Silicon-on-ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

NASA Technical Reports Server (NTRS)

Chapman, P. W.; Zook, J. D.; Heaps, J. D.; Grung, B. L.; Koepke, B.; Schuldt, S. B.

1979-01-01

Significant progress is reported in fabricating a 4 sq cm cell having a 10.1 percent conversion efficiency and a 10 sq cm cell having a 9.2 percent conversion efficiency. The continuous (SCIM) coater succeeded in producing a 16 sq cm coating exhibiting unidirectional solidification and large grain size. A layer was grown at 0.2 cm/sec in the experimental coater which was partially dendritic but also contained a large smooth area approximately 100 micron m thick. The dark characteristic measurements of a typical SCC solar cell yield shunt resistance values of 10K ohms and series resistance values and 0.4 ohm. The production dip-coater is operating at over 50 percent yield in terms of good cell quality material. The most recent run yielded 13 good substrates out of 15.

Ultralow noise up-conversion detector and spectrometer for the telecom band.

PubMed

Shentu, Guo-Liang; Pelc, Jason S; Wang, Xiao-Dong; Sun, Qi-Chao; Zheng, Ming-Yang; Fejer, M M; Zhang, Qiang; Pan, Jian-Wei

2013-06-17

We demonstrate up-conversion single-photon detection for the 1550-nm telecommunications band using a PPLN waveguide, long-wavelength pump, and narrowband filtering using a volume Bragg grating. We achieve total-system detection efficiency of around 30% with noise at the dark-count level of a Silicon APD. Based on the new detector, a single-pixel up-conversion infrared spectrometer with a noise equivalent power of -142 dBm Hz(-1/2) was demonstrated, which was as good as a liquid nitrogen cooled CCD camera.

Selective Emitters for High Efficiency TPV Conversion: Materials Preparation and Characterisation

NASA Astrophysics Data System (ADS)

Diso, D.; Licciulli, A.; Bianco, A.; Leo, G.; Torsello, G.; Tundo, S.; De Risi, A.; Mazzer, M.

2003-01-01

Optimising the spectral emissivity of the IR radiation source in a TPV generator is one of the crucial steps towards high efficiency TPV conversion. In this paper we present different approaches to the preparation of selective emitters to be coupled to high efficiency photovoltaic cells. The emitters are designed to work at a temperature of about 1500K and they have been prepared to be used either as external coatings for the burner or as a structural material for the burner itself. Composite ceramics containing rare earth cations, prepared by slip-casting, with various concentration of rare earths were prepared by Slip Casting and Slurry Coating. Rare earth oxides have been incorporated into different oxide matrices, namely Silica, Alumina, Zirconia and their combination. The final aim was to find the material that exhibits the best performance in terms of both high selective power emission, good efficiency along with acceptable thermo-structural properties (high temperature thermal shock resistance, good strength, no creep). The power density emitted by samples as function of the temperature has been tested in the range 1000nm-5000nm. The high temperature emission measurements and the structural tests indicate that a good compromise between the functional and the thermo-structural properties may be reached. The results of the tests on the emitter coatings carried out in a TPV generator at the operating conditions are also presented in this paper.

High-efficiency polarization conversion phase gradient metasurface for wideband anomalous reflection

NASA Astrophysics Data System (ADS)

Zhang, Jiameng; Yang, Lan; Li, Linpeng; Zhang, Tong; Li, Haihong; Wang, Qingmin; Hao, Yanan; Lei, Ming; Bi, Ke

2017-07-01

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14 GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3 GHz-20.5 GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below -10 dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves.

Embedding covalency into metal catalysts for efficient electrochemical conversion of CO2.

PubMed

Lim, Hyung-Kyu; Shin, Hyeyoung; Goddard, William A; Hwang, Yun Jeong; Min, Byoung Koun; Kim, Hyungjun

2014-08-13

CO2 conversion is an essential technology to develop a sustainable carbon economy for the present and the future. Many studies have focused extensively on the electrochemical conversion of CO2 into various useful chemicals. However, there is not yet a solution of sufficiently high enough efficiency and stability to demonstrate practical applicability. In this work, we use first-principles-based high-throughput screening to propose silver-based catalysts for efficient electrochemical reduction of CO2 to CO while decreasing the overpotential by 0.4-0.5 V. We discovered the covalency-aided electrochemical reaction (CAER) mechanism in which p-block dopants have a major effect on the modulating reaction energetics by imposing partial covalency into the metal catalysts, thereby enhancing their catalytic activity well beyond modulations arising from d-block dopants. In particular, sulfur or arsenic doping can effectively minimize the overpotential with good structural and electrochemical stability. We expect this work to provide useful insights to guide the development of a feasible strategy to overcome the limitations of current technology for electrochemical CO2 conversion.

Characterization and modeling of microstructured chalcogenide fibers for efficient mid-infrared wavelength conversion.

PubMed

Xing, Sida; Grassani, Davide; Kharitonov, Svyatoslav; Billat, Adrien; Brès, Camille-Sophie

2016-05-02

We experimentally demonstrate wavelength conversion in the 2 µm region by four-wave mixing in an AsSe and a GeAsSe chalcogenide photonic crystal fibers. A maximum conversion efficiency of -25.4 dB is measured for 112 mW of coupled continuous wave pump in a 27 cm long fiber. We estimate the dispersion parameters and the nonlinear refractive indexes of the chalcogenide PCFs, establishing a good agreement with the values expected from simulations. The different fiber geometries and glass compositions are compared in terms of performance, showing that GeAsSe is a more suited candidate for nonlinear optics at 2 µm. Building from the fitted parameters we then propose a new tapered GeAsSe PCF geometry to tailor the waveguide dispersion and lower the zero dispersion wavelength (ZDW) closer to the 2 µm pump wavelength. Numerical simulations shows that the new design allows both an increased conversion efficiency and bandwidth, and the generation of idler waves further in the mid-IR regions, by tuning the pump wavelength in the vicinity of the fiber ZDW.

Optical actuators for fly-by-light applications

NASA Astrophysics Data System (ADS)

Chee, Sonny H. S.; Liu, Kexing; Measures, Raymond M.

1993-04-01

A review of optomechanical interfaces is presented. A detailed quantitative and qualitative analysis of the University of Toronto Institute for Aerospace Studies (UTIAS) box, optopneumatics, optical activation of a bimetal, optical activation of the shape memory effect, and optical activation of the pyroelectric effects is given. The UTIAS box is found to display a good conversion efficiency and a high bandwidth. A preliminary UTIAS box design has achieved a conversion efficiency of about 1/6 of the theoretical limit and a bandwidth of 2 Hz. In comparison to previous optomechanical interfaces, the UTIAS box has the highest pressure development to optical power ratio (at least an order of magnitude greater).

High-efficiency thin-film GaAs solar cells, phase2

NASA Technical Reports Server (NTRS)

Yeh, Y. C. M.

1981-01-01

Thin GaAs epi-layers with good crystallographic quality were grown using a (100) Si-substrate on which a thin Ge epi-interlayer was grown by CVD from germane. Both antireflection-coated metal oxide semiconductor (AMOS) and n(+)/p homojunction structures were studied. The AMOS cells were fabricated on undoped-GaAs epi-layers deposited on bulk poly-Ge substrates using organo-metallic CVD film-growth, with the best achieved AM1 conversion efficiency being 9.1%. Both p-type and n(+)-type GaAs growth were optimized using 50 ppm dimethyl zinc and 1% hydrogen sulfide, respectively. A direct GaAs deposition method in fabricating ultra-thin top layer, epitaxial n(+)/p shallow homojunction solar cells on (100) GaAs substrates (without anodic thinning) was developed to produce large area (1 sq/cm) cells, with 19.4% AM1 conversion efficiency achieved. Additionally, an AM1 conversion efficiency of 18.4% (17.5% with 5% grid coverage) was achieved for a single crystal GaAs n(+)/p cell grown by OM-CVD on a Ge wafer.

Dual-band and high-efficiency polarization converter based on metasurfaces at microwave frequencies

NASA Astrophysics Data System (ADS)

Liu, Yajun; Xia, Song; Shi, Hongyu; Zhang, Anxue; Xu, Zhuo

2016-06-01

We present a dual-band and high-efficiency polarization converter in microwave regime. The proposed converter can convert a linearly polarized wave to its cross-polarized wave for two distinct bands: Ku (11.5-20.0 GHz) and Ka (28.8-34.0 GHz). It can also convert the linearly polarized wave to a circularly polarized wave at four other frequencies. The experimental results are in good agreement with simulation results for both frequency bands. The polarization conversion ratio is above 0.94 for the Ku-band and 0.90 for the Ka-band. Furthermore, the converter can achieve dual-band and high-efficiency polarization conversion over angles of incidence up to 45°. The converter is also polarization-selective in that only the x- and y-polarized waves can be converted. The physical mechanism of the dual-band polarization conversion effect is interpreted via decomposed electric field components that couple with different plasmon resonance modes of the structure.

A streamlined method for analysing genome-wide DNA methylation patterns from low amounts of FFPE DNA.

PubMed

Ludgate, Jackie L; Wright, James; Stockwell, Peter A; Morison, Ian M; Eccles, Michael R; Chatterjee, Aniruddha

2017-08-31

Formalin fixed paraffin embedded (FFPE) tumor samples are a major source of DNA from patients in cancer research. However, FFPE is a challenging material to work with due to macromolecular fragmentation and nucleic acid crosslinking. FFPE tissue particularly possesses challenges for methylation analysis and for preparing sequencing-based libraries relying on bisulfite conversion. Successful bisulfite conversion is a key requirement for sequencing-based methylation analysis. Here we describe a complete and streamlined workflow for preparing next generation sequencing libraries for methylation analysis from FFPE tissues. This includes, counting cells from FFPE blocks and extracting DNA from FFPE slides, testing bisulfite conversion efficiency with a polymerase chain reaction (PCR) based test, preparing reduced representation bisulfite sequencing libraries and massively parallel sequencing. The main features and advantages of this protocol are: An optimized method for extracting good quality DNA from FFPE tissues. An efficient bisulfite conversion and next generation sequencing library preparation protocol that uses 50 ng DNA from FFPE tissue. Incorporation of a PCR-based test to assess bisulfite conversion efficiency prior to sequencing. We provide a complete workflow and an integrated protocol for performing DNA methylation analysis at the genome-scale and we believe this will facilitate clinical epigenetic research that involves the use of FFPE tissue.

Comparison of lab, pilot, and industrial scale low consistency mechanical refining for improvements in enzymatic digestibility of pretreated hardwood.

PubMed

Jones, Brandon W; Venditti, Richard; Park, Sunkyu; Jameel, Hasan

2014-09-01

Mechanical refining has been shown to improve biomass enzymatic digestibility. In this study industrial high-yield sodium carbonate hardwood pulp was subjected to lab, pilot and industrial refining to determine if the mechanical refining improves the enzymatic hydrolysis sugar conversion efficiency differently at different refining scales. Lab, pilot and industrial refining increased the biomass digestibility for lignocellulosic biomass relative to the unrefined material. The sugar conversion was increased from 36% to 65% at 5 FPU/g of biomass with industrial refining at 67.0 kWh/t, which was more energy efficient than lab and pilot scale refining. There is a maximum in the sugar conversion with respect to the amount of refining energy. Water retention value is a good predictor of improvements in sugar conversion for a given fiber source and composition. Improvements in biomass digestibility with refining due to lab, pilot plant and industrial refining were similar with respect to water retention value. Published by Elsevier Ltd.

Enhanced Third-Order Optical Nonlinearity Driven by Surface-Plasmon Field Gradients.

PubMed

Kravtsov, Vasily; AlMutairi, Sultan; Ulbricht, Ronald; Kutayiah, A Ryan; Belyanin, Alexey; Raschke, Markus B

2018-05-18

Efficient nonlinear optical frequency mixing in small volumes is key for future on-chip photonic devices. However, the generally low conversion efficiency severely limits miniaturization to nanoscale dimensions. Here we demonstrate that gradient-field effects can provide for an efficient, conventionally dipole-forbidden nonlinear response. We show that a longitudinal nonlinear source current can dominate the third-order optical nonlinearity of the free electron response in gold in the technologically important near-IR frequency range where the nonlinearities due to other mechanisms are particularly small. Using adiabatic nanofocusing to spatially confine the excitation fields, from measurements of the 2ω_{1}-ω_{2} four-wave mixing response as a function of detuning ω_{1}-ω_{2}, we find up to 10^{-5} conversion efficiency with a gradient-field contribution to χ_{Au}^{(3)} of up to 10^{-19}  m^{2}/V^{2}. The results are in good agreement with the theory based on plasma hydrodynamics and underlying electron dynamics. The associated increase in the nonlinear conversion efficiency with a decreasing sample size, which can even overcompensate the volume decrease, offers a new approach for enhanced nonlinear nano-optics. This will enable more efficient nonlinear optical devices and the extension of coherent multidimensional spectroscopies to the nanoscale.

Enhanced Third-Order Optical Nonlinearity Driven by Surface-Plasmon Field Gradients

NASA Astrophysics Data System (ADS)

Kravtsov, Vasily; AlMutairi, Sultan; Ulbricht, Ronald; Kutayiah, A. Ryan; Belyanin, Alexey; Raschke, Markus B.

2018-05-01

Efficient nonlinear optical frequency mixing in small volumes is key for future on-chip photonic devices. However, the generally low conversion efficiency severely limits miniaturization to nanoscale dimensions. Here we demonstrate that gradient-field effects can provide for an efficient, conventionally dipole-forbidden nonlinear response. We show that a longitudinal nonlinear source current can dominate the third-order optical nonlinearity of the free electron response in gold in the technologically important near-IR frequency range where the nonlinearities due to other mechanisms are particularly small. Using adiabatic nanofocusing to spatially confine the excitation fields, from measurements of the 2 ω1-ω2 four-wave mixing response as a function of detuning ω1-ω2, we find up to 10-5 conversion efficiency with a gradient-field contribution to χAu(3 ) of up to 10-19 m2/V2 . The results are in good agreement with the theory based on plasma hydrodynamics and underlying electron dynamics. The associated increase in the nonlinear conversion efficiency with a decreasing sample size, which can even overcompensate the volume decrease, offers a new approach for enhanced nonlinear nano-optics. This will enable more efficient nonlinear optical devices and the extension of coherent multidimensional spectroscopies to the nanoscale.

Laser source with high pulse energy at 3-5 μm and 8-12 μm based on nonlinear conversion in ZnGeP2

NASA Astrophysics Data System (ADS)

Lippert, Espen; Fonnum, Helge; Haakestad, Magnus W.

2014-10-01

We present a high energy infrared laser source where a Tm:fiber laser is used to pump a high-energy 2-μm cryogenically cooled Ho:YLF laser. We have achieved 550 mJ of output energy at 2.05 μm, and through non-linear conversion in ZnGeP2 generated 200 mJ in the 3-5-μm range. Using a numerical simulation tool we have also investigated a setup which should generate more than 70 mJ in the 8-12-μm range. The conversion stage uses a master-oscillator-power-amplifier architecture to enable high conversion efficiency and good beam quality.

Bifacial dye-sensitized solar cells: A strategy to enhance overall efficiency based on transparent polyaniline electrode

PubMed Central

Wu, Jihuai; Li, Yan; Tang, Qunwei; Yue, Gentian; Lin, Jianming; Huang, Miaoliang; Meng, Lijian

2014-01-01

Dye-sensitized solar cell (DSSC) is a promising solution to global energy and environmental problems because of its clean, low-cost, high efficiency, good durability, and easy fabrication. However, enhancing the efficiency of the DSSC still is an important issue. Here we devise a bifacial DSSC based on a transparent polyaniline (PANI) counter electrode (CE). Owing to the sunlight irradiation simultaneously from the front and the rear sides, more dye molecules are excited and more carriers are generated, which results in the enhancement of short-circuit current density and therefore overall conversion efficiency. The photoelectric properties of PANI can be improved by modifying with 4-aminothiophenol (4-ATP). The bifacial DSSC with 4-ATP/PANI CE achieves a light-to-electric energy conversion efficiency of 8.35%, which is increased by ~24.6% compared to the DSSC irradiated from the front only. This new concept along with promising results provides a new approach for enhancing the photovoltaic performances of solar cells. PMID:24504117

Fabrication of multilayer TiO{sub 2} thin films for dye-sensitized solar cells with high conversion efficiency by electrophoresis deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Ho; Chen, Wei-An; Su, Hung-Ting

2010-01-15

This research coats a commercial TiO{sub 2} nanoparticle Degussa P25 with good roundness and size uniformity on an indium tin oxide (ITO) glass substrate and to be photoelectrical electrode by electrophoresis deposition. It combined with dye N719, electrolyte I{sup -}/ I{sub 3}{sup -} and counter-electrode of Pt layer to produce dye-sensitized solar cells (DSSCs). Through the electrophoretic technique, a multilayer film of an appropriate thickness is deposited in the suspension containing TiO{sub 2} nanoparticles and isopropanol. In this process, electric current, voltage, and the number of deposition cycles are well controlled to obtain a single TiO{sub 2} film of aroundmore » 3.3 {mu}m thick. Stacking is then performed to obtain a multilayer-typed TiO{sub 2} film of around 12 {mu}m thick. As the sintering temperature reaches 400 C, the prepared multilayer TiO{sub 2} film with a good compactness can increase the dye adsorption capability of the thin film and enhance its adsorption percentage. In addition, the heat treatment will transfer a portion of the rutile crystalline into the anatase crystalline, resulting in better material properties for DSSCs application. DSSCs produced are exposed to metal halide lamp and their energy conversion efficiency is measured. The I-V curve of the produced DSSCs shows that it has an excellent energy conversion efficiency of 6.9%. (author)« less

A fused-ring acceptor unit in d-a copolymers benefits photovoltaic performance.

PubMed

Zuo, Chuantian; Cao, Jiamin; Ding, Liming

2014-08-01

Pentacyclic lactam acceptor unit TPTI invented by our group is proved to be a good building block for efficient D-A copolymers used in organic solar cells. Here, two D-A copolymers PBTTPTI and PTTTPTI are developed by copolymerizing TPTI with 2,2'-bithiophene (BT) or thieno[3,2-b]thiophene (TT). PBTTPTI and PTTTPTI exhibit good solubility and strong interchain π-π interaction even in dilute solution. They possess deep HOMO levels (ca. -5.3 eV), partial crystallinity, and good hole mobilities. Blending with PC71 BM, PBTTPTI and PTTTPTI give decent power conversion efficiencies (PCE) up to 6.83% and 5.86%, with outstanding fill factors (FF) of 74.3% and 71.3%, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

NASA Astrophysics Data System (ADS)

Dewald, E. L.; Rosen, M.; Glenzer, S. H.; Suter, L. J.; Girard, F.; Jadaud, J. P.; Schein, J.; Constantin, C.; Wagon, F.; Huser, G.; Neumayer, P.; Landen, O. L.

2008-07-01

The conversion efficiency of 351nm laser light to soft x rays (0.1-5keV) was measured for Au, U, and high Z mixture "cocktails" used as hohlraum wall materials in indirect drive fusion experiments. For the spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates are employed to achieve constant and uniform laser intensities of 1014 and 1015W/cm2 over the target surface that are relevant for the future ignition experiments at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, 228 (2004)]. The absolute time and spectrally resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses are subtracted. After ˜0.5ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 1014W/cm2 laser intensity and of 80% at 1015W/cm2. The M-band flux (2-5keV) is negligible at 1014W/cm2 reaching ˜1% of the total x-ray flux for all target materials. In contrast, the M-band flux is significant and depends on the target material at 1015W/cm2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. LASNEX simulations [G. B. Zimmerman and W. L. Kruer, Comm. Plasma Phys. Contr. Fusion 2, 51 (1975)] show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux.

An all-solid-state perovskite-sensitized solar cell based on the dual function polyaniline as the sensitizer and p-type hole-transporting material

NASA Astrophysics Data System (ADS)

Xiao, Yaoming; Han, Gaoyi; Chang, Yunzhen; Zhou, Haihan; Li, Miaoyu; Li, Yanping

2014-12-01

High performance dual function of polyaniline (PANI) with brachyplast structure is synthesized by using a two-step cyclic voltammetry (CV) approach onto the fluorinated tin oxide (FTO) glass substrate, which acts as the sensitizer and p-type hole-transporting material (p-HTM) for the all-solid-state perovskite-sensitized solar cell (ass-PSSC) due to its π-π* transition and the localized polaron. The ass-PSSC based on the PANI delivers a photovoltaic conversion efficiency of 7.34%, and reduces from 7.34% to 6.71% after 1000 h, thereby 91.42% of the energy conversion efficiency is kept, indicating the device has a good long-term stability.

Efficient high-power frequency doubling of distributed Bragg reflector tapered laser radiation in a periodically poled MgO-doped lithium niobate planar waveguide.

PubMed

Jedrzejczyk, Daniel; Güther, Reiner; Paschke, Katrin; Jeong, Woo-Jin; Lee, Han-Young; Erbert, Götz

2011-02-01

We report on efficient single-pass, high-power second-harmonic generation in a periodically poled MgO-doped LiNbO3 planar waveguide using a distributed Bragg reflector tapered diode laser as a pump source. A coupling efficiency into the planar waveguide of 73% was realized, and 1.07 W of visible laser light at 532 nm was generated. Corresponding optical and electro-optical conversion efficiencies of 26% and 8.4%, respectively, were achieved. Good agreement between the experimental data and the theoretical predictions was observed.

High-power Broadband Organic THz Generator

PubMed Central

Jeong, Jae-Hyeok; Kang, Bong-Joo; Kim, Ji-Soo; Jazbinsek, Mojca; Lee, Seung-Heon; Lee, Seung-Chul; Baek, In-Hyung; Yun, Hoseop; Kim, Jongtaek; Lee, Yoon Sup; Lee, Jae-Hyeok; Kim, Jae-Ho; Rotermund, Fabian; Kwon, O-Pil

2013-01-01

The high-power broadband terahertz (THz) generator is an essential tool for a wide range of THz applications. Here, we present a novel highly efficient electro-optic quinolinium single crystal for THz wave generation. For obtaining intense and broadband THz waves by optical-to-THz frequency conversion, a quinolinium crystal was developed to fulfill all the requirements, which are in general extremely difficult to maintain simultaneously in a single medium, such as a large macroscopic electro-optic response and excellent crystal characteristics including a large crystal size with desired facets, good environmental stability, high optical quality, wide transparency range, and controllable crystal thickness. Compared to the benchmark inorganic and organic crystals, the new quinolinium crystal possesses excellent crystal properties and THz generation characteristics with broader THz spectral coverage and higher THz conversion efficiency at the technologically important pump wavelength of 800 nm. Therefore, the quinolinium crystal offers great potential for efficient and gap-free broadband THz wave generation. PMID:24220234

Review of nanostructured devices for thermoelectric applications

PubMed Central

2014-01-01

Summary A big research effort is currently dedicated to the development of thermoelectric devices capable of a direct thermal-to-electrical energy conversion, aiming at efficiencies as high as possible. These devices are very attractive for many applications in the fields of energy recovery and green energy harvesting. In this paper, after a quick summary of the fundamental principles of thermoelectricity, the main characteristics of materials needed for high efficiency thermoelectric conversion will be discussed, and a quick review of the most promising materials currently under development will be given. This review paper will put a particular emphasis on nanostructured silicon, which represents a valid compromise between good thermoelectric properties on one side and material availability, sustainability, technological feasibility on the other side. The most important bottom-up and top-down nanofabrication techniques for large area silicon nanowire arrays, to be used for high efficiency thermoelectric devices, will be presented and discussed. PMID:25247111

High-power broadband organic THz generator.

PubMed

Jeong, Jae-Hyeok; Kang, Bong-Joo; Kim, Ji-Soo; Jazbinsek, Mojca; Lee, Seung-Heon; Lee, Seung-Chul; Baek, In-Hyung; Yun, Hoseop; Kim, Jongtaek; Lee, Yoon Sup; Lee, Jae-Hyeok; Kim, Jae-Ho; Rotermund, Fabian; Kwon, O-Pil

2013-11-13

The high-power broadband terahertz (THz) generator is an essential tool for a wide range of THz applications. Here, we present a novel highly efficient electro-optic quinolinium single crystal for THz wave generation. For obtaining intense and broadband THz waves by optical-to-THz frequency conversion, a quinolinium crystal was developed to fulfill all the requirements, which are in general extremely difficult to maintain simultaneously in a single medium, such as a large macroscopic electro-optic response and excellent crystal characteristics including a large crystal size with desired facets, good environmental stability, high optical quality, wide transparency range, and controllable crystal thickness. Compared to the benchmark inorganic and organic crystals, the new quinolinium crystal possesses excellent crystal properties and THz generation characteristics with broader THz spectral coverage and higher THz conversion efficiency at the technologically important pump wavelength of 800 nm. Therefore, the quinolinium crystal offers great potential for efficient and gap-free broadband THz wave generation.

Entangled photon pair generation by spontaneous parametric down-conversion in finite-length one-dimensional photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Centini, M.; Sciscione, L.; Sibilia, C.

A description of spontaneous parametric down-conversion in finite-length one-dimensional nonlinear photonic crystals is developed using semiclassical and quantum approaches. It is shown that if a suitable averaging is added to the semiclassical model, its results are in very good agreement with the quantum approach. We propose two structures made with GaN/AlN that generate both degenerate and nondegenerate entangled photon pairs. Both structures are designed so as to achieve a high efficiency of the nonlinear process.

Flexible, highly efficient all-polymer solar cells

PubMed Central

Kim, Taesu; Kim, Jae-Han; Kang, Tae Eui; Lee, Changyeon; Kang, Hyunbum; Shin, Minkwan; Wang, Cheng; Ma, Biwu; Jeong, Unyong; Kim, Taek-Soo; Kim, Bumjoon J.

2015-01-01

All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymer acceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared with polymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices. PMID:26449658

Experimental demonstration of novel cascaded SFG+DFG wavelength conversion of picosecond pulses in LiNbO 3 waveguides

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang; Luo, Chuanhong

2006-06-01

A novel cascaded χ (2) wavelength conversion of picosecond pulses based on sum frequency generation and difference frequency generation (SFG+DFG) is proposed and experimentally demonstrated in LiNbO 3 waveguides. The signal pulse with 40-GHz repetition rate and 1.57-ps pulse width is adopted. First of all, high conversion efficiency about -18.93dB can be achieved with low power level required for both two pump lights, which is greatly enhanced approximately 8dB compared with the conventional cascaded second-order nonlinear interactions (SHG+DFG) with a single and much higher power pump. Secondly, the wavelength of the converted idler wave can be tuned from 1527.4 to 1540.5nm when the signal wavelength is changed from 1561.9 to 1548.4nm, and about 13.1nm converted idler bandwidth is achieved with the conversion efficiency higher than -31dB. Thirdly, two pump wavelengths can be separated as large as 17.3nm. Meanwhile, when one pump wavelength is fixed at 1549.1nm, the other can be tuned within a wide wavelength range about 7.6nm with the conversion efficiency higher than -34dB, which is much larger than that in the SHG+DFG situation. Finally, the temporal waveform of the converted idler pulse is observed with rather clear appearance achieved, and no obvious changes of the pulse shape and width are found compared with its corresponding original injected signal, showing that our proposed scheme exhibits a very good conversion performance.

Amorphous Hole-Transporting Material based on 2,2'-Bis-substituted 1,1'-Biphenyl Scaffold for Application in Perovskite Solar Cells.

PubMed

Magomedov, Artiom; Sakai, Nobuya; Kamarauskas, Egidijus; Jokubauskaitė, Gabrielė; Franckevičius, Marius; Jankauskas, Vygintas; Snaith, Henry J; Getautis, Vytautas

2017-05-04

Perovskite solar cells are considered a promising technology for solar-energy conversion, with power conversion efficiencies currently exceeding 20 %. In most of the reported devices, Spiro-OMeTAD is used for positive-charge extraction and transport layer. Although a number of alternative hole-transporting materials with different aromatic or heteroaromatic fragments have already been synthesized, a cheap and well-performing hole-transporting material is still in high demand. In this work, a two-step synthesis of a carbazole-based hole-transporting material is presented. Synthesized compounds exhibited amorphous nature, good solubility and thermal stability. The perovskite solar cells employing the newly synthesized material generated a power conversion efficiency of 16.5 % which is slightly lower than that obtained with Spiro-OMeTAD (17.5 %). The low-cost synthesis and high performance makes our hole-transport material promising for applications in perovskite-based optoelectronic devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mimic Carbonic Anhydrase Using Metal-Organic Frameworks for CO2 Capture and Conversion.

PubMed

Jin, Chaonan; Zhang, Sainan; Zhang, Zhenjie; Chen, Yao

2018-02-19

Carbonic anhydrase (CA) is a zinc-containing metalloprotein, in which the Zn active center plays the key role to transform CO 2 into carbonate. Inspired by nature, herein we used metal-organic frameworks (MOFs) to mimic CA for CO 2 conversion, on the basis of the structural similarity between the Zn coordination in MOFs and CA active center. The biomimetic activity of MOFs was investigated by detecting the hydrolysis of para-nitrophenyl acetate, which is a model reaction used to evaluate CA activity. The biomimetic materials (e.g., CFA-1) showed good catalytic activity, and excellent reusability, and solvent and thermal stability, which is very important for practical applications. In addition, ZIF-100 and CFA-1 were used to mimic CA to convert CO 2 gas, and exhibited good efficiency on CO 2 conversion compared with those of other porous materials (e.g., MCM-41, active carbon). This biomimetic study revealed a novel CO 2 treatment method. Instead of simply using MOFs to absorb CO 2 , ZIF-100 and CFA-1 were used to mimic CA for in situ CO 2 conversion, which provides a new prospect in the biological and industrial applications of MOFs.

SO2-tolerant and H2O-promoting Pt/C catalysts for efficient NO removal via fixed-bed H2-SCR.

PubMed

Tu, Baosheng; Shi, Nian; Sun, Wei; Cao, Limei; Yang, Ji

2017-01-01

In this paper, Pt supports on carbon black powder (Vulcan XC-72) were synthesized via a hydrothermal method for selective catalytic reduction (SCR) of NO with H 2 in the presence of 2 vol% O 2 over a wide temperature of 20-300 °C. The results showed that the 3 and 5 wt% Pt/C catalysts resulted in high NO conversion (>90 %) over a temperature range of 120 to 300 °C, and the maximum NO conversion of 98.6 % was achieved over 5 wt% Pt/C at 120 °C. Meanwhile, the influence of SO 2 and H 2 O on the catalyst performance of 3 wt% Pt/C was investigated. The catalysts exhibited good SO 2 poisoning resistance when the SO 2 concentration was lower than 260 ppm. Moreover, a positive effect on NO conversion was detected with the addition of 3 and 5 vol% H 2 O in the feed gas stream. Graphical abstract TEM image and good NO conversion performance of the Pt/C catalysts.

Solar-pumped gas laser development

NASA Technical Reports Server (NTRS)

Wilson, J. W.

1981-01-01

The direct conversion of solar radiation into an inverted population for extraction in an optical cavity holds promise as a relatively simple system design. Broad-band photoabsorption in the visible or near-UV range is required to excite large volumes of gas and to ensure good solar absorption efficiency. The state excited must be a metastable state which is not quenched by the parent gas. The emission bandwidth must be less than approximately 10 A. The system should show chemical reversibility and an insensitivity to increasing temperature. Other properties such as good quantum efficiency and kinetic efficiency are also implied. A search of electronic-vibrational transitions in diatomic molecules satisfying these conditions is now in progress. A photodissociation-pumped atomic iodine laser is now being tested under solar pumping conditions. Photodissociation studies for thallium spin-flip metastable formation will begin in the near future.

Potentialities of silicon nanowire forests for thermoelectric generation

NASA Astrophysics Data System (ADS)

Dimaggio, Elisabetta; Pennelli, Giovanni

2018-04-01

Silicon is a material with very good thermoelectric properties, with regard to Seebeck coefficient and electrical conductivity. Low thermal conductivities, and hence high thermal to electrical conversion efficiencies, can be achieved in nanostructures, which are smaller than the phonon mean free path but large enough to preserve the electrical conductivity. We demonstrate that it is possible to fabricate a leg of a thermoelectric generator based on large collections of long nanowires, placed perpendicularly to the two faces of a silicon wafer. The process exploits the metal assisted etching technique which is simple, low cost, and can be easily applied to large surfaces. Copper can be deposited by electrodeposition on both faces, so that contacts can be provided, on top of the nanowires. Thermal conductivity of silicon nanowire forests with more than 107 nanowires mm-2 have been measured; the result is comparable with that achieved by several groups on devices based on few nanowires. On the basis of the measured parameters, numerical calculations of the efficiency of silicon-based thermoelectric generators are reported, and the potentialities of these devices for thermal to electrical energy conversion are shown. Criteria to improve the conversion efficiency are suggested and described.

Highly efficient and completely flexible fiber-shaped dye-sensitized solar cell based on TiO2 nanotube array.

PubMed

Lv, Zhibin; Yu, Jiefeng; Wu, Hongwei; Shang, Jian; Wang, Dan; Hou, Shaocong; Fu, Yongping; Wu, Kai; Zou, Dechun

2012-02-21

A type of highly efficient completely flexible fiber-shaped solar cell based on TiO(2) nanotube array is successfully prepared. Under air mass 1.5G (100 mW cm(-2)) illumination conditions, the photoelectric conversion efficiency of the solar cell approaches 7%, the highest among all fiber-shaped cells based on TiO(2) nanotube arrays and the first completely flexible fiber-shaped DSSC. The fiber-shaped solar cell demonstrates good flexibility, which makes it suitable for modularization using weaving technologies. This journal is © The Royal Society of Chemistry 2012

Recombinant thermoactive phosphoenolpyruvate carboxylase (PEPC) from Thermosynechococcus elongatus and its coupling with mesophilic/thermophilic bacterial carbonic anhydrases (CAs) for the conversion of CO2 to oxaloacetate.

PubMed

Del Prete, Sonia; De Luca, Viviana; Capasso, Clemente; Supuran, Claudiu T; Carginale, Vincenzo

2016-01-15

With the continuous increase of atmospheric CO2 in the last decades, efficient methods for carbon capture, sequestration, and utilization are urgently required. The possibility of converting CO2 into useful chemicals could be a good strategy to both decreasing the CO2 concentration and for achieving an efficient exploitation of this cheap carbon source. Recently, several single- and multi-enzyme systems for the catalytic conversion of CO2 mainly to bicarbonate have been implemented. In order to design and construct a catalytic system for the conversion of CO2 to organic molecules, we implemented an in vitro multienzyme system using mesophilic and thermophilic enzymes. The system, in fact, was constituted by a recombinant phosphoenolpyruvate carboxylase (PEPC) from the thermophilic cyanobacterium Thermosynechococcus elongatus, in combination with mesophilic/thermophilic bacterial carbonic anhydrases (CAs), for converting CO2 into oxaloacetate, a compound of potential utility in industrial processes. The catalytic procedure is in two steps: the conversion of CO2 into bicarbonate by CA, followed by the carboxylation of phosphoenolpyruvate with bicarbonate, catalyzed by PEPC, with formation of oxaloacetate (OAA). All tested CAs, belonging to α-, β-, and γ-CA classes, were able to increase OAA production compared to procedures when only PEPC was used. Interestingly, the efficiency of the CAs tested in OAA production was in good agreement with the kinetic parameters for the CO2 hydration reaction of these enzymes. This PEPC also revealed to be thermoactive and thermostable, and when coupled with the extremely thermostable CA from Sulphurhydrogenibium azorense (SazCA) the production of OAA was achieved even if the two enzymes were exposed to temperatures up to 60 °C, suggesting a possible role of the two coupled enzymes in biotechnological processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

NONLINEAR AND FIBER OPTICS: Conversion of pulsed laser radiation from the 9.3-9.6 μm range to the second harmonic in ZnGeP2 crystals

NASA Astrophysics Data System (ADS)

Andreev, Yu M.; Bykanov, A. N.; Gribenyukov, A. I.; Zuev, V. V.; Karyshev, V. D.; Kisletsov, A. V.; Kovalev, I. O.; Konov, Vitalii I.; Kuz'min, G. P.; Nesterenko, A. A.; Osorgin, A. E.; Starodumov, Yu M.; Chapliev, N. I.

1990-04-01

A pulsed TEA CO2 laser was used in an investigation of the influence of the pump radiation parameters (mode composition, wavelength, pulse duration), of the focusing conditions, of the properties of the material (absorption coefficient), and of the operating conditions (temperature) on the efficiency of conversion to the second harmonic and on the angular dependences of phase matching in ZnGeP2 crystals. The calculated results were found to be in good agreement with the experimental data.

Synthesis of POSS-based ionic conductors with low glass transition temperatures for efficient solid-state dye-sensitized solar cells.

PubMed

Zhang, Wei; Wang, Zhong-Sheng

2014-07-09

Replacing liquid-state electrolytes with solid-state electrolytes has been proven to be an effective way to improve the durability of dye-sensitized solar cells (DSSCs). We report herein the synthesis of amorphous ionic conductors based on polyhedral oligomeric silsesquioxane (POSS) with low glass transition temperatures for solid-state DSSCs. As the ionic conductor is amorphous and in the elastomeric state at the operating temperature of DSSCs, good pore filling in the TiO2 film and good interfacial contact between the solid-state electrolyte and the TiO2 film can be guaranteed. When the POSS-based ionic conductor containing an allyl group is doped with only iodine as the solid-state electrolyte without any other additives, power conversion efficiency of 6.29% has been achieved with good long-term stability under one-sun soaking for 1000 h.

Up-Conversion Y2O3:Yb(3+),Er(3+) Hollow Spherical Drug Carrier with Improved Degradability for Cancer Treatment.

PubMed

Ge, Kun; Zhang, Cuimiao; Sun, Wentong; Liu, Huifang; Jin, Yi; Li, Zhenhua; Liang, Xing-Jie; Jia, Guang; Zhang, Jinchao

2016-09-28

The rare earth hollow spheres with up-conversion luminescence properties have shown potential applications in drug delivery and bioimaging fields. However, there have been few reports for the degradation properties of rare earth oxide drug carriers. Herein, uniform and well-dispersed Y2O3:Yb(3+),Er(3+) hollow spheres (YOHSs) have been fabricated by a general Pechini sol-gel process with melamine formaldehyde colloidal spheres as template. The novel YOHSs with up-conversion luminescence has good drug loading amount and drug-release efficiency; moreover, it exhibits pH-responsive release patterns. In particular, the YOHSs sample exhibits low cytotoxicity and excellent degradable properties in acid buffer. After the sample was loaded with anticancer drug doxorubicin (DOX), the antitumor result in vitro indicates that YOHS-DOX might be effective in cancer treatment. The animal imaging test also reveals that the YOHSs drug carrier can be used as an outstanding luminescent probe for bioimaging in vivo application prospects. The results suggest that the degradable drug carrier with up-conversion luminescence may enhance the delivery efficiency of drugs and improve the cancer therapy in clinical applications.

Process simulation and comparison of biological conversion of syngas and hydrogen in biogas plants

NASA Astrophysics Data System (ADS)

Awais Salman, Chaudhary; Schwede, Sebastian; Thorin, Eva; Yan, Jinyue

2017-11-01

Organic waste is a good source of clean energy. However, different fractions of waste have to be utilized efficiently. One way is to find pathways to convert waste into useful products via various available processes (gasification, pyrolysis anaerobic digestion, etc.) and integrate them to increase the combined efficiency of the process. The syngas and hydrogen produced from the thermal conversion of biomass can be upgraded to biomethane via biological methanation. The current study presents the simulation model to predict the amount of biomethane produced by injecting the hydrogen and syngas. Hydrogen injection is modelled both in-situ and ex-situ while for syngas solely the ex-situ case has been studied. The results showed that 85% of the hydrogen conversion was achieved for the ex-situ reactor while 81% conversion rate was achieved for the in-situ reactor. The syngas could be converted completely in the bio-reactor. However, the addition of syngas resulted in an increase of carbon dioxide. Simulation of biomethanation of gas addition showed a biomethane concentration of 87% while for hydrogen addition an increase of 74% and 80% for in-situ and ex-situ addition respectively.

Multifunctional organized mesoporous tin oxide films templated by graft copolymers for dye-sensitized solar cells.

PubMed

Park, Jung Tae; Ahn, Sung Hoon; Roh, Dong Kyu; Lee, Chang Soo; Kim, Jong Hak

2014-07-01

The synthesis of organized mesoporous SnO2 films with high porosity, larger pores, and good interconnectivity, obtained by sol-gel templating with an amphiphilic graft copolymer, poly(vinyl chloride)-graft-poly(oxyethylene methacrylate), is reported. An improved performance of dye-sensitized solar cells (DSSCs) is demonstrated by the introduction of a 400 nm thick organized mesoporous SnO2 interfacial (om-SnO2 IF) layer between nanocrystalline TiO2 (nc-TiO2 ) and a fluorine-doped tin oxide substrate. To elucidate the improved efficiency, the structural, optical, and electrochemical properties of the devices were characterized by SEM, UV/Vis spectroscopy, noncontact 3D surface profilometry, intensity-modulated photocurrent/voltage spectroscopy, incident photon-to-electron conversion efficiency, and electrochemical impedance spectroscopy measurements. The energy-conversion efficiency of the solid polymerized ionic liquid based DSSC fabricated with the om-SnO2 IF/nc-TiO2 photoanode reached 5.9% at 100 mW cm(-2) ; this is higher than those of neat nc-TiO2 (3.5%) and organized mesoporous TiO2 interfacial/nc-TiO2 layer (5.4%) photoanodes. The improved efficiency is attributed to the antireflective property, cascadal energy band gap, good interconnectivity, and high electrical conductivity of the om-SnO2 IF layer, which results in enhanced light harvesting, increased electron transport, reduced charge recombination, and decreased interfacial/internal resistance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High efficiency and good beam quality of electro-optic, cavity-dumped and double-end pumped Nd:YLF laser

NASA Astrophysics Data System (ADS)

Tang, X. X.; Fan, Z. W.; Qiu, J. S.; Lian, F. Q.; Zhang, X. L.

2012-06-01

In this paper, we describe a Nd:YLF laser based on high-speed RTP electro-optical cavity dumping technique. Two home-made 150 W fiber pump modules are used from both sides to pump Nd:YLF crystal. Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. In order to get high efficient and good quality laser output, the optical software ZEMAX is used to design a four-piece coupling system. When the pumped energy is 32 mJ at the repetition rate of 1 Hz, the output energy is 6.5 mJ with 2.5 ns pulse width. When the pumped energy is 13.1 W at the repetition rate of 200 Hz, the output energy is 2.2 W with small M 2 factor where M {/x 2} is 1.04, and M {/y 2} is 1.05, and the light-light conversion efficiency is up to 16.8%.

Evaluation of Saltzman and phenoldisulfonic acid methods for determining NO/sub x/ in engine exhaust gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groth, R.H.; Calabro, D.S.

1969-11-01

The two methods normally used for the analysis of NO/sub x/ are the Saltzman and the phenoldisulfonic acid technique. This paper describes an evaluation of these wet chemical methods to determine their practical application to engine exhaust gas analysis. Parameters considered for the Saltzman method included bubbler collection efficiency, NO to NO/sub 2/ conversion efficiency, masking effect of other contaminants usually present in exhaust gases and the time-temperature effect of these contaminants on store developed solutions. Collection efficiency and the effects of contaminants were also considered for the phenoldisulfonic acid method. Test results indicated satisfactory collection and conversion efficiencies formore » the Saltzman method, but contaminants seriously affected the measurement accuracy particularly if the developed solution was stored for a number of hours at room temperature before analysis. Storage at 32/sup 0/F minimized effect. The standard procedure for the phenoldisulfonic acid method gave good results, but the process was found to be too time consuming for routine analysis and measured only total NO/sub x/. 3 references, 9 tables.« less

Ab-Initio Calculation of Electronic Structure of Lead Halide Perovskites with Formamidinium Cation as an Active Material for Perovskite Solar Cells

NASA Astrophysics Data System (ADS)

Indari, E. D.; Wungu, T. D. K.; Hidayat, R.

2017-07-01

Organic lead halide perovskite material based solar cells show impressive power conversion efficiencies, which can reach above 19 percent for perovskite solar cell with methyl-ammonium cations. These efficiencies are originated from efficient photoexcitation and charge carrier transport and not observed in conventional perovskite crystals. In this preliminary research work, we therefore performed Density Functional Theory (DFT) calculation of formamidinium lead iodide (FAPI), an alternative to methyl-ammonium lead iodide (MAPI), to predict their electronic structure and density of state (DOS). The calculation result at the most stable lattice parameters show a good agreement with the experiment results. The obtained band gap energy is 1.307 eV. The valence band is dominantly formed by the 5p orbitals of I- anions, while the conduction band is dominantly formed by the 6p orbitals of Pb2+ cations. The DOS of valence band of this perovskite seems smaller compared to the case of methyl-ammonium lead iodide perovskite, which then may explain the observation of smaller power conversion efficiencies in perovskite solar cells with this formamidinium cations.

Self-assembly 2D zinc-phthalocyanine heterojunction: An ideal platform for high efficiency solar cell

NASA Astrophysics Data System (ADS)

Jiang, Xue; Jiang, Zhou; Zhao, Jijun

2017-12-01

As an alternative to silicon-based solar cells, organic photovoltaic cells emerge for their easy manufacture, low cost, and light weight but are limited by their less stability, low power conversion efficiencies, and low charge carrier mobilities. Here, we design a series of two-dimensional (2D) organic materials incorporating zinc-phthalocyanine (ZnPc) based building blocks which can inherit their excellent intrinsic properties but overcome those shortcomings. Our first-principles calculation shows that such 2D ZnPc-based materials exhibit excellent thermal stabilities, suitable bandgaps, small effective masses, and good absorption properties. The additional benzene rings and nitrogen atoms incorporated between ZnPc molecules are mainly responsible for the modifications of electronic and optical properties. Moreover, some heterojunction solar cells constructed using those 2D ZnPc monolayers as the donor and acceptor have an appropriate absorber gap and interface band alignment. Among them, a power conversion efficiency up to 14.04% is achieved, which is very promising for the next-generation organic solar cells.

[Improving the feed conversion rate in the pig fattening industry by optimising hygienic management].

PubMed

Riedl, Antonia M; Völkel, Inger; Schlindwein, Bernhard; Czerny, Claus-Peter

2013-01-01

Considering continuously increasing forage costs, the feed conversion rate has a major impact on the economic efficiency in hog fattening. The influence of hygienic management strategies on animal health and feed efficiency was evaluated by an online-study comprising animal health management data of 202 German pig fatteners. Data analysis included a simple comparison of averages, a linear regression analysis, and a cluster analysis. Due to geographical distribution and size of premises, the random sample was not representative but yielded in significant results. The total impact of hygienic management on feed conversion was calculated to be 23.9 %. Professional performance of rodent control (beta = 0.357; p < or = 0.001), efficient insect larvae control (beta = 0.276; p = 0.008), requiring visitors to wear protective gear (beta = 0.261; p = 0.009), and immediately performed cleaning and disinfection of emptied pens (beta = 0.247; p = 0.017) were top-ranking variables. Furthermore, a significantly better fed efficiency was observed in companies reporting stables in a good state of repair or performing further preventive strategies to control animal health on herd-level (storage of fodder retain samples, health screening based on blood and faecal samples, cross-section to verify unclear death cases). For pig fatteners the benefit resulting from improved feed conversion ranged from Euro 1.15 to and Euro 2.53 per pig. Likewise optimized growth performance as a result of improved hygienic management could partly compensate increasing feed costs. The results of this online-study reveal the need to establish reliable HACCP systems on farm level.

Dry Reforming of Methane in a Gliding Arc Plasmatron: Towards a Better Understanding of the Plasma Chemistry.

PubMed

Cleiren, Emelie; Heijkers, Stijn; Ramakers, Marleen; Bogaerts, Annemie

2017-10-23

Dry reforming of methane (DRM) in a gliding arc plasmatron is studied for different CH 4 fractions in the mixture. The CO 2 and CH 4 conversions reach their highest values of approximately 18 and 10 %, respectively, at 25 % CH 4 in the gas mixture, corresponding to an overall energy cost of 10 kJ L -1 (or 2.5 eV per molecule) and an energy efficiency of 66 %. CO and H 2 are the major products, with the formation of smaller fractions of C 2 H x (x=2, 4, or 6) compounds and H 2 O. A chemical kinetics model is used to investigate the underlying chemical processes. The calculated CO 2 and CH 4 conversion and the energy efficiency are in good agreement with the experimental data. The model calculations reveal that the reaction of CO 2 (mainly at vibrationally excited levels) with H radicals is mainly responsible for the CO 2 conversion, especially at higher CH 4 fractions in the mixture, which explains why the CO 2 conversion increases with increasing CH 4 fraction. The main process responsible for CH 4 conversion is the reaction with OH radicals. The excellent energy efficiency can be explained by the non-equilibrium character of the plasma, in which the electrons mainly activate the gas molecules, and by the important role of the vibrational kinetics of CO 2 . The results demonstrate that a gliding arc plasmatron is very promising for DRM. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hollow optical fiber induced solar cells with optical energy storage and conversion.

PubMed

Ding, Jie; Zhao, Yuanyuan; Duan, Jialong; Duan, Yanyan; Tang, Qunwei

2017-11-09

Hollow optical fiber induced dye-sensitized solar cells are made by twisting Ti wire/N719-TiO 2 nanotube photoanodes and Ti wire/Pt (CoSe, Pt 3 Ni) counter electrodes, yielding a maximized efficiency of 0.7% and good stability. Arising from optical energy storage ability, the solar cells can generate electricity without laser illumination.

A versatile chemical conversion synthesis of Cu2S nanotubes and the photovoltaic activities for dye-sensitized solar cell

PubMed Central

2014-01-01

A versatile, low-temperature, and low-cost chemical conversion synthesis has been developed to prepare copper sulfide (Cu2S) nanotubes. The successful chemical conversion from ZnS nanotubes to Cu2S ones profits by the large difference in solubility between ZnS and Cu2S. The morphology, structure, and composition of the yielded products have been examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction measurements. We have further successfully employed the obtained Cu2S nanotubes as counter electrodes in dye-sensitized solar cells. The light-to-electricity conversion results show that the Cu2S nanostructures exhibit high photovoltaic conversion efficiency due to the increased surface area and the good electrocatalytical activity of Cu2S. The present chemical route provides a simple way to synthesize Cu2S nanotubes with a high surface area for nanodevice applications. PMID:25246878

Electrical and optical modeling of poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester P3HT-PCBM bulk heterojunction solar cells

NASA Astrophysics Data System (ADS)

Brioua, Fathi; Remram, Mohamed; Nechache, Riad; Bourouina, Hicham

2017-11-01

In this work, we investigate a two-dimensional theoretical model for the photon conversion through an integration of the optical and electrical part of multilayer system in a bulk heterojunction solar cell based on poly(3-hexylthiophene) (P3HT)/6,6-phenyl C61-butyric acid methyl ester (PCBM) blend. The optical properties of the studied structure ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al, such as the exciton generation rate and the electrical field distribution, are predicted at vicinity of the active layer and have been used to solve Poisson and continuity, drift-diffusion equations of the electrical model which characterize the electrical behavior of semiconductor device using finite element method (FEM). The electrical parameters such as power conversion efficiency (PCE), open voltage circuit ( V oc), short-circuit current density ( J sc) and fill factor (FF) are extracted from the current-voltage (J-V) characteristics under illumination and in dark conditions. Highest external quantum efficiency (IPCE), up to 60%, is obtained around 520 nm, while a power conversion efficiency (PCE) value of 3.62% is found to be in good agreement with the literature results. Integration of such theoretical approach into technological applications dealing with optoelectrical material performance will rapidly provide to the user accurate data outputs required for efficient validation of proof-of-concepts.

Neutron flux spectrum revealed by Nb-based current-biased kinetic inductance detector with a 10B conversion layer

NASA Astrophysics Data System (ADS)

Miyajima, Shigeyuki; Shishido, Hiroaki; Narukami, Yoshito; Yoshioka, Naohito; Fujimaki, Akira; Hidaka, Mutsuo; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Arai, Masatoshi; Ishida, Takekazu

2017-01-01

We successfully derived the time-dependent flux of pulsed neutrons using a superconducting Nb-based current-biased kinetic inductance detector (CB-KID) with a 10B conversion layer at Japan Proton Accelerator Research Complex. Our CB-KID is a meander line made of a 40-nm-thick Nb thin film with 1 - μm line width, which is covered with a 150-nm-thick 10B conversion layer. The detector works at a temperature below 4 K. The evaluated detection efficiency of the CB-KID in this experiment is 0.23 % at the neutron energy of 25.4 meV. The time-dependent flux spectra of pulsed neutrons thus obtained are in good agreement with the results obtained by the Monte Carlo simulations.

Graphene rectenna for efficient energy harvesting at terahertz frequencies

NASA Astrophysics Data System (ADS)

Dragoman, Mircea; Aldrigo, Martino

2016-09-01

In this paper, we propose a graphene rectenna that encompasses two distinct functions in a single device, namely, antenna and rectifier, which till now were two separate components. In this way, the rectenna realizes an efficient energy harvesting technique due to the absence of impedance mismatch between antenna and diode. In particular, we have obtained a maximum conversion efficiency of 58.43% at 897 GHz for the graphene rectenna on n-doped GaAs, which is a very good value, close to the performance of an RF harvesting system. A comparison with a classical metallic antenna with an HfO2-based metal-insulator-metal diode is also provided.

