments for about 2 years. The intensity, period and frequency of watering and other factors were discussed based on a numerical analysis using the above parameters. As a result, our washout model explained adequately the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurred (pH approximately 8.3). The determined parameters and numerical analysis suggested that there is a possibility that the minimum amount of water needed for washing out TOC per unit weight of MSWI bottom ash layer could be determined, which depends on the two mass transfer coefficients and the depth of the MSWI bottom ash layer. Knowledge about the fundamental mechanism of the elution behavior of TOC from the MSWI bottom ash layer before carbonation occurs, clarified by this study, will help an effective watering plan in CSDFs. PMID:18691865