Fully-resonant, tunable, monolithic frequency conversion as a coherent UVA source.

PubMed

Zielińska, Joanna A; Zukauskas, Andrius; Canalias, Carlota; Noyan, Mehmet A; Mitchell, Morgan W

2017-01-23

We demonstrate a monolithic frequency converter incorporating up to four tuning degrees of freedom, three temperature and one strain, allowing resonance of pump and generated wavelengths simultaneous with optimal phase-matching. With a Rb-doped periodically-poled potassium titanyl phosphate (KTP) implementation, we demonstrate efficient continuous-wave second harmonic generation from 795 to 397, with low-power efficiency of 72% and high-power slope efficiency of 4.5%. The measured performance shows good agreement with theoretical modeling of the device. We measure optical bistability effects, and show how they can be used to improve the stability of the output against pump frequency and amplitude variations.

Bright broadband coherent fiber sources emitting strongly blue-shifted resonant dispersive wave pulses

PubMed Central

Tu, Haohua; Lægsgaard, Jesper; Zhang, Rui; Tong, Shi; Liu, Yuan; Boppart, Stephen A.

2013-01-01

We predict and realize the targeted wavelength conversion from the 1550-nm band of a fs Er:fiber laser to an isolated band inside 370-850 nm, corresponding to a blue-shift of 700-1180 nm. The conversion utilizes resonant dispersive wave generation in widely available optical fibers with good efficiency (~7%). The converted band has a large pulse energy (~1 nJ), high spectral brightness (~1 mW/nm), and broad Gaussian-like spectrum compressible to clean transform-limited ~17 fs pulses. The corresponding coherent fiber sources open up portable applications of optical parametric oscillators and dual-output synchronized ultrafast lasers. PMID:24104233

Synthesis of a conjugated pyrrolopyridazinedione-benzodithiophene (PPD-BDT) copolymer and its application in organic and hybrid solar cells.

PubMed

Knall, Astrid-Caroline; Jones, Andrew O F; Kunert, Birgit; Resel, Roland; Reishofer, David; Zach, Peter W; Kirkus, Mindaugas; McCulloch, Iain; Rath, Thomas

2017-01-01

Herein, we describe the synthesis and characterization of a conjugated donor-acceptor copolymer consisting of a pyrrolopyridazinedione (PPD) acceptor unit, and a benzodithiophene (BDT) donor unit. The polymerization was done via a Stille cross-coupling polycondensation. The resulting PPD-BDT copolymer revealed an optical bandgap of 1.8 eV and good processability from chlorobenzene solutions. In an organic solar cell in combination with PC 70 BM, the polymer led to a power conversion efficiency of 4.5%. Moreover, the performance of the copolymer was evaluated in polymer/nanocrystal hybrid solar cells using non-toxic CuInS 2 nanocrystals as inorganic phase, which were prepared from precursors directly in the polymer matrix without using additional capping ligands. The PPD-BDT/CuInS 2 hybrid solar cells showed comparably high photovoltages and a power conversion efficiency of 2.2%.

Thermohydrogel Containing Melanin for Photothermal Cancer Therapy.

PubMed

Kim, Miri; Kim, Hyun Soo; Kim, Min Ah; Ryu, Hyanghwa; Jeong, Hwan-Jeong; Lee, Chang-Moon

2017-05-01

Melanin is an effective absorber of light and can extend to near infrared (NIR) regions. In this study, a natural melanin is presented as a photothermal therapeutic agent (PTA) because it provides a good photothermal conversion efficiency, shows biodegradability, and does not induce long-term toxicity during retention in vivo. Poloxamer solution containing melanin (Pol-Mel) does not show any precipitation and shows sol-gel transition at body temperature. After irradiation from 808 nm NIR laser at 1.5 W cm -2 for 3 min, the photothermal conversion efficiency of Pol-Mel is enough to kill cancer cells in vitro and in vivo. The tumor growth of mice bearing CT26 tumors treated with Pol-Mel injection and laser irradiation is suppressed completely without recurrence postirradiation. All these results indicate that Pol-Mel can become an attractive PTA for photothermal cancer therapy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Variable speed control in wells turbine-based oscillating water column devices: optimum rotational speed

NASA Astrophysics Data System (ADS)

Lekube, J.; Garrido, A. J.; Garrido, I.

2018-03-01

The effects of climate change and global warming reveal the need to find alternative sources of clean energy. In this sense, wave energy power plants, and in particular Oscillating Water Column (OWC) devices, offer a huge potential of energy harnessing. Nevertheless, the conversion systems have not reached a commercially mature stage yet so as to compete with conventional power plants. At this point, the use of new control methods over the existing technology arises as a doable way to improve the efficiency of the system. Due to the non-uniform response that the turbine shows to the rotational speed variation, the speed control of the turbo-generator may offer a feasible solution for efficiency improvement during the energy conversion. In this context, a novel speed control approach for OWC systems is presented in this paper, demonstrating its goodness and affording promising results when particularized to the Mutriku’s wave power plant.

Morphology evolution in high-performance polymer solar cells processed from nonhalogenated solvent

DOE PAGES

Cai, Wanzhu; Liu, Peng; Jin, Yaocheng; ...

2015-05-26

A new processing protocol based on non-halogenated solvent and additive is developed to produce polymer solar cells with power conversion efficiencies better than those processed from commonly used halogenated solvent-additive pair. Morphology studies show that good performance correlates with a finely distributed nanomorphology with a well-defined polymer fibril network structure, which leads to balanced charge transport in device operation.

Combining light-harvesting with detachability in high-efficiency thin-film silicon solar cells.

PubMed

Ram, Sanjay K; Desta, Derese; Rizzoli, Rita; Bellettato, Michele; Lyckegaard, Folmer; Jensen, Pia B; Jeppesen, Bjarke R; Chevallier, Jacques; Summonte, Caterina; Larsen, Arne Nylandsted; Balling, Peter

2017-06-01

Efforts to realize thin-film solar cells on unconventional substrates face several obstacles in achieving good energy-conversion efficiency and integrating light-management into the solar cell design. In this report a technique to circumvent these obstacles is presented: transferability and an efficient light-harvesting scheme are combined for thin-film silicon solar cells by the incorporation of a NaCl layer. Amorphous silicon solar cells in p-i-n configuration are fabricated on reusable glass substrates coated with an interlayer of NaCl. Subsequently, the solar cells are detached from the substrate by dissolution of the sacrificial NaCl layer in water and then transferred onto a plastic sheet, with a resultant post-transfer efficiency of 9%. The light-trapping effect of the surface nanotextures originating from the NaCl layer on the overlying solar cell is studied theoretically and experimentally. The enhanced light absorption in the solar cells on NaCl-coated substrates leads to significant improvement in the photocurrent and energy-conversion efficiency in solar cells with both 350 and 100 nm thick absorber layers, compared to flat-substrate solar cells. Efficient transferable thin-film solar cells hold a vast potential for widespread deployment of off-grid photovoltaics and cost reduction.

Insight into Aluminum Sulfate-Catalyzed Xylan Conversion into Furfural in a γ-Valerolactone/Water Biphasic Solvent under Microwave Conditions.

PubMed

Yang, Tao; Zhou, Yi-Han; Zhu, Sheng-Zhen; Pan, Hui; Huang, Yao-Bing

2017-10-23

A simple and efficient biphasic system with an earth-abundant metal salt catalyst was used to produce furfural from xylan with a high yield of up to 87.8 % under microwave conditions. Strikingly, the metal salt Al 2 (SO 4 ) 3 exhibited excellent catalytic activity for xylan conversion, owing to a combination of Lewis and Brønsted acidity and its ability to promote good phase separation. The critical role of the SO 4 2- anion was first analyzed, which resulted in the aforementioned characteristics when combined with the Al 3+ cation. The mixed solvent system with γ-valerolactone (GVL) as the organic phase provided the highest furfural yield, resulting from its good dielectric properties and dissolving capacity, which facilitated the absorption of microwave energy and promoted mass transfer. Mechanistic studies suggested that the xylan-to-furfural conversion proceeded mainly through a hydrolysis-isomerization-dehydration pathway and the hexa-coordinated Lewis acidic [Al(OH) 2 (aq)] + species were the active sites for xylose-xylulose isomerization. Detailed kinetic studies of the subreaction for the xylan conversion revealed that GVL regulates the reaction rates and pathways by promoting the rates of the key steps involved for furfural production and suppressing the side reactions for humin production. Finally, the Al 2 (SO 4 ) 3 catalyst was used for the production of furfural from several lignocellulosic feedstocks, revealing its great potential for other biomass conversions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Increasing conversion efficiency of two-step photon up-conversion solar cell with a voltage booster hetero-interface.

PubMed

Asahi, Shigeo; Kusaki, Kazuki; Harada, Yukihiro; Kita, Takashi

2018-01-17

Development of high-efficiency solar cells is one of the attractive challenges in renewable energy technologies. Photon up-conversion can reduce the transmission loss and is one of the promising concepts which improve conversion efficiency. Here we present an analysis of the conversion efficiency, which can be increased by up-conversion in a single-junction solar cell with a hetero-interface that boosts the output voltage. We confirm that an increase in the quasi-Fermi gap and substantial photocurrent generation result in a high conversion efficiency.

A low complexity, low spur digital IF conversion circuit for high-fidelity GNSS signal playback

NASA Astrophysics Data System (ADS)

Su, Fei; Ying, Rendong

2016-01-01

A low complexity high efficiency and low spur digital intermediate frequency (IF) conversion circuit is discussed in the paper. This circuit is key element in high-fidelity GNSS signal playback instrument. We analyze the spur performance of a finite state machine (FSM) based numerically controlled oscillators (NCO), by optimization of the control algorithm, a FSM based NCO with 3 quantization stage can achieves 65dB SFDR in the range of the seventh harmonic. Compare with traditional lookup table based NCO design with the same Spurious Free Dynamic Range (SFDR) performance, the logic resource require to implemented the NCO is reduced to 1/3. The proposed design method can be extended to the IF conversion system with good SFDR in the range of higher harmonic components by increasing the quantization stage.

Bimodal porous TiO2 structures templated by graft copolymer/homopolymer blend for dye-sensitized solar cells with polymer electrolyte

NASA Astrophysics Data System (ADS)

Kim, Jin Kyu; Lee, Chang Soo; Lee, Sang-Yup; Cho, Hyung Hee; Kim, Jong Hak

2016-12-01

Bimodal porous TiO2 (BP-TiO2) with large surface area, high porosity, good interconnectivity, and excellent light-scattering ability are synthesized via a facile one-step method using a self-assembled blend template consisting of an amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) graft copolymer and a hydrophobic poly(vinyl chloride) (PVC) homopolymer. The hydrophilically surface-modified TiO2 nanoparticles selectively interact with the hydrophilic POEM chains, while the addition of the PVC homopolymer increases the hydrophobic domain size, resulting in the formation of dual pores (i.e., macropores and mesopores). The sizes and numbers of macropores can easily be controlled by changing the molecular weight and amount of the PVC homopolymer. The polymer electrolyte dye-sensitized solar cells (DSSCs) fabricated with BP-TiO2 photoanodes exhibited energy conversion efficiencies of up to 7.6% at 100 mW cm-2, which is much higher than those of mesoporous TiO2 (5.8%) with PVC-g-POEM only and conventional nanocrystalline TiO2 (4.9%) with commercial Dyesol paste. The enhanced energy conversion efficiencies mostly resulted from the light-scattering effects of the macropores, which increased the light-harvesting efficiencies. The improved light-harvesting and photovoltaic performances of the DSSCs were characterized by UV-vis spectroscopy, incident photon-to-current conversion efficiency analysis, electrochemical impedance spectroscopy, intensity-modulated photocurrent spectroscopy, and intensity-modulated photovoltage spectroscopy.

POSS-Based Electrolyte for Efficient Solid-State Dye-Sensitized Solar Cells at Sub-Zero Temperatures.

PubMed

Lv, Kai; Zhang, Wei; Zhang, Lu; Wang, Zhong-Sheng

2016-03-02

To expand the application of solid-state dye-sensitized solar cells (ssDSSCs) to low temperatures, it is necessary to develop new solid electrolytes with low glass transition temperature (Tg). The Tg is regulated by varying the length of alkyl chain that is connected with the nitrogen atom in the imidazolium ring linked to the polyhedral oligomeric silsesquioxane (POSS). The Tg as low as -8.8 °C is achieved with the POSS grafted with methyl-substituted imidazolium. The effect of alkyl group on the conductivity, Tg, and photovoltaic performance has also been investigated. The conductivity and power conversion efficiency increase with the alkyl length, while the Tg first increases and then decreases with the alkyl length. Among the synthesized POSS-based ionic conductors, the POSS grafted with the methyl-substituted imidazolium yields the highest power conversion efficiency of 6.98% at RT due to its highest conductivity, and the efficiency (6.52%) is still good at -4 °C, as its Tg (-8.8 °C) is lower than the working temperature (-4 °C). This finding suggests that the POSS-based solid electrolyte is promising for subzero-temperature applications of ssDSSCs.

Layered tin monoselenide as advanced photothermal conversion materials for efficient solar energy-driven water evaporation.

PubMed

Yao, Jiandong; Zheng, Zhaoqiang; Yang, Guowei

2018-02-08

Solar energy-driven water evaporation lays a solid foundation for important photothermal applications such as sterilization, seawater desalination, and electricity generation. Due to the strong light-matter coupling, broad absorption wavelength range, and prominent quantum confinement effect, layered tin monoselenide (SnSe) holds a great potential to effectively harness solar irradiation and convert it to heat energy. In this study, SnSe is successfully deposited on a centimeter-scale nickel foam using a facile one-step pulsed-laser deposition approach. Importantly, the maximum evaporation rate of SnSe-coated nickel foam (SnSe@NF) reaches 0.85 kg m -2 h -1 , which is even 21% larger than that obtained with the commercial super blue coating (0.7 kg m -2 h -1 ) under the same condition. A systematic analysis reveals that its good photothermal conversion capability is attributed to the synergetic effect of multi-scattering-induced light trapping and the optimal trade-off between light absorption and phonon emission. Finally, the SnSe@NF device is further used for seawater evaporation, demonstrating a comparable evaporation rate (0.8 kg m -2 h -1 ) to that of fresh water and good stability over many cycles of usage. In summary, the current contribution depicts a facile one-step scenario for the economical and efficient solar-enabled SnSe@NF evaporation devices. More importantly, an in-depth analysis of the photothermal conversion mechanism underneath the layered materials depicts a fundamental paradigm for the design and application of photothermal devices based on them in the future.

Structure, spectroscopic properties and laser performance of Nd:YNbO4 at 1066 nm

NASA Astrophysics Data System (ADS)

Ding, Shoujun; Peng, Fang; Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Dunlu; Dou, Renqin; Sun, Guihua

2016-12-01

We have demonstrated continuous wave (CW) laser operation of Nd:YNbO4 crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10-20 cm2) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10-20 cm2) and relative long lifetime of the 4F3/2 → 4I11/2 transition indicates good energy storage capacity of Nd:YNbO4. Moreover, the raw materials of Nd:YNbO4 are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO4 crystal is a potentially new laser material suitable for LD pumping.

Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

PubMed Central

2011-01-01

Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices. PMID:27502660

How Important Is the Organic Part of Lead Halide Perovskite Photovoltaic Cells? Efficient CsPbBr3 Cells.

PubMed

Kulbak, Michael; Cahen, David; Hodes, Gary

2015-07-02

Hybrid organic-inorganic lead halide perovskite photovoltaic cells have already surpassed 20% conversion efficiency in the few years that they have been seriously studied. However, many fundamental questions still remain unanswered as to why they are so good. One of these is "Is the organic cation really necessary to obtain high quality cells?" In this study, we show that an all-inorganic version of the lead bromide perovskite material works equally well as the organic one, in particular generating the high open circuit voltages that are an important feature of these cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behaghel, B.; Institute of Research and Development on Photovoltaic Energy; NextPV, RCAST and CNRS, The University of Tokyo, Meguro-ku, Tokyo 153-8904

We study light management in a 430 nm-thick GaAs p-i-n single junction solar cell with 10 pairs of InGaAs/GaAsP multiple quantum wells (MQWs). The epitaxial layer transfer on a gold mirror improves light absorption and increases the external quantum efficiency below GaAs bandgap by a factor of four through the excitation of Fabry-Perot resonances. We show a good agreement with optical simulation and achieve around 10% conversion efficiency. We demonstrate numerically that this promising result can be further improved by anti-reflection layers. This study paves the way to very thin MQWs solar cells.

Application of 3A molecular sieve layer in dye-sensitized solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yuan; Wang, Jinzhong, E-mail: jinzhong-wang@hit.edu.cn, E-mail: qingjiang.yu@hit.edu.cn; Yu, Qingjiang, E-mail: jinzhong-wang@hit.edu.cn, E-mail: qingjiang.yu@hit.edu.cn

2014-08-25

3A molecular sieve layer was used as dehydration and electronic-insulation layer on the TiO{sub 2} electrode of dye-sensitized solar cells. This layer diminished the effect of water in electrolyte efficiently and enhanced the performance of cells. The conversion efficiency increased from 9.58% to 10.2%. The good moisture resistance of cells was attributed to the three-dimensional interconnecting structure of 3A molecular sieve with strong adsorption of water molecule. While the performance enhancement benefited from the suppression of the charge recombination of electronic-insulation layer and scattering effect of large particles.

Genetic improvement of native xylose-fermenting yeasts for ethanol production.

PubMed

Harner, Nicole K; Wen, Xin; Bajwa, Paramjit K; Austin, Glen D; Ho, Chi-Yip; Habash, Marc B; Trevors, Jack T; Lee, Hung

2015-01-01

Lignocellulosic substrates are the largest source of fermentable sugars for bioconversion to fuel ethanol and other valuable compounds. To improve the economics of biomass conversion, it is essential that all sugars in potential hydrolysates be converted efficiently into the desired product(s). While hexoses are fermented into ethanol and some high-value chemicals, the bioconversion of pentoses in hydrolysates remains inefficient. This remains one of the key challenges in lignocellulosic biomass conversion. Native pentose-fermenting yeasts can ferment both glucose and xylose in lignocellulosic biomass to ethanol. However, they perform poorly in the presence of hydrolysate inhibitors, exhibit low ethanol tolerance and glucose repression, and ferment pentoses less efficiently than the main hexoses glucose and mannose. This paper reviews classical and molecular strain improvement strategies applied to native pentose-fermenting yeasts for improved ethanol production from xylose and lignocellulosic substrates. We focus on Pachysolen tannophilus, Scheffersomyces (Candida) shehatae, Scheffersomyces (Pichia) stipitis, and Spathaspora passalidarum which are good ethanol producers among the native xylose-fermenting yeasts. Strains obtained thus far are not robust enough for efficient ethanol production from lignocellulosic hydrolysates and can benefit from further improvements.

All-optical 40Gbit/s format conversion from NRZ to RZ based on SFG in a PPLN waveguide

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang

2006-01-01

A novel all-optical 40Gbit/s NRZ-to-RZ data format conversion scheme based on sum-frequency generation (SFG) interaction in a periodically poled LiNbO 3 (PPLN) waveguide is presented for the first time, using a Mach-Zehnder interferometer (MZI). The conversion mechanism relies on the combination of attenuation and nonlinear phase shift Φ NL induced on the signal field. The performance of the conversion is numerically evaluated, with the result showing that it is more effective to yield Φ NL when appropriately phase mismatched for SFG process but Φ NL~0 when quasi-phase-matching (QPM). Compared with the cascaded second-order nonlinear interactions (SHG+DFG) with the influence of walk-off effect, a high conversion efficiency and good performance are achieved with peak power 500mw and width 2ps of the pump, which can be used in super high-speed situation (40Gbit/s and above). Finally, the inverse process of SFG and corresponding walk-off effect are analyzed and the optimum arrangement of power is proposed, showing that proper power, pump width, and waveguide length are necessary for achieving a satisfied conversion effect.

Efficient Photothermoelectric Conversion in Lateral Topological Insulator Heterojunctions.

PubMed

Mashhadi, Soudabeh; Duong, Dinh Loc; Burghard, Marko; Kern, Klaus

2017-01-11

Tuning the electron and phonon transport properties of thermoelectric materials by nanostructuring has enabled improving their thermopower figure of merit. Three-dimensional topological insulators, including many bismuth chalcogenides, attract increasing attention for this purpose, as their topologically protected surface states are promising to further enhance the thermoelectric performance. While individual bismuth chalcogenide nanostructures have been studied with respect to their photothermoelectric properties, nanostructured p-n junctions of these compounds have not yet been explored. Here, we experimentally investigate the room temperature thermoelectric conversion capability of lateral heterostructures consisting of two different three-dimensional topological insulators, namely, the n-type doped Bi 2 Te 2 Se and the p-type doped Sb 2 Te 3 . Scanning photocurrent microscopy of the nanoplatelets reveals efficient thermoelectric conversion at the p-n heterojunction, exploiting hot carriers of opposite sign in the two materials. From the photocurrent data, a Seebeck coefficient difference of ΔS = 200 μV/K was extracted, in accordance with the best values reported for the corresponding bulk materials. Furthermore, it is in very good agreement with the value of ΔS = 185 μV/K obtained by DFT calculation taking into account the specific doping levels of the two nanostructured components.

Polycatechol nanosheet: a superior nanocarrier for highly effective chemo-photothermal synergistic therapy in vivo

NASA Astrophysics Data System (ADS)

Bai, J.; Jia, X. D.; Ma, Z. F.; Jiang, X. E.; Sun, X. P.

2016-02-01

The integration of phototherapy and chemotherapy in a single system holds great promise to improve the therapeutic efficacy of tumor treatment, but it remains a key challenge. In this study, we describe our recent finding that polycatechol nanosheet (PCCNS) can be facilely prepared on a large scale via chemical polymerization at 4 °C, as an effective nanocarrier for loading high-density CuS nanocrystals as a photothermal agent. The resulting CuS/PCCNS nanocomposites exhibit good biocompatibility, strong stability, and a high photothermal conversion efficiency of ~45.7%. The subsequent loading of anticancer drug doxorubicin (Dox) creates a superior theranostic agent with pH- and heat-responsive drug release, leading to almost complete destruction of mouse cervical tumor under NIR laser irradiation. This development offers an attractive theranostic agent for in vivo chemo-photothermal synergistic therapy toward biomedical applications.The integration of phototherapy and chemotherapy in a single system holds great promise to improve the therapeutic efficacy of tumor treatment, but it remains a key challenge. In this study, we describe our recent finding that polycatechol nanosheet (PCCNS) can be facilely prepared on a large scale via chemical polymerization at 4 °C, as an effective nanocarrier for loading high-density CuS nanocrystals as a photothermal agent. The resulting CuS/PCCNS nanocomposites exhibit good biocompatibility, strong stability, and a high photothermal conversion efficiency of ~45.7%. The subsequent loading of anticancer drug doxorubicin (Dox) creates a superior theranostic agent with pH- and heat-responsive drug release, leading to almost complete destruction of mouse cervical tumor under NIR laser irradiation. This development offers an attractive theranostic agent for in vivo chemo-photothermal synergistic therapy toward biomedical applications. Electronic supplementary information (ESI) available: The calculation of the photothermal conversion efficiency and supplementary figures. See DOI: 10.1039/c5nr07723k

Exploring the Photovoltaic Performance of All-Inorganic Ag2PbI4/PbI2 Blends.

PubMed

Frolova, Lyubov A; Anokhin, Denis V; Piryazev, Alexey A; Luchkin, Sergey Yu; Dremova, Nadezhda N; Troshin, Pavel A

2017-04-06

We present an all-inorganic photoactive material composed of Ag 2 PbI 4 and PbI 2 , which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies.

Radioisotopic energy conversion system (RECS): A new radioisotopic power cell, based on nuclear, atomic, and radiation transport principles

NASA Astrophysics Data System (ADS)

Steinfelds, Eric Victor

The topic of this thesis is the development of the Radioisotope Energy Conversion System (RECS) in a project which is utilizing analytical computational assisted design and some experimental Research in the investigation of fluorescers and effective transducers with the appropriate energy range choice for the conversion of energy. It is desirable to increase the efficiency in electrical power from the raw kinetic power available from the radioactive material within radioisotope power generators. A major step in this direction is the development and use of Radioisotope Energy Conversion Systems to supplement and ideally replace Radioactive Thermal Generators (RTG). It is possible to achieve electrical conversion efficiencies exceeding 25% for RECS power devices compared to only 9 percent efficiency for RTG's. The theoretical basis with existent materials for the potential achievability of efficiencies above 25% is documented within this thesis. The fundamental RECS consists of a radioisotope radiative source (C1), a mediating fluorescent gas (C2) which readily absorbs energy from the beta particles (or alpha's) and subsequently emits blue or UV photons, photovoltaic cells (C3) to convert the blue and UV photons into electrical energy [2], and electrical circuitry (C4). Solid State inspired component (C3), due to its theoretical (and attainable) high efficiency, is a large step ahead of the RTG design concept. The radioisotope flux source produces the beta(-) particles or alpha particles. Geometrically, presently, we prefer to have the ambient fluorescent gas surround the radioisotope flux source. Our fluorescer shall be a gas such as Krypton. Our specifically wide band-gap photovoltaic cells shall have gap energies which are slightly less than that of UV photons produced by the fluorescing gas. Diamond and Aluminum Nitride sample materials are good potential choices for photovoltaic cells, as is explained here in. Out of the material examples discussed, the highest electric power to mass ratio is found to be readily attainable with strontium-90 as the radiative source. Krypton-85 is indisputably the most efficient in RECS devices. In the conclusion in chapter VI, suggestions are given on acceptable ways of containing krypton-85 and providing sufficient shielding on deep space probes destined to use krypton-85 powered 'batteries'.

Ecological conversion efficiency and its influencers in twelve species of fish in the Yellow Sea Ecosystem

NASA Astrophysics Data System (ADS)

Tang, Qisheng; Guo, Xuewu; Sun, Yao; Zhang, Bo

2007-09-01

The ecological conversion efficiencies in twelve species of fish in the Yellow Sea Ecosystem, i.e., anchovy ( Engraulis japonicus), rednose anchovy ( Thrissa kammalensis), chub mackerel ( Scomber japonicus), halfbeak ( Hyporhamphus sajori), gizzard shad ( Konosirus punctatus), sand lance ( Ammodytes personatus), red seabream ( Pagrus major), black porgy ( Acanthopagrus schlegeli), black rockfish ( Sebastes schlegeli), finespot goby ( Chaeturichthys stigmatias), tiger puffer ( Takifugu rubripes), and fat greenling ( Hexagrammos otakii), were estimated through experiments conducted either in situ or in a laboratory. The ecological conversion efficiencies were significantly different among these species. As indicated, the food conversion efficiencies and the energy conversion efficiencies varied from 12.9% to 42.1% and from 12.7% to 43.0%, respectively. Water temperature and ration level are the main factors influencing the ecological conversion efficiencies of marine fish. The higher conversion efficiency of a given species in a natural ecosystem is acquired only under the moderate environment conditions. A negative relationship between ecological conversion efficiency and trophic level among ten species was observed. Such a relationship indicates that the ecological efficiency in the upper trophic levels would increase after fishing down marine food web in the Yellow Sea ecosystem.

A new near infrared photosensitizing nanoplatform containing blue-emitting up-conversion nanoparticles and hypocrellin A for photodynamic therapy of cancer cells

NASA Astrophysics Data System (ADS)

Jin, Shan; Zhou, Liangjun; Gu, Zhanjun; Tian, Gan; Yan, Liang; Ren, Wenlu; Yin, Wenyan; Liu, Xiaodong; Zhang, Xiao; Hu, Zhongbo; Zhao, Yuliang

2013-11-01

The utilization of up-conversion nanoparticles (UCNPs) for photodynamic therapy (PDT) has gained significant interest due to their unique ability to convert near infrared light to UV/visible light. Previous work mainly focused on the fabrication of green and red emitting UCNPs to load photosensitizers (PSs) for PDT. In this work, we firstly developed a new multifunctional nanoplatform combining blue-emitting UCNPs with blue-light excited PS (hypocrellin A, HA) as a NIR photosensitizing nanoplatform for PDT of cancer cells. Tween 20 coated NaYbF4:Tm, Gd@NaGdF4 UCNPs (Tween 20-UCNPs) with strong blue up-conversion luminescence and good water dispersibility were prepared for use as PS carriers. The blue emission band matched well with the efficient absorption band of HA, thereby facilitating the resonance energy transfer from UCNPs to HA and then activating HA to produce singlet oxygen (1O2). The in vitro study showed that these Tween 20-UCNPs@HA complexes could efficiently produce 1O2 to kill cancer cells under 980 nm NIR excitation. Moreover, these Gd3+ and Yb3+ containing nanoparticles also exhibited positive contrast effects in both T1 weighted magnetic resonance imaging (MRI) and computed tomography (CT) imaging, making them become a multifunctional platform for simultaneous PDT and bio-imaging.The utilization of up-conversion nanoparticles (UCNPs) for photodynamic therapy (PDT) has gained significant interest due to their unique ability to convert near infrared light to UV/visible light. Previous work mainly focused on the fabrication of green and red emitting UCNPs to load photosensitizers (PSs) for PDT. In this work, we firstly developed a new multifunctional nanoplatform combining blue-emitting UCNPs with blue-light excited PS (hypocrellin A, HA) as a NIR photosensitizing nanoplatform for PDT of cancer cells. Tween 20 coated NaYbF4:Tm, Gd@NaGdF4 UCNPs (Tween 20-UCNPs) with strong blue up-conversion luminescence and good water dispersibility were prepared for use as PS carriers. The blue emission band matched well with the efficient absorption band of HA, thereby facilitating the resonance energy transfer from UCNPs to HA and then activating HA to produce singlet oxygen (1O2). The in vitro study showed that these Tween 20-UCNPs@HA complexes could efficiently produce 1O2 to kill cancer cells under 980 nm NIR excitation. Moreover, these Gd3+ and Yb3+ containing nanoparticles also exhibited positive contrast effects in both T1 weighted magnetic resonance imaging (MRI) and computed tomography (CT) imaging, making them become a multifunctional platform for simultaneous PDT and bio-imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03515h

Raman shifting of KrF laser radiation for tropospheric ozone measurements

NASA Technical Reports Server (NTRS)

Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Ismail, Syed

1991-01-01

The differential absorption lidar (DIAL) measurement of tropospheric ozone requires use of high average power UV lasers operating at two appropriate DIAL wavelengths. Laboratory experiments have demonstrated that a KrF excimer laser can be used to generate several wavelengths with good energy conversion efficiencies by stimulated Raman shifting using hydrogen (H2) and deuterium (D2). Computer simulations for an airborne lidar have shown that these laser emissions can be used for the less than 5 percent random error, high resolution measuremment of ozone across the troposphere using the DIAL technique. In the region of strong ozone absorption, laser wavelengths of 277.0 and 291.7 nm were generated using H2 and D2, respectively. In addition, a laser wavelength at 302.0 nm was generated using two cells in series, with the first containing D2 and the second containing H2. The energy conversion efficiency for each wavelength was between 14 and 27 percent.

An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells.

PubMed

Seo, Seongrok; Park, Ik Jae; Kim, Myungjun; Lee, Seonhee; Bae, Changdeuck; Jung, Hyun Suk; Park, Nam-Gyu; Kim, Jin Young; Shin, Hyunjung

2016-06-02

NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis.

Nanostructured organosilicon luminophores as a new concept of nanomaterials for highly efficient down-conversion of light

NASA Astrophysics Data System (ADS)

Ponomarenko, Sergey A.; Surin, Nikolay M.; Borshchev, Oleg V.; Skorotetcky, Maxim S.; Muzafarov, Aziz M.

2015-10-01

Nanostructured organosilicon luminophores (NOLs) are branched molecular structures having two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time, good processability and low toxicity. A smart choice of organic luminophores allowed us to design and synthesize a library of NOLs, absorbing from VUV to visible region and emitting at the desired wavelengths from 390 to 650 nm. They can be used as unique wavelength shifters in plastic scintillators and other applications.

Development of a liquid tin microjet target for an efficient laser-produced plasma extreme ultraviolet source.

PubMed

Higashiguchi, Takeshi; Hamada, Masaya; Kubodera, Shoichi

2007-03-01

A regenerative tin liquid microjet target was developed for a high average power extreme ultraviolet (EUV) source. The diameter of the target was smaller than 160 microm and good vacuum lower than 0.5 Pa was maintained during the operation. A maximum EUV conversion efficiency of 1.8% at the Nd:yttrium-aluminum-garnet laser intensity of around 2 x 10(11) Wcm(2) with a spot diameter of 175 microm (full width at half maximum) was observed. The angular distribution of the EUV emission remained almost isotropic, whereas suprathermal ions mainly emerged toward the target normal.

Development of a liquid tin microjet target for an efficient laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Hamada, Masaya; Kubodera, Shoichi

2007-03-01

A regenerative tin liquid microjet target was developed for a high average power extreme ultraviolet (EUV) source. The diameter of the target was smaller than 160 μm and good vacuum lower than 0.5 Pa was maintained during the operation. A maximum EUV conversion efficiency of 1.8% at the Nd:yttrium-aluminum-garnet laser intensity of around 2×1011 W/cm2 with a spot diameter of 175 μm (full width at half maximum) was observed. The angular distribution of the EUV emission remained almost isotropic, whereas suprathermal ions mainly emerged toward the target normal.

A Triphenylamine-Based Conjugated Polymer with Donor-π-Acceptor Architecture as Organic Sensitizer for Dye-Sensitized Solar Cells.

PubMed

Zhang, Wei; Fang, Zhen; Su, Mingjuan; Saeys, Mark; Liu, Bin

2009-09-17

A conjugated polymer containing an electron donating backbone (triphenylamine) and an electron accepting side chain (cyanoacetic acid) with conjugated thiophene units as the linkers has been synthesized. Dye-sensitized solar cells (DSSCs) are fabricated utilizing this material as the dye sensitizer, resulting a typical power conversion efficiency of 3.39% under AM 1.5 G illumination, which represents the highest efficiency for polymer dye-sensitized DSSCs reported so far. The results show the good promise of conjugated polymers as sensitizers for DSSC applications. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two dimensional self-assembly zinc porphyrins and zinc phthalocyanines heterojunctions with record high power conversion efficiencies.

PubMed

Yu, Junting; Jiang, Zhou; Hao, Yifan; Zhu, Qianhong; Zhao, Mingliang; Jiang, Xue; Zhao, Jijun

2018-05-15

Compared to inorganic solar cells, the power conversion efficiencies (PCEs) of organic solar cells are much lower, but they are compensated by many merits such as lower cost, less weight, and tunable structures, making them prospective for further applications. Porphyrin and phthalocyanine are the two most significant materials for organic solar cells due to their strong light-absorbing properties and semiconductor characteristics. However, there is little research on the 2D heterojunction solar cells based on these two materials, meanwhile the PCEs of them are still low. Here we have self-assembled several 2D Zinc-porphyrins (ZnPors) and performed first-principles simulation to demonstrate their good stability, suitable light harvesting, and high charge carrier mobility. By perfectly matching lattice constants and band levels between those 2D ZnPors and our previous proposed ZnPcs, eleven type-II organic heterojunctions are constructed to further improve their charge separation capability. Those advantages endow 2D ZnPors and ZnPcs appreciable PCEs for solar cell. Among them, the theoretical PCE of 2D ZnPors/ZnPcs heterojunctions achieves as high as 19.84%, which prevails all reported organic solar cells, and even approaches the PCEs of inorganic solar cells. These results indicate that our 2D ZnPors and 2D ZnPcs are good candidate materials for future organic solar cells. © 2018 IOP Publishing Ltd.

Two dimensional self-assembly zinc porphyrin and zinc phthalocyanine heterojunctions with record high power conversion efficiencies

NASA Astrophysics Data System (ADS)

Yu, Junting; Jiang, Zhou; Hao, Yifan; Zhu, Qianhong; Zhao, Mingliang; Jiang, Xue; Zhao, Jijun

2018-06-01

Compared to inorganic solar cells, the power conversion efficiencies (PCEs) of organic solar cells are much lower, but they are compensated by many merits such as lower cost, less weight, and tunable structures, making them prospective for further applications. Porphyrin and phthalocyanine are the two most significant materials for organic solar cells due to their strong light-absorbing properties and semiconductor characteristics. However, there is little research on the 2D heterojunction solar cells based on these two materials, meanwhile the PCEs of them are still low. Here we have self-assembled several 2D zinc porphyrins (ZnPors) and performed first-principles simulation to demonstrate their good stability, suitable light harvesting, and high charge carrier mobility. By perfectly matching lattice constants and molecular energy levels between those 2D ZnPors and our previous proposed zinc phthalocyanines (ZnPcs), 11 type-II organic heterojunctions are constructed to further improve their charge separation capability. Those advantages endow 2D ZnPors and ZnPcs appreciable PCEs for solar cells. Among them, the theoretical PCE of 2D ZnPors/ZnPcs heterojunctions achieves as high as 19.84%, which exceeds all reported organic solar cells, and even approaches the PCEs of inorganic solar cells. These results indicate that our 2D ZnPors and 2D ZnPcs are good candidate materials for future organic solar cells.

Oligomer Molecules for Efficient Organic Photovoltaics.

PubMed

Lin, Yuze; Zhan, Xiaowei

2016-02-16

Solar cells, a renewable, clean energy technology that efficiently converts sunlight into electricity, are a promising long-term solution for energy and environmental problems caused by a mass of production and the use of fossil fuels. Solution-processed organic solar cells (OSCs) have attracted much attention in the past few years because of several advantages, including easy fabrication, low cost, lightweight, and flexibility. Now, OSCs exhibit power conversion efficiencies (PCEs) of over 10%. In the early stage of OSCs, vapor-deposited organic dye materials were first used in bilayer heterojunction devices in the 1980s, and then, solution-processed polymers were introduced in bulk heterojunction (BHJ) devices. Relative to polymers, vapor-deposited small molecules offer potential advantages, such as a defined molecular structure, definite molecular weight, easy purification, mass-scale production, and good batch-to-batch reproducibility. However, the limited solubility and high crystallinity of vapor-deposited small molecules are unfavorable for use in solution-processed BHJ OSCs. Conversely, polymers have good solution-processing and film-forming properties and are easily processed into flexible devices, whereas their polydispersity of molecular weights and difficulty in purification results in batch to batch variation, which may hamper performance reproducibility and commercialization. Oligomer molecules (OMs) are monodisperse big molecules with intermediate molecular weights (generally in the thousands), and their sizes are between those of small molecules (generally with molecular weights <1000) and polymers (generally with molecular weights >10000). OMs not only overcome shortcomings of both vapor-deposited small molecules and solution-processed polymers, but also combine their advantages, such as defined molecular structure, definite molecular weight, easy purification, mass-scale production, good batch-to-batch reproducibility, good solution processability, and film-forming properties. Therefore, OMs are a good choice for solution-processed reproducible OSCs toward scalable commercialized applications. Considerable efforts have been dedicated to developing new OM electron donors and electron acceptors for OSCs. So far, the highest PCEs of solution-processed OSCs based on OM donors and acceptors are 9-10% and 6-7%, respectively. OM materials have become promising alternatives to polymer and/or fullerene materials for efficient and stable OSCs. In this Account, we present a brief survey of the recent developments in solution-processable OM electron donors and acceptors and their application in OSCs. Rational design of OMs with star- and linear-shaped structures based on triphenylamine, benzodithiophene, and indacenodithiophene units and their impacts on device performance are discussed. Structure-property relationships are also proposed. Furthermore, the remaining challenges and the key research directions in the near future are also addressed. In the next years, an interdisciplinary approach involving novel OM materials, especially electron acceptor materials, accurate morphology optimization, and advanced device technologies will probably bring high-efficiency and stable OSCs to final commercialization.

Optimization of single photon detection model based on GM-APD

NASA Astrophysics Data System (ADS)

Chen, Yu; Yang, Yi; Hao, Peiyu

2017-11-01

One hundred kilometers high precision laser ranging hopes the detector has very strong detection ability for very weak light. At present, Geiger-Mode of Avalanche Photodiode has more use. It has high sensitivity and high photoelectric conversion efficiency. Selecting and designing the detector parameters according to the system index is of great importance to the improvement of photon detection efficiency. Design optimization requires a good model. In this paper, we research the existing Poisson distribution model, and consider the important detector parameters of dark count rate, dead time, quantum efficiency and so on. We improve the optimization of detection model, select the appropriate parameters to achieve optimal photon detection efficiency. The simulation is carried out by using Matlab and compared with the actual test results. The rationality of the model is verified. It has certain reference value in engineering applications.

High-performance NiO/Ag/NiO transparent electrodes for flexible organic photovoltaic cells.

PubMed

Xue, Zhichao; Liu, Xingyuan; Zhang, Nan; Chen, Hong; Zheng, Xuanming; Wang, Haiyu; Guo, Xiaoyang

2014-09-24

Transparent electrodes with a dielectric-metal-dielectric (DMD) structure can be implemented in a simple manufacturing process and have good optical and electrical properties. In this study, nickel oxide (NiO) is introduced into the DMD structure as a more appropriate dielectric material that has a high conduction band for electron blocking and a low valence band for efficient hole transport. The indium-free NiO/Ag/NiO (NAN) transparent electrode exhibits an adjustable high transmittance of ∼82% combined with a low sheet resistance of ∼7.6 Ω·s·q(-1) and a work function of 5.3 eV after UVO treatment. The NAN electrode shows excellent surface morphology and good thermal, humidity, and environmental stabilities. Only a small change in sheet resistance can be found after NAN electrode is preserved in air for 1 year. The power conversion efficiencies of organic photovoltaic cells with NAN electrodes deposited on glass and polyethylene terephthalate (PET) substrates are 6.07 and 5.55%, respectively, which are competitive with those of indium tin oxide (ITO)-based devices. Good photoelectric properties, the low-cost material, and the room-temperature deposition process imply that NAN electrode is a striking candidate for low-cost and flexible transparent electrode for efficient flexible optoelectronic devices.

Quantum Confined Semiconductors for High Efficiency Photovoltaics

NASA Astrophysics Data System (ADS)

Beard, Matthew

2014-03-01

Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photon-to-free energy conversion step. In this discussion, I will present the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. Different chemical treatments of the QD layer are employed in order to obtain good electrical communication while maintaining the quantum-confined properties of the QDs. We have characterized the transport and carrier dynamics using a transient absorption, time-resolved THz, and temperature-dependent photoluminescence. I will discuss the interplay between carrier generation, recombination, and mobility within the QD layers. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor.

Organic-Inorganic Hybrid Perovskite with Controlled Dopant Modification and Application in Photovoltaic Device.

PubMed

Zhao, Wangen; Yang, Dong; Liu, Shengzhong Frank

2017-07-01

Organic-inorganic hybrid perovskite as a kind of promising photovoltaic material is booming due to its low-cost, high defect tolerance, and easy fabrication, which result in the huge potential in industrial production. In the pursuit of high efficiency photovoltaic devices, high-quality absorbing layer is essential. Therefore, developing organic-inorganic hybrid perovskite thin films with good coverage, improved uniformity, and crystalline in a single pass deposition is of great concern in realizing good performance of perovskite thin-film solar cell. Here, it is found that the introduction of suitable amounts of LiI plays a dramatically positive role in enlarging the grain size and reducing the grain boundaries of absorbing layer. In addition, the carrier lifetime and built-in potential of the LiI doped perovskite device are observed to increase. Thus, it leads to about 15% gain in solar cell efficiency comparing to that without the LiI doping. Meanwhile, a hysteresis reduction is observed and 18.16% power conversion efficiency is achieved in LiI doped perovskite device, as well. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of Neutral Atom Imagers

NASA Technical Reports Server (NTRS)

Shappirio, M.; Coplan, M.; Balsamo, E.; Chornay, D.; Collier, M.; Hughes, P.; Keller, J.; Ogilvie, K.; Williams, E.

2008-01-01

The interactions between plasma structures and neutral atom populations in interplanetary space can be effectively studied with energetic neutral atom imagers. For neutral atoms with energies less than 1 keV, the most efficient detection method that preserves direction and energy information is conversion to negative ions on surfaces. We have examined a variety of surface materials and conversion geometries in order to identify the factors that determine conversion efficiency. For chemically and physically stable surfaces smoothness is of primary importance while properties such as work function have no obvious correlation to conversion efficiency. For the noble metals, tungsten, silicon, and graphite with comparable smoothness, conversion efficiency varies by a factor of two to three. We have also examined the way in which surface conversion efficiency varies with the angle of incidence of the neutral atom and have found that the highest efficiencies are obtained at angles of incidence greater then 80deg. The conversion efficiency of silicon, tungsten and graphite were examined most closely and the energy dependent variation of conversion efficiency measured over a range of incident angles. We have also developed methods for micromachining silicon in order to reduce the volume to surface area over that of a single flat surface and have been able to reduce volume to surface area ratios by up to a factor of 60. With smooth micro-machined surfaces of the optimum geometry, conversion efficiencies can be increased by an order of magnitude over instruments like LENA on the IMAGE spacecraft without increase the instruments mass or volume.

Electroviscous effect and electrokinetic energy conversion in time periodic pressure-driven flow through a parallel-plate nanochannel with surface charge-dependent slip

NASA Astrophysics Data System (ADS)

Buren, Mandula; Jian, Yongjun; Zhao, Yingchun; Chang, Long

2018-05-01

In this paper we analytically investigate the electroviscous effect and electrokinetic energy conversion in the time periodic pressure-driven flow of an incompressible viscous Newtonian liquid through a parallel-plate nanochannel with surface charge-dependent slip. Analytical and semi-analytical solutions for electric potential, velocity and streaming electric field are obtained and are utilized to compute electrokinetic energy conversion efficiency. The results show that velocity amplitude and energy conversion efficiency are reduced when the effect of surface charge on slip length is considered. The surface charge effect increases with zeta potential and ionic concentration. In addition, the energy conversion efficiency is large when the ratio of channel half-height to the electric double layer thickness is small. The boundary slip results in a large increase in energy conversion. Higher values of the frequency of pressure pulsation lead to higher values of the energy conversion efficiency. We also obtain the energy conversion efficiency in constant pressure-driven flow and find that the energy conversion efficiency in periodical pressure-driven flow becomes larger than that in constant pressure-driven flow when the frequency is large enough.

Method to monitor HC-SCR catalyst NOx reduction performance for lean exhaust applications

DOEpatents

Viola, Michael B [Macomb Township, MI; Schmieg, Steven J [Troy, MI; Sloane, Thompson M [Oxford, MI; Hilden, David L [Shelby Township, MI; Mulawa, Patricia A [Clinton Township, MI; Lee, Jong H [Rochester Hills, MI; Cheng, Shi-Wai S [Troy, MI

2012-05-29

A method for initiating a regeneration mode in selective catalytic reduction device utilizing hydrocarbons as a reductant includes monitoring a temperature within the aftertreatment system, monitoring a fuel dosing rate to the selective catalytic reduction device, monitoring an initial conversion efficiency, selecting a determined equation to estimate changes in a conversion efficiency of the selective catalytic reduction device based upon the monitored temperature and the monitored fuel dosing rate, estimating changes in the conversion efficiency based upon the determined equation and the initial conversion efficiency, and initiating a regeneration mode for the selective catalytic reduction device based upon the estimated changes in conversion efficiency.

Pyrrolic-N-doped graphene oxide/Fe2O3 mesocrystal nanocomposite: Efficient charge transfer and enhanced photo-Fenton catalytic activity

NASA Astrophysics Data System (ADS)

Liu, Bing; Tian, Lihong; Wang, Ran; Yang, Jinfeng; Guan, Rong; Chen, Xiaobo

2017-11-01

Though α-Fe2O3 has attracted much attention in photocatalytic or Fenton-catalytic degradation of organic contaminants, its performance is still unsatisfactory due to fast recombination of electrons and holes in photocatalytic process and the difficult conversion of Fe(II) and Fe(III) in Fenton reaction. Herein, a pyrrolic N-doped graphene oxide/Fe2O3 mesocrystal (NG-Fe2O3) nanocomposite with good distribution is synthesized by a simple solvothermal method and adjusting the oxygen-containing groups on graphene oxide. The morphology of NG-Fe2O3 contributes to a relatively large BET surface area and an intimate contact between NG and Fe2O3. These two important factors along with the excellent electro-conductivity of pyrrolic-N doped GO result in the efficient separation of electron-hole pairs and fast conversion of Fe(II)and Fe(III) in photo-Fenton synergistic reaction. Thus, a remarkably improved photo-Fenton catalytic activity of NG-Fe2O3 is obtained. The degrading rate on methyl blue increases by 1.5 times and the conversion rate of glyphosate increases by 2.3 times under visible light irradiation, compared to pristine α-Fe2O3 mesocrystals.

CdS/CdSe quantum dot shell decorated vertical ZnO nanowire arrays by spin-coating-based SILAR for photoelectrochemical cells and quantum-dot-sensitized solar cells.

PubMed

Zhang, Ran; Luo, Qiu-Ping; Chen, Hong-Yan; Yu, Xiao-Yun; Kuang, Dai-Bin; Su, Cheng-Yong

2012-04-23

A CdS/CdSe composite shell is assembled onto the surface of ZnO nanowire arrays with a simple spin-coating-based successive ionic layer adsorption and reaction method. The as-prepared photoelectrode exhibit a high photocurrent density in photoelectrochemical cells and also generates good power conversion efficiency in quantum-dot-sensitized solar cells. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

"Light sail" acceleration reexamined.

PubMed

Macchi, Andrea; Veghini, Silvia; Pegoraro, Francesco

2009-08-21

The dynamics of the acceleration of ultrathin foil targets by the radiation pressure of superintense, circularly polarized laser pulses is investigated by analytical modeling and particle-in-cell simulations. By addressing self-induced transparency and charge separation effects, it is shown that for "optimal" values of the foil thickness only a thin layer at the rear side is accelerated by radiation pressure. The simple "light sail" model gives a good estimate of the energy per nucleon, but overestimates the conversion efficiency of laser energy into monoenergetic ions.

Heterostructure solar cells

NASA Technical Reports Server (NTRS)

Chang, K. I.; Yeh, Y. C. M.; Iles, P. A.; Morris, R. K.

1987-01-01

The performance of gallium arsenide solar cells grown on Ge substrates is discussed. In some cases the substrate was thinned to reduce overall cell weight with good ruggedness. The conversion efficiency of 2 by 2 cm cells under AMO reached 17.1 percent with a cell thickness of 6 mils. The work described forms the basis for future cascade cell structures, where similar interconnecting problems between the top cell and the bottom cell must be solved. Applications of the GaAs/Ge solar cell in space and the expected payoffs are discussed.

Solar power satellite system definition study. Part 2, volume 4: Microwave power transmission systems

NASA Technical Reports Server (NTRS)

1977-01-01

A slotted waveguide planar array was established as the baseline design for the spaceborne transmitter antenna. Key aspects of efficient energy conversion at both ends of the power transfer link were analyzed and optimized alternate approaches in the areas of antenna and tube design are discussed. An integrated design concept was developed which meets design requirements, observes structural and thermal constraints, exhibits good performance and was developed in adequate depth to permit cost estimating at the subsystem/component level.

Twenty natural organic pigments for application in dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Castillo, D.; Sánchez Juárez, A.; Espinosa Tapia, S.; Guaman, A.; Obregón Calderón, D.

2016-09-01

In this work we present the results of a study of twenty natural pigments obtained from plants and insects from southern Ecuador. Many of them will be considered as a potential natural sensitizer for the construction of DSSCs. The results indicate that these pigments have a good performance in the absorbance and wavelength spectra. Were selected four best pigments for the construction of DSSCs, Rumex tolimensis Wedd, Raphanus sativus, Hibiscus sabdariffa, and Prunus serótina, however the conversion efficiency is lower than 1%.

Room-temperature processed films of colloidal carved rod-shaped nanocrystals of reduced tungsten oxide as interlayers for perovskite solar cells.

PubMed

Masi, Sofia; Mastria, Rosanna; Scarfiello, Riccardo; Carallo, Sonia; Nobile, Concetta; Gambino, Salvatore; Sibillano, Teresa; Giannini, Cinzia; Colella, Silvia; Listorti, Andrea; Cozzoli, P Davide; Rizzo, Aurora

2018-04-25

Thanks to their high stability, good optoelectronic and extraordinary electrochromic properties, tungsten oxides are among the most valuable yet underexploited materials for energy conversion applications. Herein, colloidal one-dimensional carved nanocrystals of reduced tungsten trioxide (WO3-x) are successfully integrated, for the first time, as a hole-transporting layer (HTL) into CH3NH3PbI3 perovskite solar cells with a planar inverted device architecture. Importantly, the use of such preformed nanocrystals guarantees the facile solution-cast-only deposition of a homogeneous WO3-x thin film at room temperature, allowing achievement of the highest power conversion efficiency ever reported for perovskite solar cells incorporating raw and un-doped tungsten oxide based HTL.

Cysteine optical sensing with an up-conversion host and two chemosensors derived from rhodamine: Construction, characterization and performance

NASA Astrophysics Data System (ADS)

Lin, Chen; Zhigang, Fang

2017-03-01

This paper focused on two rhodamine chemosensors for cysteine optical sensing. To minimize their photobleaching caused by excitation light, up-conversion NaYF4:Yb3 +/Er3 + nanocrystals were prepared and used as excitation host. Photophysical measurement on this host and the two chemosensors suggested that chemosensor absorption matched well with host emission. An efficient energy transfer between them was discussed and confirmed by their spectral analysis and emission lifetime comparison. Job's plot suggested that our chemosensors followed a simple recognition mechanism towards cysteine with binding stoichiometry of 1:1. Both chemosensors showed emission "off-on" effect triggered by cysteine and good photostability. Linear working curves with maximum sensitivity of 2.61 were obtained. S substituent was positive to improve selectivity.

Catalytic conversion of corncob and corncob pretreatment hydrolysate to furfural in a biphasic system with addition of sodium chloride.

PubMed

Qing, Qing; Guo, Qi; Zhou, Linlin; Wan, Yilun; Xu, Youqing; Ji, Huilong; Gao, Xiaohang; Zhang, Yue

2017-02-01

Catalytic conversion of corncob pretreatment hydrolysate and raw corncob into furfural in a modified biphasic system by SO 4 2- /SnO 2 - MMT solid catalyst has been developed. The influence of the organic solvent type, organic to water phase ratio, sodium chloride concentration, reaction temperature and time on the furfural production were comparatively evaluated. The results showed that furfural yields of 81.7% and 66.1% were achieved at 190°C for 15mins and 190°C for 20mins, respectively, for corncob pretreatment hydrolysate and raw corncob by this solid catalyst. The solid catalyst used in this study exhibited good stability and high efficiency applied in the modified biphasic system in addition to excellent recyclability. The proposed catalytic system displayed high performance for catalytic conversion of lignocellulosic biomass into important platform chemicals and has great potential in industrial application. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of microwave exposure on the photo anode of DSSC sensitized with natural dye

NASA Astrophysics Data System (ADS)

Swathi, K. E.; Jinchu, I.; Sreelatha, K. S.; Sreekala, C. O.; Menon, Sreedevi K.

2018-02-01

Dye Sensitized solar cells (DSSC) are also referred to as dye sensitised cells (DSC) or Graetzel cell are the device that converts solar energy in to electricity by the photovoltaic effect. This is the class of advanced cell that mimics the artificial photosynthesis. DSSC fabrication is simple and can be done using readily available low cost materials that are nontoxic, environment friendly and works even under low flux of sunlight. DSSC exhibits good efficiency of ~ 10-14 %. This paper emphasis on the study of enhancing the efficiency of DSSC by exposing the photo anode to microwave frequency. Effect of duration of microwave exposure at 2.6 GHz on energy efficiency of solar cell is studied in detail. The SEM analysis and dye desorption studies of the photo anode confirms an increased solar energy conversion efficiency of the DSSC.

Aqueous-Containing Precursor Solutions for Efficient Perovskite Solar Cells.

PubMed

Liu, Dianyi; Traverse, Christopher J; Chen, Pei; Elinski, Mark; Yang, Chenchen; Wang, Lili; Young, Margaret; Lunt, Richard R

2018-01-01

Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous-containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water-perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.

Analyses of conversion efficiency in high-speed clock recovery based on Mach-Zehnder modulator

NASA Astrophysics Data System (ADS)

Dong, H.; Sun, H.; Zhu, G.; Dutta, N. K.

2006-09-01

In this paper, detailed analyses of the conversion efficiency in high-speed clock recovery based on Mach-Zehnder (MZ) modulator has been carried out. The theoretical results show the conversion efficiency changes with RF driving power and the mixing order. For high order clock recovery, the cascaded MZ modulator provides higher conversion efficiency. A study of clock recovery at 160 Gb/s using the cascaded MZ modulator has been carried out. The experimental results agree with the results of the analysis.

Chapter 1: Reliably Measuring the Performance of Emerging Photovoltaic Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rumbles, Garry; Reese, Matthew O; Marshall, Ashley

Determining the power conversion efficiency of photovoltaic solar cells, especially those from new, emerging areas of technology, is important if advances in performance are to be made. However, although precise measurements are important, it is the accuracy of these types of measurements that can cause issues. Accurate measurements not only promote the development of new technology platforms, but they also enable comparisons with established technologies and allow assessments of advancements within the same field. This chapter provides insights into how measurements can be made with reasonable accuracy using both the components of the measuring system and a good protocol tomore » acquire good data. The chapter discusses how to measure a calibrated lamp spectrum, determine a spectral mismatch factor, identify the correct reference cell and filter, define the illuminated active area, measure J-V curves to avoid any hysteresis effects, take note of sample degradation issues and avoid the temptation to artificially enhance efficiency data.« less

The News Delivery Sequence: Bad News and Good News in Conversational Interaction.

ERIC Educational Resources Information Center

Maynard, Douglas W.

1997-01-01

Explores the conditional nature of good and bad news while focusing on three topics: (1) the status of information as news according the participants in a conversation; (2) the valence of this information with regard to its perception as good or bad; and (3) the effect of news on individuals. Notes that good news is privileged over bad news in…

ZnO Photoanode Effect on the Efficiency Performance of Organic Based Dye Sensitized Solar Cell

NASA Astrophysics Data System (ADS)

Mohamad, I. S.; Ismail, S. S.; Norizan, M. N.; Murad, S. A. Z.; Abdullah, M. M. A.

2017-06-01

Dye sensitized solar cell has been emerged as one of the most promising candidates for photovoltaics applications in good quality of their low manufacturing cost and impressive conversion energy. Titanium dioxide (TiO2) which is used as photoanode in the market has the advantage of wide bandgap energy but low in electron mobility (∼10 cm2/(V.s)). Ruthenium in the other hand, as the dye sensitizer is a rare noble metal and harmful to human health. Thus, this article reveals the performance of photo-to-electric conversion efficiency with the usage of Zinc Oxide as photoanode with higher electron mobility (155 cm2/(V.s)) compared to TiO2 utilizing three natural fruit dyes of Prunus domestica, Magnifera indica and Citrus limon. ZnO and TiO2 photoanodes were fabricated using sol gel and dr blade method respectively. The morphology of the photoanodes were characterized using Scanning Electron Microscope and the efficiency of the complete DSSC with all different fruit dyes were characterized using Semiconductor Parametric Analyzer. The different property of electron mobility photoanodes effect in DSSC proved to give better performance with the photoconversion efficiency of 3.082% using ZnO with Prunus domestica dye. This article also reveals that pH indicator does not affect the selection and the performance of DSSC.

Low temperature synthesis of hierarchical TiO 2 nanostructures for high performance perovskite solar cells by pulsed laser deposition

DOE PAGES

Yang, Bin; Mahjouri-Samani, Masoud; Rouleau, Christopher M.; ...

2016-06-10

A promising way to advance perovskite solar cells is to improve the quality of the electron transport material e.g., titanium dioxide (TiO 2) in a direction that increases electron transport and extraction. Although dense TiO 2 films are easily grown in solution, efficient electron extraction suffers due to a lack of interfacial contact area with the perovskite. Conversely, mesoporous films do offer high surface-area-to-volume ratios, thereby promoting efficient electron extraction, but their morphology is relatively difficult to control via conventional solution synthesis methods. Here, a pulsed laser deposition method was used to assemble TiO 2 nanoparticles into TiO 2 hierarchicalmore » nanoarchitectures having the anatase crystal structure, and prototype solar cells employing these structures yielded power conversion efficiencies of ~ 14%. Our approach demonstrates a way to grow high aspect-ratio TiO 2 nanostructures for improved interfacial contact between TiO 2 and perovskite materials, leading to high electron-hole pair separation and electron extraction efficiencies for superior photovoltaic performance. In addition, compared to conventional solution-processed TiO 2 films that require 500 °C to obtain a good crystallinity, our relatively low temperature (300 °C) TiO 2 processing method may promote reduced energy-consumption during device fabrication as well as enable compatibility with various flexible polymer substrates.« less

Effect of band-aligned double absorber layers on photovoltaic characteristics of chemical bath deposited PbS/CdS thin film solar cells.

PubMed

Ho Yeon, Deuk; Chandra Mohanty, Bhaskar; Lee, Seung Min; Soo Cho, Yong

2015-09-23

Here we report the highest energy conversion efficiency and good stability of PbS thin film-based depleted heterojunction solar cells, not involving PbS quantum dots. The PbS thin films were grown by the low cost chemical bath deposition (CBD) process at relatively low temperatures. Compared to the quantum dot solar cells which require critical and multistep complex procedures for surface passivation, the present approach, leveraging the facile modulation of the optoelectronic properties of the PbS films by the CBD process, offers a simpler route for optimization of PbS-based solar cells. Through an architectural modification, wherein two band-aligned junctions are stacked without any intervening layers, an enhancement of conversion efficiency by as much as 30% from 3.10 to 4.03% facilitated by absorption of a wider range of solar spectrum has been obtained. As an added advantage of the low band gap PbS stacked over a wide gap PbS, the devices show stability over a period of 10 days.

Revisiting Photoemission and Inverse Photoemission Spectra of Nickel Oxide from First Principles: Implications for Solar Energy Conversion

PubMed Central

2015-01-01

We use two different ab initio quantum mechanics methods, complete active space self-consistent field theory applied to electrostatically embedded clusters and periodic many-body G0W0 calculations, to reanalyze the states formed in nickel(II) oxide upon electron addition and ionization. In agreement with interpretations of earlier measurements, we find that the valence and conduction band edges consist of oxygen and nickel states, respectively. However, contrary to conventional wisdom, we find that the oxygen states of the valence band edge are localized whereas the nickel states at the conduction band edge are delocalized. We argue that these characteristics may lead to low electron–hole recombination and relatively efficient electron transport, which, coupled with band gap engineering, could produce higher solar energy conversion efficiency compared to that of other transition-metal oxides. Both methods find a photoemission/inverse-photoemission gap of 3.6–3.9 eV, in good agreement with the experimental range, lending credence to our analysis of the electronic structure of NiO. PMID:24689856

A general theory of DC electromagnetic launchers

NASA Astrophysics Data System (ADS)

Engel, Thomas G.; Timpson, Erik J.

2015-08-01

The non-linear, transient operation of DC electromagnetic launchers (EMLs) complicates their theoretical understanding and prevents scaling studies and performance comparisons without the aid of detailed numerical models. This paper presents a general theory for DC electromagnetic launchers that has simplified these tasks by identifying critical EML parameters and relationships affecting the EML's voltage, current, and power scaling, as well as its performance and energy conversion efficiency. EML parameters and relationships discussed in this paper include the specific force, the operating mode, the launcher constant, the launcher characteristic velocity, the contact characteristic velocity, the energy conversion efficiency, and the kinetic power and voltage-current scaling relationship. The concepts of the ideal EML, same-scale comparisons, and EML impedance are discussed. This paper defines conditions needed for the EML to operate in the steady-state. A comparison of the general theory with experimental results of several different types of DC (i.e., non-induction) electromagnetic launchers ranging from medium velocity (100's m/s) to high velocity (1000's m/s) is performed. There is good agreement between the general theory and the experimental results.

Overview of CMOS process and design options for image sensor dedicated to space applications

NASA Astrophysics Data System (ADS)

Martin-Gonthier, P.; Magnan, P.; Corbiere, F.

2005-10-01

With the growth of huge volume markets (mobile phones, digital cameras...) CMOS technologies for image sensor improve significantly. New process flows appear in order to optimize some parameters such as quantum efficiency, dark current, and conversion gain. Space applications can of course benefit from these improvements. To illustrate this evolution, this paper reports results from three technologies that have been evaluated with test vehicles composed of several sub arrays designed with some space applications as target. These three technologies are CMOS standard, improved and sensor optimized process in 0.35μm generation. Measurements are focussed on quantum efficiency, dark current, conversion gain and noise. Other measurements such as Modulation Transfer Function (MTF) and crosstalk are depicted in [1]. A comparison between results has been done and three categories of CMOS process for image sensors have been listed. Radiation tolerance has been also studied for the CMOS improved process in the way of hardening the imager by design. Results at 4, 15, 25 and 50 krad prove a good ionizing dose radiation tolerance applying specific techniques.

Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation.

PubMed

Suizu, Koji; Koketsu, Kaoru; Shibuya, Takayuki; Tsutsui, Toshihiro; Akiba, Takuya; Kawase, Kodo

2009-04-13

Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such a development of efficient and wide tunable THz-wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-wave generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-wave generation. Here, we show that Cherenkov radiation with waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide with 3.8 microm of thickness and demonstrated difference frequency generation of THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-wave generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10(-5) %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-wave sources.

New type of x-ray-wafer image intensifier with CsI-CsI/MCP photocathodes: its design and assessment

NASA Astrophysics Data System (ADS)

Xiang, Shiming; Zhao, Hong

1993-04-01

The article introduces a new type of x-ray wafer image intensifier with a double proximity focusing system, (Phi) 50 CsI-CsI/MCP photocathode, and a series of welding constructions of glass window or ceramic components with metal rings. This kind of x-ray image intensifier has been widely used in the field of medical diagnosis and industrial non-destructive detection by means of sophisticated portable x-ray diagnoscopes, featuring a number of satisfactory performances such as low x-ray dosage, miniature x-ray tube and power supply, high output brightness and good resolution, light weight, small volume, low cost, and easy operation without any condition constrained by working environment and illumination. In the paper, the authors have given a series of formulae to determine characteristic parameters of the device, i.e., the quantum detection efficiencies of both reflection mode (CsI/MCP) and transmission mode (glass window CsI/MCP) photocathode, the brightness conversion factor, and resolution. The relations of the mentioned parameters with the performances of constituent components, which include CsI photocathodes layer thickness, MCP bias angle and gain, phosphor screen conversion efficiency, and double proximity focusing distances, are also briefly analyzed. The analysis thought and methods mentioned in the paper have been successfully used for the optimal design and assessment work of our devices and shows that they have a good coincidence with experimental results.

Revealing the arc dynamics in a gliding arc plasmatron: a better insight to improve CO2 conversion

NASA Astrophysics Data System (ADS)

Ramakers, Marleen; Medrano, Jose A.; Trenchev, Georgi; Gallucci, Fausto; Bogaerts, Annemie

2017-12-01

A gliding arc plasmatron (GAP) is very promising for CO2 conversion into value-added chemicals, but to further improve this important application, a better understanding of the arc behavior is indispensable. Therefore, we study here for the first time the dynamic arc behavior of the GAP by means of a high-speed camera, for different reactor configurations and in a wide range of operating conditions. This allows us to provide a complete image of the behavior of the gliding arc. More specifically, the arc body shape, diameter, movement and rotation speed are analyzed and discussed. Clearly, the arc movement and shape relies on a number of factors, such as gas turbulence, outlet diameter, electrode surface, gas contraction and buoyance force. Furthermore, we also compare the experimentally measured arc movement to a state-of-the-art 3D-plasma model, which predicts the plasma movement and rotation speed with very good accuracy, to gain further insight in the underlying mechanisms. Finally, we correlate the arc dynamics with the CO2 conversion and energy efficiency, at exactly the same conditions, to explain the effect of these parameters on the CO2 conversion process. This work is important for understanding and optimizing the GAP for CO2 conversion.

Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells.

PubMed

Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

2016-06-15

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.

Limits to solar power conversion efficiency with applications to quantum and thermal systems

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.; Smith, B. T.

1983-01-01

An analytical framework is presented that permits examination of the limit to the efficiency of various solar power conversion devices. Thermodynamic limits to solar power efficiency are determined for both quantum and thermal systems, and the results are applied to a variety of devices currently considered for use in space systems. The power conversion efficiency for single-threshold energy quantum systems receiving unconcentrated air mass zero solar radiation is limited to 31 percent. This limit applies to photovoltaic cells directly converting solar radiation, or indirectly, as in the case of a thermophotovoltaic system. Photoelectrochemical cells rely on an additional chemical reaction at the semiconductor-electrolyte interface, which introduces additional second-law demands and a reduction of the solar conversion efficiency. Photochemical systems exhibit even lower possible efficiencies because of their relatively narrow absorption bands. Solar-powered thermal engines in contact with an ambient reservoir at 300 K and operating at maximum power have a peak conversion efficiency of 64 percent, and this occurs for a thermal reservoir at a temperature of 2900 K. The power conversion efficiency of a solar-powered liquid metal magnetohydrodydnamic generator, a solar-powered steam turbine electric generator, and an alkali metal thermoelectric converter is discussed.

Enzymatic hydrolysis of steam-pretreated lignocellulosic materials with Trichoderma atroviride enzymes produced in-house

PubMed Central

Kovacs, Krisztina; Macrelli, Stefano; Szakacs, George; Zacchi, Guido

2009-01-01

Background Improvement of the process of cellulase production and development of more efficient lignocellulose-degrading enzymes are necessary in order to reduce the cost of enzymes required in the biomass-to-bioethanol process. Results Lignocellulolytic enzyme complexes were produced by the mutant Trichoderma atroviride TUB F-1663 on three different steam-pretreated lignocellulosic substrates, namely spruce, wheat straw and sugarcane bagasse. Filter paper activities of the enzymes produced on the three materials were very similar, while β-glucosidase and hemicellulase activities were more dependent on the nature of the substrate. Hydrolysis of the enzyme preparations investigated produced similar glucose yields. However, the enzymes produced in-house proved to degrade the xylan and the xylose oligomers less efficiently than a commercial mixture of cellulase and β-glucosidase. Furthermore, accumulation of xylose oligomers was observed when the TUB F-1663 supernatants were applied to xylan-containing substrates, probably due to the low β-xylosidase activity of the enzymes. The efficiency of the enzymes produced in-house was enhanced by supplementation with extra commercial β-glucosidase and β-xylosidase. When the hydrolytic capacities of various mixtures of a commercial cellulase and a T. atroviride supernatant produced in the lab were investigated at the same enzyme loading, the glucose yield appeared to be correlated with the β-glucosidase activity, while the xylose yield seemed to be correlated with the β-xylosidase level in the mixtures. Conclusion Enzyme supernatants produced by the mutant T. atroviride TUB F-1663 on various pretreated lignocellulosic substrates have good filter paper activity values combined with high levels of β-glucosidase activities, leading to cellulose conversion in the enzymatic hydrolysis that is as efficient as with a commercial cellulase mixture. On the other hand, in order to achieve good xylan conversion, the supernatants produced by the mutant have to be supplemented with additional β-xylosidase activity. PMID:19580644

Fiber and fabric solar cells by directly weaving carbon nanotube yarns with CdSe nanowire-based electrodes

NASA Astrophysics Data System (ADS)

Zhang, Luhui; Shi, Enzheng; Ji, Chunyan; Li, Zhen; Li, Peixu; Shang, Yuanyuan; Li, Yibin; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai; Cao, Anyuan

2012-07-01

Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications of semiconducting nanowires and carbon nanotubes in woven photovoltaics.Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications of semiconducting nanowires and carbon nanotubes in woven photovoltaics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr31440a

Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells.

PubMed

Mane, Sandeep B; Sutanto, Albertus Adrian; Cheng, Chih-Fu; Xie, Meng-Yu; Chen, Chieh-I; Leonardus, Mario; Yeh, Shih-Chieh; Beyene, Belete Bedemo; Diau, Eric Wei-Guang; Chen, Chin-Ti; Hung, Chen-Hsiung

2017-09-20

The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH 3 NH 3 PbI 3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V oc = 1.09 V, J sc = 20.9 mA cm -2 , fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V oc = 1.07 V, J sc = 22.9 mA cm -2 , FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH 3 NH 3 PbI 3 .

Investigation for all polarization conversions of the guided-modes in a bending waveguide

NASA Astrophysics Data System (ADS)

Shi, Yunjie; Shang, Hongpeng; Sun, DeGui

2018-03-01

In this work, a new solution to the partial differential Maxwell equations is first derived to investigate all polarization conversions of the transverse and the longitudinal components of guided-modes in a bending waveguide. Then, for the silica-waveguides, the polarization conversion efficiencies are numerical calculated and a significant finding is that the transverse-longitudinal polarization conversion efficiency is much higher than that of transverse-transverse polarization conversion. Furthermore, the dependences of all the conversion efficiencies on waveguide parameters are found. The agreeable results between the numerical calculation and the finite difference time-domain (FDTD) simulation show that for two 100 μm long bending waveguides of 0.75 and 1.50% index contrasts, the amplitude conversion efficiencies from ∼10-3 to ∼10-2 can be realized for the transverse-transverse polarization components and that of ∼10-1 can be realized for the transverse-longitudinal polarization components.

Physical effects of DCNQI derivatives doping as an N type organic semiconductor in organic photovoltaic cell performance.

PubMed

Lee, Joo Hyung; Oh, Se Young

2014-08-01

In the previous work, we have reported that organic photovoltaic (OPV) cells using DMDCNQI as an n-type second dopant material showed a high power conversion efficiency (PCE). In the present work, we have synthesized a novel DHDCNQI with long alkyl chains to improve the compatibility between the DHDCNQI dopant molecule and host P3HT polymer. We have fabricated OPV cells consisting of ITO/PEDOT:PSS/P3HT:PCBM:DHDCNQI/Al. We have investigated the characteristics of theses OPV cells using DCNQI derivative dopants from the measurements of the incident photon-to-current collection efficiency and photocurrent. The OPV cell using 3 wt% DHDCNQI exhibited a high PCE of 3.29% due to the high charge separation efficiency, good compatibility and low trap site effect.

A 1 kW-class multi-stage heat-driven thermoacoustic cryocooler system operating at liquefied natural gas temperature range

NASA Astrophysics Data System (ADS)

Zhang, L. M.; Hu, J. Y.; Wu, Z. H.; Luo, E. C.; Xu, J. Y.; Bi, T. J.

2015-07-01

This article introduces a multi-stage heat-driven thermoacoustic cryocooler capable of reaching cooling capacity about 1 kW at liquefied natural gas temperature range without any moving mechanical parts. The cooling system consists of an acoustically resonant double-acing traveling wave thermoacoustic heat engine and three identical pulse tube coolers. Unlike other traditional traveling wave thermoacoustic heat engines, the acoustically resonant double-acting thermoacoustic heat engine is a closed-loop configuration consists of three identical thermoacoustic conversion units. Each pulse tube cooler is bypass driven by one thermoacoustic heat engine unit. The device is acoustically completely symmetric and therefore "self-matching" for efficient traveling-wave thermoacoustic conversion. In the experiments, with 7 MPa helium gas as working gas, when the heating temperature reaches 918 K, total cooling capacity of 0.88 kW at 110 K is obtained with a resonant frequency of about 55 Hz. When the heating temperature is 903 K, a maximum total cooling capacity at 130 K of 1.20 kW is achieved, with a thermal-to-cold exergy efficiency of 8%. Compared to previously developed heat-driven thermoacoustic cryocoolers, this device has higher thermal efficiency and higher power density. It shows a good prospect of application in the field of natural gas liquefaction and recondensation.

Conversion of CO2 to CO using radio-frequency atmospheric pressure plasmas

NASA Astrophysics Data System (ADS)

Foote, Alexander; Dedrick, James; O'Connell, Deborah; North, Michael; Gans, Timo

2016-09-01

Low temperature plasmas can be used for the in situ generation of CO, from relatively non-toxic CO2 . CO is very useful in many industrial chemical processes and so, via low temperature plasmas, CO2, a waste product, can be converted into a valuable chemical. The key challenges in using this method, for CO production, are optimising the energy efficiency, maximising the conversion of CO2 into CO and then separating the CO from the other species produced in the plasma. Very high yields of CO, greater than 90%, have been achieved at atmospheric pressure using argon as a carrier gas with admixtures up to 1.5% with energy efficiencies of up to 4%. The plasma generated in continuous and spatially homogeneous and is driven at a frequency of 40.68 MHz. A zero dimensional global model has also been used to simulate the chemical kinetics of the plasma to determine the dominant dissociation processes and is in good agreement with the experimentally determined yields. The model is used to determine how important a role the vibrational states of CO2 are, in a highly collisional plasma, to the production of CO and there can provide insight into how to improve the energy efficiency and suppress unwanted reactions.

Cobalt selenide hollow nanorods array with exceptionally high electrocatalytic activity for high-efficiency quasi-solid-state dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Jin, Zhitong; Zhang, Meirong; Wang, Min; Feng, Chuanqi; Wang, Zhong-Sheng

2018-02-01

In quasi-solid-state dye-sensitized solar cells (QSDSSCs), electron transport through a random network of catalyst in the counter electrode (CE) and electrolyte diffusion therein are limited by the grain boundaries of catalyst particles, thus diminishing the electrocatalytic performance of CE and the corresponding photovoltaic performance of QSDSSCs. We demonstrate herein an ordered Co0.85Se hollow nanorods array film as the Pt-free CE of QSDSSCs. The Co0.85Se hollow nanorods array displays excellent electrocatalytic activity for the reduction of I3- in the quasi-solid-state electrolyte with extremely low charge transfer resistance at the CE/electrolyte interface, and the diffusion of redox species within the Co0.85Se hollow nanorods array CE is pretty fast. The QSDSSC device with the Co0.85Se hollow nanorods array CE produces much higher photovoltaic conversion efficiency (8.35%) than that (4.94%) with the Co0.85Se randomly packed nanorods CE, against the control device with the Pt CE (7.75%). Moreover, the QSDSSC device based on the Co0.85Se hollow nanorods array CE presents good long-term stability with only 4% drop of power conversion efficiency after 1086 h one-sun soaking.

High efficiency ZnO-based dye-sensitized solar cells with a 1H,1H,2H,2H-perfluorodecyltriethoxysilane chain barrier for cutting on interfacial recombination

NASA Astrophysics Data System (ADS)

Xie, Yahong; Zhou, Xiaofeng; Mi, Hongyu; Ma, Junhong; Yang, Jianya; Cheng, Jian

2018-03-01

Charge recombination at the ZnO photoanode/electrolyte interface is one of the major limitations for high performance dye-sensitized solar cells (DSSCs) toward their theoretical power conversion efficiency (PCE). Here, we proposed an efficient approach for reducing this interfacial losses and consequently facilitating charge transfer by decorating a hydrophobic thin-film on the surface of the dye-coated zinc oxide photoanode via 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) hexane solution immersing. As a result, a high PCE of 8.22% was obtained, which far exceeded the efficiency of 5.40% in a conventional DSSC without PFDTES treatment. Furthermore, PFDTES treatment also largely elongated the lifetime of photogenerated electrons, and maintained a good photo-response at the photoelectrode. This work provides a comprehensive explanation of electron injection, transfer and recombination at the ZnO photoanode/electrolyte interface, and a promising strategy to explore high efficiency ZnO-based DSSCs.

Carbon-Coated Honeycomb Ni-Mn-Co-O Inverse Opal: A High Capacity Ternary Transition Metal Oxide Anode for Li-ion Batteries

PubMed Central

McNulty, David; Geaney, Hugh; O’Dwyer, Colm

2017-01-01

We present the formation of a carbon-coated honeycomb ternary Ni-Mn-Co-O inverse opal as a conversion mode anode material for Li-ion battery applications. In order to obtain high capacity via conversion mode reactions, a single phase crystalline honeycombed IO structure of Ni-Mn-Co-O material was first formed. This Ni-Mn-Co-O IO converts via reversible redox reactions and Li2O formation to a 3D structured matrix assembly of nanoparticles of three (MnO, CoO and NiO) oxides, that facilitates efficient reactions with Li. A carbon coating maintains the structure without clogging the open-worked IO pore morphology for electrolyte penetration and mass transport of products during cycling. The highly porous IO was compared in a Li-ion half-cell to nanoparticles of the same material and showed significant improvement in specific capacity and capacity retention. Further optimization of the system was investigated by incorporating a vinylene carbonate additive into the electrolyte solution which boosted performance, offering promising high-rate performance and good capacity retention over extended cycling. The analysis confirms the possibility of creating a ternary transition metal oxide material with binder free accessible open-worked structure to allow three conversion mode oxides to efficiently cycle as an anode material for Li-ion battery applications. PMID:28186183

Microfluidic Analysis with Front-Face Fluorometric Detection for the Determination of Total Inorganic Iodine in Drinking Water.

PubMed

Inpota, Prawpan; Strzelak, Kamil; Koncki, Robert; Sripumkhai, Wisaroot; Jeamsaksiri, Wutthinan; Ratanawimarnwong, Nuanlaor; Wilairat, Prapin; Choengchan, Nathawut; Chantiwas, Rattikan; Nacapricha, Duangjai

2018-01-01

A microfluidic method with front-face fluorometric detection was developed for the determination of total inorganic iodine in drinking water. A polydimethylsiloxane (PDMS) microfluidic device was employed in conjunction with the Sandell-Kolthoff reaction, in which iodide catalyzed the redox reaction between Ce(IV) and As(III). Direct alignment of an optical fiber attached to a spectrofluorometer was used as a convenient detector for remote front-face fluorometric detection. Trace inorganic iodine (IO 3 - and I - ) present naturally in drinking water was measured by on-line conversion of iodate to iodide for determination of total inorganic iodine. On-line conversion efficiency of iodate to iodide using the microfluidic device was investigated. Excellent conversion efficiency of 93 - 103% (%RSD = 1.6 - 11%) was obtained. Inorganic iodine concentrations in drinking water samples were measured, and the results obtained were in good agreement with those obtained by an ICP-MS method. Spiked sample recoveries were in the range of 86%(±5) - 128%(±8) (n = 12). Interference of various anions and cations were investigated with tolerance limit concentrations ranging from 10 -6 to 2.5 M depending on the type of ions. The developed method is simple and convenient, and it is a green method for iodine analysis, as it greatly reduces the amount of toxic reagent consumed with reagent volumes in the microfluidic scale.

Carbon-Coated Honeycomb Ni-Mn-Co-O Inverse Opal: A High Capacity Ternary Transition Metal Oxide Anode for Li-ion Batteries.

PubMed

McNulty, David; Geaney, Hugh; O'Dwyer, Colm

2017-02-10

We present the formation of a carbon-coated honeycomb ternary Ni-Mn-Co-O inverse opal as a conversion mode anode material for Li-ion battery applications. In order to obtain high capacity via conversion mode reactions, a single phase crystalline honeycombed IO structure of Ni-Mn-Co-O material was first formed. This Ni-Mn-Co-O IO converts via reversible redox reactions and Li 2 O formation to a 3D structured matrix assembly of nanoparticles of three (MnO, CoO and NiO) oxides, that facilitates efficient reactions with Li. A carbon coating maintains the structure without clogging the open-worked IO pore morphology for electrolyte penetration and mass transport of products during cycling. The highly porous IO was compared in a Li-ion half-cell to nanoparticles of the same material and showed significant improvement in specific capacity and capacity retention. Further optimization of the system was investigated by incorporating a vinylene carbonate additive into the electrolyte solution which boosted performance, offering promising high-rate performance and good capacity retention over extended cycling. The analysis confirms the possibility of creating a ternary transition metal oxide material with binder free accessible open-worked structure to allow three conversion mode oxides to efficiently cycle as an anode material for Li-ion battery applications.

Silicon trench photodiodes on a wafer for efficient X-ray-to-current signal conversion using side-X-ray-irradiation mode

NASA Astrophysics Data System (ADS)

Ariyoshi, Tetsuya; Takane, Yuta; Iwasa, Jumpei; Sakamoto, Kenji; Baba, Akiyoshi; Arima, Yutaka

2018-04-01

In this paper, we report a direct-conversion-type X-ray sensor composed of trench-structured silicon photodiodes, which achieves a high X-ray-to-current conversion efficiency under side X-ray irradiation. The silicon X-ray sensor with a length of 22.6 mm and a trench depth of 300 µm was fabricated using a single-poly single-metal 0.35 µm process. X-rays with a tube voltage of 80 kV were irradiated along the trench photodiode from the side of the test chip. The theoretical limit of X-ray-to-current conversion efficiency of 83.8% was achieved at a low reverse bias voltage of 25 V. The X-ray-to-electrical signal conversion efficiency of conventional indirect-conversion-type X-ray sensors is about 10%. Therefore, the developed sensor has a conversion efficiency that is about eight times higher than that of conventional sensors. It is expected that the developed X-ray sensor will be able to markedly lower the radiation dose required for X-ray diagnoses.

Estimating Hardwood Sawmill Conversion Efficiency Based on Sawing Machine and Log.

Treesearch

Michael W. Wade; Steven H. Bullard; Philip H. Steele; Philip A. Araman

1992-01-01

Increased problems of hardwood timber availability have caused many sawmillers, industry analysts, and planners to recognize the importance of sawmill conversion efficiency. Conversion efficiency not only affects sawmill profits, but is also important on a much broader level. Timber supply issues have caused resource planners and policy makers to consider the effects...

Current matching using CdSe quantum dots to enhance the power conversion efficiency of InGaP/GaAs/Ge tandem solar cells.

PubMed

Lee, Ya-Ju; Yao, Yung-Chi; Tsai, Meng-Tsan; Liu, An-Fan; Yang, Min-De; Lai, Jiun-Tsuen

2013-11-04

A III-V multi-junction tandem solar cell is the most efficient photovoltaic structure that offers an extremely high power conversion efficiency. Current mismatching between each subcell of the device, however, is a significant challenge that causes the experimental value of the power conversion efficiency to deviate from the theoretical value. In this work, we explore a promising strategy using CdSe quantum dots (QDs) to enhance the photocurrent of the limited subcell to match with those of the other subcells and to enhance the power conversion efficiency of InGaP/GaAs/Ge tandem solar cells. The underlying mechanism of the enhancement can be attributed to the QD's unique capacity for photon conversion that tailors the incident spectrum of solar light; the enhanced efficiency of the device is therefore strongly dependent on the QD's dimensions. As a result, by appropriately selecting and spreading 7 mg/mL of CdSe QDs with diameters of 4.2 nm upon the InGaP/GaAs/Ge solar cell, the power conversion efficiency shows an enhancement of 10.39% compared to the cell's counterpart without integrating CdSe QDs.

The impact of donor policies in Europe: a steady increase, but not everywhere

PubMed Central

Coppen, Remco; Friele, Roland D; Gevers, Sjef KM; Blok, Geke A; van der Zee, Jouke

2008-01-01

Background Transplantable organs are scarce everywhere. Therefore, countries have developed policies to support the efficient use of potential donors. Nevertheless, the shortage of organs remains. Were these policies in vain? The aim of this study is to assess the impact of donor policies on donor procurement in 10 Western European countries from 1995 to 2005. Method To assess the impact of the donor policies we studied the conversion of potential donors into effectuated donors. 80% of the donors died from CVAs or a (traffic) accident. We considered these mortality rates to be a good proxy for potential donors. Here we call the conversion of potential donors into actual donors 'the donor efficiency rate by proxy'. Results The mortality rates for CVA and (traffic) accidents have decreased in the countries under study. At the same time, in most countries the donor efficiency rates have steadily increased. The variance in donor efficiency rates between countries has also increased from 1995 to 2005. Four countries introduced a new consent system or changed their existing system, without (visible) long-term effects. Conclusion The overall increase in donor efficiency means that the efforts to improve donor policies have paid off. However, substantial differences between countries were found. The success of donor policies in terms of the number of absolute donors is blurred by the success of policies on traffic safety and CVA treatment. It remains unclear which specific policy measures are responsible for the increase in donor efficiency rates. This increase is not related to having a presumed consent system. Furthermore, an analysis of countries that introduced a new consent system or changed their system showed no effect on donor efficiency. PMID:19014536

Scalable UWB photonic generator based on the combination of doublet pulses.

PubMed

Moreno, Vanessa; Rius, Manuel; Mora, José; Muriel, Miguel A; Capmany, José

2014-06-30

We propose and experimentally demonstrate a scalable and reconfigurable optical scheme to generate high order UWB pulses. Firstly, various ultra wideband doublets are created through a process of phase-to-intensity conversion by means of a phase modulation and a dispersive media. In a second stage, doublets are combined in an optical processing unit that allows the reconfiguration of UWB high order pulses. Experimental results both in time and frequency domains are presented showing good performance related to the fractional bandwidth and spectral efficiency parameters.

Conjugated polymers and their use in optoelectronic devices

DOEpatents

Marks, Tobin J.; Guo, Xugang; Zhou, Nanjia; Chang, Robert P. H.; Drees, Martin; Facchetti, Antonio

2016-10-18

The present invention relates to certain polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The present compounds can provide improved device performance, for example, as measured by power conversion efficiency, fill factor, open circuit voltage, field-effect mobility, on/off current ratios, and/or air stability when used in photovoltaic cells or transistors. The present compounds can have good solubility in common solvents enabling device fabrication via solution processes.

Reduced T(sub c) Niobium Superconducting HEB Mixers

NASA Technical Reports Server (NTRS)

Siddiqi, I.; Prober, D. E.; Bumble, B.; LeDuc, H. G.

2001-01-01

A reduction in the mixer noise is expected when using superconductors with a lower transition temperature (T(sub c)) since the thermal noise components of the mixer noise should scale with T(sub c). Also, the local oscillator (LO) power required for a diffusion-cooled device should decrease as T(sub c) when T(sub bath) << T(sub c). We previously studied mixing in aluminum based hot-electron bolometers (HEBs) at microwave frequencies (approximately 30 GHz), and observed a significant improvement in noise performance, and a reduction in LO power as predicted. However, the bias voltage range over which good mixer performance was observed was approximately 5 - 10 microV. These devices are thus susceptible to saturation effects, in particular output saturation. In the present work, we have investigated Nb HEBs whose T(sub c) is lowered by applying a magnetic field. The goal is to study a case intermediate between Nb and Al, and hopefully to find properties that will allow use in practical receivers. A 15 kOe perpendicular magnetic field was applied to a Nb HEB (L = 0.16 micrometers, W = 0.08 micrometers, R(sub N) = 90 ohms) to reduce T(sub c) from 5.2 K to 2.4 K. The mixer noise, as inferred from the output noise and the conversion efficiency, decreased from 390 K, DSB to 171 K, DSB. The LO power required for near optimum mixer conversion efficiency (eta(sub mixer) = -9 dB in this device) was 8 nW in zero field, and approximately 2 nW when T(sub c) was reduced to 2.4 K. T(sub bath) = 0.22 K. The conversion bandwidth was previously measured to be 2.4 GHz and the same bandwidth was observed in the presence of a magnetic field. By lowering T(sub c), the voltage range over which good mixing was observed also decreased. However, even with T(sub c) reduced to 2.4 K, the conversion efficiency dropped by 3 dB from its maximum value only when the bias voltage was changed by approximately 90 microV. Saturation effects should thus be much less of a concern in these devices than in Al HEBS. In situations where the application of a large magnetic field is not feasible, we suggest using Ta based HEBS. Ta HEBs should have T(sub c) = 3 - 3.5 K and material properties very similar to Nb.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells

NASA Astrophysics Data System (ADS)

Sahin, Mehmet

2018-05-01

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p–n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy () of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same . The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same , become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Near-IR, blue, and UV generation by frequency conversion of a Tm:YAP laser

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew; Chinn, Steve

2018-02-01

We describe generation of near-infrared (944nm, 970nm), blue (472nm, 485nm), and UV (236 nm) light by frequency up-conversion of 2 μm output of a compact and efficient passively Q-switched Tm:YAP laser. The Tm:YAP laser source was near diffraction limited with maximum Q-switched pulse peak power of 190 kW. For second harmonic generation (SHG) of NIR, both periodically poled lithium niobate (PPLN) and lithium tri-borate (LBO) were evaluated, with 58% conversion efficiency and 3.1 W of 970 nm power achieved with PPLN. The PPLN 970nm emission was frequency doubled in 20mm long type I LBO, generating 1.1 W at 485nm with a conversion efficiency of 34%. With LBO used for frequency doubling of 2.3 W of 1888 nm Tm:YAP output to 944nm, 860mW was generated, with 37% conversion efficiency. Using a second LBO crystal to generate the 4th harmonic, 545mW of 472nm power was generated, corresponding to 64% conversion efficiency. To generate the 8th harmonic of Tm:YAP laser emission, the 472nm output of the second LBO was frequency doubled in a 7mm long BBO crystal, generating 110 mW at 236nm, corresponding to 21% conversion efficiency.

Status of photoelectrochemical production of hydrogen and electrical energy

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Walker, G. H.

1976-01-01

The efficiency for conversion of electromagnetic energy to chemical and electrical energy utilizing semiconductor single crystals as photoanodes in electrochemical cells was investigated. Efficiencies as high as 20 percent were achieved for the conversion of 330 nm radiation to chemical energy in the form of hydrogen by the photoelectrolysis of water in a SrTiO3 based cell. The SrTiO3 photoanodes were shown to be stable in 9.5 M NaOH solutions for periods up to 48 hours. Efficiencies of 9 percent were measured for the conversion of broadband visible radiation to hydrogen using n-type GaAs crystals as photoanodes. Crystals of GaAs coated with 500 nm of gold, silver, or tin for surface passivation show no significant change in efficiency. By suppressing the production of hydrogen in a CdSe-based photogalvanic cell, an efficiency of 9 percent was obtained in conversion of 633 nm light to electrical energy. A CdS-based photogalvanic cell produced a conversion efficiency of 5 percent for 500 nm radiation.

Hierarchical Graphene Foam for Efficient Omnidirectional Solar-Thermal Energy Conversion.

PubMed

Ren, Huaying; Tang, Miao; Guan, Baolu; Wang, Kexin; Yang, Jiawei; Wang, Feifan; Wang, Mingzhan; Shan, Jingyuan; Chen, Zhaolong; Wei, Di; Peng, Hailin; Liu, Zhongfan

2017-10-01

Efficient solar-thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar-thermal materials. Carbon-based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar-thermal energy conversion. However, to date, graphene-based solar-thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h-G foam) with continuous porosity grown via plasma-enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar-thermal energy conversion efficiency of the h-G foam impressively reaches up to ≈93.4%, and the solar-vapor conversion efficiency exceeds 90% for seawater desalination with high endurance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Status report on the fusion breeder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moir, R.W.

1980-12-12

The rationale for hybrid fusion-fission reactors is the production of fissile fuel for fission reactors. A new class of reactor, the fission-suppressed hybrid promises unusually good safety features as well as the ability to support 25 light-water reactors of the same nuclear power rating, or even more high-conversion-ratio reactors such as the heavy-water type. One 4000-MW nuclear hybrid can produce 7200 kg of /sup 233/U per year. To obtain good economics, injector efficiency times plasma gain (eta/sub i/Q) should be greater than 2, the wall load should be greater than 1 MW m/sup -2/, and the hybrid should cost lessmore » than 6 times the cost of a light-water reactor. Introduction rates for the fission-suppressed hybrid are unusually rapid.« less

Recyclable organic solar cells on cellulose nanocrystal substrates

PubMed Central

Zhou, Yinhua; Fuentes-Hernandez, Canek; Khan, Talha M.; Liu, Jen-Chieh; Hsu, James; Shim, Jae Won; Dindar, Amir; Youngblood, Jeffrey P.; Moon, Robert J.; Kippelen, Bernard

2013-01-01

Solar energy is potentially the largest source of renewable energy at our disposal, but significant advances are required to make photovoltaic technologies economically viable and, from a life-cycle perspective, environmentally friendly, and consequently scalable. Cellulose nanomaterials are emerging high-value nanoparticles extracted from plants that are abundant, renewable, and sustainable. Here, we report on the first demonstration of efficient polymer solar cells fabricated on optically transparent cellulose nanocrystal (CNC) substrates. The solar cells fabricated on the CNC substrates display good rectification in the dark and reach a power conversion efficiency of 2.7%. In addition, we demonstrate that these solar cells can be easily separated and recycled into their major components using low-energy processes at room temperature, opening the door for a truly recyclable solar cell technology. Efficient and easily recyclable organic solar cells on CNC substrates are expected to be an attractive technology for sustainable, scalable, and environmentally-friendly energy production. PMID:23524333

Recyclable organic solar cells on cellulose nanocrystal substrates.

PubMed

Zhou, Yinhua; Fuentes-Hernandez, Canek; Khan, Talha M; Liu, Jen-Chieh; Hsu, James; Shim, Jae Won; Dindar, Amir; Youngblood, Jeffrey P; Moon, Robert J; Kippelen, Bernard

2013-01-01

Solar energy is potentially the largest source of renewable energy at our disposal, but significant advances are required to make photovoltaic technologies economically viable and, from a life-cycle perspective, environmentally friendly, and consequently scalable. Cellulose nanomaterials are emerging high-value nanoparticles extracted from plants that are abundant, renewable, and sustainable. Here, we report on the first demonstration of efficient polymer solar cells fabricated on optically transparent cellulose nanocrystal (CNC) substrates. The solar cells fabricated on the CNC substrates display good rectification in the dark and reach a power conversion efficiency of 2.7%. In addition, we demonstrate that these solar cells can be easily separated and recycled into their major components using low-energy processes at room temperature, opening the door for a truly recyclable solar cell technology. Efficient and easily recyclable organic solar cells on CNC substrates are expected to be an attractive technology for sustainable, scalable, and environmentally-friendly energy production.

Effect of the Molecular Nature of Mutation on the Efficiency of Intrachromosomal Gene Conversion in Mouse Cells

PubMed Central

Letsou, Anthea; Liskay, R. Michael

1987-01-01

With the intent of further exploring the nature of gene conversion in mammalian cells, we systematically addressed the effects of the molecular nature of mutation on the efficiency of intrachromosomal gene conversion in cultured mouse cells. Comparison of conversion rates revealed that all mutations studied were suitable substrates for gene conversion; however, we observed that the rates at which different mutations converted to wild-type could differ by two orders of magnitude. Differences in conversion rates were correlated with the molecular nature of the mutations. In general, rates of conversion decreased with increasing size of the molecular lesions. In comparisons of conversion rates for single base pair insertions and deletions we detected a genotype-directed path for conversion, by which an insertion was converted to wild-type three to four times more efficiently than was a deletion which maps to the same site. The data are discussed in relation to current theories of gene conversion, and are consistent with the idea that gene conversion in mammalian cells can result from repair of heteroduplex DNA (hDNA) intermediates. PMID:2828159

A strategy to minimize the energy offset in carrier injection from excited dyes to inorganic semiconductors for efficient dye-sensitized solar energy conversion.

PubMed

Fujisawa, Jun-Ichi; Osawa, Ayumi; Hanaya, Minoru

2016-08-10

Photoinduced carrier injection from dyes to inorganic semiconductors is a crucial process in various dye-sensitized solar energy conversions such as photovoltaics and photocatalysis. It has been reported that an energy offset larger than 0.2-0.3 eV (threshold value) is required for efficient electron injection from excited dyes to metal-oxide semiconductors such as titanium dioxide (TiO2). Because the energy offset directly causes loss in the potential of injected electrons, it is a crucial issue to minimize the energy offset for efficient solar energy conversions. However, a fundamental understanding of the energy offset, especially the threshold value, has not been obtained yet. In this paper, we report the origin of the threshold value of the energy offset, solving the long-standing questions of why such a large energy offset is necessary for the electron injection and which factors govern the threshold value, and suggest a strategy to minimize the threshold value. The threshold value is determined by the sum of two reorganization energies in one-electron reduction of semiconductors and typically-used donor-acceptor (D-A) dyes. In fact, the estimated values (0.21-0.31 eV) for several D-A dyes are in good agreement with the threshold value, supporting our conclusion. In addition, our results reveal that the threshold value is possible to be reduced by enlarging the π-conjugated system of the acceptor moiety in dyes and enhancing its structural rigidity. Furthermore, we extend the analysis to hole injection from excited dyes to semiconductors. In this case, the threshold value is given by the sum of two reorganization energies in one-electron oxidation of semiconductors and D-A dyes.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells.

PubMed

Sahin, Mehmet

2018-05-23

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p-n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy ([Formula: see text]) of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same [Formula: see text]. The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same [Formula: see text], become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

A high-efficiency real-time digital signal averager for time-of-flight mass spectrometry.

PubMed

Wang, Yinan; Xu, Hui; Li, Qingjiang; Li, Nan; Huang, Zhengxu; Zhou, Zhen; Liu, Husheng; Sun, Zhaolin; Xu, Xin; Yu, Hongqi; Liu, Haijun; Li, David D-U; Wang, Xi; Dong, Xiuzhen; Gao, Wei

2013-05-30

Analog-to-digital converter (ADC)-based acquisition systems are widely applied in time-of-flight mass spectrometers (TOFMS) due to their ability to record the signal intensity of all ions within the same pulse. However, the acquisition system raises the requirement for data throughput, along with increasing the conversion rate and resolution of the ADC. It is therefore of considerable interest to develop a high-performance real-time acquisition system, which can relieve the limitation of data throughput. We present in this work a high-efficiency real-time digital signal averager, consisting of a signal conditioner, a data conversion module and a signal processing module. Two optimization strategies are implemented using field programmable gate arrays (FPGAs) to enhance the efficiency of the real-time processing. A pipeline procedure is used to reduce the time consumption of the accumulation strategy. To realize continuous data transfer, a high-efficiency transmission strategy is developed, based on a ping-pong procedure. The digital signal averager features good responsiveness, analog bandwidth and dynamic performance. The optimal effective number of bits reaches 6.7 bits. For a 32 µs record length, the averager can realize 100% efficiency with an extraction frequency below 31.23 kHz by modifying the number of accumulation steps. In unit time, the averager yields superior signal-to-noise ratio (SNR) compared with data accumulation in a computer. The digital signal averager is combined with a vacuum ultraviolet single-photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS). The efficiency of the real-time processing is tested by analyzing the volatile organic compounds (VOCs) from ordinary printed materials. In these experiments, 22 kinds of compounds are detected, and the dynamic range exceeds 3 orders of magnitude. Copyright © 2013 John Wiley & Sons, Ltd.

Simulation and experimental study of a novel bifacial structure of silicon heterojunction solar cell for high efficiency and low cost

NASA Astrophysics Data System (ADS)

Huang, Haibin; Tian, Gangyu; Zhou, Lang; Yuan, Jiren; Fahrner, Wolfgang R.; Zhang, Wenbin; Li, Xingbing; Chen, Wenhao; Liu, Renzhong

2018-03-01

A novel structure of Ag grid/SiN x /n+-c-Si/n-c-Si/i-a-Si:H/p+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifacial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current (J sc), while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover, real cells composed of the novel structure with dimensions of 75 mm ×75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the J sc of 41.7 mA/cm2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm2. We conclude that the configuration of the Ag grid/SiN x /n+-c-Si/n-c-Si/i-a-Si:H/p+-a-Si:H/TCO/Ag grid is a promising structure for high efficiency and low cost. Project supported by the Jiangxi Provincial Key Research and Development Foundation, China (Grant No. 2016BBH80043), the Open Fund of Jiangsu Key Laboratory of Materials and Technology for Energy Conversion, China (Grant No. NJ20160032), and the National Natural Science Foundation of China (Grant Nos. 61741404, 61464007, and 51561022).

Efficient and selective molecular catalyst for the CO2-to-CO electrochemical conversion in water.

PubMed

Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel; Tatin, Arnaud

2015-06-02

Substitution of the four paraphenyl hydrogens of iron tetraphenylporphyrin by trimethylammonio groups provides a water-soluble molecule able to catalyze the electrochemical conversion of carbon dioxide into carbon monoxide. The reaction, performed in pH-neutral water, forms quasi-exclusively carbon monoxide with very little production of hydrogen, despite partial equilibration of CO2 with carbonic acid-a low pKa acid. This selective molecular catalyst is endowed with a good stability and a high turnover frequency. On this basis, prescribed composition of CO-H2 mixtures can be obtained by adjusting the pH of the solution, optionally adding an electroinactive buffer. The development of these strategies will be greatly facilitated by the fact that one operates in water. The same applies for the association of the cathode compartment with a proton-producing anode by means of a suitable separator.

Characterization and cysteine sensing performance of nanocomposites based on up-conversion excitation host and rhodamine-derived probes

NASA Astrophysics Data System (ADS)

Yuqing, Zhao; Yi, Xing; Lihua, Li; Juanjuan, Ma

2018-02-01

Optical sensing for cysteine (Cys) recognition is an interesting topic due to Cys biological participation. In this paper, two rhodamine-based chemosensors were designed for Cys optical sensing. For chemosensor photostability improvement, up-conversion nanocrystals were synthesized and used as excitation host. These nanocrystals were modified with a phase transfer reagent α-cyclodextrin (α-CD) to improve their compatibility with chemosensors. An efficient energy transfer from these nanocrystals to chemosensors under 980 nm radiation was observed and confirmed by spectral match analysis, energy transfer radius calculation and emission decay lifetime comparison. A direct bonding mechanism between Cys and chemosensors with bonding stoichiometry of 1:1 was established by Job's plot experiment. Given the presence of Cys, chemosensor emission was increased, showing emission turn on effect. These two chemosensors showed good selectivity, improved photostability and linear sensing response towards Cys.

Ultra-wideband and broad-angle linear polarization conversion metasurface

NASA Astrophysics Data System (ADS)

Sun, Hengyi; Gu, Changqing; Chen, Xinlei; Li, Zhuo; Liu, Liangliang; Martín, Ferran

2017-05-01

In this work, a metasurface acting as a linear polarization rotator, that can efficiently convert linearly polarized electromagnetic waves to cross polarized waves within an ultra wide frequency band and with a broad incident angle, is proposed. Based on the electric and magnetic resonant features of the unit cell, composed by a double-head arrow, a cut-wire, and two short V-shaped wire structures, three resonances, which lead to the bandwidth expansion of cross-polarization reflections, are generated. The simulation results show that an average polarization conversion ratio of 90% from 17.3 GHz to 42.2 GHz can be achieved. Furthermore, the designed metasurface exhibits polarization insensitivity within a broad incident angle, from 0° to 50°. The experiments conducted on the fabricated metasurface are in good agreement with the simulations. The proposed metasurface can find potential applications in reflector antennas, imaging systems, and remote sensors operating at microwave frequencies.

Nitrogen-doped carbon quantum dots from biomass via simple one-pot method and exploration of their application

NASA Astrophysics Data System (ADS)

Yang, Qiming; Duan, Jialong; Yang, Wen; Li, Xueming; Mo, Jinghui; Yang, Peizhi; Tang, Qunwei

2018-03-01

Pursuit of low-cost and large-scale method to prepare carbon quantum dots (CQDs) is a persistent objective in recent years. In this work, we have successfully synthesized a series of nitrogen-doped carbon quantum dots (N-CQDs) under different hydrothermal temperature employing Eichhornia crassipes (ECs) as precursors. Considering the pollution ability to water and low-cost, this study may direct the novel path to convert waste material to useful quantum dots. After measurements such as TEM, XRD, Raman, XPS, PL as well as the UV-vis absorbance ability, outstanding optical properties have been discovered. In this fashion, solar cells are tentative to be fabricated, yielding the maximized solar-to-electrical conversion efficiency of 0.17% with a good fill factor of 67%. Meanwhile, the above-mentioned quantum dots also show the up-conversion ability, suggesting the potential application in infrared detection or broadening light-absorbing devices.

Perovskite- and Heusler based materials for thermoelectric converters

NASA Astrophysics Data System (ADS)

Weidenkaff, Anke

2015-03-01

The broad application of thermoelectric converters in future energy technologies requires the development of active, stable, low cost and sustainable materials. Semiconductors based on perovskite and heusler structures show substantial potential for thermoelectric energy conversion processes. Their good performance can be explained based on their suitable band structure, adjusted charge carrier density, mass and mobility, limited phonon transport, electron filtering possibilities, strongly correlated electronic systems, etc. These properties are widely tuneable by following theoretical concepts and a deep composition-structure-property understanding to change the composition, structure and size of the crystallites in innovative scalable synthesis procedures. Improved thermoelectric materials are developed, synthesised and tested in diverse high temperature applications to improve the efficiency and energy density of the thermoelectric conversion process. The lecture will provide a summary on the field of advanced perovskite-type ceramics and Heusler compounds gaining importance for a large number of future energy technologies.

Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.

PubMed

Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

2014-06-14

The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell.

Degradable Hollow Mesoporous Silicon/Carbon Nanoparticles for Photoacoustic Imaging-Guided Highly Effective Chemo-Thermal Tumor Therapy in Vitro and in Vivo

PubMed Central

Zhang, Jinfeng; Zhang, Jun; Li, Wenyue; Chen, Rui; Zhang, Zhenyu; Zhang, Wenjun; Tang, Yongbing; Chen, Xiaoyuan; Liu, Gang; Lee, Chun-Sing

2017-01-01

The development of nanoscaled theranostic agents for cancer combination therapies has received intensive attention in recent years. In this report, a degradable hollow mesoporous PEG-Si/C-DOX NP is designed and fabricated for pH-responsive, photoacoustic imaging-guided highly effective chemo-thermal combination therapy. The intrinsic hollow mesoporous structure endows the as-synthesized nanoparticles (NPs) with a high drug loading capacity (31.1%). Under NIR (808 nm) irradiation, the photothermal conversion efficiency of the Si/C NPs is as high as 40.7%. Preferential accumulation of the PEG-Si/C-DOX NPs around tumor tissue was demonstrated with photoacoustic images. Cellular internalization of the NPs and release of the DOX in nuclei are shown with fluorescent images. With efficient NIR photothermal conversion and high DOX loading capacity, the PEG-Si/C-DOX NPs are demonstrated to have remarkable cancer-cell-killing ability and to achieve complete in vivo tumor elimination via combinational chemo-thermal therapy. Last but not least, the NPs show good biodegradability and biosafety, making them a promising candidate for multifunctional drug delivery and cancer theranostic. PMID:28839460

TiO2-Photoanode-Assisted Direct-Solar-Energy Harvesting and Storage in a Solar-Powered Redox Cell Using Halides as Active Materials.

PubMed

Zhang, Shun; Chen, Chen; Zhou, Yangen; Qian, Yumin; Ye, Jing; Xiong, Shiyun; Zhao, Yu; Zhang, Xiaohong

2018-06-27

The rapid deployment of renewable energy is resulting in significant energy security, climate change mitigation, and economic benefits. We demonstrate here the direct solar-energy harvesting and storage in a rechargeable solar-powered redox cell, which can be charged solely by solar irradiation. The cell follows a conventional redox-flow cell design with one integrated TiO 2 photoanode in the cathode side. Direct charging of the cell by solar irradiation results in the conversion of solar energy in to chemical energy. Whereas discharging the cell leads to the release of chemical energy in the form of electricity. The cell integrates energy conversion and storage processes in a single device, making the solar energy directly and efficiently dispatchable. When using redox couples of Br 2 /Br - and I 3 - /I - in the cathode side and anode side, respectively, the cell can be directly charged upon solar irradiation, yielding a discharge potential of 0.5 V with good round-trip efficiencies. This design is expected to be a potential alternative toward the development of affordable, inexhaustible, and clean solar-energy technologies.

Efficiency of Energy Harvesting in Ni-Mn-Ga Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Lindquist, Paul; Hobza, Tony; Patrick, Charles; Müllner, Peter

2018-03-01

Many researchers have reported on the voltage and power generated while energy harvesting using Ni-Mn-Ga shape memory alloys; few researchers report on the power conversion efficiency of energy harvesting. We measured the magneto-mechanical behavior and energy harvesting of Ni-Mn-Ga shape memory alloys to quantify the efficiency of energy harvesting using the inverse magneto-plastic effect. At low frequencies, less than 150 Hz, the power conversion efficiency is less than 0.1%. Power conversion efficiency increases with (i) increasing actuation frequency, (ii) increasing actuation stroke, and (iii) decreasing twinning stress. Extrapolating the results of low-frequency experiments to the kHz actuation regime yields a power conversion factor of about 20% for 3 kHz actuation frequency, 7% actuation strain, and 0.05 MPa twinning stress.

Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

Thermoelectric silicides: A review

NASA Astrophysics Data System (ADS)

Nozariasbmarz, Amin; Agarwal, Aditi; Coutant, Zachary A.; Hall, Michael J.; Liu, Jie; Liu, Runze; Malhotra, Abhishek; Norouzzadeh, Payam; Öztürk, Mehmet C.; Ramesh, Viswanath P.; Sargolzaeiaval, Yasaman; Suarez, Francisco; Vashaee, Daryoosh

2017-05-01

Traditional research on thermoelectric materials focused on improving the figure-of-merit z T to enhance the energy conversion efficiency. With further growth and commercialization of thermoelectric technology beyond niche applications, other factors such as materials availability, toxicity, cost, recyclability, thermal stability, chemical and mechanical properties, and ease of fabrication become important for making viable technologies. Several silicide alloys were identified that have the potential to fulfill these requirements. These materials are of interest due to their abundancy in earth’s crust (e.g., silicon), non-toxicity, and good physical and chemical properties. In this paper, an overview of the silicide thermoelectrics from traditional alloys to advanced material structures is presented. In addition, some of the most effective approaches as well as fundamental physical concepts for designing and developing efficient thermoelectric materials are presented and future perspectives are discussed.

Simultaneous enhancement of photo- and electroluminescence in white organic light-emitting devices by localized surface plasmons of silver nanoclusters

NASA Astrophysics Data System (ADS)

Yu, Jingting; Zhu, Wenqing; Shi, Guanjie; Zhai, Guangsheng; Qian, Bingjie; Li, Jun

2017-02-01

White organic light-emitting devices (WOLEDs) with enhanced current efficiency and negligible color shifting equipped with an internal color conversion layer (CCL) were fabricated. They were attained by embedding a single layer of silver nanoclusters (SNCs) between the CCL and light-emitting layer (EML). The simultaneous enhancement of the photoluminescence (PL) of the CCL and electroluminescence (EL) of the EML were realized by controlling the thickness and size of the SNCs to match the localized surface plasmon resonance spectrum with the PL spectrum of the CCL and the EL spectrum of the EML. The WOLED with optimal SNCs demonstrated a 25.81% enhancement in current efficiency at 60 mA cm-2 and good color stability over the entire range of current density.

Highly flexible InSnO electrodes on thin colourless polyimide substrate for high-performance flexible CH3NH3PbI3 perovskite solar cells

NASA Astrophysics Data System (ADS)

Park, Jeong-Il; Heo, Jin Hyuck; Park, Sung-Hyun; Hong, Ki Il; Jeong, Hak Gee; Im, Sang Hyuk; Kim, Han-Ki

2017-02-01

We fabricated high-performance flexible CH3NH3PbI3 (MAPbI3) perovskite solar cells with a power conversion efficiency of 15.5% on roll-to-roll sputtered ITO films on 60 μm-thick colourless polyimide (CPI) substrate. Due to the thermal stability of the CPI substrate, an ITO/CPI sample subjected to rapid thermal annealing at 300 °C showed a low sheet resistance of 57.8 Ω/square and high transmittance of 83.6%, which are better values than those of an ITO/PET sample. Outer and inner bending tests demonstrated that the mechanical flexibility of the ITO/CPI was superior to that of the conventional ITO/PET sample owing to the thinness of the CPI substrate. In addition, due to its good mechanical flexibility, the ITO/CPI showed no change in resistance after 10,000 cycle outer and inner dynamic fatigue tests. Flexible perovskite solar cells with the structure of Au/PTAA/MAPbI3/ZnO/ITO/CPI showed a high power conversion efficiency of 15.5%. The successful operation of these flexible perovskite solar cells on ITO/CPI substrate indicated that the ITO film on thermally stable CPI substrate is a promising of flexible substrate for high-temperature processing, a finding likely to advance the commercialization of cost-efficient flexible perovskite solar cells.

Highly-efficient enzymatic conversion of crude algal oils into biodiesel.

PubMed

Wang, Yao; Liu, Jin; Gerken, Henri; Zhang, Chengwu; Hu, Qiang; Li, Yantao

2014-11-01

Energy-intensive chemical conversion of crude algal oils into biodiesel is a major barrier for cost-effective algal biofuel production. To overcome this problem, we developed an enzyme-based platform for conversion of crude algal oils into fatty acid methyl esters. Crude algal oils were extracted from the oleaginous microalga Nannochloropsis oceanica IMET1 and converted by an immobilized lipase from Candida antarctica. The effects of different acyl acceptors, t-butanol as a co-solvent, oil to t-butanol ratio, oil to methanol ratio, temperature and reaction time on biodiesel conversion efficiency were studied. The conversion efficiency reached 99.1% when the conversion conditions were optimized, i.e., an oil to t-butanol weight ratio of 1:1, an oil to methanol molar ratio of 1:12, and a reaction time of 4h at 25°C. The enzymatic conversion process developed in this study may hold a promise for low energy consumption, low wastewater-discharge biochemical conversion of algal feedstocks into biofuels. Published by Elsevier Ltd.

Gold Redox Catalysis through Base-Initiated Diazonium Decomposition toward Alkene, Alkyne, and Allene Activation.

PubMed

Dong, Boliang; Peng, Haihui; Motika, Stephen E; Shi, Xiaodong

2017-08-16

The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au I catalyst was used in combination with Na 2 CO 3 and diazonium salts to produce a Au III intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au III reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Insight into D-A-π-A Structured Sensitizers: A Promising Route to Highly Efficient and Stable Dye-Sensitized Solar Cells.

PubMed

Wu, Yongzhen; Zhu, Wei-Hong; Zakeeruddin, Shaik M; Grätzel, Michael

2015-05-13

The dye-sensitized solar cell (DSSC) is one of the most promising photovoltaic technologies with potential of low cost, light weight, and good flexibility. The practical application of DSSCs requires further improvement in power conversion efficiency and long-term stability. Recently, significant progress has been witnessed in DSSC research owing to the novel concept of the D-A-π-A motif for the molecular engineering of organic photosensitizers. New organic and porphyrin dyes based on the D-A-π-A motif can not only enhance photovoltaic performance, but also improve durability in DSSC applications. This Spotlight on Applications highlights recent advances in the D-A-π-A-based photosensitizers, specifically focusing on the mechanism of efficiency and stability enhancements. Also, we find insight into the additional acceptor as well as the trade-off of long wavelength response. The basic principles are involved in molecular engineering of efficient D-A-π-A sensitizers, providing a clear road map showing how to modulate the energy bands, rationally extending the response wavelength, and optimizing photovoltaic efficiency step by step.

Fused thiophene-based conjugated polymers and their use in optoelectronic devices

DOEpatents

Facchetti, Antonio; Marks, Tobin J; Takai, Atsuro; Seger, Mark; Chen, Zhihua

2015-11-03

The present teachings relate to certain polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The disclosed compounds can provide improved device performance, for example, as measured by power conversion efficiency, fill factor, open circuit voltage, field-effect mobility, on/off current ratios, and/or air stability when used in photovoltaic cells or transistors. The disclosed compounds can have good solubility in common solvents enabling device fabrication via solution processes.

On Study of Application of Micro-reactor in Chemistry and Chemical Field

NASA Astrophysics Data System (ADS)

Zhang, Yunshen

2018-02-01

Serving as a micro-scale chemical reaction system, micro-reactor is characterized by high heat transfer efficiency and mass transfer, strictly controlled reaction time and good safety performance; compared with the traditional mixing reactor, it can effectively shorten reaction time by virtue of these advantages and greatly enhance the chemical reaction conversion rate. However, problems still exist in the process where micro-reactor is used for production in chemistry and chemical field, and relevant researchers are required to optimize and perfect the performance of micro-reactor. This paper analyzes specific application of micro-reactor in chemistry and chemical field.

CMOS-Compatible SOI MESFETS for Radiation-Hardened DC-to-DC Converters

NASA Technical Reports Server (NTRS)

Thornton, Trevor; Lepkowski, William; Wilk, Seth

2013-01-01

A radiation-tolerant transistor switch has been developed that can operate between 196 and +150 C for DC-to-DC power conversion applications. A prototype buck regulator component was demonstrated to be performing well after a total ionizing dose of 300 krad(Si). The prototype buck converters showed good efficiencies at ultra-high switching speeds in the range of 1 to 10 MHz. Such high switching frequency will enable smaller, lighter buck converters to be developed as part of the next project. Switching regulators are widely used in commercial applications including portable consumer electronics.

Maximum efficiency of state-space models of nanoscale energy conversion devices

NASA Astrophysics Data System (ADS)

Einax, Mario; Nitzan, Abraham

2016-07-01

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

Maximum efficiency of state-space models of nanoscale energy conversion devices.

PubMed

Einax, Mario; Nitzan, Abraham

2016-07-07

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

10.2% power conversion efficiency polymer tandem solar cells consisting of two identical sub-cells.

PubMed

You, Jingbi; Chen, Chun-Chao; Hong, Ziruo; Yoshimura, Ken; Ohya, Kenichiro; Xu, Run; Ye, Shenglin; Gao, Jing; Li, Gang; Yang, Yang

2013-08-07

Polymer tandem solar cells with 10.2% power conversion efficiency are demonstrated via stacking two PDTP-DFBT:PC₇₁ BM bulk heterojunctions, connected by MoO₃/PEDOT:PSS/ZnO as an interconnecting layer. The tandem solar cells increase the power conversion efficiency of the PDTP-DFBT:PC₇₁ BM system from 8.1% to 10.2%, successfully demonstrating polymer tandem solar cells with identical sub-cells of double-digit efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Research on Efficiency of a Wave Energy Conversion System

NASA Astrophysics Data System (ADS)

Lu, Zhongyue; Shang, Jianzhong; Luo, Zirong; Sun, Chongfei; Chen, Gewei

2018-02-01

The oceans are rich in wave energy that is green energy, and the wave energy are now being used to generate electricity on a massive scale. It can also be used as a single generator for beacon, buoy or underwater vehicle. Micro small wave energy power generation device is a kind of wave energy power generation devices, main characteristic is mobility is good, and can be directly assembled on various kinds of equipment for the power supply, with good prospects for development. The research object of the paper is a new adaptive reversing wave energy generating device belongs to micro-sized wave energy generating device. Using the upper and lower absorber blade groups, the low speed and large torque wave energy can be converted into electric energy which can be used for load and lithium battery charging.

A method for determining the conversion efficiency of multiple-cell photovoltaic devices

NASA Astrophysics Data System (ADS)

Glatfelter, Troy; Burdick, Joseph

A method for accurately determining the conversion efficiency of any multiple-cell photovoltaic device under any arbitrary reference spectrum is presented. This method makes it possible to obtain not only the short-circuit current, but also the fill factor, the open-circuit voltage, and hence the conversion efficiency of a multiple-cell device under any reference spectrum. Results are presented which allow a comparison of the I-V parameters of two-terminal, two- and three-cell tandem devices measured under a multiple-source simulator with the same parameters measured under different reference spectra. It is determined that the uncertainty in the conversion efficiency of a multiple-cell photovoltaic device obtained with this method is less than +/-3 percent.

In-use catalyst surface area and its relation to HC conversion efficiency and FTP emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donahue, K.S.; Sabourin, M.A.; Larson, R.E.

1986-01-01

Surface area data, steady-state hydrocarbon conversion efficiency data, and hydrocarbon emissions results have been determined for catalysts collected by the U.S. Environmental Protection Agency from properly maintained 1981 and 1982 model year vehicles. Catalysts covered in this study were limited to those with three-way-plus-oxidation monolith technologies. Catalyst surface areas were measured using the BET method, conversion efficiencies were measured on an exhaust gas generator, and emissions results were determined using the Urban Driving Schedule of the Federal Test Procedure. Results indicate that correlation of catalyst surface area data with hydrocarbon conversion efficiency data and hydrocarbon emissions results is significant formore » the sample studied.« less

Evidence of significant down-conversion in a Si-based solar cell using CuInS2/ZnS core shell quantum dots

NASA Astrophysics Data System (ADS)

Gardelis, Spiros; Nassiopoulou, Androula G.

2014-05-01

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS2/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

High-Efficiency Photovoltaic System Using Partially-Connected DC-DC Converter

NASA Astrophysics Data System (ADS)

Uno, Masatoshi; Kukita, Akio; Tanaka, Koji

Power conversion electronics for photovoltaic (PV) systems are desired to operate as efficiently as possible to exploit the power generated by PV modules. This paper proposes a novel PV system in which a dc-dc converter is partially connected to series-connected PV modules. The proposed system achieves high power-conversion efficiency by reducing the passing power and input/output voltages of the converter. The theoretical operating principle was experimentally validated. Resultant efficiency performances of the proposed and conventional systems demonstrated that the proposed system was more efficient in terms of power conversion though the identical converter was used for the both systems.

Exceeding the solar cell Shockley-Queisser limit via thermal up-conversion of low-energy photons

NASA Astrophysics Data System (ADS)

Boriskina, Svetlana V.; Chen, Gang

2014-03-01

Maximum efficiency of ideal single-junction photovoltaic (PV) cells is limited to 33% (for 1 sun illumination) by intrinsic losses such as band edge thermalization, radiative recombination, and inability to absorb below-bandgap photons. This intrinsic thermodynamic limit, named after Shockley and Queisser (S-Q), can be exceeded by utilizing low-energy photons either via their electronic up-conversion or via the thermophotovoltaic (TPV) conversion process. However, electronic up-conversion systems have extremely low efficiencies, and practical temperature considerations limit the operation of TPV converters to the narrow-gap PV cells. Here we develop a conceptual design of a hybrid TPV platform, which exploits thermal up-conversion of low-energy photons and is compatible with conventional silicon PV cells by using spectral and directional selectivity of the up-converter. The hybrid platform offers sunlight-to-electricity conversion efficiency exceeding that imposed by the S-Q limit on the corresponding PV cells across a broad range of bandgap energies, under low optical concentration (1-300 suns), operating temperatures in the range 900-1700 K, and in simple flat panel designs. We demonstrate maximum conversion efficiency of 73% under illumination by non-concentrated sunlight. A detailed analysis of non-ideal hybrid platforms that allows for up to 15% of absorption/re-emission losses yields limiting efficiency value of 45% for Si PV cells.

Development of a high efficiency thin silicon solar cell

NASA Technical Reports Server (NTRS)

Storti, G.; Culik, J.; Wrigley, C.

1980-01-01

Significant improvements in open-circuit voltage and conversion efficiency, even on relatively high bulk resistivity silicon, were achieved by using a screen-printed aluminum paste back surface field. A 4 sq cm 50 micron m thick cell was fabricated from textured 10 omega-cm silicon which had an open-circuit voltage of 595 mV and AMO conversion efficiency at 25 C of 14.3%. The best 4 sq cm 50 micron thick cell (2 omega-cm silicon) produced had an open-circuit voltage of 607 mV and an AMO conversion efficiency of 15%. Processing modifications are described which resulted in better front contact integrity and reduced breakage. These modifications were utilized in the thin cell pilot line to fabricate 4 sq cm cells with an average AMO conversion efficiency at 25 C of better than 12.5% and with lot yields as great as 51% of starts; a production rate of 10,000 cells per month was demonstrated. A pilot line was operated which produced large area (25 cm) ultra-thin cells with an average AMO conversion efficiency at 25 deg of better than 11.5% and a lot yield as high as 17%.

Amine-functionalized Zn(ii) MOF as an efficient multifunctional catalyst for CO2 utilization and sulfoxidation reaction.

PubMed

Patel, Parth; Parmar, Bhavesh; Kureshy, Rukhsana I; Khan, Noor-Ul H; Suresh, Eringathodi

2018-06-19

Herein, a zinc(ii)-based 3D mixed ligand metal organic framework (MOF) was synthesized via versatile routes including green mechanochemical synthesis. The MOF {[Zn(ATA)(L)·H2O]}n (ZnMOF-1-NH2) has been characterized by various physico-chemical techniques, including SCXRD, and composed of the bipyridyl-based Schiff base (E)-N'-(pyridin-4-ylmethylene)isonicotinohydrazide (L) and 2-aminoterephthalic acid (H2ATA) ligands as linkers. The MOF material has been explored as a multifunctional heterogeneous catalyst for the cycloaddition of alkyl and aryl epoxides with CO2 and sulfoxidation reactions of aryl sulfides. The influence of various reaction parameters is examined to optimize the performance of the catalytic reactions. It is found that solvent-free catalytic reaction conditions offer good catalytic conversion in the case of cyclic carbonates, and for sulfoxide, good conversion and selectivity are achieved in the presence of DCM as a solvent medium under ambient reaction conditions. The chemical and thermal stability of the catalyst are excellent and it is active for up to four catalytic cycles without significant loss in activity. Furthermore, based on the catalytic activity and structural evidence, a plausible mechanism for both catalytic reactions is proposed.

Identification of bioconversion quantitative trait loci in the interspecific cross Sorghum bicolor × Sorghum propinquum.

PubMed

Vandenbrink, Joshua P; Goff, Valorie; Jin, Huizhe; Kong, Wenqian; Paterson, Andrew H; Feltus, F Alex

2013-09-01

For lignocellulosic bioenergy to be economically viable, genetic improvements must be made in feedstock quality including both biomass total yield and conversion efficiency. Toward this goal, multiple studies have considered candidate genes and discovered quantitative trait loci (QTL) associated with total biomass accumulation and/or grain production in bioenergy grass species including maize and sorghum. However, very little research has been focused on genes associated with increased biomass conversion efficiency. In this study, Trichoderma viride fungal cellulase hydrolysis activity was measured for lignocellulosic biomass (leaf and stem tissue) obtained from individuals in a F5 recombinant inbred Sorghum bicolor × Sorghum propinquum mapping population. A total of 49 QTLs (20 leaf, 29 stem) were associated with enzymatic conversion efficiency. Interestingly, six high-density QTL regions were identified in which four or more QTLs overlapped. In addition to enzymatic conversion efficiency QTLs, two QTLs were identified for biomass crystallinity index, a trait which has been shown to be inversely correlated with conversion efficiency in bioenergy grasses. The identification of these QTLs provides an important step toward identifying specific genes relevant to increasing conversion efficiency of bioenergy feedstocks. DNA markers linked to these QTLs could be useful in marker-assisted breeding programs aimed at increasing overall bioenergy yields concomitant with selection of high total biomass genotypes.

Down-conversion emission of Ce3+-Tb3+ co-doped CaF2 hollow spheres and application for solar cells

NASA Astrophysics Data System (ADS)

Cheng, Yufei; Wang, Yongbo; Teng, Feng; Dong, Hua; Chen, Lida; Mu, Jianglong; Sun, Qian; Fan, Jun; Hu, Xiaoyun; Miao, Hui

2018-03-01

Luminescent downconversion is a promising way to harvest ultraviolet sunlight and transform it into visible light that can be absorbed by solar cells, and has potential to improve their photoelectric conversion efficiency. In this work, the uniform hollow spheres and well dispersed CaF2 phosphors doped with rare-earth Ce3+ and Tb3+ ions are prepared by a one-step hydrothermal synthesis method. Benefiting from the stronger ability of absorption and emission and excellent transparency property, we demonstrate that the application of the doped nanocrystals can efficiently improve visible light transmittance. The chosen phosphors are added in the SiO2 sols so as to get the anti-reflection coatings with wavelength conversion bi-functional films, promoting the optical transmittance in the visible and near-infrared range which matches with the range of the band gap energy of silicon semiconductor. Optimized photoelectric conversion efficiency of 14.35% and the external quantum efficiency over 70% from 450 to 950 nm are obtained through the silicon solar cells with 0.10 g phosphors coating. Compared with the pure glass devices, the photoelectric conversion efficiency is enhanced by 0.69%. This work indicates that fluorescent downconversion not only can serve as proof of principles for improving photoelectric conversion efficiency of solar cells but also may be helpful to practical application in the future.

75 FR 31461 - Notice of Submission of Proposed Information Collection to OMB; Emergency Comment Request...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-03

... Proposed Information Collection to OMB; Emergency Comment Request; Conversion of Efficiencies Units to One... via Housing Notice and attached forms to permit the conversion of efficiencies to one-bedrooms provided it can be demonstrated that the conversion is warranted by local demands and results in the long...

Potential use and the energy conversion efficiency analysis of fermentation effluents from photo and dark fermentative bio-hydrogen production.

PubMed

Zhang, Zhiping; Li, Yameng; Zhang, Huan; He, Chao; Zhang, Quanguo

2017-12-01

Effluent of bio-hydrogen production system also can be adopted to produce methane for further fermentation, cogeneration of hydrogen and methane will significantly improve the energy conversion efficiency. Platanus Orientalis leaves were taken as the raw material for photo- and dark-fermentation bio-hydrogen production. The resulting concentrations of acetic, butyric, and propionic acids and ethanol in the photo- and dark-fermentation effluents were 2966mg/L and 624mg/L, 422mg/L and 1624mg/L, 1365mg/L and 558mg/L, and 866mg/L and 1352mg/L, respectively. Subsequently, we calculated the energy conversion efficiency according to the organic contents of the effluents and their energy output when used as raw material for methane production. The overall energy conversion efficiencies increased by 15.17% and 22.28%, respectively, when using the effluents of photo and dark fermentation. This two-step bio-hydrogen and methane production system can significantly improve the energy conversion efficiency of anaerobic biological treatment plants. Copyright © 2017. Published by Elsevier Ltd.

Improving Si solar cell performance using Mn:ZnSe quantum dot-doped PLMA thin film

PubMed Central

2013-01-01

Poly(lauryl methacrylate) (PLMA) thin film doped with Mn:ZnSe quantum dots (QDs) was spin-deposited on the front surface of Si solar cell for enhancing the solar cell efficiency via photoluminescence (PL) conversion. Significant solar cell efficiency enhancements (approximately 5% to 10%) under all-solar-spectrum (AM0) condition were observed after QD-doped PLMA coatings. Furthermore, the real contribution of the PL conversion was precisely assessed by investigating the photovoltaic responses of the QD-doped PLMA to monochromatic and AM0 light sources as functions of QD concentration, combined with reflectance and external quantum efficiency measurements. At a QD concentration of 1.6 mg/ml for example, among the efficiency enhancement of 5.96%, about 1.04% was due to the PL conversion, and the rest came from antireflection. Our work indicates that for the practical use of PL conversion in solar cell performance improvement, cautions are to be taken, as the achieved efficiency enhancement might not be wholly due to the PL conversion. PMID:23787125

Thermionic/AMTEC cascade converter concept for high-efficiency space power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagan, T.H. van; Smith, J.N. Jr.; Schuller, M.

1996-12-31

This paper presents trade studies that address the use of the thermionic/AMTEC cell--a cascaded, high-efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as highmore » as 35--40%, such a cascade offers the following perceived benefits: survivability; simplicity; technology readiness; and technology growth. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems.« less

Radiated microwave power transmission system efficiency measurements

NASA Technical Reports Server (NTRS)

Dickinson, R. M.; Brown, W. C.

1975-01-01

The measured and calculated results from determining the operating efficiencies of a laboratory version of a system for transporting electric power from one point to another via a wireless free space radiated microwave beam are reported. The system's overall end-to-end efficiency as well as intermediated conversion efficiencies were measured. The maximum achieved end-to-end dc-to-ac system efficiency was 54.18% with a probable error of + or - 0.94%. The dc-to-RF conversion efficiency was measured to be 68.87% + or - 1.0% and the RF-to-dc conversion efficiency was 78.67 + or - 1.1%. Under these conditions a dc power of 495.62 + or - 3.57 W was received with a free space transmitter antenna receiver antenna separation of 170.2 cm (67 in).

Enhanced Conversion Efficiency of III–V Triple-junction Solar Cells with Graphene Quantum Dots

PubMed Central

Lin, Tzu-Neng; Santiago, Svette Reina Merden S.; Zheng, Jie-An; Chao, Yu-Chiang; Yuan, Chi-Tsu; Shen, Ji-Lin; Wu, Chih-Hung; Lin, Cheng- An J.; Liu, Wei-Ren; Cheng, Ming-Chiang; Chou, Wu-Ching

2016-01-01

Graphene has been used to synthesize graphene quantum dots (GQDs) via pulsed laser ablation. By depositing the synthesized GQDs on the surface of InGaP/InGaAs/Ge triple-junction solar cells, the short-circuit current, fill factor, and conversion efficiency were enhanced remarkably. As the GQD concentration is increased, the conversion efficiency in the solar cell increases accordingly. A conversion efficiency of 33.2% for InGaP/InGaAs/Ge triple-junction solar cells has been achieved at the GQD concentration of 1.2 mg/ml, corresponding to a 35% enhancement compared to the cell without GQDs. On the basis of time-resolved photoluminescence, external quantum efficiency, and work-function measurements, we suggest that the efficiency enhancement in the InGaP/InGaAs/Ge triple-junction solar cells is primarily caused by the carrier injection from GQDs to the InGaP top subcell. PMID:27982073

A theoretical analysis of the current-voltage characteristics of solar cells. [and their energy conversion efficiency

NASA Technical Reports Server (NTRS)

Dunbar, P. M.; Hauser, J. R.

1976-01-01

Various mechanisms which limit the conversion efficiency of silicon solar cells were studied. The effects of changes in solar cell geometry such as layer thickness on performance were examined. The effects of various antireflecting layers were also examined. It was found that any single film antireflecting layer results in a significant surface loss of photons. The use of surface texturing techniques or low loss antireflecting layers can enhance by several percentage points the conversion efficiency of silicon cells. The basic differences between n(+)-p-p(+) and p(+)-n-n(+) cells are treated. A significant part of the study was devoted to the importance of surface region lifetime and heavy doping effects on efficiency. Heavy doping bandgap reduction effects are enhanced by low surface layer lifetimes, and conversely, the reduction in solar cell efficiency due to low surface layer lifetime is further enhanced by heavy doping effects. A series of computer studies is reported which seeks to determine the best cell structure and doping levels for maximum efficiency.

Efficient second-harmonic conversion of CW single-frequency Nd:YAG laser light by frequency locking to a monolithic ring frequency doubler

NASA Technical Reports Server (NTRS)

Gerstenberger, D. C.; Tye, G. E.; Wallace, R. W.

1991-01-01

Efficient second-harmonic conversion of the 1064-nm output of a diode-pumped CW single-frequency Nd:YAG laser to 532 nm was obtained by frequency locking the laser to a monolithic ring resonator constructed of magnesium-oxide-doped lithium niobate. The conversion efficiency from the fundamental to the second harmonic was 65 percent. Two hundred milliwatts of CW single-frequency 532-nm light were produced from 310 mW of power of 1064-nm light. This represents a conversion efficiency of 20 percent from the 1-W diode laser used to pump the Nd:YAG laser to single-frequency 532-nm output. No signs of degradation were observed for over 500 h of operation.

Ethanol production from renewable resources.

PubMed

Gong, C S; Cao, N J; Du, J; Tsao, G T

1999-01-01

Vast amounts of renewable biomass are available for conversion to liquid fuel, ethanol. In order to convert biomass to ethanol, the efficient utilization of both cellulose-derived and hemicellulose-derived carbohydrates is essential. Six-carbon sugars are readily utilized for this purpose. Pentoses, on the other hand, are more difficult to convert. Several metabolic factors limit the efficient utilization of pentoses (xylose and arabinose). Recent developments in the improvement of microbial cultures provide the versatility of conversion of both hexoses and pentoses to ethanol more efficiently. In addition, novel bioprocess technologies offer a promising prospective for the efficient conversion of biomass and recovery of ethanol.

Genuine Conversation: The Enabler in Good Mentoring of Pre-Service Teachers

ERIC Educational Resources Information Center

Sheridan, Lynn; Young, Marie

2017-01-01

This study confirms the role of genuine conversation as the enabler in good mentoring of pre-service teachers. The practicum plays an essential role in moving the pre-service teacher beyond learning about teaching to the practice of teaching. Yet the benefit of the practicum is often constrained by relational tensions, disappointment and…

Bi2S3microspheres grown on graphene sheets as low-cost counter-electrode materials for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Li, Guang; Chen, Xiaoshuang; Gao, Guandao

2014-02-01

In this work, we synthesized 3D Bi2S3 microspheres comprised of nanorods grown along the (211) facet on graphene sheets by a solvothermal route, and investigated its catalytic activities through I-V curves and conversion efficiency tests as the CE in DSSCs. Although the (211) facet has a large band gap for a Bi2S3 semiconductor, owing to the introduction of graphene into the system, its short-circuit current density, open-circuit voltage, fill factor, and efficiency were Jsc = 12.2 mA cm-2, Voc = 0.75 V, FF = 0.60, and η = 5.5%, respectively. By integrating it with graphene sheets, our material achieved the conversion efficiency of 5.5%, which is almost triple the best conversion efficiency value of the DSSCs with (211)-faceted 3D Bi2S3 without graphene (1.9%) reported in the latest literature. Since this conversion-efficient 3D material grown on the graphene sheets significantly improves its catalytic properties, it paves the way for designing and applying low-cost Pt-free CE materials in DSSC from inorganic nanostructures.In this work, we synthesized 3D Bi2S3 microspheres comprised of nanorods grown along the (211) facet on graphene sheets by a solvothermal route, and investigated its catalytic activities through I-V curves and conversion efficiency tests as the CE in DSSCs. Although the (211) facet has a large band gap for a Bi2S3 semiconductor, owing to the introduction of graphene into the system, its short-circuit current density, open-circuit voltage, fill factor, and efficiency were Jsc = 12.2 mA cm-2, Voc = 0.75 V, FF = 0.60, and η = 5.5%, respectively. By integrating it with graphene sheets, our material achieved the conversion efficiency of 5.5%, which is almost triple the best conversion efficiency value of the DSSCs with (211)-faceted 3D Bi2S3 without graphene (1.9%) reported in the latest literature. Since this conversion-efficient 3D material grown on the graphene sheets significantly improves its catalytic properties, it paves the way for designing and applying low-cost Pt-free CE materials in DSSC from inorganic nanostructures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06093d

Enhanced energy conversion efficiency from high strength synthetic organic wastewater by sequential dark fermentative hydrogen production and algal lipid accumulation.

PubMed

Ren, Hong-Yu; Liu, Bing-Feng; Kong, Fanying; Zhao, Lei; Xing, Defeng; Ren, Nan-Qi

2014-04-01

A two-stage process of sequential dark fermentative hydrogen production and microalgal cultivation was applied to enhance the energy conversion efficiency from high strength synthetic organic wastewater. Ethanol fermentation bacterium Ethanoligenens harbinense B49 was used as hydrogen producer, and the energy conversion efficiency and chemical oxygen demand (COD) removal efficiency reached 18.6% and 28.3% in dark fermentation. Acetate was the main soluble product in dark fermentative effluent, which was further utilized by microalga Scenedesmus sp. R-16. The final algal biomass concentration reached 1.98gL(-1), and the algal biomass was rich in lipid (40.9%) and low in protein (23.3%) and carbohydrate (11.9%). Compared with single dark fermentation stage, the energy conversion efficiency and COD removal efficiency of two-stage system remarkably increased 101% and 131%, respectively. This research provides a new approach for efficient energy production and wastewater treatment using a two-stage process combining dark fermentation and algal cultivation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Supported black phosphorus nanosheets as hydrogen-evolving photocatalyst achieving 5.4% energy conversion efficiency at 353 K.

PubMed

Tian, Bin; Tian, Bining; Smith, Bethany; Scott, M C; Hua, Ruinian; Lei, Qin; Tian, Yue

2018-04-11

Solar-driven water splitting using powdered catalysts is considered as the most economical means for hydrogen generation. However, four-electron-driven oxidation half-reaction showing slow kinetics, accompanying with insufficient light absorption and rapid carrier combination in photocatalysts leads to low solar-to-hydrogen energy conversion efficiency. Here, we report amorphous cobalt phosphide (Co-P)-supported black phosphorus nanosheets employed as photocatalysts can simultaneously address these issues. The nanosheets exhibit robust hydrogen evolution from pure water (pH = 6.8) without bias and hole scavengers, achieving an apparent quantum efficiency of 42.55% at 430 nm and energy conversion efficiency of over 5.4% at 353 K. This photocatalytic activity is attributed to extremely efficient utilization of solar energy (~75% of solar energy) by black phosphorus nanosheets and high-carrier separation efficiency by amorphous Co-P. The hybrid material design realizes efficient solar-to-chemical energy conversion in suspension, demonstrating the potential of black phosphorus-based materials as catalysts for solar hydrogen production.

Electrochemically Reduced Graphene Oxide Multilayer Films as Efficient Counter Electrode for Dye-Sensitized Solar Cells

PubMed Central

Xu, Xiaobao; Huang, Dekang; Cao, Kun; Wang, Mingkui; Zakeeruddin, Shaik M.; Grätzel, Michael

2013-01-01

We report on a new counter electrode for dye-sensitized solar cells (DSCs), which is prepared using layer-by-layer assembly of negatively charged graphene oxide and positively charged poly (diallyldimethylammonium chloride) followed by an electrochemical reduction procedure. The DSC devises using the heteroleptic Ru complex C106TBA as sensitizer and this new counter electrode reach power conversion efficiencies of 9.5% and 7.6% in conjunction with low volatility and solvent free ionic liquid electrolytes, respectively. The new counter electrode exhibits good durability (60°C for 1000 h in a solar simulator, 100 mW cm−2) during the accelerated tests when used in combination with an ionic liquid electrolyte. This work identifies a new class of electro-catalysts with potential for low cost photovoltaic devices. PMID:23508212

Cavity-enhanced frequency doubling from 795nm to 397.5nm ultra-violet coherent radiation with PPKTP crystals in the low pump power regime.

PubMed

Wen, Xin; Han, Yashuai; Bai, Jiandong; He, Jun; Wang, Yanhua; Yang, Baodong; Wang, Junmin

2014-12-29

We demonstrate a simple, compact and cost-efficient diode laser pumped frequency doubling system at 795 nm in the low power regime. In two configurations, a bow-tie four-mirror ring enhancement cavity with a PPKTP crystal inside and a semi-monolithic PPKTP enhancement cavity, we obtain 397.5nm ultra-violet coherent radiation of 35mW and 47mW respectively with a mode-matched fundamental power of about 110mW, corresponding to a conversion efficiency of 32% and 41%. The low loss semi-monolithic cavity leads to the better results. The constructed ultra-violet coherent radiation has good power stability and beam quality, and the system has huge potential in quantum optics and cold atom physics.

Experimental Study on the Velocity and Efficiency Characteristics of a Serial Staged Needle Array-Mesh Type EHD Gas Pump

NASA Astrophysics Data System (ADS)

Qiu, Wei; Xia, Lingzhi; Yang, Lanjun; Zhang, Qiaogen; Xiao, Lei; Chen, Li

2011-12-01

The ionic wind has good application prospects in the fields of air flow control and heat transfer enhancement. The key for successful applications is how to improve the velocity and how to increase the active area of the ionic wind. This paper designed a needle array-mesh type electrohydrodynamic (EHD) gas pump. The use of needle array electrode where corona discharge started simultaneously could enlarge the active area. The velocity of the ionic wind could increase by placing several single-stage ionic wind generators in series appropriately, called as serial staged generator. The maximum average flow velocity of 16.1 m/s and volumetric flow of 303.5 L/min were achieved at the outlet of a 25-stage gas pump and the conversion efficiency was approximately 2.2%.

Resonant detectors and focal plane arrays for infrared detection

NASA Astrophysics Data System (ADS)

Choi, K. K.; Allen, S. C.; Sun, J. G.; DeCuir, E. A.

2017-08-01

We are developing resonator-QWIPs for narrowband and broadband long wavelength infrared detection. Detector pixels with 25 μm and 30 μm pitches were hybridized to fanout circuits and readout integrated electronics for radiometric measurements. With a low to moderate doping of 0.2-0.5 × 1018 cm-3 and a thin active layer thickness of 0.6-1.3 μm, we achieved a quantum efficiency between 25 and 37% and a conversion efficiency between of 15 and 20%. The temperature at which photocurrent equals dark current is about 65 K under F/2 optics for a cutoff wavelength up to 11 μm. The NEΔT of the FPAs is estimated to be 20 mK at 2 ms integration time and 60 K operating temperature. This good performance confirms the advantages of the resonator-QWIP approach.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamann, Thomas

Dye-sensitized solar cells (DSSCs) have attracted a lot of interest as they proffer the possibility of extremely inexpensive and efficient solar energy conversion. The excellent performance of the most efficient DSSCs relies on two main features: 1) a high surface area nanoparticle semiconductor photoanode to allow for excellent light absorption with moderate extinction molecular dyes and 2) slow recombination rates from the photoanode to I 3 - allowing good charge collection. The I 3 -/I - couple, however, has some disadvantages, notably the redox potential limits the maximum open-circuit voltage, and the dye regeneration requires a large driving force whichmore » constrains the light harvesting ability. Thus, the design features that allow DSSCs to perform as well as they do also prevent further significant improvements in performance. As a consequence, the most efficient device configuration, and the maximum efficiency, has remained essentially unchanged over the last 16 years. Significant gains in performance are possible; however it will likely require a substantial paradigm shift. The general goal of this project is to understand the fundamental role of dye-sensitized solar cell, DSSC, components (sensitizer, redox shuttle, and photoanode) involved in key processes in order to overcome the kinetic and energetic constraints of current generation DSSCs. For example, the key to achieving high energy conversion efficiency DSSCs is the realization of a redox shuttle which fulfills the dual requirements of 1) efficient dye regeneration with a minimal driving force and 2) efficient charge collection. In current generation DSSCs, however, only one or the other of these requirements is met. We are currently primarily interested in understanding the physical underpinnings of the regeneration and recombination reactions. Our approach is to systematically vary the components involved in reactions and interrogate them with a series of photoelectrochemical (PEC) measurements. The lessons learned will ultimately be used to develop design rules for next generation DSSCs.« less

The Influence of Deposition Methods of Support Layer on Cordierite Substrate on the Characteristics of a MnO2–NiO–Co3O4/Ce0.2Zr0.8O2/Cordierite Three Way Catalyst

PubMed Central

Pham, Phuong Thi Mai; Le, Minh Thang; Nguyen, Tien The; Bruneel, Els; Van Driessche, Isabel

2014-01-01

This paper compares different coating methods (in situ solid combustion, hybrid deposition, secondary growth on seed, suspension, double deposition of wet impregnation and suspension) to deposit Ce0.2Zr0.8O2 mixed oxides on cordierite substrates, for use as a three way catalyst. Among them, the double deposition was proven to be the most efficient one. The coated sample shows a BET (Brunauer–Emmett–Teller) surface area of 25 m2/g, combined with a dense and crack free surface. The catalyst with a layer of MnO2–NiO–Co3O4 mixed oxides on top of the Ce0.2Zr0.8O2/cordierite substrate prepared by this method exhibits good activity for the treatment of CO, NO and C3H6 in exhaust gases (CO conversion of 100% at 250 °C, C3H6 conversion of 100% at 400 °C and NO conversion of 40% at 400 °C). PMID:28788189

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Shiwei; Wang, Huan; Mo, Daize

A new family of thieno[3,4-b]thiophene benzodithiophene terpolymers (PBTClx) have been designed and synthesized, in which the chlorine/fluorine content has been adjusted and optimized. As the content of chlorine is increased in polymers, the twist angle between the donor and acceptor is increased, which leads to a diminishment in the planarity and conjugation. As a result, the UV vis absorption is continuous blue-shifted, and the band gap increases from 1.57 to 2.04 eV when the chlorinated moieties increased from 0 to 100%. The highest occupied molecular orbital (HOMO) levels of those polymers are decreased by increasing the content of chlorinated moiety,more » which opens a window to constantly modify the V-oc values and eventually meets a balance point for optimized solar energy conversion. The highest power conversion efficiency of 8.31% is obtained by using PBTCl25 as the donor and PC71BM as the acceptor in polymer solar cells (PSCs), in which the Voc increased from 0.79 to 0.82 V after 25% chlorinated monomer involved in copolymerization. Herein, the chlorine replacement could be a good method to further pump the solar conversion by increasing the open circuit voltage without reducing other factors of the polymer solar cells.« less

Ultra-broad band, low power, highly efficient coherent wavelength conversion in quantum dot SOA.

PubMed

Contestabile, G; Yoshida, Y; Maruta, A; Kitayama, K

2012-12-03

We report broadband, all-optical wavelength conversion over 100 nm span, in full S- and C-band, with positive conversion efficiency with low optical input power exploiting dual pump Four-Wave-Mixing in a Quantum Dot Semiconductor Optical Amplifier (QD-SOA). We also demonstrate by Error Vector Magnitude analysis the full transparency of the conversion scheme for coherent modulation formats (QPSK, 8-PSK, 16-QAM, OFDM-16QAM) in the whole C-band.

Gliding Arc Plasmatron: Providing an Alternative Method for Carbon Dioxide Conversion.

PubMed

Ramakers, Marleen; Trenchev, Georgi; Heijkers, Stijn; Wang, Weizong; Bogaerts, Annemie

2017-06-22

Low-temperature plasmas are gaining a lot of interest for environmental and energy applications. A large research field in these applications is the conversion of CO 2 into chemicals and fuels. Since CO 2 is a very stable molecule, a key performance indicator for the research on plasma-based CO 2 conversion is the energy efficiency. Until now, the energy efficiency in atmospheric plasma reactors is quite low, and therefore we employ here a novel type of plasma reactor, the gliding arc plasmatron (GAP). This paper provides a detailed experimental and computational study of the CO 2 conversion, as well as the energy cost and efficiency in a GAP. A comparison with thermal conversion, other plasma types and other novel CO 2 conversion technologies is made to find out whether this novel plasma reactor can provide a significant contribution to the much-needed efficient conversion of CO 2 . From these comparisons it becomes evident that our results are less than a factor of two away from being cost competitive and already outperform several other new technologies. Furthermore, we indicate how the performance of the GAP can still be improved by further exploiting its non-equilibrium character. Hence, it is clear that the GAP is very promising for CO 2 conversion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Free-space microwave-to-optical conversion via six-wave mixing in Rydberg atoms

NASA Astrophysics Data System (ADS)

Han, Jingshan; Vogt, Thibault; Gross, Christian; Jaksch, Dieter; Kiffner, Martin; Li, Wenhui

2017-04-01

The interconversion of millimeter waves and optical fields is an important and highly topical subject for classical and quantum technologies. In this talk, we report an experimental demonstration of coherent and efficient microwave-to-optical conversion in free space via six-wave mixing in Rydberg atoms. Our scheme utilizes the strong coupling of millimeter waves to Rydberg atoms as well as the frequency mixing based on electromagnetically induced transparency (EIT) that greatly enhances the nonlinearity for the conversion process. We achieve a free-space conversion efficiency of 0.25% with a bandwidth of about 4 MHz in our experiment. Optimized geometry and energy level configurations should enable the broadband interconversion of microwave and optical fields with near-unity efficiency. These results indicate the tremendous potential of Rydberg atoms for the efficient conversion between microwave and optical fields, and thus paves the way to many applications. This work is supported by Singapore Ministry of Education Academic Research Fund Tier 2 (Grant No. MOE2015-T2-1-085).

Apparatus and method for enabling quantum-defect-limited conversion efficiency in cladding-pumped Raman fiber lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heebner, John E.; Sridharan, Arun K.; Dawson, Jay Walter

Cladding-pumped Raman fiber lasers and amplifiers provide high-efficiency conversion efficiency at high brightness enhancement. Differential loss is applied to both single-pass configurations appropriate for pulsed amplification and laser oscillator configurations applied to high average power cw source generation.

Design of multi-energy Helds coupling testing system of vertical axis wind power system

NASA Astrophysics Data System (ADS)

Chen, Q.; Yang, Z. X.; Li, G. S.; Song, L.; Ma, C.

2016-08-01

The conversion efficiency of wind energy is the focus of researches and concerns as one of the renewable energy. The present methods of enhancing the conversion efficiency are mostly improving the wind rotor structure, optimizing the generator parameters and energy storage controller and so on. Because the conversion process involves in energy conversion of multi-energy fields such as wind energy, mechanical energy and electrical energy, the coupling effect between them will influence the overall conversion efficiency. In this paper, using system integration analysis technology, a testing system based on multi-energy field coupling (MEFC) of vertical axis wind power system is proposed. When the maximum efficiency of wind rotor is satisfied, it can match to the generator function parameters according to the output performance of wind rotor. The voltage controller can transform the unstable electric power to the battery on the basis of optimizing the parameters such as charging times, charging voltage. Through the communication connection and regulation of the upper computer system (UCS), it can make the coupling parameters configure to an optimal state, and it improves the overall conversion efficiency. This method can test the whole wind turbine (WT) performance systematically and evaluate the design parameters effectively. It not only provides a testing method for system structure design and parameter optimization of wind rotor, generator and voltage controller, but also provides a new testing method for the whole performance optimization of vertical axis wind energy conversion system (WECS).

Fabrication of efficient low-bandgap perovskite solar cells by combining formamidinium tin iodide with methylammonium lead iodide

DOE PAGES

Liao, Weiqiang; Zhao, Dewei; Yu, Yue; ...

2016-09-13

Mixed tin (Sn)-lead (Pb) perovskites with high Sn content exhibit low bandgaps suitable for fabricating the bottom cell of perovskite-based tandem solar cells. In this work, we report on the fabrication of efficient mixed Sn-Pb perovskite solar cells using precursors combining formamidinium tin iodide (FASnI 3) and methylammonium lead iodide (MAPbI 3). The best-performing cell fabricated using a (FASnI 3) 0.6(MAPbI 3) 0.4 absorber with an absorption edge of ~1.2 eV achieved a power conversion efficiency (PCE) of 15.08 (15.00)% with an open-circuit voltage of 0.795 (0.799) V, a short-circuit current density of 26.86(26.82) mA/cm 2, and a fill factormore » of 70.6(70.0)% when measured under forward (reverse) voltage scan. In conclusion, the average PCE of 50 cells we have fabricated is 14.39 ± 0.33%, indicating good reproducibility.« less

Tungsten Oxide Nanorods: An Efficient Nanoplatform for Tumor CT Imaging and Photothermal Therapy

PubMed Central

Zhou, Zhiguo; Kong, Bin; Yu, Chao; Shi, Xiangyang; Wang, Mingwei; Liu, Wei; Sun, Yanan; Zhang, Yingjian; Yang, Hong; Yang, Shiping

2014-01-01

We report here a facile thermal decomposition approach to creating tungsten oxide nanorods (WO2.9 NRs) with a length of 13.1 ± 3.6 nm and a diameter of 4.4 ± 1.5 nm for tumor theranostic applications. The formed WO2.9 NRs were modified with methoxypoly(ethylene glycol) (PEG) carboxyl acid via ligand exchange to have good water dispersability and biocompatibility. With the high photothermal conversion efficiency irradiated by a 980 nm laser and the better X-ray attenuation property than clinically used computed tomography (CT) contrast agent Iohexol, the formed PEGylated WO2.9 NRs are able to inhibit the growth of the model cancer cells in vitro and the corresponding tumor model in vivo, and enable effective CT imaging of the tumor model in vivo. Our “killing two birds with one stone” strategy could be extended for fabricating other nanoplatforms for efficient tumor theranostic applications. PMID:24413483

Three-dimensional nitrogen doped holey reduced graphene oxide framework as metal-free counter electrodes for high performance dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Yu, Mei; Zhang, Jindan; Li, Songmei; Meng, Yanbing; Liu, Jianhua

2016-03-01

Three-dimensional nitrogen doped holey reduced graphene oxide framework (NHGF) with hierarchical porosity structure was developed as high-performance metal-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). With plenty of exposed active sites, efficient electron and ion transport pathways as well as a high surface hydrophilicity, NHGF-CE exhibits good electrocatalytic performances for I- /I3- redox couple and a low charge transfer resistance (Rct). The Rct of NHGF-CE is 1.46 Ω cm2, which is much lower than that of Pt-CE (4.02 Ω cm2). The DSSC with NHGF-CE reaches a power conversion efficiency of 5.56% and a fill factor of 65.5%, while those of the DSSC with Pt-CE are only 5.45% and 62.3%, respectively. The achievement of the highly efficient 3D structure presents a potential way to fabricate low-cost and metal-free counter electrodes with excellent performance.

D-A-D-Typed Hole Transport Materials for Efficient Perovskite Solar Cells: Tuning Photovoltaic Properties via the Acceptor Group.

PubMed

Xu, Peng; Liu, Peng; Li, Yuanyuan; Xu, Bo; Kloo, Lars; Sun, Licheng; Hua, Yong

2018-06-13

Two D-A-D-structured hole-transport materials (YN1 and YN2) have been synthesized and used in perovskite solar cells. The two HTMs have low-lying HOMO levels and impressive mobility. Perovskite-based solar cells (PSCs) fabricated with YN2 showed a power conversion efficiency (PCE) value of 19.27% in ambient air, which is significantly higher than that of Spiro-OMeTAD (17.80%). PSCs based on YN1 showed an inferior PCE of 16.03%. We found that the incorporation of the stronger electron-withdrawing group in the HTM YN2 improves the PCE of PSCs. Furthermore, the YN2-based PSCs exhibit good long-term stability retaining 91.3% of its initial efficiency, whereas PSCs based on Spiro-OMeTAD retained only 42.2% after 1000 h lifetime (dark conditions). These promising results can provide a new strategy for the design of D-A-D HTMs for PSC applications in future.

Helicon thruster plasma modeling: Two-dimensional fluid-dynamics and propulsive performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahedo, Eduardo; Navarro-Cavalle, Jaume

2013-04-15

An axisymmetric macroscopic model of the magnetized plasma flow inside the helicon thruster chamber is derived, assuming that the power absorbed from the helicon antenna emission is known. Ionization, confinement, subsonic flows, and production efficiency are discussed in terms of design and operation parameters. Analytical solutions and simple scaling laws for ideal plasma conditions are obtained. The chamber model is then matched with a model of the external magnetic nozzle in order to characterize the whole plasma flow and assess thruster performances. Thermal, electric, and magnetic contributions to thrust are evaluated. The energy balance provides the power conversion between ionsmore » and electrons in chamber and nozzle, and the power distribution among beam power, ionization losses, and wall losses. Thruster efficiency is assessed, and the main causes of inefficiency are identified. The thermodynamic behavior of the collisionless electron population in the nozzle is acknowledged to be poorly known and crucial for a complete plasma expansion and good thrust efficiency.« less

A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ling, Junpu, E-mail: lingjunpu@163.com; Zhang, Jiande; He, Juntao

2014-02-15

A novel coaxial transit radiation oscillator without external guiding magnetic field is designed to generate high power microwave at Ku-band. By using a coaxial structure, the space-charge potential energy is suppressed significantly, that is good for enhancing efficient beam-wave interaction. In order to improve the transmission stability of the unmagnetized intense relativistic electron beam, a Pierce-like cathode is employed in the novel device. By contrast with conventional relativistic microwave generators, this kind of device has the advantages of high stability, non-guiding magnetic field, and high efficiency. Moreover, with the coaxial design, it is possible to improve the power-handing capacity bymore » increasing the radial dimension of the Ku-band device. With a 550 keV and 7.5 kA electron beam, a 1.25 GW microwave pulse at 12.08 GHz has been obtained in the simulation. The power conversion efficiency is about 30%.« less

Efficient implementation of neural network deinterlacing

NASA Astrophysics Data System (ADS)

Seo, Guiwon; Choi, Hyunsoo; Lee, Chulhee

2009-02-01

Interlaced scanning has been widely used in most broadcasting systems. However, there are some undesirable artifacts such as jagged patterns, flickering, and line twitters. Moreover, most recent TV monitors utilize flat panel display technologies such as LCD or PDP monitors and these monitors require progressive formats. Consequently, the conversion of interlaced video into progressive video is required in many applications and a number of deinterlacing methods have been proposed. Recently deinterlacing methods based on neural network have been proposed with good results. On the other hand, with high resolution video contents such as HDTV, the amount of video data to be processed is very large. As a result, the processing time and hardware complexity become an important issue. In this paper, we propose an efficient implementation of neural network deinterlacing using polynomial approximation of the sigmoid function. Experimental results show that these approximations provide equivalent performance with a considerable reduction of complexity. This implementation of neural network deinterlacing can be efficiently incorporated in HW implementation.

Achieving over 9.8% Efficiency in Nonfullerene Polymer Solar Cells by Environmentally Friendly Solvent Processing.

PubMed

Wu, Yue; Zou, Yan; Yang, Hang; Li, Yaowen; Li, Hongkun; Cui, Chaohua; Li, Yongfang

2017-10-25

Nowadays, most of the solution-processed high-efficiency polymer solar cell (PSC) devices are fabricated by halogenated solvents (such as chlorobenzene, 1,2-dichlorobenzene, chloroform, etc.) which are harmful to people and the environment. Therefore, it is essential to develop high-efficiency PSC devices processed by environmentally friendly solvent processing for their industrialization. In this regard, we report a new alkylthio chain-based conjugated polymer PBDB-TS as donor material for environmentally friendly solvent-processed PSCs. PBDB-TS possesses a low-lying HOMO energy level at -5.42 eV and a good solubility in toluene and o-xylene. By using o-xylene and 1% N-methylpyrrolidone as processing solvent, following by the thermal annealing treatment for PBDB-TS:ITIC blend films, well-developed morphological features, and balanced charge transport properties are observed, leading to a high power conversion efficiency (PCE) of 9.85%, higher than that of the device cast from halogenated solvent (PCE = 9.65%). The results suggest that PBDB-TS is an attractive donor material for nonhalogen solvents-processing PSCs.

49 CFR 375.609 - What must I do for shippers who store household goods in transit?

Code of Federal Regulations, 2013 CFR

2013-10-01

... transit? (a) If you are holding goods for storage-in-transit (SIT) and the period of time is about to... following four items: (1) The date of conversion to permanent storage. (2) The existence of a nine-month period after the date of conversion to permanent storage when the individual shipper may file claims...

49 CFR 375.609 - What must I do for shippers who store household goods in transit?

Code of Federal Regulations, 2012 CFR

2012-10-01

... transit? (a) If you are holding goods for storage-in-transit (SIT) and the period of time is about to... following four items: (1) The date of conversion to permanent storage. (2) The existence of a nine-month period after the date of conversion to permanent storage when the individual shipper may file claims...

49 CFR 375.609 - What must I do for shippers who store household goods in transit?

Code of Federal Regulations, 2010 CFR

2010-10-01

... transit? (a) If you are holding goods for storage-in-transit (SIT) and the period of time is about to... following four items: (1) The date of conversion to permanent storage. (2) The existence of a nine-month period after the date of conversion to permanent storage when the individual shipper may file claims...

49 CFR 375.609 - What must I do for shippers who store household goods in transit?

Code of Federal Regulations, 2011 CFR

2011-10-01

... transit? (a) If you are holding goods for storage-in-transit (SIT) and the period of time is about to... following four items: (1) The date of conversion to permanent storage. (2) The existence of a nine-month period after the date of conversion to permanent storage when the individual shipper may file claims...

49 CFR 375.609 - What must I do for shippers who store household goods in transit?

Code of Federal Regulations, 2014 CFR

2014-10-01

... transit? (a) If you are holding goods for storage-in-transit (SIT) and the period of time is about to... following four items: (1) The date of conversion to permanent storage. (2) The existence of a nine-month period after the date of conversion to permanent storage when the individual shipper may file claims...

Performance analysis of hybrid vibrational energy harvesters with experimental verification

NASA Astrophysics Data System (ADS)

Sriramdas, Rammohan; Pratap, Rudra

2018-07-01

In the present work, performance indices for a hybrid energy harvester (HEH) that is composed of piezoelectric and electrodynamic or electromagnetic mechanisms of energy conversion are analyzed. Performance of a HEH is defined in terms of Q-normalized power factor and efficiency of conversion. They are observed to acutely depend on coupling strength or figures of merit in both piezoelectric and electrodynamic domains. The influence of figures of merit on the Q-normalized power factor, and the limits of conversion efficiency are explored. Based on the studies, a suitable range for figures of merit that would maximize both Q-normalized power factor and conversion efficiency in hybrid harvesters is proposed. The proposed idea is verified experimentally for the appropriate values of figures of merit and efficiencies by fabricating and testing four experimental models of the HEHs.

Betavoltaic Battery Conversion Efficiency Improvement Based on Interlayer Structures

NASA Astrophysics Data System (ADS)

Li, Da-Rang; Jiang, Lan; Yin, Jian-Hua; Tan, Yuan-Yuan; Lin, Nai

2012-07-01

Significant differences among the doping densities of PN junctions in semiconductors cause lattice mismatch and lattice defects that increase the recombination current of betavoltaic batteries. This extensively decreases the open circuit voltage and the short current, which results in low conversion efficiency. This study proposes P+PINN+-structure based betavoltaic batteries by adding an interlayer to typical PIN structures to improve conversion efficiency. Numerical simulations are conducted for the energy deposition of beta particles along the thickness direction in semiconductors. Based on this, 63Ni-radiation GaAs batteries with PIN and P+PINN+ structures are designed and fabricated to experimentally verify the proposed design. It turns out that the conversion efficiency of the betavoltaic battery with the proposed P+PINN+ structure is about 1.45 times higher than that with the traditional PIN structure.

Performance of conversion efficiency of a crystalline silicon solar cell with base doping density

NASA Astrophysics Data System (ADS)

Sahin, Gokhan; Kerimli, Genber; Barro, Fabe Idrissa; Sane, Moustapha; Alma, Mehmet Hakkı

In this study, we investigate theoretically the electrical parameters of a crystalline silicon solar cell in steady state. Based on a one-dimensional modeling of the cell, the short circuit current density, the open circuit voltage, the shunt and series resistances and the conversion efficiency are calculated, taking into account the base doping density. Either the I-V characteristic, series resistance, shunt resistance and conversion efficiency are determined and studied versus base doping density. The effects applied of base doping density on these parameters have been studied. The aim of this work is to show how short circuit current density, open circuit voltage and parasitic resistances are related to the base doping density and to exhibit the role played by those parasitic resistances on the conversion efficiency of the crystalline silicon solar.

High-efficiency frequency doubling of continuous-wave laser light.

PubMed

Ast, Stefan; Nia, Ramon Moghadas; Schönbeck, Axel; Lastzka, Nico; Steinlechner, Jessica; Eberle, Tobias; Mehmet, Moritz; Steinlechner, Sebastian; Schnabel, Roman

2011-09-01

We report on the observation of high-efficiency frequency doubling of 1550 nm continuous-wave laser light in a nonlinear cavity containing a periodically poled potassium titanyl phosphate crystal (PPKTP). The fundamental field had a power of 1.10 W and was converted into 1.05 W at 775 nm, yielding a total external conversion efficiency of 95±1%. The latter value is based on the measured depletion of the fundamental field being consistent with the absolute values derived from numerical simulations. According to our model, the conversion efficiency achieved was limited by the nonperfect mode matching into the nonlinear cavity and by the nonperfect impedance matching for the maximum input power available. Our result shows that cavity-assisted frequency conversion based on PPKTP is well suited for low-decoherence frequency conversion of quantum states of light.

Seeking to Improve Low Energy Neutral Atom Detection in Space

NASA Technical Reports Server (NTRS)

Shappirio, M.; Coplan, M.; Chornay, D.; Collier, M.; Herrero, F.; Ogilvie, K.; Williams, E.

2007-01-01

The detection of energetic neutral atoms allows for the remote examination of the interactions between plasmas and neutral populations in space. Before these neutral atoms can be measured, they must first be converted to ions. For the low energy end of this spectrum, interaction with a conversion surface is often the most efficient method to convert neutrals into ions. It is generally thought that the most efficient surfaces are low work functions materials. However, by their very nature, these surfaces are highly reactive and unstable, and therefore are not suitable for space missions where conditions cannot be controlled as they are in a laboratory. We therefore are looking to optimize a stable surface for conversion efficiency. Conversion efficiency can be increased either by changing the incident angle of the neutral particles to be grazing incidence and using stable surfaces with high conversion efficiencies. We have examined how to increase the angle of incidence from -80 degrees to -89 degrees, while maintaining or improving the total active conversion surface area without increasing the overall volume of the instrument. We are developing a method to micro-machine silicon, which will reduce the volume to surface area ratio by a factor of 60. We have also examined the material properties that affect the conversion efficiency of the surface for stable surfaces. Some of the parameters we have examined are work function, smoothness, and bond structure. We find that for stable surfaces, the most important property is the smoothness of the surface.

Lead-Sulfide-Selenide Quantum Dots and Gold-Copper Alloy Nanoparticles Augment the Light-Harvesting Ability of Solar Cells.

PubMed

Das, Aparajita; Deepa, Melepurath; Ghosal, Partha

2017-04-05

Lead-sulfide-selenide (PbSSe) quantum dots (QDs) and gold-copper (AuCu) alloy nanoparticles (NPs) were incorporated into a cadmium sulfide (CdS)/titanium oxide (TiO 2 ) photoanode for the first time to achieve enhanced conversion of solar energy into electricity. PbSSe QDs with a band gap of 1.02 eV extend the light-harvesting range of the photoanode from the visible region to the near-infrared region. The conduction band (CB) edge of the PbSSe QDs is wedged between the CBs of TiO 2 and CdS; this additional level coupled with the good electrical conductivity of the dots facilitate charge transport and collection, and a high power conversion efficiency (PCE) of 4.44 % is achieved for the champion cell with the TiO 2 /PbSSe/CdS electrode. Upon including AuCu alloy NPs in the QD-sensitized electrodes, light absorption is enhance by plasmonic and light-scattering effects and also by the injection of hot electrons to the CBs of the QDs. Comparison of the incident photon-to-current conversion efficiency enhancement factors in addition to fluorescence decay and impedance studies reveal that the PbSSe QDs and AuCu alloy NPs promote charge injection to the current collector and increase the photogenerated charges produced, which thus enables the TiO 2 /PbSSe/CdS/AuCu cell to deliver the highest PCE of 5.26 % among all the various photoanode compositions used. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative evaluation of the accuracy and variance of individual pixels in a scientific CMOS (sCMOS) camera for computational imaging

NASA Astrophysics Data System (ADS)

Watanabe, Shigeo; Takahashi, Teruo; Bennett, Keith

2017-02-01

The"scientific" CMOS (sCMOS) camera architecture fundamentally differs from CCD and EMCCD cameras. In digital CCD and EMCCD cameras, conversion from charge to the digital output is generally through a single electronic chain, and the read noise and the conversion factor from photoelectrons to digital outputs are highly uniform for all pixels, although quantum efficiency may spatially vary. In CMOS cameras, the charge to voltage conversion is separate for each pixel and each column has independent amplifiers and analog-to-digital converters, in addition to possible pixel-to-pixel variation in quantum efficiency. The "raw" output from the CMOS image sensor includes pixel-to-pixel variability in the read noise, electronic gain, offset and dark current. Scientific camera manufacturers digitally compensate the raw signal from the CMOS image sensors to provide usable images. Statistical noise in images, unless properly modeled, can introduce errors in methods such as fluctuation correlation spectroscopy or computational imaging, for example, localization microscopy using maximum likelihood estimation. We measured the distributions and spatial maps of individual pixel offset, dark current, read noise, linearity, photoresponse non-uniformity and variance distributions of individual pixels for standard, off-the-shelf Hamamatsu ORCA-Flash4.0 V3 sCMOS cameras using highly uniform and controlled illumination conditions, from dark conditions to multiple low light levels between 20 to 1,000 photons / pixel per frame to higher light conditions. We further show that using pixel variance for flat field correction leads to errors in cameras with good factory calibration.

Numerical modelling of CIGS/CdS solar cell

NASA Astrophysics Data System (ADS)

Devi, Nisha; Aziz, Anver; Datta, Shouvik

2018-05-01

In this work, we design and analyze the Cu(In,Ga)Se2 (CIGS) solar cell using simulation software "Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D)". The conventional CIGS solar cell uses various layers, like intrinsic ZnO/Aluminium doped ZnO as transparent oxide, antireflection layer MgF2, and electron back reflection (EBR) layer at CIGS/Mo interface for good power conversion efficiency. We replace this conventional model by a simple model which is easy to fabricate and also reduces the cost of this cell because of use of lesser materials. The new designed model of CIGS solar cell is ITO/CIGS/OVC/CdS/Metal contact, where OVC is ordered vacancy compound. From this simple structure, even at very low illumination we are getting good results. We simulate this CIGS solar cell model by varying various physical parameters of CIGS like thickness, carrier density, band gap and temperature.

Enhancement of Energy Conversion Efficiency for Dye Sensitized Solar Cell Using Zinc Oxide Photoanode

NASA Astrophysics Data System (ADS)

Jamalullail, N.; Smohamad, I.; Nnorizan, M.; Mahmed, N.

2018-06-01

Dye sensitized solar cell (DSSC) is a third generation solar cell that is well known for its low cost, simple fabrication process and promised reasonable energy conversion efficiency. Basic structure of DSSC is composed of photoanode, dye sensitizer, electrolyte that is sandwiched together in between two transparent conductive oxide (TCO) glasses. Each of the components in the DSSC contributes important role that affect the energy conversion efficiency. In this research, the commonly used titanium dioxide (TiO2) photoanode has previously reported to have high recombination rate and low electron mobility which caused efficiency loss had been compared with the zinc oxide (ZnO) photoanode with high electron mobility (155 cm2V-1s-1). Both of these photoanodes had been deposited through doctor blade technique. The electrical performance of the laboratory based DSSCs were tested using solar cell simulator and demonstrated that ZnO is a better photoanode compared to TiO2 with the energy conversion efficiency of 0.34% and 0.29% respectively. Nanorods shape morphology was observed in ZnO photoanode with average particle size of 41.60 nm and average crystallite size of 19.13 nm. This research proved that the energy conversion efficiency of conventional TiO2 based photoanode can be improved using ZnO material.

Supersensitization of CdS quantum dots with a near-infrared organic dye: toward the design of panchromatic hybrid-sensitized solar cells.

PubMed

Choi, Hyunbong; Nicolaescu, Roxana; Paek, Sanghyun; Ko, Jaejung; Kamat, Prashant V

2011-11-22

The photoresponse of quantum dot solar cells (QDSCs) has been successfully extended to the near-IR (NIR) region by sensitizing nanostructured TiO(2)-CdS films with a squaraine dye (JK-216). CdS nanoparticles anchored on mesoscopic TiO(2) films obtained by successive ionic layer adsorption and reaction (SILAR) exhibit limited absorption below 500 nm with a net power conversion efficiency of ~1% when employed as a photoanode in QDSC. By depositing a thin barrier layer of Al(2)O(3), the TiO(2)-CdS films were further modified with a NIR absorbing squaraine dye. Quantum dot sensitized solar cells supersensitized with a squariand dye (JK-216) showed good stability during illumination with standard global AM 1.5 solar conditions, delivering a maximum overall power conversion efficiency (η) of 3.14%. Transient absorption and pulse radiolysis measurements provide further insight into the excited state interactions of squaraine dye with SiO(2), TiO(2), and TiO(2)/CdS/Al(2)O(3) films and interfacial electron transfer processes. The synergy of combining semiconductor quantum dots and NIR absorbing dye provides new opportunities to harvest photons from different regions of the solar spectrum. © 2011 American Chemical Society

Interplay of Cation Ordering and Ferroelectricity in Perovskite Tin Iodides: Designing a Polar Halide Perovskite for Photovoltaic Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gou, Gaoyang; Young, Joshua; Liu, Xian

2016-09-28

Owing to its ideal semiconducting band gap and good carrier transport properties, the fully inorganic perovskite CsSnI 3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic inorganic lead halide perovskite CH 3NH 3PbI 3, CsSnI 3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI 3. Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI 3, including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to createmore » the double perovskite (CsRb)Sn 2I 6. We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI 6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI 3. More importantly, unlike nonpolar CsSnI 3, the electric polarization present in ferroelectric (CsRb)Sn 2I 6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with,potentially enhanced energy conversion efficiency.« less

Plasmon-mediated Energy Conversion in Metal Nanoparticle-doped Hybrid Nanomaterials

NASA Astrophysics Data System (ADS)

Dunklin, Jeremy R.

Climate change and population growth demand long-term solutions for clean water and energy. Plasmon-active nanomaterials offer a promising route towards improved energetics for efficient chemical separation and light harvesting schemes. Two material platforms featuring highly absorptive plasmonic gold nanoparticles (AuNPs) are advanced herein to maximize photon conversion into thermal or electronic energy. Optical extinction, attributable to diffraction-induced internal reflection, was enhanced up to 1.5-fold in three-dimensional polymer films containing AuNPs at interparticle separations approaching the resonant wavelength. Comprehensive methods developed to characterize heat dissipation following plasmonic absorption was extended beyond conventional optical and heat transfer descriptions, where good agreement was obtained between measured and estimated thermal profiles for AuNP-polymer dispersions. Concurrently, in situ reduction of AuNPs on two-dimensional semiconducting tungsten disulfide (WS2) addressed two current material limitations for efficient light harvesting: low monolayer content and lack of optoelectronic tunability. Order-of-magnitude increases in WS2 monolayer content, enhanced broadband optical extinction, and energetic electron injection were probed using a combination of spectroscopic techniques and continuum electromagnetic descriptions. Together, engineering these plasmon-mediated hybrid nanomaterials to facilitate local exchange of optical, thermal, and electronic energy supports design and implementation into several emerging sustainable water and energy applications.

Mid-infrared Raman amplification and wavelength conversion in dispersion engineered silicon-on-sapphire waveguides

NASA Astrophysics Data System (ADS)

Wang, Zhaolu; Liu, Hongjun; Huang, Nan; Sun, Qibing; Li, Xuefeng

2014-01-01

Raman amplification based on stimulated Stokes Raman scattering (SSRS) and wavelength conversion based on coherent anti-Stokes Raman scattering (CARS) are theoretically investigated in silicon-on-sapphire (SOS) waveguides in the mid-infrared (IR) region. When the linear phase mismatch Δk is close to zero, the Stokes gain and conversion efficiency drop down quickly due to the effect of parametric gain suppression when the Stokes-pump input ratio is sufficiently large. The Stokes gain increases with the increase of Δk, whereas efficient wavelength conversion needs appropriate Δk under different pump intensities. The conversion efficiency at exact linear phase matching (Δk = 0) is smaller than that at optimal linear phase mismatch by a factor of about 28 dB when the pump intensity is 2 GW cm-2.

Calorimetric Measurement for Internal Conversion Efficiency of Photovoltaic Cells/Modules Based on Electrical Substitution Method

NASA Astrophysics Data System (ADS)

Saito, Terubumi; Tatsuta, Muneaki; Abe, Yamato; Takesawa, Minato

2018-02-01

We have succeeded in the direct measurement for solar cell/module internal conversion efficiency based on a calorimetric method or electrical substitution method by which the absorbed radiant power is determined by replacing the heat absorbed in the cell/module with the electrical power. The technique is advantageous in that the reflectance and transmittance measurements, which are required in the conventional methods, are not necessary. Also, the internal quantum efficiency can be derived from conversion efficiencies by using the average photon energy. Agreements of the measured data with the values estimated from the nominal values support the validity of this technique.

Lamb wave propagation in monocrystalline silicon wafers.

PubMed

Fromme, Paul; Pizzolato, Marco; Robyr, Jean-Luc; Masserey, Bernard

2018-01-01

Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. Guided ultrasonic waves offer the potential to efficiently detect micro-cracks in the thin wafers. Previous studies of ultrasonic wave propagation in silicon focused on effects of material anisotropy on bulk ultrasonic waves, but the dependence of the wave propagation characteristics on the material anisotropy is not well understood for Lamb waves. The phase slowness and beam skewing of the two fundamental Lamb wave modes A 0 and S 0 were investigated. Experimental measurements using contact wedge transducer excitation and laser measurement were conducted. Good agreement was found between the theoretically calculated angular dependency of the phase slowness and measurements for different propagation directions relative to the crystal orientation. Significant wave skew and beam widening was observed experimentally due to the anisotropy, especially for the S 0 mode. Explicit finite element simulations were conducted to visualize and quantify the guided wave beam skew. Good agreement was found for the A 0 mode, but a systematic discrepancy was observed for the S 0 mode. These effects need to be considered for the non-destructive testing of wafers using guided waves.

Sustainable, efficient livestock production with high biodiversity and good welfare for animals

PubMed Central

Broom, D. M.; Galindo, F. A.; Murgueitio, E.

2013-01-01

What is the future for livestock agriculture in the world? Consumers have concerns about sustainability but many widely used livestock production methods do not satisfy consumers' requirements for a sustainable system. However, production can be sustainable, occurring in environments that: supply the needs of the animals resulting in good welfare, allow coexistence with a wide diversity of organisms native to the area, minimize carbon footprint and provide a fair lifestyle for the people working there. Conservation need not just involve tiny islands of natural vegetation in a barren world of agriculture, as there can be great increases in biodiversity in farmed areas. Herbivores, especially ruminants that consume materials inedible by humans, are important for human food in the future. However, their diet should not be just ground-level plants. Silvopastoral systems, pastures with shrubs and trees as well as herbage, are described which are normally more productive than pasture alone. When compared with widely used livestock production systems, silvopastoral systems can provide efficient feed conversion, higher biodiversity, enhanced connectivity between habitat patches and better animal welfare, so they can replace existing systems in many parts of the world and should be further developed. PMID:24068362

An easily regenerable enzyme reactor prepared from polymerized high internal phase emulsions.

PubMed

Ruan, Guihua; Wu, Zhenwei; Huang, Yipeng; Wei, Meiping; Su, Rihui; Du, Fuyou

2016-04-22

A large-scale high-efficient enzyme reactor based on polymerized high internal phase emulsion monolith (polyHIPE) was prepared. First, a porous cross-linked polyHIPE monolith was prepared by in-situ thermal polymerization of a high internal phase emulsion containing styrene, divinylbenzene and polyglutaraldehyde. The enzyme of TPCK-Trypsin was then immobilized on the monolithic polyHIPE. The performance of the resultant enzyme reactor was assessed according to the conversion ability of Nα-benzoyl-l-arginine ethyl ester to Nα-benzoyl-l-arginine, and the protein digestibility of bovine serum albumin (BSA) and cytochrome (Cyt-C). The results showed that the prepared enzyme reactor exhibited high enzyme immobilization efficiency and fast and easy-control protein digestibility. BSA and Cyt-C could be digested in 10 min with sequence coverage of 59% and 78%, respectively. The peptides and residual protein could be easily rinsed out from reactor and the reactor could be regenerated easily with 4 M HCl without any structure destruction. Properties of multiple interconnected chambers with good permeability, fast digestion facility and easily reproducibility indicated that the polyHIPE enzyme reactor was a good selector potentially applied in proteomics and catalysis areas. Copyright © 2016 Elsevier Inc. All rights reserved.

Sustainable, efficient livestock production with high biodiversity and good welfare for animals.

PubMed

Broom, D M; Galindo, F A; Murgueitio, E

2013-11-22

What is the future for livestock agriculture in the world? Consumers have concerns about sustainability but many widely used livestock production methods do not satisfy consumers' requirements for a sustainable system. However, production can be sustainable, occurring in environments that: supply the needs of the animals resulting in good welfare, allow coexistence with a wide diversity of organisms native to the area, minimize carbon footprint and provide a fair lifestyle for the people working there. Conservation need not just involve tiny islands of natural vegetation in a barren world of agriculture, as there can be great increases in biodiversity in farmed areas. Herbivores, especially ruminants that consume materials inedible by humans, are important for human food in the future. However, their diet should not be just ground-level plants. Silvopastoral systems, pastures with shrubs and trees as well as herbage, are described which are normally more productive than pasture alone. When compared with widely used livestock production systems, silvopastoral systems can provide efficient feed conversion, higher biodiversity, enhanced connectivity between habitat patches and better animal welfare, so they can replace existing systems in many parts of the world and should be further developed.

Blended news delivery in healthcare: a framework for injecting good news into bad news conversations.

PubMed

Legg, Angela M; Sweeny, Kate

2015-01-01

Clinicians often inject good news into bad news delivery, and they do so for a variety of reasons. We present a framework that draws from research in the fields of health and social psychology to shed light on situations in which clinicians add superfluous good news into bad news conversations in an effort to ease the conversation or mitigate patients' distress, a broad strategy we refer to as blended news delivery. Our framework includes predictors of clinicians' use of blended news delivery, characteristics of blended news and outcomes of this strategy for both patients and clinicians. This framework addresses a common aspect of health communication and can direct future research on ideal strategies for and likely consequences of blended news delivery and communication more broadly.

Current Issues in Molecular Catalysis Illustrated by Iron Porphyrins as Catalysts of the CO2-to-CO Electrochemical Conversion.

PubMed

Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel

2015-12-15

Recent attention aroused by the reduction of carbon dioxide has as main objective the production of useful products, the "solar fuels", in which solar energy would be stored. One route to this goal is the design of photochemical schemes that would operate this conversion using directly sun light energy. An indirect approach consists in first converting sunlight energy into electricity then using it to reduce CO2 electrochemically. Conversion of carbon dioxide into carbon monoxide is thus a key step through the classical dihydrogen-reductive Fischer-Tropsch chemistry. Direct and catalytic electrochemical CO2 reduction already aroused active interest during the 1980-1990 period. The new wave of interest for these matters that has been growing since 2012 is in direct conjunction with modern energy issues. Among molecular catalysts, electrogenerated Fe(0) porphyrins have proved to be particularly efficient and robust. Recent progress in this field has closely associated the search of more and more efficient catalysts in the iron porphyrin family with an unprecedentedly rigorous deciphering of mechanisms. Accordingly, the coupling of proton transfer with electron transfer and breaking of one of the two C-O bonds of CO2 have been the subjects of relentless scrutiny and mechanistic analysis with systematic investigation of the degree of concertedness of these three events. Catalysis of the electrochemical CO2-to-CO conversion has thus been a good testing ground for the mechanism diagnostic strategies and the all concerted reactivity model proposed then. The role of added Brönsted acids, both as H-bond providers and proton donors, has been elucidated. These efforts have been a preliminary to the inclusion of the acid functionalities within the catalyst molecule, giving rise to considerable increase of the catalytic efficiency. The design of more and more efficient catalysts made it necessary to propose "catalytic Tafel plots" relating the turnover frequency to the overpotential as a rational way of benchmarking the catalysts within iron porphyrins and among all available molecular catalysts, independently of the characteristics of the electrolytic cell in use. To be reliable, such assignments of the intrinsic characteristics of catalysts are grounded in the accurate elucidation of mechanisms. Without forgetting the importance of large scale electrolysis, not only mobilization of all resources of nondestructive techniques such as cyclic voltammetry was necessary to achieve this challenge, but also new approaches, such as foot-of-the-wave analysis combined with raising of scan rate, had to be applied. The latest improvement in catalyst design was to render it water-soluble while preserving, or even augmenting, its catalytic efficiency. The replacement of the nonaqueous solvents so far used by water makes the CO2-to-CO half-cell reaction much more attractive for applications, allowing its association with a water-oxidation anode through a proton-exchange membrane. Manipulation of pH and buffering then allow CO2-to-CO conversions from those involving complete CO-selectivity to ones with prescribed CO-H2 mixtures. Overall, it appears that not only are iron porphyrins the most efficient catalysts of the CO2-to-CO electrochemical conversion but also they can serve to illustrate general issues concerning the field of molecular catalysis as a whole, including other reductive or oxidative processes.

Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, Yan; Chen, Changhua; Sun, Jun

2015-11-07

This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the frontmore » end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.« less

DNA-mediated excitonic upconversion FRET switching

DOE PAGES

Kellis, Donald L.; Rehn, Sarah M.; Cannon, Brittany L.; ...

2015-11-17

Excitonics is a rapidly expanding field of nanophotonics in which the harvesting of photons, ensuing creation and transport of excitons via Förster resonant energy transfer (FRET), and subsequent charge separation or photon emission has led to the demonstration of excitonic wires, switches, Boolean logic and light harvesting antennas for many applications. FRET funnels excitons down an energy gradient resulting in energy loss with each step along the pathway. Conversely, excitonic energy up conversion via up conversion nanoparticles (UCNPs), although currently inefficient, serves as an energy ratchet to boost the exciton energy. Although FRET-based up conversion has been demonstrated, it suffersmore » from low FRET efficiency and lacks the ability to modulate the FRET. We have engineered an up conversion FRET-based switch by combining lanthanide-doped UCNPs and fluorophores that demonstrates excitonic energy up conversion by nearly a factor of 2, an excited state donor to acceptor FRET efficiency of nearly 25%, and an acceptor fluorophore quantum efficiency that is close to unity. These findings offer a promising path for energy up conversion in nanophotonic applications including artificial light harvesting, excitonic circuits, photovoltaics, nanomedicine, and optoelectronics.« less

Hydroacylation of 2-vinyl benzaldehyde systems: an efficient method for the synthesis of chiral 3-substituted indanones.

PubMed

Kundu, Kousik; McCullagh, James V; Morehead, Andrew T

2005-11-23

Asymmetric rhodium-catalyzed hydroacylation has been utilized in the synthesis of 3-substituted indanones with high conversions and enantioselectivity. The hydroacylation reaction of 2-vinyl benzaldehyde had been previously reported to give a low yield of indanone and an unidentified product. We have identified this compound as a dimer of the starting material. Substitution at the alpha-position of the 2-vinyl benzaldehyde substrates blocks the competitive dimerization reaction and allows the reaction to proceed with yields generally greater than 90%. Utilization of BINAP as a chiral ligand results in good chemical yields and enantioselectivity greater than 95% in most cases.

Reconfigurable radio-over-fiber system based on optical switch and tunable filter

NASA Astrophysics Data System (ADS)

Li, Xiao; Yin, Rui; Ji, Wei; Sun, Kai; Zhang, Shicheng

2017-09-01

As the best candidate for wireless-access networks, radio-over-fiber (RoF) technology can carry a variety of business. It is necessary to provide differentiated services for different users, so the network needs to produce signals with different modulation formats and different frequencies. A reconfigurable RoF system based on a switch and tunable optical filter that can realize modulation format conversion and multiple frequency signal switching functions is designed. It has a good performance in terms of bit error rate and an eye diagram. The design can help to use radio frequency resources efficiently and make dynamic bandwidth resources controllable.

Preparation of ZnS microdisks using chemical bath deposition and ZnS/p-Si heterojunction solar cells

NASA Astrophysics Data System (ADS)

Hsiao, Y. J.; Meen, T. H.; Ji, L. W.; Tsai, J. K.; Wu, Y. S.; Huang, C. J.

2013-10-01

The synthesis and heterojunction solar cell properties of ZnS microdisks prepared by the chemical bath deposition method were investigated. The ZnS deposited on the p-Si blanket substrate exhibits good coverage. The lower reflectance spectra were found as the thickness of the ZnS film increased. The optical absorption spectra of the 80 °C ZnS microdisk exhibited a band-gap energy of 3.4 eV and the power conversion efficiency (PCE) of the AZO/ZnS/p-Si heterojunction solar cell with a 300 nm thick ZnS film was η=2.72%.

36 W Q-switched Ho:YAG laser at 2097 nm pumped by a Tm fiber laser: evaluation of different Ho3+ doping concentrations

NASA Astrophysics Data System (ADS)

Antipov, O. L.; Eranov, I. D.; Kositsyn, R. I.

2017-01-01

A laser oscillator based on Ho:YAG crystal pumped by a Tm fiber laser with an acousto-optical Q-switch was optimized for maximum output power and pulse-to-pulse stability. Stable operation at 2097 nm in Q-switched mode is demonstrated, with pulse repetition rates from 10 to 30 kHz, and output power of 36 W (at 55 W of pump power at 1908 nm) in the good quality beam. The influence of Ho ion up-conversion and thermal lensing on the oscillation efficiency is discussed.

Impacts of kafirin allelic diversity, starch content, and protein digestibility on ethanol conversion efficiency in grain sorghum

USDA-ARS?s Scientific Manuscript database

Seed protein and starch composition determines the efficiency of ethanol conversion in the production of grain-based biofuels. Sorghum, highly water- and nutrient-efficient, has the potential to replace fuel crops with greater irrigation and fertiliser requirements, such as maize. However, sorghum g...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todt, Michael A.; Isenberg, Allan E.; Nanayakkara, Sanjini U.

Semiconducting transition-metal dichalcogenide (TMD) nanoflake thin films are promising large-area electrodes for photo-electrochemical solar energy conversion applications. However, their energy conversion efficiencies are typically much lower than those of bulk electrodes. It is unclear to what extent this efficiency gap stems from differences among nanoflakes (e.g., area, thickness, and surface structural features). It is also unclear whether individual exfoliated nanoflakes can achieve energy conversion efficiencies similar to those of bulk crystals. Here, we use a single-nanoflake photo-electrochemical approach to show that there are both highly active and completely inactive nanoflakes within a film. For the exfoliated MoSe 2 samples studiedmore » herein, 7% of nanoflakes are highly active champions, whose photocurrent efficiency exceeds that of the bulk crystal. However, 66% of nanoflakes are inactive spectators, which are mostly responsible for the overall lower photocurrent efficiency compared to the bulk crystal. The photocurrent collection efficiency increases with nanoflake area and decreases more at perimeter edges than at interior step edges. These observations, which are hidden in ensemble-level measurements, reveal the underlying performance issues of exfoliated TMD electrodes for photo-electrochemical energy conversion applications.« less

Spectroscopic insights on selfassembly and excited state interactions between rhodamine and phthalocyanine molecules.

PubMed

Geng, Hao; Zhang, Xian-Fu

2015-03-15

The absorption and fluorescence spectra as well as fluorescence lifetimes of tetrasulfonated zinc phthalocyanine ZnPc(SO3Na)4 were measured in the absence and presence of four rhodamine dyes, Rhodamine B (RB), Ethyl rhodamine B (ERB), Rhodamine 6G (R6G), Rhodamine 110 (R110), and Pyronine B (PYB). The ground state complexes of phthalocyanine-(Rhodamine)2 were observed which exhibit new absorption bands. The binding constants are all very large (0.86×10(5)-0.22×10(8) M(-1)), suggesting rhodamine-phthalocyanine pairs are very good combinations for efficient selfassembly. Both the fluorescence intensity and the lifetime values of ZnPc(SO3Na)4 were decreased by the presence of rhodamines. The structural effect of rhodamines on selfassembly is significant. The ground state binding and dynamic quenching capability is PYB>R6G>ERB>RB>R110. The dynamic fluorescence quenching is due to the photoinduced electron transfer (PET). The PET rate constant is very large and in the order of 10(13) M(-1) s(-1), much greater than kf and kic (in the order of 10(8) M(-1) s(-1)), which means that the PET efficiency is almost 100%. Therefore the non-covalent Pc-rhodamine is a very good pair of donor/acceptor for potential efficient solar energy conversion. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanotechnology in lithium niobate for integrated optic frequency conversion in the UV

NASA Astrophysics Data System (ADS)

Busacca, Alessandro C.; Santini, Claudia; Oliveri, Luigi; Riva-Sanseverino, Stefano; Parisi, Antonino; Cino, Alfonso C.; Assanto, Gaetano

2017-11-01

In the domain of Earth Explorer satellites nanoengineered nonlinear crystals can optimize UV tunable solid-state laser converters. Lightweight sources can be based on Lithium Niobate (LN) domain engineering by electric field poling and guided wave interactions. In this Communication we report the preliminary experimental results and the very first demonstration of UltraViolet second-harmonic generation by first-order quasi-phase-matching in a surface-periodically-poled proton-exchanged LN waveguide. The pump source was a Ti-Sapphire laser with a tunability range of 700- 980 nm and a 40 GHz linewidth. We have measured UV continuous-wave light at 390 nm by means of a lock-in amplifier and of a photodiode with enhanced response in the UV. Measured conversion efficiency was about 1%W-1cm-2. QPM experiments show good agreement with theory and pave the way for a future implementation of the technique in materials less prone to photorefractive damage and wider transparency in the UV, such as Lithium Tantalate.

Determination of epichlorohydrin and 1,3-dichloro-2-propanol in synthesis of cationic etherifying reagent by headspace gas chromatography.

PubMed

Tao, Zheng-Yi; Chai, Xin-Sheng; Wu, Shu-Bin

2011-09-16

This study demonstrates a headspace gas chromatographic(HS-GC) technique for the determination of residual epichlorohydrin (ECH) and generated 1,3-dichloro-2-propanol (DCP) in synthesis process of 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHTAC). By a weight-based sampling method, coupled with significant dilution in 15.8% sodium sulfate and 0.1% silver nitrate mixed solution rapidly, the sample for HS-GC analysis is prepared. Based on the reaction stoichiometry, the conversion (R) of CHTAC during the synthesis process can be calculated from sampling weight and GC peak area. The results showed that the method has a good measurement precision (RSD<2.5%) and accuracy (recovery=101-104%) for the quantification of both ECH and DCP in the process samples. The present method is simple and accurate, which can be used for the efficient determination of the CHTAC conversion in the synthesis research. Copyright © 2011 Elsevier B.V. All rights reserved.

Understanding chemically processed solar cells based on quantum dots

NASA Astrophysics Data System (ADS)

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-12-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

Understanding chemically processed solar cells based on quantum dots.

PubMed

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO 2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

Mode conversion efficiency to Laguerre-Gaussian OAM modes using spiral phase optics.

PubMed

Longman, Andrew; Fedosejevs, Robert

2017-07-24

An analytical model for the conversion efficiency from a TEM 00 mode to an arbitrary Laguerre-Gaussian (LG) mode with null radial index spiral phase optics is presented. We extend this model to include the effects of stepped spiral phase optics, spiral phase optics of non-integer topological charge, and the reduction in conversion efficiency due to broad laser bandwidth. We find that through optimization, an optimal beam waist ratio of the input and output modes exists and is dependent upon the output azimuthal mode number.

Indium oxide/n-silicon heterojunction solar cells

DOEpatents

Feng, Tom; Ghosh, Amal K.

1982-12-28

A high photo-conversion efficiency indium oxide/n-silicon heterojunction solar cell is spray deposited from a solution containing indium trichloride. The solar cell exhibits an Air Mass One solar conversion efficiency in excess of about 10%.

Fully Controllable Pancharatnam-Berry Metasurface Array with High Conversion Efficiency and Broad Bandwidth

PubMed Central

Liu, Chuanbao; Bai, Yang; Zhao, Qian; Yang, Yihao; Chen, Hongsheng; Zhou, Ji; Qiao, Lijie

2016-01-01

Metasurfaces have powerful abilities to manipulate the properties of electromagnetic waves flexibly, especially the modulation of polarization state for both linearly polarized (LP) and circularly polarized (CP) waves. However, the transmission efficiency of cross-polarization conversion by a single-layer metasurface has a low theoretical upper limit of 25% and the bandwidth is usually narrow, which cannot be resolved by their simple additions. Here, we efficiently manipulate polarization coupling in multilayer metasurface to promote the transmission of cross-polarization by Fabry-Perot resonance, so that a high conversion coefficient of 80–90% of CP wave is achieved within a broad bandwidth in the metasurface with C-shaped scatters by theoretical calculation, numerical simulation and experiments. Further, fully controlling Pancharatnam-Berry phase enables to realize polarized beam splitter, which is demonstrated to produce abnormal transmission with high conversion efficiency and broad bandwidth. PMID:27703254

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler.

PubMed

Kardaś, Tomasz M; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-22

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

NASA Astrophysics Data System (ADS)

Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-01

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Plasma Accelerator and Energy Conversion Research

DTIC Science & Technology

1982-10-29

performance tests have been accomplished. A self-contained recirculating AMTEC device with a thermal to electric conversion efficiency of 19% has been...combined efficiency . These two match up particularly well, because thermionic conversion is a high temperature technique, whereas AMTEC is limited to...EXPERIENTAL: Samples: The samples were prepared with a high rate DC magnetron sputtering apparatus ( SFI model 1 ). The sample set consisted of four

Comparative efficiency of technologies for conversion and transportation of energy resources of Russia's eastern regions to NEA countries

NASA Astrophysics Data System (ADS)

Kler, Aleksandr; Tyurina, Elina; Mednikov, Aleksandr

2018-01-01

The paper presents perspective technologies for combined conversion of fossil fuels into synthetic liquid fuels and electricity. The comparative efficiency of various process flows of conversion and transportation of energy resources of Russia's east that are aimed at supplying electricity to remote consumers is presented. These also include process flows based on production of synthetic liquid fuel.

Investigation of Saturation Effects in Ceramic Phosphors for Laser Lighting

PubMed Central

Krasnoshchoka, Anastasiia; Dam-Hansen, Carsten; Corell, Dennis Dan; Petersen, Paul Michael

2017-01-01

We report observations of saturation effects in a Ce:LuAG and Eu-doped nitride ceramic phosphor for conversion of blue laser light for white light generation. The luminous flux from the phosphors material increases linearly with the input power until saturation effects limit the conversion. It is shown that the temperature of the phosphor layer influences the saturation power level and the conversion efficiency. It is also shown that the correlated color temperature (CCT), phosphor conversion efficiency and color rendering index (CRI) are dependent both on the incident power and spot size diameter of the illumination. A phosphor conversion efficiency up to 140.8 lm/W with CRI of 89.4 was achieved. The saturation in a ceramic phosphor, when illuminated by high intensity laser diodes, is estimated to play the main role in limiting the available luminance from laser-based lighting systems. PMID:29292770

Solvent-free enzymatic synthesis of 1, 3-Diacylglycerols by direct esterification of glycerol with saturated fatty acids

PubMed Central

2013-01-01

Background Pure 1, 3-diacylglycerols (1, 3-DAG) have been considered to be significant surfactants in food, cosmetics and pharmaceutical industries, as well as the effect on obesity prevention. Methods In this study, a vacuum-driven air bubbling operation mode was developed and evaluated for the enzymatic synthesis of 1, 3-DAG of saturated fatty acids, by direct esterification of glycerol with fatty acids in a solvent-free system. The employed vacuum-driven air bubbling operation mode was comparable to vacuum-driven N2 bubbling protocol, in terms of lauric acid conversion and 1, 3-dilaurin content. Results Some operation parameters were optimized, and 95.3% of lauric acid conversion and 80.3% of 1, 3-dilaurin content was obtained after 3-h reaction at 50°C, with 5 wt% of Lipozyme RM IM (based on reactants) amount. Of the lipases studied, both Lipozyme RM IM and Novozym 435 exhibited good performance in terms of lauric acid conversion. Lipozyme TL IM, however, showed low activity. Lipozyme RM IM showed good operational stability in this operation protocol, 80.2% of the original catalytic activity remained after 10 consecutive batch applications. Some other 1, 3-DAG were prepared and high content was obtained after purification: 98.5% for 1, 3-dicaprylin, 99.2% for 1, 3-dicaprin, 99.1% for 1, 3-dilaurin, 99.5 for 1, 3-dipalmitin and 99.4% for 1, 3-disterin. Conclusion The established vacuum-driven air bubbling operation protocol had been demonstrated to be a simple-operating, cost-effective, application practical and efficient methodology for 1, 3-DAG preparation. PMID:23656739

Efficiency enhancement of organic solar cells using transparent plasmonic Ag nanowire electrodes.

PubMed

Kang, Myung-Gyu; Xu, Ting; Park, Hui Joon; Luo, Xiangang; Guo, L Jay

2010-10-15

Surface plasmon enhanced photo-current and power conversion efficiency of organic solar cells using periodic Ag nanowires as transparent electrodes are reported, as compared to the device with conventional ITO electrodes. External quantum efficiencies are enhanced about 2.5 fold around the peak solar spectrum wavelength of 560 nm, resulting in 35% overall increase in power conversion efficiency than the ITO control device under normal unpolarized light.

Innovative open air brayton combined cycle systems for the next generation nuclear power plants

NASA Astrophysics Data System (ADS)

Zohuri, Bahman

The purpose of this research was to model and analyze a nuclear heated multi-turbine power conversion system operating with atmospheric air as the working fluid. The air is heated by a molten salt, or liquid metal, to gas heat exchanger reaching a peak temperature of 660 0C. The effects of adding a recuperator or a bottoming steam cycle have been addressed. The calculated results are intended to identify paths for future work on the next generation nuclear power plant (GEN-IV). This document describes the proposed system in sufficient detail to communicate a good understanding of the overall system, its components, and intended uses. The architecture is described at the conceptual level, and does not replace a detailed design document. The main part of the study focused on a Brayton --- Rankine Combined Cycle system and a Recuperated Brayton Cycle since they offer the highest overall efficiencies. Open Air Brayton power cycles also require low cooling water flows relative to other power cycles. Although the Recuperated Brayton Cycle achieves an overall efficiency slightly less that the Brayton --- Rankine Combined Cycle, it is completely free of a circulating water system and can be used in a desert climate. Detailed results of modeling a combined cycle Brayton-Rankine power conversion system are presented. The Rankine bottoming cycle appears to offer a slight efficiency advantage over the recuperated Brayton cycle. Both offer very significant advantages over current generation Light Water Reactor steam cycles. The combined cycle was optimized as a unit and lower pressure Rankine systems seem to be more efficient. The combined cycle requires a lot less circulating water than current power plants. The open-air Brayton systems appear to be worth investigating, if the higher temperatures predicted for the Next Generation Nuclear Plant do materialize.

A cascaded QSAR model for efficient prediction of overall power conversion efficiency of all-organic dye-sensitized solar cells.

PubMed

Li, Hongzhi; Zhong, Ziyan; Li, Lin; Gao, Rui; Cui, Jingxia; Gao, Ting; Hu, Li Hong; Lu, Yinghua; Su, Zhong-Min; Li, Hui

2015-05-30

A cascaded model is proposed to establish the quantitative structure-activity relationship (QSAR) between the overall power conversion efficiency (PCE) and quantum chemical molecular descriptors of all-organic dye sensitizers. The cascaded model is a two-level network in which the outputs of the first level (JSC, VOC, and FF) are the inputs of the second level, and the ultimate end-point is the overall PCE of dye-sensitized solar cells (DSSCs). The model combines quantum chemical methods and machine learning methods, further including quantum chemical calculations, data division, feature selection, regression, and validation steps. To improve the efficiency of the model and reduce the redundancy and noise of the molecular descriptors, six feature selection methods (multiple linear regression, genetic algorithms, mean impact value, forward selection, backward elimination, and +n-m algorithm) are used with the support vector machine. The best established cascaded model predicts the PCE values of DSSCs with a MAE of 0.57 (%), which is about 10% of the mean value PCE (5.62%). The validation parameters according to the OECD principles are R(2) (0.75), Q(2) (0.77), and Qcv2 (0.76), which demonstrate the great goodness-of-fit, predictivity, and robustness of the model. Additionally, the applicability domain of the cascaded QSAR model is defined for further application. This study demonstrates that the established cascaded model is able to effectively predict the PCE for organic dye sensitizers with very low cost and relatively high accuracy, providing a useful tool for the design of dye sensitizers with high PCE. © 2015 Wiley Periodicals, Inc.

Solar photocatalytic gas-phase degradation of n-decane--a comparative study using cellulose acetate monoliths coated with P25 or sol-gel TiO₂ films.

PubMed

Miranda, Sandra M; Lopes, Filipe V S; Rodrigues-Silva, Caio; Martins, Susana D S; Silva, Adrián M T; Faria, Joaquim L; Boaventura, Rui A R; Vilar, Vítor J P

2015-01-01

Cellulose acetate monoliths (CAM) were used as the substrate for the deposition of TiO2 films to produce honeycombed photoactive structures to fill a tubular photoreactor equipped with a compound parabolic collector. By using such a setup, an efficient single-pass gas-phase conversion was achieved in the degradation of n-decane, a model volatile organic compound. The CAM three-dimensional, gas-permeable transparent structure with a rugged surface enables a good adhesion of the catalytic coating. It also provides a rigid structure for packing the tubular photoreactor, and maximizing the illuminated catalyst surface. The efficiency of the photocatalytic oxidation (PCO) process on n-decane degradation was evaluated under different operating conditions, such as feeding concentration (73 and 146 ppm), gas stream flow rate (73, 150, and 300 mL min(-1)), relative humidity (3 and 25 %), and UV irradiance (18.9, 29.1, and 38.4 WUV m(-2)). The results show that n-decane degradation by neat photolysis is negligible, but mineralization efficiencies of 86 and 82 % were achieved with P25-CAM and SG-CAM, respectively, for parent pollutant conversions above 95 %, under steady-state conditions. A mass transfer model, considering the mass balance to the plug-flow packed photoreactor, and PCO reaction given by a Langmuir-Hinshelwood bimolecular non-competitive two types of sites equation, was able to predict well the PCO kinetics under steady-state conditions, considering all the operational parameters tested. Overall, the performance of P25-CAM was superior taking into account mineralization efficiency, cost of preparation, surface roughness, and robustness of the deposited film.

Hollow Fluffy Co3O4 Cages as Efficient Electroactive Materials for Supercapacitors and Oxygen Evolution Reaction.

PubMed

Zhou, Xuemei; Shen, Xuetao; Xia, Zhaoming; Zhang, Zhiyun; Li, Jing; Ma, Yuanyuan; Qu, Yongquan

2015-09-16

Nano-/micrometer multiscale hierarchical structures not only provide large surface areas for surface redox reactions but also ensure efficient charge conductivity, which is of benefit for utilization in areas of electrochemical energy conversion and storage. Herein, hollow fluffy cages (HFC) of Co3O4, constructed of ultrathin nanosheets, were synthesized by the formation of Co(OH)2 hollow cages and subsequent calcination at 250 °C. The large surface area (245.5 m2 g(-1)) of HFC Co3O4 annealed at 250 °C ensures the efficient interaction between electrolytes and electroactive components and provides more active sites for the surface redox reactions. The hierarchical structures minimize amount of the grain boundaries and facilitate the charge transfer process. Thin thickness of nanosheets (2-3 nm) ensures the highly active sites for the surface redox reactions. As a consequence, HFC Co3O4 as the supercapacitor electrode exhibits a superior rate capability, shows an excellent cycliability of 10,000 cycles at 10 A g(-1), and delivers large specific capacitances of 948.9 and 536.8 F g(-1) at 1 and 40 A g(-1), respectively. Catalytic studies of HFC Co3O4 for oxygen evolution reaction display a much higher turnover frequency of 1.67×10(-2) s(-1) in pH 14.0 KOH electrolyte at 400 mV overpotential and a lower Tafel slope of 70 mV dec(-1). HFC Co3O4 with the efficient electrochemical activity and good stability can remain a promising candidate for the electrochemical energy conversion and storage.

Carbon quantum dots coated BiVO{sub 4} inverse opals for enhanced photoelectrochemical hydrogen generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nan, Feng; Shen, Mingrong; Fang, Liang, E-mail: zhkang@suda.edu.cn, E-mail: lfang@suda.edu.cn

Carbon quantum dots (CQDs) coated BiVO{sub 4} inverse opal (io-BiVO{sub 4}) structure that shows dramatic improvement of photoelectrochemical hydrogen generation has been fabricated using electrodeposition with a template. The io-BiVO{sub 4} maximizes photon trapping through slow light effect, while maintaining adequate surface area for effective redox reactions. CQDs are then incorporated to the io-BiVO{sub 4} to further improve the photoconversion efficiency. Due to the strong visible light absorption property of CQDs and enhanced separation of the photoexcited electrons, the CQDs coated io-BiVO{sub 4} exhibit a maximum photo-to-hydrogen conversion efficiency of 0.35%, which is 6 times higher than that of themore » pure BiVO{sub 4} thin films. This work is a good example of designing composite photoelectrode by combining quantum dots and photonic crystal.« less

Strong efficiency improvement in dye-sensitized solar cells by novel multi-dimensional TiO2 photoelectrode

NASA Astrophysics Data System (ADS)

Zhao, Fengyang; Ma, Rong; Jiang, Yongjian

2018-03-01

Titanium dioxide (TiO2) based dye-sensitized solar cells (DSSCs) often exhibit superior power conversion performance. Here we report a DSSC with novel hierarchical TiO2 composite structure (TCS) composed of anatase TiO2 micro-spheres and rutile TiO2 nanobelt framework by hydrothermal approach for high-performance. As photoanode, the TCS based DSSC shows a strong efficiency enhancement by 58% compared with Degussa TiO2 (P25)-DSSC (4.33%). The excellent performance is mainly attribute to its special multi-dimensional structures of TiO2: much active sites of 0D nanoparticle with exposed excellent {001} facet, special electronic transmission channel of 1D nanobelt, good dye adsorption capacity of 2D nanosheet and high light scattering ability of 3D micro-spheres. The novel multi-dimensional TCS materials will open up a new avenue to the electronic devices fields.

Evolved phase separation toward balanced charge transport and high efficiency in polymer solar cells.

PubMed

Fan, Haijun; Zhang, Maojie; Guo, Xia; Li, Yongfang; Zhan, Xiaowei

2011-09-01

Understanding effect of morphology on charge carrier transport within polymer/fullerene bulk heterojunction is necessary to develop high-performance polymer solar cells. In this work, we synthesized a new benzodithiophene-based polymer with good self-organization behavior as well as favorable morphology evolution of its blend films with PC(71)BM under improved processing conditions. Charge carrier transport behavior of blend films was characterized by space charge limited current method. Evolved blend film morphology by controlling blend composition and additive content gradually reaches an optimized state, featured with nanoscale fibrilla polymer phase in moderate size and balanced mobility ratio close to 1:1 for hole and electron. This optimized morphology toward more balanced charge carrier transport accounts for the best power conversion efficiency of 3.2%, measured under simulated AM 1.5 solar irradiation 100 mW/cm(2), through enhancing short circuit current and reducing geminate recombination loss.

Hollow mesoporous TiO2 microspheres for enhanced photocatalytic degradation of acetaminophen in water.

PubMed

Lin, Chin Jung; Yang, Wen-Ta; Chou, Chen-Yi; Liou, Sofia Ya Hsuan

2016-06-01

Hollow core-shell mesoporous TiO2 microspheres were synthesized by a template-free solvothermal route for efficient photocatalytic degradation of acetaminophen. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Barrett-Joyner-Halenda data revealed a micrometer-sized mesoporous anatase TiO2 hollow sphere with large surface area and efficient light harvesting. For the photocatalytic degradation of acetaminophen in 60 min, the conversion fraction of the drug increased from 88% over commercial Degussa P25 TiO2 to 94% over hollow spheres with about 25% increase in the initial reaction rate. Even after 10 repeated runs, the recycled hollow spheres showed good photodegradation activity. The intermediates generated in the photocatalytic reactions were eventually converted into molecules that are easier to handle. The simple fabrication route would facilitate the development of photocatalysts for the decomposition of environmental contaminants. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Polyoxovanadate-Resorcin[4]arene-Based Porous Metal-Organic Framework as an Efficient Multifunctional Catalyst for the Cycloaddition of CO2 with Epoxides and the Selective Oxidation of Sulfides.

PubMed

Lu, Bing-Bing; Yang, Jin; Liu, Ying-Ying; Ma, Jian-Fang

2017-10-02

In this work, we report a new polyoxovanadate-resorcin[4]arene-based metal-organic framework (PMOF), [Co 2 L 0.5 V 4 O 12 ]·3DMF·5H 2 O (1), assembled with a newly functionalized wheel-like resorcin[4]arene ligand (L). 1 features an elegant porous motif and represents a rare example of PMOFs composed of both a resorcin[4]arene ligand and polyoxovanadate. Remarkably, 1 shows open V sites in the channel, which makes 1 an efficient heterogeneous Lewis acid catalyst for the cycloaddition of carbon dioxide to epoxides with high conversion and selectivity. Strikingly, 1 also exhibits high catalytic activity for the heterogeneous oxidative desulfurization of sulfides. Particularly, the heterogeneous catalyst 1 can be easily separated and reused with good catalytic activity.

The effect of porous lead iodide precursor film on perovskite film formation and its photovoltaic property after an effective pretreatment

NASA Astrophysics Data System (ADS)

Yan, Jian-Jun; Li, Yan; Chang, Yin; Jiang, Pan; Wang, Cheng-Wei

2016-06-01

An effective solvent sealed natural drying (SND) pretreatment was introduced for forming a satisfactory crystalline porous iodide (PbI2) precursor film, which could help to generate excellent CH3NH3PbI3 perovskite films for high performance of planar heterojunction perovskite solar cells. And the influence of SND pretreated time on the device performance was investigated in detail. We found that the PbI2 precursor film after 10 min pretreatment could make the perovskite device achieve the optimal power conversion efficiency (PCE) of 8.6%, significantly increased up to 95.5% and 28.4% compared to without pretreatment or traditional treatment. The results show that the time of SND pretreatment is critical to forming large grain size and good crystallinity for PbI2 precursor film, which would markedly improve the efficiency of planar heterojunction perovskite solar cells.

Optimization of Norbornadiene Compounds for Solar Thermal Storage by First-Principles Calculations.

PubMed

Kuisma, Mikael; Lundin, Angelica; Moth-Poulsen, Kasper; Hyldgaard, Per; Erhart, Paul

2016-07-21

Molecular photoswitches capable of storing solar energy are interesting candidates for future renewable energy applications. Here, using quantum mechanical calculations, we carry out a systematic screening of crucial optical (solar spectrum match) and thermal (storage energy density) properties of 64 such compounds based on the norbornadiene-quadricyclane system. Whereas a substantial number of these molecules reach the theoretical maximum solar power conversion efficiency, this requires a strong red-shift of the absorption spectrum, which causes undesirable absorption by the photoisomer as well as reduced thermal stability. These compounds typically also have a large molecular mass, leading to low storage densities. By contrast, single-substituted systems achieve a good compromise between efficiency and storage density, while avoiding competing absorption by the photo-isomer. This establishes guiding principles for the future development of molecular solar thermal storage systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Co@Co3O4 nanoparticle embedded nitrogen-doped carbon architectures as efficient bicatalysts for oxygen reduction and evolution reactions

NASA Astrophysics Data System (ADS)

Qi, Chunling; Zhang, Li; Xu, Guancheng; Sun, Zhipeng; Zhao, Aihua; Jia, Dianzeng

2018-01-01

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play crucial roles in efficient energy conversion and storage solutions. Here, Co@Co3O4 nanoparticle embedded nitrogen-doped carbon architectures (denoted as Co@Co3O4/NCs) are prepared via a simple two-step and in situ approach by carbonization and subsequent oxidation of Co-MOF containing high contents of carbon and nitrogen. When evaluated as electrocatalyst towards both ORR and OER in a KOH electrolyte solution, the as-fabricated Co@Co3O4/NC-2 exhibits similar ORR catalytic activity to the commercial Pt/C catalyst, but superior stability and good methanol tolerance. Furthermore, the as-fabricated catalysts also show promising catalytic activity for OER. The effective catalytic activities originate from the synergistic effects between well wrapped Co@Co3O4 nanoparticles and nitrogen doped carbon structures.

Enhancement of photoelectrochemical activity of SnS thin-film photoelectrodes using TiO2, Nb2O5, and Ta2O5 metal oxide layers

NASA Astrophysics Data System (ADS)

Vequizo, Junie Jhon M.; Yokoyama, Masanori; Ichimura, Masaya; Yamakata, Akira

2016-06-01

Tin sulfide (SnS) fine photoelectrodes fabricated by three-step pulsed electrodeposition were active for H2 evolution. The incident-photon-conversion-efficiency increases from 900 nm and offers a good fit with the absorption spectrum. The activity was enhanced by 3.4, 3.0, and 1.8 times compared to bare SnS by loading Nb2O5, TiO2, and Ta2O5, respectively. Nb2O5 was most efficient because its conduction band is low enough to facilitate effective electron transfer from SnS; it also has sufficiently high potential for H2 evolution. The overall activity is determined by the competitive interfacial electron transfer between SnS/metal-oxide and metal-oxide/water. Therefore, constructing appropriate heterojunctions is necessary for further improving photoelectrochemical systems.

Method for forming indium oxide/n-silicon heterojunction solar cells

DOEpatents

Feng, Tom; Ghosh, Amal K.

1984-03-13

A high photo-conversion efficiency indium oxide/n-silicon heterojunction solar cell is spray deposited from a solution containing indium trichloride. The solar cell exhibits an Air Mass One solar conversion efficiency in excess of about 10%.

Adaptability of solar energy conversion systems on ships

NASA Astrophysics Data System (ADS)

Visa, I.; Cotorcea, A.; Neagoe, M.; Moldovan, M.

2016-08-01

International trade of goods largely uses maritime/transoceanic ships driven by engines using fossil fuels. This two centuries tradition is technologically mature but significantly adds to the CO2 emissions; therefore, recent trends focus on on-board implementation of systems converting the solar energy into power (photovoltaic systems) or heat (solar-thermal systems). These systems are carbon-emissions free but are still under research and plenty of effort is devoted to fast reach maturity and feasibility. Unlike the systems implemented in a specific continental location, the design of solar energy conversion systems installed on shipboard has to face the problem generated by the system base motion along with the ship travelling on routes at different latitudes: the navigation direction and sense and roll-pitch combined motion with reduced amplitude, but with relatively high frequency. These raise highly interesting challenges in the design and development of mechanical systems that support the maximal output in terms of electricity or heat. The paper addresses the modelling of the relative position of a solar energy conversion surface installed on a ship according to the current position of the sun; the model is based on the navigation trajectory/route, ship motion generated by waves and the relative sun-earth motion. The model describes the incidence angle of the sunray on the conversion surface through five characteristic angles: three used to define the ship orientation and two for the solar angles; based on, their influence on the efficiency in solar energy collection is analyzed by numerical simulations and appropriate recommendations are formulated for increasing the solar energy conversion systems adaptability on ships.

Red laser based on intra-cavity Nd:YAG/CH4 frequency doubled Raman lasers

NASA Astrophysics Data System (ADS)

Wang, Yanchao; Wang, Pengyuan; Liu, Jinbo; Liu, Wanfa; Guo, Jingwei

2017-01-01

Stimulated Raman scattering (SRS) is a powerful tool for the extension of the spectral range of lasers. To obtain efficient Raman conversion in SRS, many researchers have studied different types of Raman laser configurations. Among these configurations, the intra-cavity type is particularly attractive. Intra-cavity SRS has the advantages of high intra-cavity laser intensity, low-SRS threshold, and high Raman conversion efficiency. In this paper, An Q-switched intra-cavity Nd: YAG/CH4 frequency-doubled Raman lasers is reported. A negative branch confocal resonator with M= 1.25 is used for the frequency-doubling of Nd: YAG laser. The consequent 532nm light is confined in intra- cavity SRS with travelling wave resonator, and the focal of one mirror of cavity is overlap with the center of the other mirror of the cavity. We found this design is especially efficient to reduce the threshold of SRS, and increase conversion efficiency. The threshold is measured to be 0.62 MW, and at the pump energy of 16.1 mJ, the conversion efficiency is 34%. With the smaller magnification M, the threshold could further decrease, and the conversion efficiency could be improved further. This is a successful try to extend the spectral range of a laser to the shorter wavelength by SRS, and this design may play an important role in the fulfillment of high power red lasers.

Theoretical limits of the multistacked 1D and 2D microstructured inorganic solar cells

NASA Astrophysics Data System (ADS)

Yengel, Emre; Karaagac, Hakan; VJ, Logeeswaran; Islam, M. Saif

2015-09-01

Recent studies in monocrystalline semiconductor solar cells are focused on mechanically stacking multiple cells from different materials to increase the power conversion efficiency. Although, the results show promising increase in the device performance, the cost remains as the main drawback. In this study, we calculated the theoretical limits of multistacked 1D and 2D microstructered inorganic monocrstalline solar cells. This system is studied for Si and Ge material pair. The results show promising improvements in the surface reflection due to enhanced light trapping caused by photon-microstructures interactions. The theoretical results are also supported with surface reflection and angular dependent power conversion efficiency measurements of 2D axial microwall solar cells. We address the challenge of cost reduction by proposing to use our recently reported mass-manufacturable fracture-transfer- printing method which enables the use of a monocrystalline substrate wafer for repeated fabrication of devices by consuming only few microns of materials in each layer of devices. We calculated thickness dependent power conversion efficiencies of multistacked Si/Ge microstructured solar cells and found the power conversion efficiency to saturate at 26% with a combined device thickness of 30 μm. Besides having benefits of fabricating low-cost, light weight, flexible, semi-transparent, and highly efficient devices, the proposed fabrication method is applicable for other III-V materials and compounds to further increase the power conversion efficiency above 35% range.

A program for the calculation of paraboloidal-dish solar thermal power plant performance

NASA Technical Reports Server (NTRS)

Bowyer, J. M., Jr.

1985-01-01

A program capable of calculating the design-point and quasi-steady-state annual performance of a paraboloidal-concentrator solar thermal power plant without energy storage was written for a programmable calculator equipped with suitable printer. The power plant may be located at any site for which a histogram of annual direct normal insolation is available. Inputs required by the program are aperture area and the design and annual efficiencies of the concentrator; the intercept factor and apparent efficiency of the power conversion subsystem and a polynomial representation of its normalized part-load efficiency; the efficiency of the electrical generator or alternator; the efficiency of the electric power conditioning and transport subsystem; and the fractional parasitic loses for the plant. Losses to auxiliaries associated with each individual module are to be deducted when the power conversion subsystem efficiencies are calculated. Outputs provided by the program are the system design efficiency, the annualized receiver efficiency, the annualized power conversion subsystem efficiency, total annual direct normal insolation received per unit area of concentrator aperture, and the system annual efficiency.

Infrared Signal Detection by Upconversion Technique

NASA Technical Reports Server (NTRS)

Wong, Teh-Hwa; Yu, Jirong; Bai, Yingxin; Johnson, William E.

2014-01-01

We demonstrated up-conversion assisted detection of a 2.05-micron signal by using a bulk periodically poled Lithium niobate crystal. The 94% intrinsic up-conversion efficiency and 22.58% overall detection efficiency at pW level of 2.05-micron was achieved.

Sustainable and efficient pathways for bioenergy recovery from low-value process streams via bioelectrochemical systems in biorefineries

DOE PAGES

Borole, Abhijeet P.

2015-08-25

Conversion of biomass into bioenergy is possible via multiple pathways resulting in production of biofuels, bioproducts and biopower. Efficient and sustainable conversion of biomass, however, requires consideration of many environmental and societal parameters in order to minimize negative impacts. Integration of multiple conversion technologies and inclusion of upcoming alternatives such as bioelectrochemical systems can minimize these impacts and improve conservation of resources such as hydrogen, water and nutrients via recycle and reuse. This report outlines alternate pathways integrating microbial electrolysis in biorefinery schemes to improve energy efficiency while evaluating environmental sustainability parameters.

Cascaded-cladding-pumped cascaded Raman fiber amplifier.

PubMed

Jiang, Huawei; Zhang, Lei; Feng, Yan

2015-06-01

The conversion efficiency of double-clad Raman fiber laser is limited by the cladding-to-core area ratio. To get high conversion efficiency, the inner-cladding-to-core area ratio has to be less than about 8, which limits the brightness enhancement. To overcome the problem, a cascaded-cladding-pumped cascaded Raman fiber laser with multiple-clad fiber as the Raman gain medium is proposed. A theoretical model of Raman fiber amplifier with multiple-clad fiber is developed, and numerical simulation proves that the proposed scheme can improve the conversion efficiency and brightness enhancement of cladding pumped Raman fiber laser.

Efficient 525 nm laser generation in single or double resonant cavity

NASA Astrophysics Data System (ADS)

Liu, Shilong; Han, Zhenhai; Liu, Shikai; Li, Yinhai; Zhou, Zhiyuan; Shi, Baosen

2018-03-01

This paper reports the results of a study into highly efficient sum frequency generation from 792 and 1556 nm wavelength light to 525 nm wavelength light using either a single or double resonant ring cavity based on a periodically poled potassium titanyl phosphate crystal (PPKTP). By optimizing the cavity's parameters, the maximum power achieved for the resultant 525 nm laser was 263 and 373 mW for the single and double resonant cavity, respectively. The corresponding quantum conversion efficiencies were 8 and 77% for converting 1556 nm photons to 525 nm photons with the single and double resonant cavity, respectively. The measured intra-cavity single pass conversion efficiency for both configurations was about 5%. The performances of the sum frequency generation in these two configurations was studied and compared in detail. This work will provide guidelines for optimizing the generation of sum frequency generated laser light for a variety of configurations. The high conversion efficiency achieved in this work will help pave the way for frequency up-conversion of non-classical quantum states, such as the squeezed vacuum and single photon states. The proposed green laser source will be used in our future experiments, which includes a plan to generate two-color entangled photon pairs and achieve the frequency down-conversion of single photons carrying orbital angular momentum.

Potential natural sensitizers extracted from the skin of Canarium odontophyllum fruits for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lim, Andery; Kumara, N. T. R. N.; Tan, Ai Ling; Mirza, Aminul Huq; Chandrakanthi, R. L. N.; Petra, Mohammad Iskandar; Ming, Lim Chee; Senadeera, G. K. R.; Ekanayake, Piyasiri

2015-03-01

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs. The detected pigment constituents of the extract consist of aurone (maritimein), anthocyanidin (pelargonidin) and anthocyanidin (cyanidin derivatives). When tested in DSSC, the highest conversion efficiency of 1.43% is exhibited by cyanidin derivatives, and this is followed by conversion efficiencies of 0.51% and 0.79% for aurone and pelargonidin, respectively. It is shown that individual pigments, like cyanidin derivatives and pelargonidin, exhibit higher power conversion efficiency when compared to that of C.odontophyllum skin pigment mixture (with a conversion efficiency of only 0.68%). The results indicate a possibility of masking effects of the pigments when used as a mixture. The acidification of C.odontophyllum skin pigments with concentrated hydrochloric acid improves the conversion efficiency of the mixture from 0.68% to 0.99%. The discussion in this paper will draw data and observations from the variation in absorption and adsorption properties, the HOMO-LUMO levels, the energy band gaps and the functional group compositions of the detected flavonoids.

Bioinspired model of mechanical energy harvesting based on flexoelectric membranes.

PubMed

Rey, Alejandro D; Servio, P; Herrera-Valencia, E E

2013-02-01

Membrane flexoelectricity is an electromechanical coupling process that describes membrane electrical polarization due to bending and membrane bending under electric fields. In this paper we propose, formulate, and characterize a mechanical energy harvesting system consisting of a deformable soft flexoelectric thin membrane subjected to harmonic forcing from contacting bulk fluids. The key elements of the energy harvester are formulated and characterized, including (i) the mechanical-to-electrical energy conversion efficiency, (ii) the electromechanical shape equation connecting fluid forces with membrane curvature and electric displacement, and (iii) the electric power generation and efficiency. The energy conversion efficiency is cast as the ratio of flexoelectric coupling to the product of electric and bending elasticity. The device is described by a second-order curvature dynamics coupled to the electric displacement equation and as such results in mechanical power absorption with a resonant peak whose amplitude decreases with bending viscosity. The electric power generation is proportional to the conversion factor and the power efficiency decreases with frequency. Under high bending viscosity, the power efficiency increases with the conversion factor and under low viscosities it decreases with the conversion factor. The theoretical results presented contribute to the ongoing experimental efforts to develop mechanical energy harvesting from fluid flow energy through solid-fluid interactions and electromechanical transduction.

Experimental investigation on the hydrodynamic performance of a wave energy converter

NASA Astrophysics Data System (ADS)

Zheng, Xiong-bo; Ma, Yong; Zhang, Liang; Jiang, Jin; Liu, Heng-xu

2017-06-01

Wave energy is an important type of marine renewable energy. A wave energy converter (WEC) moored with two floating bodies was developed in the present study. To analyze the dynamic performance of the WEC, an experimental device was designed and tested in a tank. The experiment focused on the factors which impact the motion and energy conversion performance of the WEC. Dynamic performance was evaluated by the relative displacements and velocities of the oscillator and carrier which served as the floating bodies of WEC. Four factors were tested, i.e. wave height, wave period, power take-off (PTO) damping, and mass ratio ( R M) of the oscillator and carrier. Experimental results show that these factors greatly affect the energy conversion performance, especially when the wave period matches R M and PTO damping. According to the results, we conclude that: (a) the maximization of the relative displacements and velocities leads to the maximization of the energy conversion efficiency; (b) the larger the wave height, the higher the energy conversion efficiency will be; (c) the relationships of energy conversion efficiency with wave period, PTO damping, and R M are nonlinear, but the maximum efficiency is obtained when these three factors are optimally matched. Experimental results demonstrated that the energy conversion efficiency reached the peak at 28.62% when the wave height was 120 mm, wave period was 1.0 s, R M was 0.21, and the PTO damping was corresponding to the resistance of 100 Ω.

X-ray imaging using avalanche multiplication in amorphous selenium: investigation of intrinsic avalanche noise.

PubMed

Hunt, D C; Tanioka, Kenkichi; Rowlands, J A

2007-12-01

The flat-panel detector (FPD) is the state-of-the-art detector for digital radiography. The FPD can acquire images in real-time, has superior spatial resolution, and is free of the problems of x-ray image intensifiers-veiling glare, pin-cushion and magnetic distortion. However, FPDs suffer from poor signal to noise ratio performance at typical fluoroscopic exposure rates where the quantum noise is reduced to the point that it becomes comparable to the fixed electronic noise. It has been shown previously that avalanche multiplication gain in amorphous selenium (a-Se) can provide the necessary amplification to overcome the electronic noise of the FPD. Avalanche multiplication, however, comes with its own intrinsic contribution to the noise in the form of gain fluctuation noise. In this article a cascaded systems analysis is used to present a modified metric related to the detective quantum efficiency. The modified metric is used to study a diagnostic x-ray imaging system in the presence of intrinsic avalanche multiplication noise independently from other noise sources, such as electronic noise. An indirect conversion imaging system is considered to make the study independent of other avalanche multiplication related noise sources, such as the fluctuations arising from the depth of x-ray absorption. In this case all the avalanche events are initiated at the surface of the avalanche layer, and there are no fluctuations in the depth of absorption. Experiments on an indirect conversion x-ray imaging system using avalanche multiplication in a layer of a-Se are also presented. The cascaded systems analysis shows that intrinsic noise of avalanche multiplication will not have any deleterious influence on detector performance at zero spatial frequency in x-ray imaging provided the product of conversion gain, coupling efficiency, and optical quantum efficiency are much greater than a factor of 2. The experimental results show that avalanche multiplication in a-Se behaves as an intrinsic noise free avalanche multiplication, in accordance with our theory. Provided good coupling efficiency and high optical quantum efficiency are maintained, avalanche multiplication in a-Se has the potential to increase the gain and make negligible contribution to the noise, thereby improving the performance of indirect FPDs in fluoroscopy.

X-ray imaging using avalanche multiplication in amorphous selenium: Investigation of intrinsic avalanche noise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunt, D. C.; Tanioka, Kenkichi; Rowlands, J. A.

2007-12-15

The flat-panel detector (FPD) is the state-of-the-art detector for digital radiography. The FPD can acquire images in real-time, has superior spatial resolution, and is free of the problems of x-ray image intensifiers--veiling glare, pin-cushion and magnetic distortion. However, FPDs suffer from poor signal to noise ratio performance at typical fluoroscopic exposure rates where the quantum noise is reduced to the point that it becomes comparable to the fixed electronic noise. It has been shown previously that avalanche multiplication gain in amorphous selenium (a-Se) can provide the necessary amplification to overcome the electronic noise of the FPD. Avalanche multiplication, however, comesmore » with its own intrinsic contribution to the noise in the form of gain fluctuation noise. In this article a cascaded systems analysis is used to present a modified metric related to the detective quantum efficiency. The modified metric is used to study a diagnostic x-ray imaging system in the presence of intrinsic avalanche multiplication noise independently from other noise sources, such as electronic noise. An indirect conversion imaging system is considered to make the study independent of other avalanche multiplication related noise sources, such as the fluctuations arising from the depth of x-ray absorption. In this case all the avalanche events are initiated at the surface of the avalanche layer, and there are no fluctuations in the depth of absorption. Experiments on an indirect conversion x-ray imaging system using avalanche multiplication in a layer of a-Se are also presented. The cascaded systems analysis shows that intrinsic noise of avalanche multiplication will not have any deleterious influence on detector performance at zero spatial frequency in x-ray imaging provided the product of conversion gain, coupling efficiency, and optical quantum efficiency are much greater than a factor of 2. The experimental results show that avalanche multiplication in a-Se behaves as an intrinsic noise free avalanche multiplication, in accordance with our theory. Provided good coupling efficiency and high optical quantum efficiency are maintained, avalanche multiplication in a-Se has the potential to increase the gain and make negligible contribution to the noise, thereby improving the performance of indirect FPDs in fluoroscopy.« less

Biomass and Nitrogen Budgets During Larval Development of Lymantria dispar and Choristoneura fumiferana: Allometric Relationships

Treesearch

Michael E. Montgomery

1983-01-01

Spruce budworm larvae grew faster than gypsy moth larvae both in a temporal and relative sense. The budworm larvae had a higher relative growth rate (RGR), biomass conversion efficiency (EGI), and nitrogen utilization efficiency (NOE) than the gypsy moth larvae. As both species matured, relative growth rates, rates of consumption, and conversion efficiencies declined....

Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe 2 Films

DOE PAGES

Todt, Michael A.; Isenberg, Allan E.; Nanayakkara, Sanjini U.; ...

2018-03-06

Semiconducting transition-metal dichalcogenide (TMD) nanoflake thin films are promising large-area electrodes for photo-electrochemical solar energy conversion applications. However, their energy conversion efficiencies are typically much lower than those of bulk electrodes. It is unclear to what extent this efficiency gap stems from differences among nanoflakes (e.g., area, thickness, and surface structural features). It is also unclear whether individual exfoliated nanoflakes can achieve energy conversion efficiencies similar to those of bulk crystals. Here, we use a single-nanoflake photo-electrochemical approach to show that there are both highly active and completely inactive nanoflakes within a film. For the exfoliated MoSe 2 samples studiedmore » herein, 7% of nanoflakes are highly active champions, whose photocurrent efficiency exceeds that of the bulk crystal. However, 66% of nanoflakes are inactive spectators, which are mostly responsible for the overall lower photocurrent efficiency compared to the bulk crystal. The photocurrent collection efficiency increases with nanoflake area and decreases more at perimeter edges than at interior step edges. These observations, which are hidden in ensemble-level measurements, reveal the underlying performance issues of exfoliated TMD electrodes for photo-electrochemical energy conversion applications.« less

Battle for Climate and Scarcity Rents: Beyond the Linear-Quadratic Case.

PubMed

Kagan, Mark; van der Ploeg, Frederick; Withagen, Cees

Industria imports oil, produces final goods and wishes to mitigate global warming. Oilrabia exports oil and buys final goods from the other country. Industria uses the carbon tax to impose an import tariff on oil and steal some of Oilrabia's scarcity rent. Conversely, Oilrabia has monopoly power and sets the oil price to steal some of Industria's climate rent. We analyze the relative speeds of oil extraction and carbon accumulation under these strategic interactions for various production function specifications and compare these with the efficient and competitive outcomes. We prove that for the class of HARA production functions, the oil price is initially higher and subsequently lower in the open-loop Nash equilibrium than in the efficient outcome. The oil extraction rate is thus initially too low and in later stages too high. The HARA class includes linear, loglinear and semi-loglinear demand functions as special cases. For non-HARA production functions, Oilrabia may in the open-loop Nash equilibrium initially price oil lower than the efficient level, thus resulting in more oil extraction and climate damages. We also contrast the open-loop Nash and efficient outcomes numerically with the feedback Nash outcomes. We find that the optimal carbon tax path in the feedback Nash equilibrium is flatter than in the open-loop Nash equilibrium. It turns out that for certain demand functions using the carbon tax as an import tariff may hurt consumers' welfare as the resulting user cost of oil is so high that the fall in welfare wipes out the gain from higher tariff revenues.

Platinum-Free Counter Electrode Comprised of Metal-Organic-Framework (MOF)-Derived Cobalt Sulfide Nanoparticles for Efficient Dye-Sensitized Solar Cells (DSSCs)

PubMed Central

Hsu, Shao-Hui; Li, Chun-Ting; Chien, Heng-Ta; Salunkhe, Rahul R.; Suzuki, Norihiro; Yamauchi, Yusuke; Ho, Kuo-Chuan; Wu, Kevin C.-W.

2014-01-01

We fabricated a highly efficient (with a solar-to-electricity conversion efficiency (η) of 8.1%) Pt-free dye-sensitized solar cell (DSSC). The counter electrode was made of cobalt sulfide (CoS) nanoparticles synthesized via surfactant-assisted preparation of a metal organic framework, ZIF-67, with controllable particle sizes (50 to 320 nm) and subsequent oxidation and sulfide conversion. In contrast to conventional Pt counter electrodes, the synthesized CoS nanoparticles exhibited higher external surface areas and roughness factors, as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) element mapping, and electrochemical analysis. Incident photon-to-current conversion efficiency (IPCE) results showed an increase in the open circuit voltage (VOC) and a decrease in the short-circuit photocurrent density (Jsc) for CoS-based DSSCs compared to Pt-based DSSCs, resulting in a similar power conversion efficiency. The CoS-based DSSC fabricated in the study show great potential for economically friendly production of Pt-free DSSCs. PMID:25382139

Two-step photon up-conversion solar cells

PubMed Central

Asahi, Shigeo; Teranishi, Haruyuki; Kusaki, Kazuki; Kaizu, Toshiyuki; Kita, Takashi

2017-01-01

Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al0.3Ga0.7As and GaAs. The below-gap photons for Al0.3Ga0.7As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al0.3Ga0.7As barrier by below-gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs. PMID:28382945

Highly Efficient Protein Misfolding Cyclic Amplification

PubMed Central

Ostapchenko, Valeriy G.; Savtchenk, Regina; Alexeeva, Irina; Rohwer, Robert G.; Baskakov, Ilia V.

2011-01-01

Protein misfolding cyclic amplification (PMCA) provides faithful replication of mammalian prions in vitro and has numerous applications in prion research. However, the low efficiency of conversion of PrPC into PrPSc in PMCA limits the applicability of PMCA for many uses including structural studies of infectious prions. It also implies that only a small sub-fraction of PrPC may be available for conversion. Here we show that the yield, rate, and robustness of prion conversion and the sensitivity of prion detection are significantly improved by a simple modification of the PMCA format. Conducting PMCA reactions in the presence of Teflon beads (PMCAb) increased the conversion of PrPC into PrPSc from ∼10% to up to 100%. In PMCAb, a single 24-hour round consistently amplified PrPSc by 600-700-fold. Furthermore, the sensitivity of prion detection in one round (24 hours) increased by 2-3 orders of magnitude. Using serial PMCAb, a 1012-fold dilution of scrapie brain material could be amplified to the level detectible by Western blotting in 3 rounds (72 hours). The improvements in amplification efficiency were observed for the commonly used hamster 263K strain and for the synthetic strain SSLOW that otherwise amplifies poorly in PMCA. The increase in the amplification efficiency did not come at the expense of prion replication specificity. The current study demonstrates that poor conversion efficiencies observed previously have not been due to the scarcity of a sub-fraction of PrPC susceptible to conversion nor due to limited concentrations of essential cellular cofactors required for conversion. The new PMCAb format offers immediate practical benefits and opens new avenues for developing fast ultrasensitive assays and for producing abundant quantities of PrPSc in vitro. PMID:21347353

Isolation and characterization of two chlorophyll-deficient genes in soybean

USDA-ARS?s Scientific Manuscript database

We have identified a viable-yellow and a lethal-yellow mutant in soybean. The three phenotypes green, lethal- and viable-yellow were easily distinguished based on their light reflectance indices, chlorophyll abundance and photochemical conversion efficiency. Photochemical conversion efficiency was r...

Electrochemistry of the Zinc-Silver Oxide System. Part 2: Practical Measurements of Energy Conversion Using Commercial Miniature Cells.

ERIC Educational Resources Information Center

Smith, Michael J.; Vincent, Colin A.

1989-01-01

Summarizes the quantitative relationships pertaining to the operation of electrochemical cells. Energy conversion efficiency, cycle efficiency, battery power, and energy/power density of two types of zinc-silver oxide cells are discussed. (YP)

[Research on the photoelectric conversion efficiency of grating antireflective layer solar cells].

PubMed

Zhong, Hui; Gao, Yong-Yi; Zhou, Ren-Long; Zhou, Bing-ju; Tang, Li-qiang; Wu, Ling-xi; Li, Hong-jian

2011-07-01

A numerical investigation of the effect of grating antireflective layer structure on the photoelectric conversion efficiency of solar cells was carried out by the finite-difference time-domain method. The influence of grating shape, height and the metal film thickness coated on grating surface on energy storage was analyzed in detail. It was found that the comparison between unoptimized and optimized surface grating structure on solar cells shows that the optimization of surface by grating significantly increases the energy storage capability and greatly improves the efficiency, especially of the photoelectric conversion efficiency and energy storage of the triangle grating. As the film thickness increases, energy storage effect increases, while as the film thickness is too thick, energy storage effect becomes lower and lower.

Nonlinear frequency conversion of radiation from a copper-vapor laser

NASA Astrophysics Data System (ADS)

Polunin, Iu. P.; Troitskii, V. O.

1987-11-01

The nonlinear frequency conversion of copper-vapor laser radiation in a KDP crystal was studied experimentally. Output powers of 600 mW and 120 mW were obtained at wavelengths of 271 nm (the sum frequency) and 289 nm (the second harmonic of the yellow line), respectively. The conversion efficiency in both cases was about 3 percent; when selector losses were taken into accounted, the efficiency amounted to 5 percent.

Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

2015-04-01

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

Achieving copper sulfide leaf like nanostructure electrode for high performance supercapacitor and quantum-dot sensitized solar cells

NASA Astrophysics Data System (ADS)

Durga, Ikkurthi Kanaka; Rao, S. Srinivasa; Reddy, Araveeti Eswar; Gopi, Chandu V. V. M.; Kim, Hee-Je

2018-03-01

Copper sulfide is an important multifunctional semiconductor that has attracted considerable attention owing to its outstanding properties and multiple applications, such as energy storage and electrochemical energy conversion. This paper describes a cost-effective and simple low-temperature solution approach to the preparation of copper sulfide for supercapacitors (SCs) and quantum-dot sensitized solar cells (QDSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed that the nickel foam with a coriander leaf like nanostructure had been coated successfully with copper sulfide. As an electrode material for SCs, the CC-3 h showed excellent specific capacitance (5029.28 at 4 A g-1), energy density (169.73 W h kg-1), and superior cycling durability with 107% retention after 2000 cycles. Interestingly, the QDSSCs equipped with CC-2 h and CC-3 h counter electrodes (CEs) exhibited a maximum power conversion efficiency of 2.52% and 3.48%, respectively. The improved performance of the CC-3 h electrode was attributed mainly to the large surface area (which could contribute sufficient electroactive species), good conductivity, and high electrocatalytic activity. Overall, this work delivers novel insights into the use of copper sulfide and offers an important guidelines for the fabrication of next level energy storage and conversion devices.

On-Chip Strong Coupling and Efficient Frequency Conversion between Telecom and Visible Optical Modes.

PubMed

Guo, Xiang; Zou, Chang-Ling; Jung, Hojoong; Tang, Hong X

2016-09-16

While the frequency conversion of photons has been realized with various approaches, the realization of strong coupling between optical modes of different colors has never been reported. Here, we present an experimental demonstration of strong coupling between telecom (1550 nm) and visible (775 nm) optical modes on an aluminum nitride photonic chip. The nonreciprocal normal-mode splitting is demonstrated as a result of the coherent interference between photons with different colors. Furthermore, a wideband, bidirectional frequency conversion with 0.14 on-chip conversion efficiency and a bandwidth up to 1.2 GHz is demonstrated.

Functionalization of graphene for efficient energy conversion and storage.

PubMed

Dai, Liming

2013-01-15

As global energy consumption accelerates at an alarming rate, the development of clean and renewable energy conversion and storage systems has become more important than ever. Although the efficiency of energy conversion and storage devices depends on a variety of factors, their overall performance strongly relies on the structure and properties of the component materials. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. As a building block for carbon materials of all other dimensionalities (such as 0D buckyball, 1D nanotube, 3D graphite), the two-dimensional (2D) single atomic carbon sheet of graphene has emerged as an attractive candidate for energy applications due to its unique structure and properties. Like other materials, however, a graphene-based material that possesses desirable bulk properties rarely features the surface characteristics required for certain specific applications. Therefore, surface functionalization is essential, and researchers have devised various covalent and noncovalent chemistries for making graphene materials with the bulk and surface properties needed for efficient energy conversion and storage. In this Account, I summarize some of our new ideas and strategies for the controlled functionalization of graphene for the development of efficient energy conversion and storage devices, such as solar cells, fuel cells, supercapacitors, and batteries. The dangling bonds at the edge of graphene can be used for the covalent attachment of various chemical moieties while the graphene basal plane can be modified via either covalent or noncovalent functionalization. The asymmetric functionalization of the two opposite surfaces of individual graphene sheets with different moieties can lead to the self-assembly of graphene sheets into hierarchically structured materials. Judicious application of these site-selective reactions to graphene sheets has opened up a rich field of graphene-based energy materials with enhanced performance in energy conversion and storage. These results reveal the versatility of surface functionalization for making sophisticated graphene materials for energy applications. Even though many covalent and noncovalent functionalization methods have already been reported, vast opportunities remain for developing novel graphene materials for highly efficient energy conversion and storage systems.

Optimization of K-shell emission in aluminum z-pinch implosions: Theory versus experiment

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Thornhill, J. W.; Giuliani, J. L.; Davis, J.; Miles, L. A.; Nolting, E. E.; Kenyon, V. L.; Speicer, W. A.; Draper, J. A.; Parsons, C. R.; Dang, P.; Spielman, R. B.; Nash, T. J.; McGurn, J. S.; Ruggles, L. E.; Deeney, C.; Prasad, R. R.; Warren, L.

1994-09-01

Two sets of z-pinch experiments were recently completed at the Saturn and Phoenix facilities of Sandia National Laboratories and the Naval Surface Warfare Center, respectively, using aluminum wire arrays of different wire and array diameters. Measurements of the total x-ray yield from the K shell of aluminum were made. In this paper, a comparison of these measurements is made to both theoretical predictions and to a similar set of earlier measurements that were made at the Double Eagle facility of Physics International Company. These three sets of yield measurements have points of agreement with predicted yields and with each other, but they also show points of mutual disagreement, whose significance is discussed. The data are analyzed using a slightly revised version of a previously published K-shell yield scaling law, and they support the existence of a reasonably well defined region in (load mass)-(implosion velocity) space in which plasma kinetic energy is efficiently converted into K-shell x rays. Furthermore, a correlation is observed between the inferred conversion efficiencies and the times in which the implosions occur relative to the times when each generator's short-circuit current reaches its peak value. Finally, unlike the Double Eagle experiments, the largest measured yields in the new experiments were observed to occur at the upper velocity boundary of the efficient emission region. Moreover, the observed yields are in fairly good quantitative agreement with an earlier scaling law prediction of the maximum K-shell x-ray yield from aluminum as a function of load mass assuming kinetic energy conversion alone.

Investigation of operating parameters on CO2 splitting by dielectric barrier discharge plasma

NASA Astrophysics Data System (ADS)

Pan, CHEN; Jun, SHEN; Tangchun, RAN; Tao, YANG; Yongxiang, YIN

2017-12-01

Experiments of CO2 splitting by dielectric barrier discharge (DBD) plasma were carried out, and the influence of CO2 flow rate, plasma power, discharge voltage, discharge frequency on CO2 conversion and process energy efficiency were investigated. It was shown that the absolute quantity of CO2 decomposed was only proportional to the amount of conductive electrons across the discharge gap, and the electron amount was proportional to the discharge power; the energy efficiency of CO2 conversion was almost a constant at a lower level, which was limited by CO2 inherent discharge character that determined a constant gap electric field strength. This was the main reason why CO2 conversion rate decreased as the CO2 flow rate increase and process energy efficiency was decreased a little as applied frequency increased. Therefore, one can improve the CO2 conversion by less feed flow rate or larger discharge power in DBD plasma, but the energy efficiency is difficult to improve.

Ultra-wideband high-efficiency reflective linear-to-circular polarization converter based on metasurface at terahertz frequencies.

PubMed

Jiang, Yannan; Wang, Lei; Wang, Jiao; Akwuruoha, Charles Nwakanma; Cao, Weiping

2017-10-30

The polarization conversion of electromagnetic (EM) waves, especially linear-to-circular (LTC) polarization conversion, is of great significance in practical applications. In this study, we propose an ultra-wideband high-efficiency reflective LTC polarization converter based on a metasurface in the terahertz regime. It consists of periodic unit cells, each cell of which is formed by a double split resonant square ring, dielectric layer, and fully reflective gold mirror. In the frequency range of 0.60 - 1.41 THz, the magnitudes of the reflection coefficients reach approximately 0.7, and the phase difference between the two orthogonal electric field components of the reflected wave is close to 90° or -270°. The results indicate that the relative bandwidth reaches 80% and the efficiency is greater than 88%, thus, ultra-wideband high-efficiency LTC polarization conversion has been realized. Finally, the physical mechanism of the polarization conversion is revealed. This converter has potential applications in antenna design, EM measurement, and stealth technology.

Solar energy conversion with photon-enhanced thermionic emission

NASA Astrophysics Data System (ADS)

Kribus, Abraham; Segev, Gideon

2016-07-01

Photon-enhanced thermionic emission (PETE) converts sunlight to electricity with the combined photonic and thermal excitation of charge carriers in a semiconductor, leading to electron emission over a vacuum gap. Theoretical analyses predict conversion efficiency that can match, or even exceed, the efficiency of traditional solar thermal and photovoltaic converters. Several materials have been examined as candidates for radiation absorbers and electron emitters, with no conclusion yet on the best set of materials to achieve high efficiency. Analyses have shown the complexity of the energy conversion and transport processes, and the significance of several loss mechanisms, requiring careful control of material properties and optimization of the device structure. Here we survey current research on PETE modeling, materials, and device configurations, outline the advances made, and stress the open issues and future research needed. Based on the substantial progress already made in this young topic, and the potential of high conversion efficiency based on theoretical performance limits, continued research in this direction is very promising and may yield a competitive technology for solar electricity generation.

Study of solid-conversion gaseous detector based on GEM for high energy X-ray industrial CT.

PubMed

Zhou, Rifeng; Zhou, Yaling

2014-01-01

The general gaseous ionization detectors are not suitable for high energy X-ray industrial computed tomography (HEICT) because of their inherent limitations, especially low detective efficiency and large volume. The goal of this study was to investigate a new type of gaseous detector to solve these problems. The novel detector was made by a metal foil as X-ray convertor to improve the conversion efficiency, and the Gas Electron Multiplier (hereinafter "GEM") was used as electron amplifier to lessen its volume. The detective mechanism and signal formation of the detector was discussed in detail. The conversion efficiency was calculated by using EGSnrc Monte Carlo code, and the transport course of photon and secondary electron avalanche in the detector was simulated with the Maxwell and Garfield codes. The result indicated that this detector has higher conversion efficiency as well as less volume. Theoretically this kind of detector could be a perfect candidate for replacing the conventional detector in HEICT.

Energy conversion in isothermal nonlinear irreversible processes - struggling for higher efficiency

NASA Astrophysics Data System (ADS)

Ebeling, W.; Feistel, R.

2017-06-01

First we discuss some early work of Ulrike Feudel on structure formation in nonlinear reactions including ions and the efficiency of the conversion of chemical into electrical energy. Then we give some survey about isothermal energy conversion from chemical to higher forms of energy like mechanical, electrical and ecological energy. Isothermal means here that there are no temperature gradients within the model systems. We consider examples of energy conversion in several natural processes and in some devices like fuel cells. Further, as an example, we study analytically the dynamics and efficiency of a simple "active circuit" converting chemical into electrical energy and driving currents which is roughly modeling fuel cells. Finally we investigate an analogous ecological system of Lotka-Volterra type consisting of an "active species" consuming some passive "chemical food". We show analytically for both these models that the efficiency increases with the load, reaches values higher then 50 percent in a narrow regime of optimal load and goes beyond some maximal load abruptly to zero.

Reversible thermodynamic cycle for AMTEC power conversion. [Alkali Metal Thermal-to-Electric Converter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vining, C.B.; Williams, R.M.; Underwood, M.L.

1993-10-01

An AMTEC cell, may be described as performing two distinct energy conversion processes: (i) conversion of heat to mechanical energy via a sodium-based heat engine and (ii) conversion of mechanical energy to electrical energy by utilizing the special properties of the electrolyte material. The thermodynamic cycle appropriate to an alkali metal thermal-to-electric converter cell is discussed for both liquid- and vapor-fed modes of operation, under the assumption that all processes can be performed reversibly. In the liquid-fed mode, the reversible efficiency is greater than 89.6% of Carnot efficiency for heat input and rejection temperatures (900--1,300 and 400--800 K, respectively) typicalmore » of practical devices. Vapor-fed cells can approach the efficiency of liquid-fed cells. Quantitative estimates confirm that the efficiency is insensitive to either the work required to pressurize the sodium liquid or the details of the state changes associated with cooling the low pressure sodium gas to the heat rejection temperature.« less

Glucose buffer is suitable for blood group conversion with α-N acetylgalactosaminidase and α-galactosidase.

PubMed

Gao, Hong-Wei; Li, Su-Bo; Bao, Guo-Qiang; Zhang, Xue; Li, Hui; Wang, Ying-Li; Tan, Ying-Xia; Ji, Shou-Ping; Gong, Feng

2014-01-01

It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by α-N-acetylgalactosaminidase or α-galactosidase. We compared the binding ability of α-N-acetylgalactosaminidase/α-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes' ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion.

Potential active materials for photo-supercapacitor: A review

NASA Astrophysics Data System (ADS)

Ng, C. H.; Lim, H. N.; Hayase, S.; Harrison, I.; Pandikumar, A.; Huang, N. M.

2015-11-01

The need for an endless renewable energy supply, typically through the utilization of solar energy in most applications and systems, has driven the expansion, versatility, and diversification of marketed energy storage devices. Energy storage devices such as hybridized dye-sensitized solar cell (DSSC)-capacitors and DSSC-supercapacitors have been invented for energy reservation. The evolution and vast improvement of these devices in terms of their efficiencies and flexibilities have further sparked the invention of the photo-supercapacitor. The idea of coupling a DSSC and supercapacitor as a complete energy conversion and storage device arose because the solar energy absorbed by dye molecules can be efficiently transferred and converted to electrical energy by adopting a supercapacitor as the energy delivery system. The conversion efficiency of a photo-supercapacitor is mainly dependent on the use of active materials during its fabrication. The performances of the dye, photoactive metal oxide, counter electrode, redox electrolyte, and conducting polymer are the primary factors contributing to high-energy-efficient conversion, which enhances the performance and shelf-life of a photo-supercapacitor. Moreover, the introduction of compact layer as a primary adherent film has been earmarked as an effort in enhancing power conversion efficiency of solar cell. Additionally, the development of electrolyte-free solar cell such as the invention of hole-conductor or perovskite solar cell is currently being explored extensively. This paper reviews and analyzes the potential active materials for a photo-supercapacitor to enhance the conversion and storage efficiencies.

Localised and delocalised optically induced conversion of composite glow peak 5 in LiF:Mg,Ti (TLD-100) to glow peak 4 as a function of postirradiation annealing temperature.

PubMed

Horowitz, Y S; Einav, Y; Biderman, S; Oster, L

2002-01-01

The composite structure of glow peak 5 in LiF:Mg,Ti (TLD-100) has been investigated using optical bleaching by 310 nm (4 eV) light. The glow peak conversion efficiency of peak 5a (Tm = 187 degrees C) to peak 4 traps is very high at a value of 3+/-0.5 (1 SD) whereas the glow peak conversion efficiency of peak 5 (Tm = 205 degrees C) to peak 4 traps is 0.0026+/-0.0012 (1 SD). The high conversion efficiency of peak 5a to peak 4 arises from direct optical ionisation of the electron in the electron-hole pair. leaving behind a singly-trapped hole (peak 4), a direct mechanism, relatively free of competitive mechanisms. Optical ionisation of the 'singly-trapped' electron (peak 5), however, can lead to peak 4 only via multi-stage mechanisms involving charge carrier transport in the valence and conduction bands, a mechanism subject to competitive processes. The conduction/valence band competitive processes lead to the factor of one thousand decrease in the conversion efficiency of peak 5 compared to peak 5a.

Synthesis of substituted tetrahydroisoquinolines by lithiation then electrophilic quench.

PubMed

Talk, Ruaa A; Duperray, Alexia; Li, Xiabing; Coldham, Iain

2016-06-07

Substituted N-tert-butoxycarbonyl (Boc)-1,2,3,4-tetrahydroisoquinolines were prepared and treated with n-butyllithium in THF at -50 °C to test the scope of the metallation and electrophilic quench. The lithiation was optimised by using in situ ReactIR spectroscopy and the rate of rotation of the carbamate was determined. The 1-lithiated intermediates could be trapped with a variety of electrophiles to give good yields of 1-substituted tetrahydroisoquinoline products. Treatment with acid or reduction with LiAlH4 allows conversion to the N-H or N-Me compound. The chemistry was applied to the efficient total syntheses of the alkaloids (±)-crispine A and (±)-dysoxyline.

Development of a multikilowatt ion thruster power processor

NASA Technical Reports Server (NTRS)

Schoenfeld, A. D.; Goldin, D. S.; Biess, J. J.

1972-01-01

A feasibility study was made of the application of silicon-controlled, rectifier series, resonant inverter, power conditioning technology to electric propulsion power processing operating from a 200 to 400 Vdc solar array bus. A power system block diagram was generated to meet the electrical requirements of a 20 CM hollow cathode, mercury bombardment, ion engine. The SCR series resonant inverter was developed as a primary means of power switching and conversion, and the analog signal-to-discrete-time-interval converter control system was applied to achieve good regulation. A complete breadboard was designed, fabricated, and tested with a resistive load bank, and critical power processor areas relating to efficiency, weight, and part count were identified.

Manganese-catalyzed selective oxidation of aliphatic C-H groups and secondary alcohols to ketones with hydrogen peroxide.

PubMed

Dong, Jia Jia; Unjaroen, Duenpen; Mecozzi, Francesco; Harvey, Emma C; Saisaha, Pattama; Pijper, Dirk; de Boer, Johannes W; Alsters, Paul; Feringa, Ben L; Browne, Wesley R

2013-09-01

An efficient and simple method for selective oxidation of secondary alcohols and oxidation of alkanes to ketones is reported. An in situ prepared catalyst is employed based on manganese(II) salts, pyridine-2-carboxylic acid, and butanedione, which provides good-to-excellent conversions and yields with high turnover numbers (up to 10 000) with H2 O2 as oxidant at ambient temperatures. In substrates bearing multiple alcohol groups, secondary alcohols are converted to ketones selectively and, in general, benzyl C-H oxidation proceeds in preference to aliphatic C-H oxidation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nutrigenetic screening strains of the mulberry silkworm, Bombyx mori, for nutritional efficiency.

PubMed

Ramesha, Chinnaswamy; Lakshmi, Hothur; Kumari, Savarapu Sugnana; Anuradha, Chevva M; Kumar, Chitta Suresh

2012-01-01

The activity of sericulture is declining due the reduction of mulberry production area in sericulture practicing countries lead to adverse effects on silkworm rearing and cocoon production. Screening for nutrigenetic traits in silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) is an essential prerequisite for better understanding and development of nutritionally efficient breeds/hybrids, which show less food consumption with higher efficiency conversion. The aim of this study was to identify nutritionally efficient polyvoltine silkworm strains using the germplasm breeds RMW(2), RMW(3), RMW(4), RMG(3), RMG(1), RMG(4), RMG(5), RMG(6) and APM(1) as the control. The 1(st) day of 5(th) stage silkworm larvae of polyvoltine strains were subjected to standard gravimetric analysis until spinning for three consecutive generations covering 3 different seasons on 19 nutrigenetic traits. Highly significant (p ≤ 0.001) differences were found among all nutrigenetic traits of polyvoltine silkworm strains in the experimental groups. The nutritionally efficient polvoltine silkworm strains were resulted by utilizing nutrition consumption index and efficiency of conversion of ingesta/cocoon traits as the index. Higher nutritional efficiency conversions were found in the polyvoltine silkworm strains on efficiency of conversion of ingesta to cocoon and shell than control. Comparatively smaller consumption index, respiration, metabolic rate with superior relative growth rate, and quantum of food ingesta and digesta requisite per gram of cocoon and shell were found; the lowest amount was in new polyvoltine strains compared to the control. Furthermore, based on the overall nutrigenetic traits utilized as index or 'biomarkers', three polyvoltine silkworm strains (RMG(4), RMW(2), and RMW(3)) were identified as having the potential for nutrition efficiency conversion. The data from the present study advances our knowledge for the development of nutritionally efficient silkworm breeds/hybrids and their effective commercial utilization in the sericulture industry.

Nutrigenetic screening strains of the mulberry silkworm, Bombyx mori, for nutritional efficiency.

PubMed

Chinnaswamy, Ramesha; Lakshmi, Hothur; Kumari, Savarapu S; Anuradha, Chebba M; Kumar, Chitta S

2012-01-01

The activity of sericulture is declining due the reduction of mulberry production area in sericulture practicing countries lead to adverse effects on silkworm rearing and cocoon production. Screening for nutrigenetic traits in silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) is an essential prerequisite for better understanding and development of nutritionally efficient breeds/hybrids, which show less food consumption with higher efficiency conversion. The aim of this study was to identify nutritionally efficient polyvoltine silkworm strains using the germplasm breeds RMW(2), RMW(3), RMW(4), RMG(3), RMG(1), RMG(4), RMG(5), RMG(6) and APM(1) as the control. The 1(st) day of 5(th) stage silkworm larvae of polyvoltine strains were subjected to standard gravimetric analysis until spinning for three consecutive generations covering three different seasons on 19 nutrigenetic traits. Highly significant (p ≤ 0.001) differences were found among all nutrigenetic traits of polyvoltine silkworm strains in the experimental groups. The nutritionally efficient polvoltine silkworm strains were resulted by utilizing nutrition consumption index and efficiency of conversion of ingesta/cocoon traits as the index. Higher nutritional efficiency conversions were found in the polyvoltine silkworm strains on efficiency of conversion of ingesta to cocoon and shell than control. Comparatively smaller consumption index, respiration, metabolic rate with superior relative growth rate, and quantum of food ingesta and digesta requisite per gram of cocoon and shell were shown; the lowest amount was in new polyvoltine strains compared to the control. Furthermore, based on the overall nutrigenetic traits utilized as index or 'biomarkers', three polyvoltine silkworm strains (RMG(4), RMW(2), and RMW(3)) were identified as having the potential for nutrition efficiency conversion. The data from the present study advances our knowledge for the development of nutritionally efficient silkworm breeds/hybrids and their effective commercial utilization in the sericulture industry.

Nutrigenetic Screening Strains of the Mulberry Silkworm, Bombyx mori, for Nutritional Efficiency

PubMed Central

Chinnaswamy, Ramesha; Lakshmi, Hothur; Kumari, Savarapu S.; Anuradha, Chebba M.; Kumar, Chitta S.

2012-01-01

The activity of sericulture is declining due the reduction of mulberry production area in sericulture practicing countries lead to adverse effects on silkworm rearing and cocoon production. Screening for nutrigenetic traits in silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) is an essential prerequisite for better understanding and development of nutritionally efficient breeds/hybrids, which show less food consumption with higher efficiency conversion. The aim of this study was to identify nutritionally efficient polyvoltine silkworm strains using the germplasm breeds RMW2, RMW3, RMW4, RMG3, RMG1, RMG4, RMG5, RMG6 and APM1 as the control. The 1st day of 5th stage silkworm larvae of polyvoltine strains were subjected to standard gravimetric analysis until spinning for three consecutive generations covering three different seasons on 19 nutrigenetic traits. Highly significant (p ≤ 0.001) differences were found among all nutrigenetic traits of polyvoltine silkworm strains in the experimental groups. The nutritionally efficient polvoltine silkworm strains were resulted by utilizing nutrition consumption index and efficiency of conversion of ingesta/cocoon traits as the index. Higher nutritional efficiency conversions were found in the polyvoltine silkworm strains on efficiency of conversion of ingesta to cocoon and shell than control. Comparatively smaller consumption index, respiration, metabolic rate with superior relative growth rate, and quantum of food ingesta and digesta requisite per gram of cocoon and shell were shown; the lowest amount was in new polyvoltine strains compared to the control. Furthermore, based on the overall nutrigenetic traits utilized as index or ‘biomarkers’, three polyvoltine silkworm strains (RMG4, RMW2, and RMW3) were identified as having the potential for nutrition efficiency conversion. The data from the present study advances our knowledge for the development of nutritionally efficient silkworm breeds/hybrids and their effective commercial utilization in the sericulture industry. PMID:22938037

Nutrigenetic Screening Strains of the Mulberry Silkworm, Bombyx mori, for Nutritional Efficiency

PubMed Central

Ramesha, Chinnaswamy; Lakshmi, Hothur; Kumari, Savarapu Sugnana; Anuradha, Chevva M.; Kumar, Chitta Suresh

2012-01-01

The activity of sericulture is declining due the reduction of mulberry production area in sericulture practicing countries lead to adverse effects on silkworm rearing and cocoon production. Screening for nutrigenetic traits in silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) is an essential prerequisite for better understanding and development of nutritionally efficient breeds/hybrids, which show less food consumption with higher efficiency conversion. The aim of this study was to identify nutritionally efficient polyvoltine silkworm strains using the germplasm breeds RMW2, RMW3, RMW4, RMG3, RMG1, RMG4, RMG5, RMG6 and APM1 as the control. The 1st day of 5th stage silkworm larvae of polyvoltine strains were subjected to standard gravimetric analysis until spinning for three consecutive generations covering 3 different seasons on 19 nutrigenetic traits. Highly significant (p ≤ 0.001) differences were found among all nutrigenetic traits of polyvoltine silkworm strains in the experimental groups. The nutritionally efficient polvoltine silkworm strains were resulted by utilizing nutrition consumption index and efficiency of conversion of ingesta/cocoon traits as the index. Higher nutritional efficiency conversions were found in the polyvoltine silkworm strains on efficiency of conversion of ingesta to cocoon and shell than control. Comparatively smaller consumption index, respiration, metabolic rate with superior relative growth rate, and quantum of food ingesta and digesta requisite per gram of cocoon and shell were found; the lowest amount was in new polyvoltine strains compared to the control. Furthermore, based on the overall nutrigenetic traits utilized as index or ‘biomarkers’, three polyvoltine silkworm strains (RMG4, RMW2, and RMW3) were identified as having the potential for nutrition efficiency conversion. The data from the present study advances our knowledge for the development of nutritionally efficient silkworm breeds/hybrids and their effective commercial utilization in the sericulture industry. PMID:22934597

Photon energy conversion by near-zero permittivity nonlinear materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; Sinclair, Michael B.; Campione, Salvatore

Efficient harmonic light generation can be achieved with ultrathin films by coupling an incident pump wave to an epsilon-near-zero (ENZ) mode of the thin film. As an example, efficient third harmonic generation from an indium tin oxide nanofilm (.lamda./42 thick) on a glass substrate for a pump wavelength of 1.4 .mu.m was demonstrated. A conversion efficiency of 3.3.times.10.sup.-6 was achieved by exploiting the field enhancement properties of the ENZ mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Numerical analysis of СО laser frequency conversion efficiency in BaGa2GeSe6 crystal

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Kinyaevskiy, I. O.; Mozhaeva, V. A.

2018-03-01

Non-linear optical characteristics of a new BaGa2GeSe6 crystal were numerically studied and compared with ones of the well-known mid-IR nonlinear crystal ZnGeP2 (ZGP). The calculations demonstrated the new crystal to be more efficient or, at least, competitive with the ZGP crystal for frequency conversion of CO- and CO2-laser radiation. It was found that a broadband two-stage frequency conversion of multi-line CO-laser radiation in this crystal is possible within the 2.5-9.0 µm wavelength range, with higher efficiency than in the ZGP crystal.

Quantitative Analysis of Defects in Silicon. [to predict energy conversion efficiency of silicon samples for solar cells

NASA Technical Reports Server (NTRS)

Natesh, R.; Smith, J. M.; Qidwai, H. A.; Bruce, T.

1979-01-01

The evaluation and prediction of the conversion efficiency for a variety of silicon samples with differences in structural defects, such as grain boundaries, twin boundaries, precipitate particles, dislocations, etc. are discussed. Quantitative characterization of these structural defects, which were revealed by etching the surface of silicon samples, is performed by using an image analyzer. Due to different crystal growth and fabrication techniques the various types of silicon contain a variety of trace impurity elements and structural defects. The two most important criteria in evaluating the various silicon types for solar cell applications are cost and conversion efficiency.

Theoretical Analysis of Two Novel Hybrid Thermoelectric-Photovoltaic Systems Based on Cu₂ZnSnS₄ Solar Cells.

PubMed

Lorenzi, Bruno; Contento, Gaetano; Sabatelli, Vincenzo; Rizzo, Antonella; Narducci, Dario

2017-03-01

The development and commercialization of Photovoltaic (PV) cells with good cost-efficiency trade-off not using critical raw materials (CRMs) is one of the strategies chosen by the European Community (EC) to address the Energy Roadmap 2050. In this context Cu2ZnSnS4 (CZTS) solar cells are attracting a major interest since they have the potential to combine low price with relatively high conversion efficiencies. Although a ≈9% lab scale efficiency has already been reported for CZTS this technology is still far from being competitive in terms of cost per peak-power (€/Wp) with other common materials. One possible near-future solution to increase the CZTS competiveness comes from thermoelectrics. Actually it has already been shown that Hybrid Thermoelectric-Photovoltaic Systems (HTEPVs) based on CIGS, another kesterite very similar to CZTS, can lead to a significant efficiency improvement. However it has been also clarified how the optimal hybridization strategy cannot come from the simple coupling of solar cells with commercial TEGs, but special layouts have to be implemented. Furthermore, since solar cell performances are well known to decrease with temperature, thermal decoupling strategies of the PV and TEG sections have to be taken. To address these issues, we developed a model for two different HTEPV solutions, both coupled with CZTS solar cells. In the first case we considered a Thermally-Coupled HTEPV device (TC-HTEPV) in which the TEG is placed underneath the solar cell and in thermal contact with it. The second system consists instead of an Optically-Coupled but thermally decoupled device (OC-HTEPV) in which part of the solar spectrum is focused by a non-imaging optical concentrator on the TEG hot side. For both solutions the model returns conversion efficiencies higher than that of the CZTS solar cell alone. Specifically, increases of ≈30% are predicted for both kind of systems considered.

Energy dissipation in the blade tip region of an axial fan

NASA Astrophysics Data System (ADS)

Bizjan, B.; Milavec, M.; Širok, B.; Trenc, F.; Hočevar, M.

2016-11-01

A study of velocity and pressure fluctuations in the tip clearance flow of an axial fan is presented in this paper. Two different rotor blade tip designs were investigated: the standard one with straight blade tips and the modified one with swept-back tip winglets. Comparison of integral sound parameters indicates a significant noise level reduction for the modified blade tip design. To study the underlying mechanisms of the energy conversion and noise generation, a novel experimental method based on simultaneous measurements of local flow velocity and pressure has also been developed and is presented here. The method is based on the phase space analysis by the use of attractors, which enable more accurate identification and determination of the local flow structures and turbulent flow properties. Specific gap flow energy derived from the pressure and velocity time series was introduced as an additional attractor parameter to assess the flow energy distribution and dissipation within the phase space, and thus determines characteristic sources of the fan acoustic emission. The attractors reveal a more efficient conversion of the pressure to kinetic flow energy in the case of the modified (tip winglet) fan blade design, and also a reduction in emitted noise levels. The findings of the attractor analysis are in a good agreement with integral fan characteristics (efficiency and noise level), while offering a much more accurate and detailed representation of gap flow phenomena.

An Efficient Approach for Lipase-Catalyzed Synthesis of Retinyl Laurate Nutraceutical by Combining Ultrasound Assistance and Artificial Neural Network Optimization.

PubMed

Huang, Shang-Ming; Li, Hsin-Ju; Liu, Yung-Chuan; Kuo, Chia-Hung; Shieh, Chwen-Jen

2017-11-15

Although retinol is an important nutrient, retinol is highly sensitive to oxidation. At present, some ester forms of retinol are generally used in nutritional supplements because of its stability and bioavailability. However, such esters are commonly synthesized by chemical procedures which are harmful to the environment. Thus, this study utilized a green method using lipase as a catalyst with sonication assistance to produce a retinol derivative named retinyl laurate. Moreover, the process was optimized by an artificial neural network (ANN). First, a three-level-four-factor central composite design (CCD) was employed to design 27 experiments, which the highest relative conversion was 82.64%. Further, the optimal architecture of the CCD-employing ANN was developed, including the learning Levenberg-Marquardt algorithm, the transfer function (hyperbolic tangent), iterations (10,000), and the nodes of the hidden layer (6). The best performance of the ANN was evaluated by the root mean squared error (RMSE) and the coefficient of determination ( R ²) from predicting and observed data, which displayed a good data-fitting property. Finally, the process performed with optimal parameters actually obtained a relative conversion of 88.31% without long-term reactions, and the lipase showed great reusability for biosynthesis. Thus, this study utilizes green technology to efficiently produce retinyl laurate, and the bioprocess is well established by ANN-mediated modeling and optimization.

Two-Step Physical Deposition of a Compact CuI Hole-Transport Layer and the Formation of an Interfacial Species in Perovskite Solar Cells.

PubMed

Gharibzadeh, Saba; Nejand, Bahram Abdollahi; Moshaii, Ahmad; Mohammadian, Nasim; Alizadeh, Amir Hossein; Mohammadpour, Rahele; Ahmadi, Vahid; Alizadeh, Abdolali

2016-08-09

A simple and practical approach is introduced for the deposition of CuI as an inexpensive inorganic hole-transport material (HTM) for the fabrication of low cost perovskite solar cells (PSCs) by gas-solid phase transformation of Cu to CuI. The method provides a uniform and well-controlled CuI layer with large grains and good compactness that prevents the direct connection between the contact electrodes. Solar cells prepared with CuI as the HTM with Au electrodes displays an exceptionally high short-circuit current density of 32 mA cm(-2) , owing to an interfacial species formed between the perovskite and the Cu resulting in a long wavelength contribution to the incident photon-to-electron conversion efficiency (IPCE), and an overall power conversion efficiency (PCE) of 7.4 %. The growth of crystalline and uniform CuI on a low roughness perovskite layer leads to remarkably high charge extraction in the cells, which originates from the high hole mobility of CuI in addition to a large number of contact points between CuI and the perovskite layer. In addition, the solvent-free method has no damaging side effect on the perovskite layer, which makes it an appropriate method for large scale applications of CuI in perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unity-Efficiency Parametric Down-Conversion via Amplitude Amplification.

PubMed

Niu, Murphy Yuezhen; Sanders, Barry C; Wong, Franco N C; Shapiro, Jeffrey H

2017-03-24

We propose an optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an n-photon Fock-state pump to n signal-idler photon pairs when the down-converters' crystal lengths are chosen appropriately. The proof of this assertion relies on amplitude amplification, analogous to that employed in Grover search, applied to the full quantum dynamics of single-mode parametric down-conversion. When we require that all Grover iterations use the same crystal, and account for potential experimental limitations on crystal-length precision, our optimized conversion efficiencies reach unity for 1≤n≤5, after which they decrease monotonically for n values up to 50, which is the upper limit of our numerical dynamics evaluations. Nevertheless, our conversion efficiencies remain higher than those for a conventional (no NSGs) down-converter.

Auger Up-Conversion of Low-Intensity Infrared Light in Engineered Quantum Dots

DOE PAGES

Makarov, Nikolay S.; Lin, Qianglu; Pietryga, Jeffrey M.; ...

2016-11-29

One source of efficiency losses in photovoltaic cells is their transparency toward solar photons with energies below the band gap of the absorbing layer. This loss can be reduced using a process of up-conversion whereby two or more sub-band-gap photons generate a single above-gap exciton. Traditional approaches to up-conversion, such as nonlinear two-photon absorption (2PA) or triplet fusion, suffer from low efficiency at solar light intensities, a narrow absorption bandwidth, nonoptimal absorption energies, and difficulties for implementing in practical devices. We show that these deficiencies can be alleviated using the effect of Auger up-conversion in thick-shell PbSe/CdSe quantum dots. Thismore » process relies on Auger recombination whereby two low-energy, core-based excitons are converted into a single higher-energy, shell-based exciton. When compared to their monocomponent counterparts, the tailored PbSe/CdSe heterostructures feature enhanced absorption cross-sections, a higher efficiency of the “productive” Auger pathway involving re-excitation of a hole, and longer lifetimes of both core- and shell-localized excitons. These features lead to effective up-conversion cross-sections that are more than 6 orders of magnitude higher than for standard nonlinear 2PA, which allows for efficient up-conversion of continuous wave infrared light at intensities as low as a few watts per square centimeter.« less

High-density defects on PdAg nanowire networks as catalytic hot spots for efficient dehydrogenation of formic acid and reduction of nitrate.

PubMed

Liu, Hu; Yu, Yongsheng; Yang, Weiwei; Lei, Wenjuan; Gao, Manyi; Guo, Shaojun

2017-07-13

Controlling the surface defects of nanocrystals is a new way of tuning/boosting their catalytic properties. Herein, we report networked PdAg nanowires (NWs) with high-density defects as catalytic hot spots for efficient catalytic dehydrogenation of formic acid (FA) and catalytic reduction of nitrates. The networked PdAg NWs exhibit composition-dependent catalytic activity for the dehydrogenation reaction of FA without any additive, with Pd 5 Ag 5 NWs exhibiting the highest activity. They also show good durability, reflected by the retention of their initial activity during the dehydrogenation reaction of FA even after five cycles. Their initial TOF is 419 h -1 at 60 °C in water solution, much higher than those of the most Pd-based catalysts with a support. Moreover, they can efficiently reduce nitrates to alleviate nitrate pollution in water (conversion yield >99%). This strategy opens up a new green synthetic technique to design support-free heterogeneous catalysts with high-density defects as catalytic hot spots for efficient dehydrogenation catalysis of FA to meet the requirement of fuel cell applications and catalytic reduction of nitrates in water polluted with nitrates.

Development and manufacture of reactive-transfer-printed CIGS photovoltaic modules

NASA Astrophysics Data System (ADS)

Eldada, Louay; Sang, Baosheng; Lu, Dingyuan; Stanbery, Billy J.

2010-09-01

In recent years, thin-film photovoltaic (PV) companies started realizing their low manufacturing cost potential, and grabbing an increasingly larger market share from multicrystalline silicon companies. Copper Indium Gallium Selenide (CIGS) is the most promising thin-film PV material, having demonstrated the highest energy conversion efficiency in both cells and modules. However, most CIGS manufacturers still face the challenge of delivering a reliable and rapid manufacturing process that can scale effectively and deliver on the promise of this material system. HelioVolt has developed a reactive transfer process for CIGS absorber formation that has the benefits of good compositional control, high-quality CIGS grains, and a fast reaction. The reactive transfer process is a two stage CIGS fabrication method. Precursor films are deposited onto substrates and reusable print plates in the first stage, while in the second stage, the CIGS layer is formed by rapid heating with Se confinement. High quality CIGS films with large grains were produced on a full-scale manufacturing line, and resulted in high-efficiency large-form-factor modules. With 14% cell efficiency and 12% module efficiency, HelioVolt started to commercialize the process on its first production line with 20 MW nameplate capacity.

Advanced Thermionic Technology Program

NASA Technical Reports Server (NTRS)

1977-01-01

Topics include surface studies (surface theory, basic surface experiments, and activation chamber experiments); plasma studies (converter theory and enhanced mode conversion experiments); and component development (low temperature conversion experiments, high efficiency conversion experiments, and hot shell development).

Conversational Entrainment of Vocal Fry in Young Adult Female American English Speakers.

PubMed

Borrie, Stephanie A; Delfino, Christine R

2017-07-01

Conversational entrainment, the natural tendency for people to modify their behaviors to more closely match their communication partner, is examined as one possible mechanism modulating the prevalence of vocal fry in the speech of young American women engaged in spoken dialogue. Twenty young adult female American English speakers engaged in two spoken dialogue tasks-one with a young adult female American English conversational partner who exhibited substantial vocal fry and one with a young adult female American English conversational partner who exhibited quantifiably less vocal fry. Dialogues were analyzed for proportion of vocal fry, by speaker, and two measures of communicative success (efficiency and enjoyment). Participants employed significantly more vocal fry when conversing with the partner who exhibited substantial vocal fry than when conversing with the partner who exhibited quantifiably less vocal fry. Further, greater similarity between communication partners in their use of vocal fry tracked with higher scores of communicative efficiency and communicative enjoyment. Conversational entrainment offers a mechanistic framework that may be used to explain, to some degree, the frequency with which vocal fry is employed by young American women engaged in spoken dialogue. Further, young American women who modulated their vocal patterns during dialogue to match those of their conversational partner gained more efficiency and enjoyment from their interactions, demonstrating the cognitive and social benefits of entrainment. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Design of batch audio/video conversion platform based on JavaEE

NASA Astrophysics Data System (ADS)

Cui, Yansong; Jiang, Lianpin

2018-03-01

With the rapid development of digital publishing industry, the direction of audio / video publishing shows the diversity of coding standards for audio and video files, massive data and other significant features. Faced with massive and diverse data, how to quickly and efficiently convert to a unified code format has brought great difficulties to the digital publishing organization. In view of this demand and present situation in this paper, basing on the development architecture of Sptring+SpringMVC+Mybatis, and combined with the open source FFMPEG format conversion tool, a distributed online audio and video format conversion platform with a B/S structure is proposed. Based on the Java language, the key technologies and strategies designed in the design of platform architecture are analyzed emphatically in this paper, designing and developing a efficient audio and video format conversion system, which is composed of “Front display system”, "core scheduling server " and " conversion server ". The test results show that, compared with the ordinary audio and video conversion scheme, the use of batch audio and video format conversion platform can effectively improve the conversion efficiency of audio and video files, and reduce the complexity of the work. Practice has proved that the key technology discussed in this paper can be applied in the field of large batch file processing, and has certain practical application value.

Lead-free inverted planar formamidinium tin triiodide perovskite solar cells achieving power conversion efficiencies up to 6.22%

DOE PAGES

Liao, Weiqiang; Zhao, Dewei; Yu, Yue; ...

2016-08-29

Efficient lead (Pb)-free inverted planar formamidinium tin triiodide (FASnI 3) perovskite solar cells (PVSCs) are demonstrated. Our FASnI 3 PVSCs achieved average power conversion efficiencies (PCEs) of 5.41% ± 0.46% and a maximum PCE of 6.22% under forward voltage scan. Here, the PVSCs exhibit small photocurrent–voltage hysteresis and high reproducibility. The champion cell shows a steady-state efficiency of ≈6.00% for over 100 s.

Thermodynamic limits to the conversion of blackbody radiation by quantum systems. [with application to solar energy conversion devices

NASA Technical Reports Server (NTRS)

Buoncristiani, A. M.; Smith, B. T.; Byvik, C. E.

1982-01-01

Using general thermodynamic arguments, we analyze the conversion of the energy contained in the radiation from a blackbody to useful work by a quantum system. We show that the energy available for conversion is bounded above by the change in free energy in the incident and reradiated fields and that this free energy change depends upon the temperature of the receiving device. Universal efficiency curves giving the ultimate thermodynamic conversion efficiency of the quantum system are presented in terms of the blackbody temperature and the temperature and threshold energy of the quantum system. Application of these results is made to a variety of systems including biological photosynthetic, photovoltaic, and photoelectrochemical systems.

Potential natural sensitizers extracted from the skin of Canarium odontophyllum fruits for dye-sensitized solar cells.

PubMed

Lim, Andery; Kumara, N T R N; Tan, Ai Ling; Mirza, Aminul Huq; Chandrakanthi, R L N; Petra, Mohammad Iskandar; Ming, Lim Chee; Senadeera, G K R; Ekanayake, Piyasiri

2015-03-05

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs. The detected pigment constituents of the extract consist of aurone (maritimein), anthocyanidin (pelargonidin) and anthocyanidin (cyanidin derivatives). When tested in DSSC, the highest conversion efficiency of 1.43% is exhibited by cyanidin derivatives, and this is followed by conversion efficiencies of 0.51% and 0.79% for aurone and pelargonidin, respectively. It is shown that individual pigments, like cyanidin derivatives and pelargonidin, exhibit higher power conversion efficiency when compared to that of C.odontophyllum skin pigment mixture (with a conversion efficiency of only 0.68%). The results indicate a possibility of masking effects of the pigments when used as a mixture. The acidification of C.odontophyllum skin pigments with concentrated hydrochloric acid improves the conversion efficiency of the mixture from 0.68% to 0.99%. The discussion in this paper will draw data and observations from the variation in absorption and adsorption properties, the HOMO-LUMO levels, the energy band gaps and the functional group compositions of the detected flavonoids. Copyright © 2014 Elsevier B.V. All rights reserved.

Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

PubMed Central

Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

2016-01-01

Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe−containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push−pull mechanism. Bio−inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe−Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe−Fe separation distance. PMID:27087483

Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings.

PubMed

Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori

2016-04-18

Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

NASA Astrophysics Data System (ADS)

Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

2016-04-01

Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

A Facile Synthesis of Nitrogen-Doped Highly Porous Carbon Nanoplatelets: Efficient Catalysts for Oxygen Electroreduction

NASA Astrophysics Data System (ADS)

Zhang, Yaqing; Zhang, Xianlei; Ma, Xiuxiu; Guo, Wenhui; Wang, Chunchi; Asefa, Tewodros; He, Xingquan

2017-02-01

The oxygen reduction reaction (ORR) is of great importance for various renewable energy conversion technologies such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanomaterials have proven to be robust metal-free electrocatalysts for ORR in the above-mentioned energy devices. Herein, we demonstrate the synthesis of novel highly porous N-doped carbon nanoplatelets (N-HPCNPs) derived from oatmeal (or a biological material) and we show the materials’ high-efficiency as electrocatalyst for ORR. The obtained N-HPCNPs hybrid materials exhibit superior electrocatalytic activities towards ORR, besides excellent stability and good methanol tolerance in both basic and acidic electrolytes. The unique nanoarchitectures with rich micropores and mesopores, as well as the high surface area-to-volume ratios, present in the materials significantly increase the density of accessible catalytically active sites in them and facilitate the transport of electrons and electrolyte within the materials. Consequently, the N-HPCNPs catalysts hold a great potential to serve as low-cost and highly efficient cathode materials in direct methanol fuel cells (DMFCs).

An Optimal Control Method for Maximizing the Efficiency of Direct Drive Ocean Wave Energy Extraction System

PubMed Central

Chen, Zhongxian; Yu, Haitao; Wen, Cheng

2014-01-01

The goal of direct drive ocean wave energy extraction system is to convert ocean wave energy into electricity. The problem explored in this paper is the design and optimal control for the direct drive ocean wave energy extraction system. An optimal control method based on internal model proportion integration differentiation (IM-PID) is proposed in this paper though most of ocean wave energy extraction systems are optimized by the structure, weight, and material. With this control method, the heavy speed of outer heavy buoy of the energy extraction system is in resonance with incident wave, and the system efficiency is largely improved. Validity of the proposed optimal control method is verified in both regular and irregular ocean waves, and it is shown that IM-PID control method is optimal in that it maximizes the energy conversion efficiency. In addition, the anti-interference ability of IM-PID control method has been assessed, and the results show that the IM-PID control method has good robustness, high precision, and strong anti-interference ability. PMID:25152913

EBW H&CD Potential for Spherical Tokamaks

NASA Astrophysics Data System (ADS)

Urban, J.; Decker, J.; Peysson, Y.; Preinhaelter, J.; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.

2011-12-01

Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-ß regimes, in which the usual EC O- and X- modes are cut-off. In this case, electron Bernstein waves (EBWs) seem to be the only option that can provide features similar to the EC waves—controllable localized heating and current drive (H&) that can be utilized for core plasma heating as well as for accurate plasma stabilization. We first derive an analytical expression for Gaussian beam OXB conversion efficiency. Then, an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX) is performed. Coupled ray-tracing (AMR) and Fokker-Planck (LUKE) codes are employed to simulate EBWs of varying frequencies and launch conditions. Our results indicate that an efficient and universal EBW H&CD system is indeed viable. In particular, power can be deposited and current reasonably efficiently driven across the whole plasma radius. Such a system could be controlled by a suitably chosen launching antenna vertical position and would also be sufficiently robust.

Performance and stability of low-cost dye-sensitized solar cell based crude and pre-concentrated anthocyanins: Combined experimental and DFT/TDDFT study

NASA Astrophysics Data System (ADS)

Chaiamornnugool, Phrompak; Tontapha, Sarawut; Phatchana, Ratchanee; Ratchapolthavisin, Nattawat; Kanokmedhakul, Somdej; Sang-aroon, Wichien; Amornkitbamrung, Vittaya

2017-01-01

The low cost DSSCs utilized by crude and pre-concentrated anthocyanins extracted from six anthocyanin-rich samples including mangosteen pericarp, roselle, red cabbage, Thai berry, black rice and blue pea were fabricated. Their photo-to-current conversion efficiencies and stability were examined. Pre-concentrated extracts were obtained by solid phase extraction (SPE) using C18 cartridge. The results obviously showed that all pre-concentrated extracts performed on photovoltaic performances in DSSCs better than crude extracts except for mangosteen pericarp. The DSSC sensitized by pre-concentrated anthocyanin from roselle and red cabbage showed maximum current efficiency η = 0.71% while DSSC sensitized by crude anthocyanin from mangosteen pericarp reached maximum efficiency η = 0.97%. In addition, pre-concentrated extract based cells possess more stability than those of crude extract based cells. This indicates that pre-concentration of anthocyanin via SPE method is very effective for DSSCs based on good photovoltaic performance and stability. The DFT/TDDFT calculations of electronic and photoelectrochemical properties of the major anthocyanins found in the samples are employed to support the experimental results.

Cobalt Phosphide Hollow Polyhedron as Efficient Bifunctional Electrocatalysts for the Evolution Reaction of Hydrogen and Oxygen.

PubMed

Liu, Mengjia; Li, Jinghong

2016-01-27

The development of efficient and low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts for renewable-energy conversion techniques is highly desired. A kind of hollow polyhedral cobalt phosphide (CoP hollow polyhedron) is developed as efficient bifunctional electrocatalysts for HER and OER templated by Co-centered metal-organic frameworks. The as-prepared CoP hollow polyhedron, which have large specific surface area and high porosity providing rich catalytic active sites, show excellent electrocatalytic performances for both HER and OER in acidic and alkaline media, respectively, with onset overpotentials of 35 and 300 mV, Tafel slopes of 59 and 57 mV dec(-1), and a current density of 10 mA cm(-2) at overpotentials of 159 and 400 mV for HER and OER, respectively, which are remarkably superior to those of particulate CoP (CoP particles) and comparable to those of commercial noble-metal catalysts. In addition, the CoP hollow polyhedron also show good durability after long-term operations.

Enhanced efficiency and air-stability of NiOX-based perovskite solar cells via PCBM electron transport layer modification with Triton X-100.

PubMed

Lee, Kisu; Ryu, Jaehoon; Yu, Haejun; Yun, Juyoung; Lee, Jungsup; Jang, Jyongsik

2017-11-02

We modified phenyl-C61-butyric acid methyl ester (PCBM) for use as a stable, efficient electron transport layer (ETL) in inverted perovskite solar cells (PSCs). PCBM containing a surfactant Triton X-100 acts as the ETL and NiO X nanocrystals act as a hole transport layer (HTL). Atomic force microscopy and scanning electron microscopy images showed that surfactant-modified PCBM (s-PCBM) forms a high-quality, uniform, and dense ETL on the rough perovskite layer. This layer effectively blocks holes and reduces interfacial recombination. Steady-state photoluminescence and electrochemical impedance spectroscopy analyses confirmed that Triton X-100 improved the electron extraction performance of PCBM. When the s-PCBM ETL was used, the average power conversion efficiency increased from 10.76% to 15.68%. This improvement was primarily caused by the increases in the open-circuit voltage and fill factor. s-PCBM-based PSCs also showed good air-stability, retaining 83.8% of their initial performance after 800 h under ambient conditions.

An optimal control method for maximizing the efficiency of direct drive ocean wave energy extraction system.

PubMed

Chen, Zhongxian; Yu, Haitao; Wen, Cheng

2014-01-01

The goal of direct drive ocean wave energy extraction system is to convert ocean wave energy into electricity. The problem explored in this paper is the design and optimal control for the direct drive ocean wave energy extraction system. An optimal control method based on internal model proportion integration differentiation (IM-PID) is proposed in this paper though most of ocean wave energy extraction systems are optimized by the structure, weight, and material. With this control method, the heavy speed of outer heavy buoy of the energy extraction system is in resonance with incident wave, and the system efficiency is largely improved. Validity of the proposed optimal control method is verified in both regular and irregular ocean waves, and it is shown that IM-PID control method is optimal in that it maximizes the energy conversion efficiency. In addition, the anti-interference ability of IM-PID control method has been assessed, and the results show that the IM-PID control method has good robustness, high precision, and strong anti-interference ability.

Energy conversion approaches and materials for high-efficiency photovoltaics.

PubMed

Green, Martin A; Bremner, Stephen P

2016-12-20

The past five years have seen significant cost reductions in photovoltaics and a correspondingly strong increase in uptake, with photovoltaics now positioned to provide one of the lowest-cost options for future electricity generation. What is becoming clear as the industry develops is that area-related costs, such as costs of encapsulation and field-installation, are increasingly important components of the total costs of photovoltaic electricity generation, with this trend expected to continue. Improved energy-conversion efficiency directly reduces such costs, with increased manufacturing volume likely to drive down the additional costs associated with implementing higher efficiencies. This suggests the industry will evolve beyond the standard single-junction solar cells that currently dominate commercial production, where energy-conversion efficiencies are fundamentally constrained by Shockley-Queisser limits to practical values below 30%. This Review assesses the overall prospects for a range of approaches that can potentially exceed these limits, based on ultimate efficiency prospects, material requirements and developmental outlook.

Molecular approaches to third generation photovoltaics: photochemical up-conversion

NASA Astrophysics Data System (ADS)

Cheng, Yuen Yap; Fückel, Burkhard; Roberts, Derrick A.; Khoury, Tony; Clady, Rapha"l. G. C. R.; Tayebjee, Murad J. Y.; Piper, Roland; Ekins-Daukes, N. J.; Crossley, Maxwell J.; Schmidt, Timothy W.

2010-08-01

We have investigated a photochemical up-conversion system comprising a molecular mixture of a palladium porphyrin to harvest light, and a polycyclic aromatic hydrocarbon to emit light. The energy of harvested photons is stored as molecular triplet states which then annihilate to bring about up-converted fluorescence. The limiting efficiency of such triplet-triplet annihilation up-conversion has been believed to be 11% for some time. However, by rigorously investigating the kinetics of delayed fluorescence following pulsed excitation, we demonstrate instantaneous annihilation efficiencies exceeding 40%, and limiting efficiencies for the current system of ~60%. We attribute the high efficiencies obtained to the electronic structure of the emitting molecule, which exhibits an exceptionally high T2 molecular state. We utilize the kinetic data obtained to model an up-converting layer irradiated with broadband sunlight, finding that ~3% efficiencies can be obtained with the current system, with this improving dramatically upon optimization of various parameters.

Integrating a dual-silicon photoelectrochemical cell into a redox flow battery for unassisted photocharging.

PubMed

Liao, Shichao; Zong, Xu; Seger, Brian; Pedersen, Thomas; Yao, Tingting; Ding, Chunmei; Shi, Jingying; Chen, Jian; Li, Can

2016-05-04

Solar rechargeable flow cells (SRFCs) provide an attractive approach for in situ capture and storage of intermittent solar energy via photoelectrochemical regeneration of discharged redox species for electricity generation. However, overall SFRC performance is restricted by inefficient photoelectrochemical reactions. Here we report an efficient SRFC based on a dual-silicon photoelectrochemical cell and a quinone/bromine redox flow battery for in situ solar energy conversion and storage. Using narrow bandgap silicon for efficient photon collection and fast redox couples for rapid interface charge injection, our device shows an optimal solar-to-chemical conversion efficiency of ∼5.9% and an overall photon-chemical-electricity energy conversion efficiency of ∼3.2%, which, to our knowledge, outperforms previously reported SRFCs. The proposed SRFC can be self-photocharged to 0.8 V and delivers a discharge capacity of 730 mAh l(-1). Our work may guide future designs for highly efficient solar rechargeable devices.

Efficient diode-end-pumped actively Q-switched Nd:YAG/SrWO4/KTP yellow laser.

PubMed

Cong, Zhenhua; Zhang, Xingyu; Wang, Qingpu; Liu, Zhaojun; Li, Shutao; Chen, Xiaohan; Zhang, Xiaolei; Fan, Shuzhen; Zhang, Huaijin; Tao, Xutang

2009-09-01

An efficient intracavity frequency-doubled Raman laser was obtained by using an SrWO(4) Raman medium, an Nd:YAG ceramic gain medium, and a KTP frequency-doubling medium. Three laser cavities, including a two-mirror cavity, a three-mirror coupled cavity, and a folded cavity, were investigated. With the coupled cavity, a 2.93 W, 590 nm laser was obtained at an incident pump power of 16.2 W and a pulse repetition frequency of 20 kHz; the corresponding conversion efficiency was 18.1%. The highest conversion efficiency of 19.2% was obtained at an incident pump power of 14.1 W and a pulse repetition frequency of 15 kHz. The obtained maximum output power and conversion efficiency were much higher than the results previously obtained with intracavity frequency-doubled solid-state Raman lasers.

Broadband high-efficiency half-wave plate: a supercell-based plasmonic metasurface approach.

PubMed

Ding, Fei; Wang, Zhuoxian; He, Sailing; Shalaev, Vladimir M; Kildishev, Alexander V

2015-04-28

We design, fabricate, and experimentally demonstrate an ultrathin, broadband half-wave plate in the near-infrared range using a plasmonic metasurface. The simulated results show that the linear polarization conversion efficiency is over 97% with over 90% reflectance across an 800 nm bandwidth. Moreover, simulated and experimental results indicate that such broadband and high-efficiency performance is also sustained over a wide range of incident angles. To further obtain a background-free half-wave plate, we arrange such a plate as a periodic array of integrated supercells made of several plasmonic antennas with high linear polarization conversion efficiency, consequently achieving a reflection-phase gradient for the cross-polarized beam. In this design, the anomalous (cross-polarized) and the normal (copolarized) reflected beams become spatially separated, hence enabling highly efficient and robust, background-free polarization conversion along with broadband operation. Our results provide strategies for creating compact, integrated, and high-performance plasmonic circuits and devices.

ZnO nanorods/AZO photoanode for perovskite solar cells fabricated in ambient air

NASA Astrophysics Data System (ADS)

La Ferrara, Vera; De Maria, Antonella; Rametta, Gabriella; Della Noce, Marco; Vittoria Mercaldo, Lucia; Borriello, Carmela; Bruno, Annalisa; Delli Veneri, Paola

2017-08-01

ZnO nanorods are a good candidate for replacing standard photoanodes, such as TiO2, in perovskite solar cells and in principle superseding the high performances already obtained. This is possible because ZnO nanorods have a fast electron transport rate due to their large surface area. An array of ZnO nanorods is grown by chemical bath deposition starting from Al-doped ZnO (AZO) used both as a seed layer and as an efficient transparent anode in the visible spectral range. In particular, in this work we fabricate methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells using glass/AZO/ZnO nanorods/perovskite/Spiro-OMeTAD/Au as the architecture. The growth of ZnO nanorods has been optimized by varying the precursor concentrations, growth time and solution temperature. All the fabrication process and photovoltaic characterizations have been carried out in ambient air and the devices have not been encapsulated. Power conversion efficiency as high as 7.0% has been obtained with a good stability over 20 d. This is the highest reported value to the best of our knowledge and it is a promising result for the development of perovskite solar cells based on ZnO nanorods and AZO.

The influence of different pretreatment methods on biogas production from Jatropha curcas oil cake.

PubMed

Jabłoński, Sławomir Jan; Kułażyński, Marek; Sikora, Ilona; Łukaszewicz, Marcin

2017-12-01

Drought and pest resistance, together with high oil content in its seeds, make Jatropha curcas a good oil source for biodiesel. Oil cake from J. curcas is not suitable for animal feeding and thus may be profitably used for additional energy production by conversion into biogas; however, the anaerobic digestion process must be optimized to obtain good efficiency. We subjected oil cake to thermal and acidic pretreatment to deactivate protease inhibitors and partially hydrolyze phytate. We then digested the samples in batch conditions to determine the effects of pretreatment on biogas production. Thermal pretreatment changed the kinetics of anaerobic digestion and reduced protease inhibitor activity and the concentration of phytate; however, biogas production efficiency was not affected (0.281 m 3  kg -1 ). To evaluate the possibility of recirculating water for SSF hydrolysis, ammonium nitrogen recovery from effluent was evaluated by its precipitation in the form of struvite (magnesium ammonium phosphate).Concentration of ammonium ions was reduced by 53% (to 980 mg L -1 ). We propose a water-saving concept based on percolation of J. curcas cake using anaerobic digestion effluent and feeding that percolate into a methanogenic bioreactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ternary Solar Cells Based on Two Small Molecule Donors with Same Conjugated Backbone: The Role of Good Miscibility and Hole Relay Process.

PubMed

Xiao, Liangang; Liang, Tianxiang; Gao, Ke; Lai, Tianqi; Chen, Xuebin; Liu, Feng; Russell, Thomas P; Huang, Fei; Peng, Xiaobin; Cao, Yong

2017-09-06

Ternary organic solar cells (OSCs) are very attractive for further enhancing the power conversion efficiencies (PCEs) of binary ones but still with a single active layer. However, improving the PCEs is still challenging because a ternary cell with one more component is more complicated on phase separation behavior. If the two donors or two acceptors have similar chemical structures, good miscibility can be expected to reduce the try-and-error work. Herein, we report ternary devices based on two small molecule donors with the same backbone but different substituents. Whereas both binary devices show PCEs about 9%, the PCE of the ternary cells is enhanced to 10.17% with improved fill factor and short-circuit current values and external quantum efficiencies almost in the whole absorption wavelength region from 440 to 850 nm. The same backbone enables the donors miscible at molecular level, and the donor with a higher HOMO level plays hole relay process to facilitate the charge transportation in the ternary devices. Since side-chain engineering has been well performed to tune the active materials' energy levels in OSCs, our results suggest that their ternary systems are promising for further improving the binary cells' performance although their absorptions are not complementary.

Solid polymeric electrolyte based dye-sensitized solar cell with improved stability

NASA Astrophysics Data System (ADS)

Prasad, Narottam; Kumar, Manish; Patel, K. R.; Roy, M. S.

2018-05-01

The impact of polymeric electrolyte was investigated over the performance of dye-sensitized solar cell made with Rose Bengal as sensitizer. Further, the selective influence of TiCl4 treatment and pre-sensitizer deoxycholic acid on nc-TiO2 photoanode was determined in terms of improvement in conversion efficiency of the cell. It is found that the effect of TiCl4 treatment was comparatively more than pre-sensitization with de-oxy cholic acid towards improving the efficiency of the cell. The conversion efficiency on TiCl4 treatment was 0.2% whereas on pre-sensitization with deoxy chollic acid it was 0.1%. The combined effect of both TiCl4 treatment & pre-sensitization with deoxycholic acid leads conversion efficiency to 0.33%.

High Photoelectric Conversion Efficiency of Metal Phthalocyanine/Fullerene Heterojunction Photovoltaic Device

PubMed Central

Lin, Chi-Feng; Zhang, Mi; Liu, Shun-Wei; Chiu, Tien-Lung; Lee, Jiun-Haw

2011-01-01

This paper introduces the fundamental physical characteristics of organic photovoltaic (OPV) devices. Photoelectric conversion efficiency is crucial to the evaluation of quality in OPV devices, and enhancing efficiency has been spurring on researchers to seek alternatives to this problem. In this paper, we focus on organic photovoltaic (OPV) devices and review several approaches to enhance the energy conversion efficiency of small molecular heterojunction OPV devices based on an optimal metal-phthalocyanine/fullerene (C60) planar heterojunction thin film structure. For the sake of discussion, these mechanisms have been divided into electrical and optical sections: (1) Electrical: Modification on electrodes or active regions to benefit carrier injection, charge transport and exciton dissociation; (2) Optical: Optional architectures or infilling to promote photon confinement and enhance absorption. PMID:21339999

High-power 671  nm laser by second-harmonic generation with 93% efficiency in an external ring cavity.

PubMed

Cui, Xing-Yang; Shen, Qi; Yan, Mei-Chen; Zeng, Chao; Yuan, Tao; Zhang, Wen-Zhuo; Yao, Xing-Can; Peng, Cheng-Zhi; Jiang, Xiao; Chen, Yu-Ao; Pan, Jian-Wei

2018-04-15

Second-harmonic generation (SHG) is useful for obtaining single-frequency continuous-wave laser sources at various wavelengths for applications ranging from biology to fundamental physics. Using an external power-enhancement cavity is an effective approach to improve the frequency conversion efficiency. However, thermal effects limit the efficiency, particularly, in high-power operation. Therefore, reducing thermal effects is important when designing a cavity. This Letter reports the use of an external ring cavity for SHG, yielding a 5.2 W, 671 nm laser light with a conversion efficiency of 93.8±0.8% which, to the best of our knowledge, is a new record of conversion efficiency for an external ring cavity. It is achieved using a 10 mm length periodically poled potassium titanyl phosphate crystal and a 65 μm radius beam waist in the cavity so as to minimize thermal dephasing and thermal lensing. Furthermore, a method is developed to determine a conversion efficiency more accurately based on measuring the pump depletion using a photodiode detector and a maximum pump depletion up to 97% is recorded. In this method, the uncertainty is much less than that achieved in a common method by direct measuring with a power meter.

A Novel Oscillating Rectenna for Wireless Microwave Power Transmission

NASA Technical Reports Server (NTRS)

McSpadden, J. O.; Dickinson, R. M.; Fan, L.; Chang, K.

1998-01-01

A new concept for solid state wireless microwave power transmission is presented. A 2.45 GHz rectenna element that was designed for over 85% RF to dc power conversion efficiency has been used to oscillate at 3.3 GHz with an approximate 1% dc to RF conversion efficiency.

Rational construction of a stable Zn4O-based MOF for highly efficient CO2 capture and conversion.

PubMed

Zhou, Hui-Fang; Liu, Bo; Hou, Lei; Zhang, Wen-Yan; Wang, Yao-Yu

2018-01-11

By employing a carboxylate ligand derived from benzene-1,4-dicarboxylate, a chemically stable Zn 4 O-based self-penetrating metal-organic framework has been rationally synthesized, which exhibits high CO 2 adsorption and efficient catalytic conversion for CO 2 cycloaddition.

Suppression of Tla1 gene expression for improved solar conversion efficiency and photosynthetic productivity in plants and algae

DOEpatents

Melis, Anastasios; Mitra, Mautusi

2010-06-29

The invention provides method and compositions to minimize the chlorophyll antenna size of photosynthesis by decreasing TLA1 gene expression, thereby improving solar conversion efficiencies and photosynthetic productivity in plants, e.g., green microalgae, under bright sunlight conditions.

Evaluating Energy Conversion Efficiency

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Smith, B. T.; Buoncristiani, A. M.

1983-01-01

Devices that convert solar radiation directly into storable chemical or electrical energy, have characteristic energy absorption spectrum; specifically, each of these devices has energy threshold. The conversion efficiency of generalized system that emcompasses all threshold devices is analyzed, resulting in family of curves for devices of various threshold energies operating at different temperatures.

Characterizing the Nature of Scan Results Discussions: Insights Into Why Patients Misunderstand Their Prognosis

PubMed Central

Singh, Sarguni; Cortez, Dagoberto; Maynard, Douglas; Cleary, James F.; DuBenske, Lori

2017-01-01

Introduction: Patients with incurable cancer have poor prognostic awareness. We present a detailed analysis of the dialogue between oncologists and patients in conversations with prognostic implications. Methods: A total of 128 audio-recorded encounters from a large multisite trial were obtained, and 64 involved scan results. We used conversation analysis, a qualitative method for studying human interaction, to analyze typical patterns and conversational devices. Results: Four components consistently occurred in sequential order: symptom-talk, scan-talk, treatment-talk, and logistic-talk. Six of the encounters (19%) were identified as good news, 15 (45%) as stable news, and 12 (36%) as bad news. The visit duration varied by the type of news: good, 15 minutes (07:00-29:00); stable, 17 minutes (07:00-41:00); and bad, 20 minutes (07:00-28:00). Conversational devices were common, appearing in half of recordings. Treatment-talk occupied 50% of bad-news encounters, 31% of good-news encounters, and 19% of stable-news encounters. Scan-talk occupied less than 10% of all conversations. There were only four instances of frank prognosis discussion. Conclusion: Oncologists and patients are complicit in constructing the typical encounter. Oncologists spend little time discussing scan results and the prognostic implications in favor of treatment-related talk. Conversational devices routinely help transition from scan-talk to detailed discussions about treatment options. We observed an opportunity to create prognosis-talk after scan-talk with a new conversational device, the question “Would you like to talk about what this means?” as the oncologist seeks permission to disclose prognostic information while ceding control to the patient. PMID:28095172

[Ecological management model of agriculture-pasture ecotone based on the theory of energy and material flow--a case study in Houshan dryland area of Inner Mongolia].

PubMed

Fan, Jinlong; Pan, Zhihua; Zhao, Ju; Zheng, Dawei; Tuo, Debao; Zhao, Peiyi

2004-04-01

The degradation of ecological environment in the agriculture-pasture ecotone in northern China has been paid more attentions. Based on our many years' research and under the guide of energy and material flow theory, this paper put forward an ecological management model, with a hill as the basic cell and according to the natural, social and economic characters of Houshan dryland farming area inside the north agriculture-pasture ecotone. The input and output of three models, i.e., the traditional along-slope-tillage model, the artificial grassland model and the ecological management model, were observed and recorded in detail in 1999. Energy and material flow analysis based on field test showed that compared with traditional model, ecological management model could increase solar use efficiency by 8.3%, energy output by 8.7%, energy conversion efficiency by 19.4%, N output by 26.5%, N conversion efficiency by 57.1%, P output by 12.1%, P conversion efficiency by 45.0%, and water use efficiency by 17.7%. Among the models, artificial grassland model had the lowest solar use efficiency, energy output and energy conversion efficiency; while the ecological management model had the most outputs and benefits, was the best model with high economic effect, and increased economic benefits by 16.1%, compared with the traditional model.

Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 5: Combined gas-steam turbine cycles. [energy conversion efficiency in electric power plants

NASA Technical Reports Server (NTRS)

Amos, D. J.; Foster-Pegg, R. W.; Lee, R. M.

1976-01-01

The energy conversion efficiency of gas-steam turbine cycles was investigated for selected combined cycle power plants. Results indicate that it is possible for combined cycle gas-steam turbine power plants to have efficiencies several point higher than conventional steam plants. Induction of low pressure steam into the steam turbine is shown to improve the plant efficiency. Post firing of the boiler of a high temperature combined cycle plant is found to increase net power but to worsen efficiency. A gas turbine pressure ratio of 12 to 1 was found to be close to optimum at all gas turbine inlet temperatures that were studied. The coal using combined cycle plant with an integrated low-Btu gasifier was calculated to have a plant efficiency of 43.6%, a capitalization of $497/kW, and a cost of electricity of 6.75 mills/MJ (24.3 mills/kwh). This combined cycle plant should be considered for base load power generation.

Design and modeling of an SJ infrared solar cell approaching upper limit of theoretical efficiency

NASA Astrophysics Data System (ADS)

Sahoo, G. S.; Mishra, G. P.

2018-01-01

Recent trends of photovoltaics account for the conversion efficiency limit making them more cost effective. To achieve this we have to leave the golden era of silicon cell and make a path towards III-V compound semiconductor groups to take advantages like bandgap engineering by alloying these compounds. In this work we have used a low bandgap GaSb material and designed a single junction (SJ) cell with a conversion efficiency of 32.98%. SILVACO ATLAS TCAD simulator has been used to simulate the proposed model using both Ray Tracing and Transfer Matrix Method (under 1 sun and 1000 sun of AM1.5G spectrum). A detailed analyses of photogeneration rate, spectral response, potential developed, external quantum efficiency (EQE), internal quantum efficiency (IQE), short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF) and conversion efficiency (η) are discussed. The obtained results are compared with previously reported SJ solar cell reports.

Direct solar-to-hydrogen conversion via inverted metamorphic multi-junction semiconductor architectures

DOE PAGES

Young, James L.; Steiner, Myles A.; Döscher, Henning; ...

2017-03-13

Solar water splitting via multi-junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance-of-systems costs. For sufficient photovoltage, water-splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water-splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p-dopedmore » photocathodes by using a buried p-n junction. Lastly, advanced on-sun benchmarking, spectrally corrected and validated with incident photon-to-current efficiency, yields over 16% solar-to-hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high-efficiency tandem III-V device.« less

Efficiency Enhancement of Hybrid Perovskite Solar Cells with MEH-PPV Hole-Transporting Layers

PubMed Central

Chen, Hsin-Wei; Huang, Tzu-Yen; Chang, Ting-Hsiang; Sanehira, Yoshitaka; Kung, Chung-Wei; Chu, Chih-Wei; Ikegami, Masashi; Miyasaka, Tsutomu; Ho, Kuo-Chuan

2016-01-01

In this study, hybrid perovskite solar cells are fabricated using poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) as dopant-free hole-transporting materials (HTMs), and two solution processes (one- and two-step methods, respectively) for preparing methylammonium lead iodide perovskite. By optimizing the concentrations and solvents of MEH-PPV solutions, a power conversion efficiency of 9.65% with hysteresis-less performance is achieved, while the device with 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′spirobifluorene (Spiro-OMeTAD) doped with lithium salts and tert-butylpyridine (TBP) exhibits an efficiency of 13.38%. This result shows that non-doped MEH-PPV is a suitable, low-cost HTM for efficient polymer-based perovskite solar cells. The effect of different morphologies of methylammonium lead iodide perovskite on conversion efficiency is also investigated by incident photon-to-electron conversion efficiency (IPCE) curves and electrochemical impedance spectroscopy (EIS). PMID:27698464

Conversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity.

PubMed

Zhu, Lin; Mochizuki, Toshimitsu; Yoshita, Masahiro; Chen, Shaoqiang; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

2016-05-16

We calculated the conversion-efficiency limit ηsc and the optimized subcell bandgap energies of 1 to 5 junction solar cells without and with intermediate reflectors under 1-sun AM1.5G and 1000-sun AM1.5D irradiations, particularly including the impact of internal radiative efficiency (ηint) below unity for realistic subcell materials on the basis of an extended detailed-balance theory. We found that the conversion-efficiency limit ηsc significantly drops when the geometric mean ηint* of all subcell ηint in the stack reduces from 1 to 0.1, and that ηsc degrades linearly to logηint* for ηint* below 0.1. For ηint*<0.1 differences in ηsc due to additional intermediate reflectors became very small if all subcells are optically thick for sun light. We obtained characteristic optimized bandgap energies, which reflect both ηint* decrease and AM1.5 spectral gaps. These results provide realistic efficiency targets and design principles.

Direct solar-to-hydrogen conversion via inverted metamorphic multi-junction semiconductor architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, James L.; Steiner, Myles A.; Döscher, Henning

Solar water splitting via multi-junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance-of-systems costs. For sufficient photovoltage, water-splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water-splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p-dopedmore » photocathodes by using a buried p-n junction. Lastly, advanced on-sun benchmarking, spectrally corrected and validated with incident photon-to-current efficiency, yields over 16% solar-to-hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high-efficiency tandem III-V device.« less

Optimization of non-thermal plasma efficiency in the simultaneous elimination of benzene, toluene, ethyl-benzene, and xylene from polluted airstreams using response surface methodology.

PubMed

Najafpoor, Ali Asghar; Jonidi Jafari, Ahmad; Hosseinzadeh, Ahmad; Khani Jazani, Reza; Bargozin, Hasan

2018-01-01

Treatment with a non-thermal plasma (NTP) is a new and effective technology applied recently for conversion of gases for air pollution control. This research was initiated to optimize the efficient application of the NTP process in benzene, toluene, ethyl-benzene, and xylene (BTEX) removal. The effects of four variables including temperature, initial BTEX concentration, voltage, and flow rate on the BTEX elimination efficiency were investigated using response surface methodology (RSM). The constructed model was evaluated by analysis of variance (ANOVA). The model goodness-of-fit and statistical significance was assessed using determination coefficients (R 2 and R 2 adj ) and the F-test. The results revealed that the R 2 proportion was greater than 0.96 for BTEX removal efficiency. The statistical analysis demonstrated that the BTEX removal efficiency was significantly correlated with the temperature, BTEX concentration, voltage, and flow rate. Voltage was the most influential variable affecting the dependent variable as it exerted a significant effect (p < 0.0001) on the response variable. According to the achieved results, NTP can be applied as a progressive, cost-effective, and practical process for treatment of airstreams polluted with BTEX in conditions of low residence time and high concentrations of pollutants.

Kinetic modeling of cellulosic biomass to ethanol via simultaneous saccharification and fermentation: Part I. Accommodation of intermittent feeding and analysis of staged reactors.

PubMed

Shao, Xiongjun; Lynd, Lee; Wyman, Charles; Bakker, André

2009-01-01

The model of South et al. [South et al. (1995) Enzyme Microb Technol 17(9): 797-803] for simultaneous saccharification of fermentation of cellulosic biomass is extended and modified to accommodate intermittent feeding of substrate and enzyme, cascade reactor configurations, and to be more computationally efficient. A dynamic enzyme adsorption model is found to be much more computationally efficient than the equilibrium model used previously, thus increasing the feasibility of incorporating the kinetic model in a computational fluid dynamic framework in the future. For continuous or discretely fed reactors, it is necessary to use particle conversion in conversion-dependent hydrolysis rate laws rather than reactor conversion. Whereas reactor conversion decreases due to both reaction and exit of particles from the reactor, particle conversion decreases due to reaction only. Using the modified models, it is predicted that cellulose conversion increases with decreasing feeding frequency (feedings per residence time, f). A computationally efficient strategy for modeling cascade reactors involving a modified rate constant is shown to give equivalent results relative to an exhaustive approach considering the distribution of particles in each successive fermenter.

Decomposing Fuel Economy and Greenhouse Gas Regulatory Standards in the Energy Conversion Efficiency and Tractive Energy Domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pannone, Greg; Thomas, John F; Reale, Michael

The three foundational elements that determine mobile source energy use and tailpipe carbon dioxide (CO2) emissions are the tractive energy requirements of the vehicle, the on-cycle energy conversion efficiency of the propulsion system, and the energy source. The tractive energy requirements are determined by the vehicle's mass, aerodynamic drag, tire rolling resistance, and parasitic drag. Oncycle energy conversion of the propulsion system is dictated by the tractive efficiency, non-tractive energy use, kinetic energy recovery, and parasitic losses. The energy source determines the mobile source CO2 emissions. For current vehicles, tractive energy requirements and overall energy conversion efficiency are readily availablemore » from the decomposition of test data. For future applications, plausible levels of mass reduction, aerodynamic drag improvements, and tire rolling resistance can be transposed into the tractive energy domain. Similarly, by combining thermodynamic, mechanical efficiency, and kinetic energy recovery fundamentals with logical proxies, achievable levels of energy conversion efficiency can be established to allow for the evaluation of future powertrain requirements. Combining the plausible levels of tractive energy and on-cycle efficiency provides a means to compute sustainable vehicle and propulsion system scenarios that can achieve future regulations. Using these principles, the regulations established in the United States (U.S.) for fuel consumption and CO2 emissions are evaluated. Fleet-level scenarios are generated and compared to the technology deployment assumptions made during rule-making. When compared to the rule-making assumptions, the results indicate that a greater level of advanced vehicle and propulsion system technology deployment will be required to achieve the model year 2025 U.S. standards for fuel economy and CO2 emissions.« less

Polymer bulk heterojunction solar cells with PEDOT:PSS bilayer structure as hole extraction layer.

PubMed

Kim, Wanjung; Kim, Namhun; Kim, Jung Kyu; Park, Insun; Choi, Yeong Suk; Wang, Dong Hwan; Chae, Heeyeop; Park, Jong Hyeok

2013-06-01

A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC₆₀BM and PCDTBT:PC₇₀BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of saw damage using diamond-coated wire in crystalline silicon solar cells by photoluminescence imaging

NASA Astrophysics Data System (ADS)

Kinoshita, Kosuke; Kojima, Takuto; Suzuki, Ryota; Kawatsu, Tomoyuki; Nakamura, Kyotaro; Ohshita, Yoshio; Ogura, Atsushi

2018-05-01

Si ingots were sliced using a diamond-coated wire, and saw damage was observed even after damage removal etching and texturization. Since invisible microscopic damage was observed only under uncontrolled slice conditions, such damage was identified as saw damage. The wafers with saw damage exhibited the degradation of solar cell conversion efficiency (approximately 1–2% absolute). The results of external quantum efficiency (EQE) measurements showed a slight deterioration of EQE in the short wavelength region. Current–voltage characteristic measurements showed similar results that agreed with the EQE measurement results. In addition, EQE mapping measurements were carried out at various irradiation wavelengths between 350 and 1150 nm. Areas with dark contrasts in EQE mapping correspond to saw damage. In the cells with a low conversion efficiency, both EQE mapping and PL images exhibited dark areas and lines. On the other hand, in the cells with a high conversion efficiency, a uniform distribution of saw damage was observed even with the saw damage in the PL images. We believe that sophisticated control to suppress saw damage during sawing is required to realize higher conversion efficiency solar cells in the future.

Numerical investigation of output beam quality in efficient broadband optical parametric chirped pulse amplification

NASA Astrophysics Data System (ADS)

Liu, Xiao-Di; Xu, Lu; Liang, Xiao-Yan

2017-01-01

We theoretically analyzed output beam quality of broad bandwidth non-collinear optical parametric chirped pulse amplification (NOPCPA) in LiB3O5 (LBO) centered at 800 nm. With a three-dimensional numerical model, the influence of the pump intensity, pump and signal spatial modulations, and the walk-off effect on the OPCPA output beam quality are presented, together with conversion efficiency and the gain spectrum. The pump modulation is a dominant factor that affects the output beam quality. Comparatively, the influence of signal modulation is insignificant. For a low-energy system with small beam sizes, walk-off effect has to be considered. Pump modulation and walk-off effect lead to asymmetric output beam profile with increased modulation. A special pump modulation type is found to optimize output beam quality and efficiency. For a high-energy system with large beam sizes, the walk-off effect can be neglected, certain back conversion is beneficial to reduce the output modulation. A trade-off must be made between the output beam quality and the conversion efficiency, especially when the pump modulation is large since. A relatively high conversion efficiency and a low output modulation are both achievable by controlling the pump modulation and intensity.

Bi2S3microspheres grown on graphene sheets as low-cost counter-electrode materials for dye-sensitized solar cells.

PubMed

Li, Guang; Chen, Xiaoshuang; Gao, Guandao

2014-03-21

In this work, we synthesized 3D Bi2S3 microspheres comprised of nanorods grown along the (211) facet on graphene sheets by a solvothermal route, and investigated its catalytic activities through I-V curves and conversion efficiency tests as the CE in DSSCs. Although the (211) facet has a large band gap for a Bi2S3 semiconductor, owing to the introduction of graphene into the system, its short-circuit current density, open-circuit voltage, fill factor, and efficiency were Jsc = 12.2 mA cm(-2), Voc = 0.75 V, FF = 0.60, and η = 5.5%, respectively. By integrating it with graphene sheets, our material achieved the conversion efficiency of 5.5%, which is almost triple the best conversion efficiency value of the DSSCs with (211)-faceted 3D Bi2S3 without graphene (1.9%) reported in the latest literature. Since this conversion-efficient 3D material grown on the graphene sheets significantly improves its catalytic properties, it paves the way for designing and applying low-cost Pt-free CE materials in DSSC from inorganic nanostructures.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion.

PubMed

Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

2016-08-14

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ∼1 kW m(-2). The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.

Rectenna session: Micro aspects. [energy conversion

NASA Technical Reports Server (NTRS)

Gutmann, R. J.

1980-01-01

Two micro aspects of the rectenna design are addressed: evaluation of the degradation in net rectenna RF to DC conversion efficiency due to power density variations across the rectenna (power combining analysis) and design of Yagi-Uda receiving elements to reduce rectenna cost by decreasing the number of conversion circuits (directional receiving elements). The first of these micro aspects involves resolving a fundamental question of efficiency potential with a rectenna, while the second involves a design modification with a large potential cost saving.

High efficiency thermal to electric energy conversion using selective emitters and spectrally tuned solar cells

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Flood, Dennis J.; Lowe, Roland A.

1992-01-01

Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1500 K. Depending on the nature of parasitic losses, overall thermal-to-electric conversion efficiencies greater than 20 percent are feasible.

Thermophotovoltaic conversion using selective infrared line emitters and large band gap photovoltaic devices

DOEpatents

Brandhorst, Jr., Henry W.; Chen, Zheng

2000-01-01

Efficient thermophotovoltaic conversion can be performed using photovoltaic devices with a band gap in the 0.75-1.4 electron volt range, and selective infrared emitters chosen from among the rare earth oxides which are thermally stimulated to emit infrared radiation whose energy very largely corresponds to the aforementioned band gap. It is possible to use thermovoltaic devices operating at relatively high temperatures, up to about 300.degree. C., without seriously impairing the efficiency of energy conversion.

Megawatt level UV output from [110] Cr⁴⁺:YAG passively Q-switched microchip laser.

PubMed

Bhandari, Rakesh; Taira, Takunori

2011-11-07

Recent development of megawatt peak power, giant pulse microchip lasers has opened new opportunities for efficient wavelength conversion, provided the output of the microchip laser is linearly polarized. We obtain > 2 MW peak power, 260 ps, 100 Hz pulses at 266 nm by fourth harmonic conversion of a linearly polarized Nd:YAG microchip laser that is passively Q-switched with [110] cut Cr⁴⁺:YAG. The SHG and FHG conversion efficiencies are 85% and 51%, respectively.

Efficient biological conversion of carbon monoxide (CO) to carbon dioxide (CO2) and for utilization in bioplastic production by Ralstonia eutropha through the display of an enzyme complex on the cell surface.

PubMed

Hyeon, Jeong Eun; Kim, Seung Wook; Park, Chulhwan; Han, Sung Ok

2015-06-25

An enzyme complex for biological conversion of CO to CO2 was anchored on the cell surface of the CO2-utilizing Ralstonia eutropha and successfully resulted in a 3.3-fold increase in conversion efficiency. These results suggest that this complexed system may be a promising strategy for CO2 utilization as a biological tool for the production of bioplastics.

A 6-bit 4 GS/s pseudo-thermometer segmented CMOS DAC

NASA Astrophysics Data System (ADS)

Yijun, Song; Wenyuan, Li

2014-06-01

A 6-bit 4 GS/s, high-speed and power-efficient DAC for ultra-high-speed transceivers in 60 GHz band millimeter wave technology is presented. A novel pseudo-thermometer architecture is proposed to realize a good compromise between the fast conversion speed and the chip area. Symmetrical and compact floor planning and layout techniques including tree-like routing, cross-quading and common-centroid method are adopted to guarantee the chip is fully functional up to near-Nyquist frequency in a standard 0.18 μm CMOS process. Post simulation results corroborate the feasibility of the designed DAC, which canperform good static and dynamic linearity without calibration. DNL errors and INL errors can be controlled within ±0.28 LSB and ±0.26 LSB, respectively. SFDR at 4 GHz clock frequency for a 1.9 GHz near-Nyquist sinusoidal output signal is 40.83 dB and the power dissipation is less than 37 mW.

CaO-MgO-Al 2O 3-SiO 2 (CMAS) corrosion of Gd 2Zr 2O 7 and Sm 2Zr 2O 7

DOE PAGES

Wang, Honglong; Bakal, Ahmet; Zhang, Xingxing; ...

2016-08-08

Ceramic thermal barrier coatings are applied to superalloys used in gas turbine engineering to increase the operating temperature and the energy conversion efficiency. However, dust consisting of CaO-MgO-Al 2O 3-SiO 2 (CMAS) from the air can be injected into the engines and corrode the thermal barrier coatings. Lanthanide zirconates are promising materials in thermal barrier coatings due to their low thermal conductivities, good phase stability and good corrosion resistance. However, the corrosion resistance mechanism of CMAS on lanthanide zirconates is still not clearly understood. In this work, the corrosion mechanism of Gd 2Zr 2O 7 and Sm 2Zr 2O 7more » in CMAS is studied. Here, the results show that the CMAS can easily react with lanthanide zirconate thermal barrier coatings to form a dense layer, which can resist further corrosion« less

Catalytic conversion of methanol/ethanol to isobutanol--a highly selective route to an advanced biofuel.

PubMed

Wingad, Richard L; Bergström, Emilie J E; Everett, Matthew; Pellow, Katy J; Wass, Duncan F

2016-04-14

Catalysts based on ruthenium diphosphine complexes convert methanol/ethanol mixtures to the advanced biofuel isobutanol, with extremely high selectivity (>99%) at good (>75%) conversion via a Guerbet-type mechanism.

Improvement of force factor of magnetostrictive vibration power generator for high efficiency

NASA Astrophysics Data System (ADS)

Kita, Shota; Ueno, Toshiyuki; Yamada, Sotoshi

2015-05-01

We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 1: Executive summary. [using coal or coal derived fuels

NASA Technical Reports Server (NTRS)

Corman, J. C.

1976-01-01

A data base for the comparison of advanced energy conversion systems for utility applications using coal or coal-derived fuels was developed. Estimates of power plant performance (efficiency), capital cost, cost of electricity, natural resource requirements, and environmental intrusion characteristics were made for ten advanced conversion systems. Emphasis was on the energy conversion system in the context of a base loaded utility power plant. All power plant concepts were premised on meeting emission standard requirements. A steam power plant (3500 psig, 1000 F) with a conventional coal-burning furnace-boiler was analyzed as a basis for comparison. Combined cycle gas/steam turbine system results indicated competitive efficiency and a lower cost of electricity compared to the reference steam plant. The Open-Cycle MHD system results indicated the potential for significantly higher efficiency than the reference steam plant but with a higher cost of electricity.

Conversion of far ultraviolet to visible radiation: absolute measurements of the conversion efficiency of tetraphenyl butadiene

NASA Astrophysics Data System (ADS)

Vest, Robert E.; Coplan, Michael A.; Clark, Charles W.

Far ultraviolet (FUV) scintillation of noble gases is used in dark matter and neutrino research and in neutron detection. Upon collisional excitation, noble gas atoms recombine into excimer molecules that decay by FUV emission. Direct detection of FUV is difficult. Another approach is to convert it to visible light using a wavelength-shifting medium. One such medium, tetraphenyl butadiene (TPB) can be vapor-deposited on substrates. Thus the quality of thin TPB films can be tightly controlled. We have measured the absolute efficiency of FUV-to-visible conversion by 1 μm-thick TPB films vs. FUV wavelengths between 130 and 300 nm, with 1 nm resolution. The energy efficiency of FUV to visible conversion varies between 1% and 5%. We make comparisons with other recent results. Work performed at the NIST SURF III Synchrotron Ultraviolet Radiation Facility,.

High-Efficiency Artificial Photosynthesis Using a Novel Alkaline Membrane Cell

NASA Technical Reports Server (NTRS)

Narayan, Sri; Haines, Brennan; Blosiu, Julian; Marzwell, Neville

2009-01-01

A new cell designed to mimic the photosynthetic processes of plants to convert carbon dioxide into carbonaceous products and oxygen at high efficiency, has an improved configuration using a polymer membrane electrolyte and an alkaline medium. This increases efficiency of the artificial photosynthetic process, achieves high conversion rates, permits the use of inexpensive catalysts, and widens the range of products generated by this type of process. The alkaline membrane electrolyte allows for the continuous generation of sodium formate without the need for any additional separation system. The electrolyte type, pH, electrocatalyst type, and cell voltage were found to have a strong effect on the efficiency of conversion of carbon dioxide to formate. Indium electrodes were found to have higher conversion efficiency compared to lead. Bicarbonate electrolyte offers higher conversion efficiency and higher rates than water solutions saturated with carbon dioxide. pH values between 8 and 9 lead to the maximum values of efficiency. The operating cell voltage of 2.5 V, or higher, ensures conversion of the carbon dioxide to formate, although the hydrogen evolution reaction begins to compete strongly with the formate production reaction at higher cell voltages. Formate is produced at indium and lead electrodes at a conversion efficiency of 48 mg of CO2/kilojoule of energy input. This efficiency is about eight times that of natural photosynthesis in green plants. The electrochemical method of artificial photosynthesis is a promising approach for the conversion, separation and sequestration of carbon dioxide for confined environments as in space habitats, and also for carbon dioxide management in the terrestrial context. The heart of the reactor is a membrane cell fabricated from an alkaline polymer electrolyte membrane and catalyst- coated electrodes. This cell is assembled and held in compression in gold-plated hardware. The cathode side of the cell is supplied with carbon dioxide-saturated water or bicarbonate solution. The anode side of the cell is supplied with sodium hydroxide solution. The solutions are circulated past the electrodes in the electrochemical cell using pumps. A regulated power supply provides the electrical energy required for the reactions. Photovoltaic cells can be used to better mimic the photosynthetic reaction. The current flowing through the electrochemical cell, and the cell voltage, are monitored during experimentation. The products of the electrochemical reduction of carbon dioxide are allowed to accumulate in the cathode reservoir. Samples of the cathode solution are withdrawn for product analysis. Oxygen is generated on the anode side and is allowed to vent out of the reservoir.

Folic acid-functionalized up-conversion nanoparticles: toxicity studies in vivo and in vitro and targeted imaging applications

NASA Astrophysics Data System (ADS)

Sun, Lining; Wei, Zuwu; Chen, Haige; Liu, Jinliang; Guo, Jianjian; Cao, Ming; Wen, Tieqiao; Shi, Liyi

2014-07-01

Folate receptors (FRs) are overexpressed on a variety of human cancer cells and tissues, including cancers of the breast, ovaries, endometrium, and brain. This over-expression of FRs can be used to target folate-linked imaging specifically to FR-expressing tumors. Fluorescence is emerging as a powerful new modality for molecular imaging in both the diagnosis and treatment of disease. Combining innovative molecular biology and chemistry, we prepared three kinds of folate-targeted up-conversion nanoparticles as imaging agents (UCNC-FA: UCNC-Er-FA, UCNC-Tm-FA, and UCNC-Er,Tm-FA). In vivo and in vitro toxicity studies showed that these nanoparticles have both good biocompatibility and low toxicity. Moreover, the up-conversion luminescence imaging indicated that they have good targeting to HeLa cells and can therefore serve as potential fluorescent contrast agents.Folate receptors (FRs) are overexpressed on a variety of human cancer cells and tissues, including cancers of the breast, ovaries, endometrium, and brain. This over-expression of FRs can be used to target folate-linked imaging specifically to FR-expressing tumors. Fluorescence is emerging as a powerful new modality for molecular imaging in both the diagnosis and treatment of disease. Combining innovative molecular biology and chemistry, we prepared three kinds of folate-targeted up-conversion nanoparticles as imaging agents (UCNC-FA: UCNC-Er-FA, UCNC-Tm-FA, and UCNC-Er,Tm-FA). In vivo and in vitro toxicity studies showed that these nanoparticles have both good biocompatibility and low toxicity. Moreover, the up-conversion luminescence imaging indicated that they have good targeting to HeLa cells and can therefore serve as potential fluorescent contrast agents. Electronic supplementary information (ESI) available: Up-conversion luminescence spectra of UCNC-Er and UCNC-Er-FA, UCNC-Tm and UCNC-Tm-FA. Confocal luminescence imaging data collected as a series along the Z optical axis. See DOI: 10.1039/c4nr02312a

Conversion of broadband thermal radiation in lithium niobate crystals of various compositions

NASA Astrophysics Data System (ADS)

Syuy, A. V.; Litvinova, M. N.; Goncharova, P. S.; Sidorov, N. V.; Palatnikov, M. N.; Krishtop, V. V.; Likhtin, V. V.

2013-05-01

The conversion of the broadband thermal radiation in stoichiometric ( R = 1) lithium niobate single crystals that are grown from melt with 58.6 mol % of LiO2, congruent ( R = Li/Nb = 0.946) melt with the K2O flux admixture (4.5 and 6.0 wt %), and congruent melt and in congruent single crystals doped with the Zn2+, Gd3+, and Er3+ cations is studied. It is demonstrated that the conversion efficiency of the stoichiometric crystal that is grown from the melt with 58.6 mol % of LiO2 is less than the conversion efficiency of congruent crystal. In addition, the stoichiometric and almost stoichiometric crystals and the doped congruent crystals exhibit the blue shift of the peak conversion intensity in comparison with a nominally pure congruent crystal. For the congruent crystals, the conversion intensities peak at 520 and 495 nm, respectively.

A linear polarization converter with near unity efficiency in microwave regime

NASA Astrophysics Data System (ADS)

Xu, Peng; Wang, Shen-Yun; Geyi, Wen

2017-04-01

In this paper, we present a linear polarization converter in the reflective mode with near unity conversion efficiency. The converter is designed in an array form on the basis of a pair of orthogonally arranged three-dimensional split-loop resonators sharing a common terminal coaxial port and a continuous metallic ground slab. It converts the linearly polarized incident electromagnetic wave at resonance to its orthogonal counterpart upon the reflection mode. The conversion mechanism is explained by an equivalent circuit model, and the conversion efficiency can be tuned by changing the impedance of the terminal port. Such a scheme of the linear polarization converter has potential applications in microwave communications, remote sensing, and imaging.

Frequency doubling in poled polymers using anomalous dispersion phase-matching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalczyk, T.C.; Singer, K.D.; Cahill, P.A.

1995-10-01

The authors report on a second harmonic generation in a poled polymer waveguide using anomalous dispersion phase-matching. Blue light ({lambda} = 407 nm) was produced by phase-matching the lowest order fundamental and harmonic modes over a distance of 32 {micro}m. The experimental conversion efficiency was {eta} = 1.2 {times} 10{sup {minus}4}, in agreement with theory. Additionally, they discuss a method of enhancing the conversion efficiency for second harmonic generation using anomalous dispersion phase-matching to optimize Cerenkov second harmonic generation. The modeling shows that a combination of phase-matching techniques creates larger conversion efficiencies and reduces critical fabrication requirements of the individualmore » phase-matching techniques.« less

Core-shell heterojunction of silicon nanowire arrays and carbon quantum dots for photovoltaic devices and self-driven photodetectors.

PubMed

Xie, Chao; Nie, Biao; Zeng, Longhui; Liang, Feng-Xia; Wang, Ming-Zheng; Luo, Linbao; Feng, Mei; Yu, Yongqiang; Wu, Chun-Yan; Wu, Yucheng; Yu, Shu-Hong

2014-04-22

Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon nanowire (SiNW) array/carbon quantum dot (CQD) core-shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 10(3) at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core-shell heterojunction device could find potential applications in future high-performance optoelectronic devices.

Design optimization of beta- and photovoltaic conversion devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wichner, R.; Blum, A.; Fischer-Colbrie, E.

1976-01-08

This report presents the theoretical and experimental results of an LLL Electronics Engineering research program aimed at optimizing the design and electronic-material parameters of beta- and photovoltaic p-n junction conversion devices. To meet this objective, a comprehensive computer code has been developed that can handle a broad range of practical conditions. The physical model upon which the code is based is described first. Then, an example is given of a set of optimization calculations along with the resulting optimized efficiencies for silicon (Si) and gallium-arsenide (GaAs) devices. The model we have developed, however, is not limited to these materials. Itmore » can handle any appropriate material--single or polycrystalline-- provided energy absorption and electron-transport data are available. To check code validity, the performance of experimental silicon p-n junction devices (produced in-house) were measured under various light intensities and spectra as well as under tritium beta irradiation. The results of these tests were then compared with predicted results based on the known or best estimated device parameters. The comparison showed very good agreement between the calculated and the measured results.« less

Understanding chemically processed solar cells based on quantum dots

PubMed Central

Malgras, Victor; Nattestad, Andrew; Kim, Jung Ho; Dou, Shi Xue; Yamauchi, Yusuke

2017-01-01

Abstract Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum. PMID:28567179

UV-driven microvalve based on a micro-nano TiO₂/SiO₂ composite surface for microscale flow control.

PubMed

Guo, Ting; Meng, Tao; Li, Wei; Qin, Jilong; Tong, Zhiping; Zhang, Qing; Li, Xueru

2014-03-28

This paper presents a novel ultraviolet (UV)-driven microvalve based on the concept of inserting a trimethyl chlorosilane (CTMS) modified TiO₂/SiO₂ composite patch of switchable wettability in a microfluidic system. A unique micro-nano hierarchical structure was designed and used to enhance the overall wetting contrast with the aim of improving the wetting-based valve performances. Field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and chemical composition of the surface. UV-driven wettability conversion on the patched microchannel was investigated using water column relative height tests, and the results confirmed the significant improvement of the hierarchical structure with the surface hydrophobic/hydrophilic conversion, which produced enhancements of 276% and 95% of the water-repellent and water-sucking pressures, respectively, compared with those of the single-scale TiO₂ nanopatterned structure. Accordingly, a good reversible and repeated on-off performance was identified by the valve tests, highlighting the potential application of the novel microvalve in the efficient control of microscale flow.

UV-driven microvalve based on a micro-nano TiO2/SiO2 composite surface for microscale flow control

NASA Astrophysics Data System (ADS)

Guo, Ting; Meng, Tao; Li, Wei; Qin, Jilong; Tong, Zhiping; Zhang, Qing; Li, Xueru

2014-03-01

This paper presents a novel ultraviolet (UV)-driven microvalve based on the concept of inserting a trimethyl chlorosilane (CTMS) modified TiO2/SiO2 composite patch of switchable wettability in a microfluidic system. A unique micro-nano hierarchical structure was designed and used to enhance the overall wetting contrast with the aim of improving the wetting-based valve performances. Field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and chemical composition of the surface. UV-driven wettability conversion on the patched microchannel was investigated using water column relative height tests, and the results confirmed the significant improvement of the hierarchical structure with the surface hydrophobic/hydrophilic conversion, which produced enhancements of 276% and 95% of the water-repellent and water-sucking pressures, respectively, compared with those of the single-scale TiO2 nanopatterned structure. Accordingly, a good reversible and repeated on-off performance was identified by the valve tests, highlighting the potential application of the novel microvalve in the efficient control of microscale flow.

Efficient production of lactulose from whey powder by cellobiose 2-epimerase in an enzymatic membrane reactor.

PubMed

Wu, Lingtian; Xu, Cen; Li, Sha; Liang, Jinfeng; Xu, Hong; Xu, Zheng

2017-06-01

In this study, the gene encoding cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus (CsCE) was successfully expressed in Bacillus subtilis WB800. After the fermentation medium optimization, the activity of recombinant strain was 4.5-fold higher than the original medium in a 7.5L fermentor. The optimal catalytic pH and temperature of crude CsCE were 7.0 and 80°C, respectively. An enzymatic synthesis of lactulose was developed using cheese-whey lactose as its substrate. The maximum conversion rate of whey powder obtained was 58.5% using 7.5 U/mL CsCE. The enzymatic membrane reactor system exhibited a great operational stability, confirmed with the higher lactose conversion (42.4%) after 10 batches. To our best knowledge, this is the first report of lactulose synthesis in food grade strain, which improve the food safety, and we not only realize the biological production of lactulose, but also make good use of industrial waste, which have positive impact on environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarov, Nikolay S.; Lin, Qianglu; Pietryga, Jeffrey M.

One source of efficiency losses in photovoltaic cells is their transparency toward solar photons with energies below the band gap of the absorbing layer. This loss can be reduced using a process of up-conversion whereby two or more sub-band-gap photons generate a single above-gap exciton. Traditional approaches to up-conversion, such as nonlinear two-photon absorption (2PA) or triplet fusion, suffer from low efficiency at solar light intensities, a narrow absorption bandwidth, nonoptimal absorption energies, and difficulties for implementing in practical devices. We show that these deficiencies can be alleviated using the effect of Auger up-conversion in thick-shell PbSe/CdSe quantum dots. Thismore » process relies on Auger recombination whereby two low-energy, core-based excitons are converted into a single higher-energy, shell-based exciton. When compared to their monocomponent counterparts, the tailored PbSe/CdSe heterostructures feature enhanced absorption cross-sections, a higher efficiency of the “productive” Auger pathway involving re-excitation of a hole, and longer lifetimes of both core- and shell-localized excitons. These features lead to effective up-conversion cross-sections that are more than 6 orders of magnitude higher than for standard nonlinear 2PA, which allows for efficient up-conversion of continuous wave infrared light at intensities as low as a few watts per square centimeter.« less

Highly Efficient Spin-to-Charge Current Conversion in Strained HgTe Surface States Protected by a HgCdTe Layer

NASA Astrophysics Data System (ADS)

Noel, P.; Thomas, C.; Fu, Y.; Vila, L.; Haas, B.; Jouneau, P.-H.; Gambarelli, S.; Meunier, T.; Ballet, P.; Attané, J. P.

2018-04-01

We report the observation of spin-to-charge current conversion in strained mercury telluride at room temperature, using spin pumping experiments. We show that a HgCdTe barrier can be used to protect the HgTe from direct contact with the ferromagnet, leading to very high conversion rates, with inverse Edelstein lengths up to 2.0 ±0.5 nm . The influence of the HgTe layer thickness on the conversion efficiency is found to differ strongly from what is expected in spin Hall effect systems. These measurements, associated with the temperature dependence of the resistivity, suggest that these high conversion rates are due to the spin momentum locking property of HgTe surface states.

Enhancement of conversion efficiency of extreme ultraviolet radiation from a liquid aqueous solution microjet target by use of dual laser pulses

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Dojyo, Naoto; Hamada, Masaya; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi

2006-03-01

We demonstrated a debris-free, efficient laser-produced plasma extreme ultraviolet (EUV) source by use of a regenerative liquid microjet target containing tin-dioxide (SnO II) nano-particles. By using a low SnO II concentration (6%) solution and dual laser pulses for the plasma control, we observed the EUV conversion efficiency of 1.2% with undetectable debris.

INFRARED SPECTROSCOPY: A TOOL FOR DETERMINATION OF THE DEGREE OF CONVERSION IN DENTAL COMPOSITES

PubMed Central

Moraes, Luciene Gonçalves Palmeira; Rocha, Renata Sanches Ferreira; Menegazzo, Lívia Maluf; de AraÚjo, Eudes Borges; Yukimitu, Keizo; Moraes, João Carlos Silos

2008-01-01

Infrared spectroscopy is one of the most widely used techniques for measurement of conversion degree in dental composites. However, to obtain good quality spectra and quantitative analysis from spectral data, appropriate expertise and knowledge of the technique are mandatory. This paper presents important details to use infrared spectroscopy for determination of the conversion degree. PMID:19089207

High efficiency and output power from second- and third-harmonic millimeter-wave InP-TED oscillators at frequencies above 170 GHz

NASA Astrophysics Data System (ADS)

Rydberg, Anders

1990-10-01

InP TED (transferred electron device) oscillators have been experimentally investigated for frequencies between 170 and 279 GHz. It has been found that output powers of more than 7 and 0.2 mW are possible at 180 and 272 GHz using second- and third-harmonic mode operation, respectively. Conversion efficiencies of more than 13 percent and 0.3 percent between fundamental and second harmonic and fundamental and third harmonic, respectively, have been found. The conversion efficiencies are comparable to GaAs TEDs. The output powers, conversion efficiencies, and tuning ranges (more than 22 percent) are the largest reported for InP TEDs at these frequencies. The output power at third harmonic was sufficient for supplying a superconducting mixer with local oscillator power.

Equivalent circuit model of converse magnetoelectric effect for the tri-layer magnetoelectric laminates with thermal and stress loadings

NASA Astrophysics Data System (ADS)

Zhou, Hao-Miao; Li, Meng-Han; Liu, Hui; Cui, Xiao-Le

2015-12-01

For the converse magnetoelectric coupling effect of the piezoelectric/magnetostrictive/piezoelectric tri-layer symmetric magnetoelectric laminates, based on the nonlinear thermo-magneto-mechanical constitutive equations of the giant magnetostrictive materials and the thermo-electro-mechanical constitutive equations of the piezoelectric materials, according to Newton's second law and the magnetic circuit theorem, an equivalent circuit is established. Then an expression of the converse magnetoelectric coefficient describing nonlinear thermo-magneto-electro-mechanical coupling is established. The curve of the nonlinear converse magnetoelectric coefficient versus the bias magnetic field, is predicted effectively by the expression, and the predictions are in good agreement with the experimental result both qualitatively and quantitatively. Furthermore, the model can predict the complex influences of the bias magnetic field, the stress and the ambient temperature on the converse magnetoelectric coefficient. It can be found from these predictions that the converse magnetoelectric coefficient decreases with the increasing temperature and increases with the increasing tensile stress. Under the common effect of the ambient temperature and the stress, it is also found that the converse magnetoelectric coefficient changes sharply with the ambient temperature when the tensile stress is applied on the laminates, but it has a good stability of temperature when a large compressive stress is applied. Therefore, this work contributes to the researches on the giant converse magnetoelectric coefficient and the designs of magnetoelectric devices based on the converse magnetoelectric coupling.

Dark states and delocalization: Competing effects of quantum coherence on the efficiency of light harvesting systems.

PubMed

Hu, Zixuan; Engel, Gregory S; Alharbi, Fahhad H; Kais, Sabre

2018-02-14

Natural light harvesting systems exploit electronic coupling of identical chromophores to generate efficient and robust excitation transfer and conversion. Dark states created by strong coupling between chromophores in the antenna structure can significantly reduce radiative recombination and enhance energy conversion efficiency. Increasing the number of the chromophores increases the number of dark states and the associated enhanced energy conversion efficiency yet also delocalizes excitations away from the trapping center and reduces the energy conversion rate. Therefore, a competition between dark state protection and delocalization must be considered when designing the optimal size of a light harvesting system. In this study, we explore the two competing mechanisms in a chain-structured antenna and show that dark state protection is the dominant mechanism, with an intriguing dependence on the parity of the number of chromophores. This dependence is linked to the exciton distribution among eigenstates, which is strongly affected by the coupling strength between chromophores and the temperature. Combining these findings, we propose that increasing the coupling strength between the chromophores can significantly increase the power output of the light harvesting system.

Numerical study of hydrodynamic behavior and conversion efficiency of a two-buoy wave energy converter

NASA Astrophysics Data System (ADS)

Yang, Cen; Zhang, Yong-liang

2018-04-01

In this paper we propose a two-buoy wave energy converter composed of a heaving semi-submerged cylindrical buoy, a fixed submerged cylindrical buoy and a power take-off (PTO) system, and investigate the effect of the fixed submerged buoy on the hydrodynamics of the heaving semi-submerged buoy based on the three-dimensional potential theory. And the dynamic response of the semi-submerged buoy and the wave energy conversion efficiency of the converter are analyzed. The difference of the hydrodynamics and the wave energy conversion efficiency of a semi-submerged buoy converter with and without a fixed submerged buoy is discussed. It is revealed that the influence of the fixed submerged buoy on the exciting wave force, the added mass, the radiation damping coefficient and the wave energy conversion efficiency can be significant with a considerable variation, depending on the vertical distance between the heaving semi-submerged buoy and the fixed submerged buoy, the diameter ratio of the fixed submerged buoy to the heaving semi-submerged buoy and the water depth.

Efficient extreme-UV-to-extreme-UV conversion by four-wave mixing with intense near-IR pulses in highly charged ion plasmas

NASA Astrophysics Data System (ADS)

Chu, Hsu-hsin; Wang, Jyhpyng

2018-05-01

Nonlinear optics in the extreme-ultraviolet (EUV) has been limited by lack of transparent media and small conversion efficiency. To overcome this problem we explore the advantage of using multiply charged ion plasmas as the interacting media between EUV and intense near-infrared (NIR) pulses. Such media are transparent to EUV and can withstand intense NIR driving pulses without damage. We calculate the third-order nonlinear polarizabilities of Ar2 + and Ar3 + ions for EUV and NIR four-wave mixing by using the well-proven Cowan code and find that the EUV-to-EUV conversion efficiency as high as 26% can be expected for practical experimental configurations using multi-terawatt NIR lasers. Such a high efficiency is possible because the driving pulse intensity can be scaled up to several orders of magnitude higher than in conventional nonlinear media, and the group-velocity and phase mismatch are insignificant at the experimental plasma densities. This effective scheme of wave mixing can be utilized for ultrafast EUV waveform measurement and control as well as wavelength conversion.

Efficient Solar-Thermal Energy Harvest Driven by Interfacial Plasmonic Heating-Assisted Evaporation.

PubMed

Chang, Chao; Yang, Chao; Liu, Yanming; Tao, Peng; Song, Chengyi; Shang, Wen; Wu, Jianbo; Deng, Tao

2016-09-07

The plasmonic heating effect of noble nanoparticles has recently received tremendous attention for various important applications. Herein, we report the utilization of interfacial plasmonic heating-assisted evaporation for efficient and facile solar-thermal energy harvest. An airlaid paper-supported gold nanoparticle thin film was placed at the thermal energy conversion region within a sealed chamber to convert solar energy into thermal energy. The generated thermal energy instantly vaporizes the water underneath into hot vapors that quickly diffuse to the thermal energy release region of the chamber to condense into liquids and release the collected thermal energy. The condensed water automatically flows back to the thermal energy conversion region under the capillary force from the hydrophilic copper mesh. Such an approach simultaneously realizes efficient solar-to-thermal energy conversion and rapid transportation of converted thermal energy to target application terminals. Compared to conventional external photothermal conversion design, the solar-thermal harvesting device driven by the internal plasmonic heating effect has reduced the overall thermal resistance by more than 50% and has demonstrated more than 25% improvement of solar water heating efficiency.

Synergic solventing-out crystallization with subsequent time-delay thermal annealing of PbI2 precursor in mesostructured perovskite solar cells

NASA Astrophysics Data System (ADS)

Jia, Fujin; Guo, Yanqun; Che, Lijia; Liu, Zhiyong; Zeng, Zhigang; Cai, Chuanbing

2018-06-01

Although the two-step sequential deposition method provides an efficient route to fabricate high performance perovskite solar cells (PSSCs) with increasing reproducibility, the inefficient and incomplete conversion of PbI2 to perovskite is still quite a challenge. Following pioneering works, we found that the conversion process from PbI2 to perovskite mainly involves diffusion, infiltration, contact and reaction. In order to facilitate the conversion from PbI2 to perovskite, we demonstrate an effective method to regulate supersaturation level (the driving force to crystallization) of PbI2 by solventing-out crystallization combining with subsequent time-delay thermal annealing of PbI2 wet film. Enough voids and spaces in resulting porous PbI2 layer will be in favor of efficient diffusion, infiltration of CH3NH3I solution, and further enhance the contact and reaction between PbI2 and CH3NH3I in the whole film, leading to rapid, efficient and complete perovskite conversion with a conversion level of about 99.9%. Enhancement of light harvesting ranging from visible to near-IR region was achieved for the resultant high-quality perovskite. Upon this combined method, the fabricated mesostructured solar cells show tremendous power conversion efficiency (PCE) improvement from 3.2% to about 12.3% with less hysteresis owing to the simultaneous enhancement of short-circuit photocurrent density (J sc), open-circuit voltage (V oc) and fill factor (FF).

Customization and the Common Good: A Conversation with Larry Cuban.

ERIC Educational Resources Information Center

Willis, Scott

2002-01-01

A conversation with Larry Cuban, Professor Emeritus of Education at Stanford University, about two contradictory trends in education: customization and standardization and their effect on the public schools' responsibilities to provide both individual and social benefits. (PKP)

Lead-Free Inverted Planar Formamidinium Tin Triiodide Perovskite Solar Cells Achieving Power Conversion Efficiencies up to 6.22.

PubMed

Liao, Weiqiang; Zhao, Dewei; Yu, Yue; Grice, Corey R; Wang, Changlei; Cimaroli, Alexander J; Schulz, Philip; Meng, Weiwei; Zhu, Kai; Xiong, Ren-Gen; Yan, Yanfa

2016-11-01

Efficient lead (Pb)-free inverted planar formamidinium tin triiodide (FASnI 3 ) perovskite solar cells (PVSCs) are demonstrated. Our FASnI 3 PVSCs achieved average power conversion efficiencies (PCEs) of 5.41% ± 0.46% and a maximum PCE of 6.22% under forward voltage scan. The PVSCs exhibit small photocurrent-voltage hysteresis and high reproducibility. The champion cell shows a steady-state efficiency of ≈6.00% for over 100 s. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of assessment packages for diagnostic consultations: A conversation analytic perspective.

PubMed

Rossen, Camilla B; Buus, Niels; Stenager, Egon; Stenager, Elsebeth

2015-05-01

This article reports a conversation analysis of assessment package consultations. Healthcare delivery packages belong to a highly structured mode of healthcare delivery, in which specific courses of healthcare interventions related to assessment and treatment are predefined, both as to timing and content. Assessment packages are widely used in an increasing number of medical specialities; however, there is a lack of knowledge about how packaged assessment influences the interaction between doctor and patient. In this study, we investigate the final consultation in assessment packages, which is when the final clarification of the patient's symptoms takes place. The primary data of the study were eight audio recordings of consultations, and the secondary data were ethnographic field descriptions. In most consultations, packaged assessment was a resource as it provided fast and efficient clarification. In most cases, clarification was treated as good news since it either confirmed the absence of a serious disease or resulted in a diagnosis leading to relevant treatment offers. However, in some cases, clarification was not perceived as good news. This was the case in consultations with patients whose goal was to leave the consultation with clarification in the form of a definite diagnosis, but who were not offered such clarification. These patients negotiated the outcome of the consultation by applying implicit and explicit pressure, which induced the doctors to disregard the boundaries of the package and offer the patient more tests. The study highlights some of the problems related to introducing narrow, specialized package assessment. © The Author(s) 2014.

A soft-switching coupled inductor bidirectional DC-DC converter with high-conversion ratio

NASA Astrophysics Data System (ADS)

Chao, Kuei-Hsiang; Jheng, Yi-Cing

2018-01-01

A soft-switching bidirectional DC-DC converter is presented herein as a way to improve the conversion efficiency of a photovoltaic (PV) system. Adoption of coupled inductors enables the presented converter not only to provide a high-conversion ratio but also to suppress the transient surge voltage via the release of the energy stored in leakage flux of the coupled inductors, and the cost can kept down consequently. A combined use of a switching mechanism and an auxiliary resonant branch enables the converter to successfully perform zero-voltage switching operations on the main switches and improves the efficiency accordingly. It was testified by experiments that our proposed converter works relatively efficiently in full-load working range. Additionally, the framework of the converter intended for testifying has high-conversion ratio. The results of a test, where a generating system using PV module array coupled with batteries as energy storage device was used as the low-voltage input side, and DC link was used as high-voltage side, demonstrated our proposed converter framework with high-conversion ratio on both high-voltage and low-voltage sides.

Electromechanical conversion efficiency for dielectric elastomer generator in different energy harvesting cycles

NASA Astrophysics Data System (ADS)

Cao, Jian-Bo; E, Shi-Ju; Guo, Zhuang; Gao, Zhao; Luo, Han-Pin

2017-11-01

In order to improve electromechanical conversion efficiency for dielectric elastomer generators (DEG), on the base of studying DEG energy harvesting cycles of constant voltage, constant charge and constant electric field intensity, a new combined cycle mode and optimization theory in terms of the generating mechanism and electromechanical coupling process have been built. By controlling the switching point to achieve the best energy conversion cycle, the energy loss in the energy conversion process is reduced. DEG generating test bench which was used to carry out comparative experiments has been established. Experimental results show that the collected energy in constant voltage cycle, constant charge cycle and constant electric field intensity energy harvesting cycle decreases in turn. Due to the factors such as internal resistance losses, electrical losses and so on, actual energy values are less than the theoretical values. The electric energy conversion efficiency by combining constant electric field intensity cycle with constant charge cycle is larger than that of constant electric field intensity cycle. The relevant conclusions provide a basis for the further applications of DEG.

Carbon dioxide splitting in a dielectric barrier discharge plasma: a combined experimental and computational study.

PubMed

Aerts, Robby; Somers, Wesley; Bogaerts, Annemie

2015-02-01

Plasma technology is gaining increasing interest for the splitting of CO2 into CO and O2 . We have performed experiments to study this process in a dielectric barrier discharge (DBD) plasma with a wide range of parameters. The frequency and dielectric material did not affect the CO2 conversion and energy efficiency, but the discharge gap can have a considerable effect. The specific energy input has the most important effect on the CO2 conversion and energy efficiency. We have also presented a plasma chemistry model for CO2 splitting, which shows reasonable agreement with the experimental conversion and energy efficiency. This model is used to elucidate the critical reactions that are mostly responsible for the CO2 conversion. Finally, we have compared our results with other CO2 splitting techniques and we identified the limitations as well as the benefits and future possibilities in terms of modifications of DBD plasmas for greenhouse gas conversion in general. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In silico designing of power conversion efficient organic lead dyes for solar cells using todays innovative approaches to assure renewable energy for future

NASA Astrophysics Data System (ADS)

Kar, Supratik; Roy, Juganta K.; Leszczynski, Jerzy

2017-06-01

Advances in solar cell technology require designing of new organic dye sensitizers for dye-sensitized solar cells with high power conversion efficiency to circumvent the disadvantages of silicon-based solar cells. In silico studies including quantitative structure-property relationship analysis combined with quantum chemical analysis were employed to understand the primary electron transfer mechanism and photo-physical properties of 273 arylamine organic dyes from 11 diverse chemical families explicit to iodine electrolyte. The direct quantitative structure-property relationship models enable identification of the essential electronic and structural attributes necessary for quantifying the molecular prerequisites of 11 classes of arylamine organic dyes, responsible for high power conversion efficiency of dye-sensitized solar cells. Tetrahydroquinoline, N,N'-dialkylaniline and indoline have been least explored classes under arylamine organic dyes for dye-sensitized solar cells. Therefore, the identified properties from the corresponding quantitative structure-property relationship models of the mentioned classes were employed in designing of "lead dyes". Followed by, a series of electrochemical and photo-physical parameters were computed for designed dyes to check the required variables for electron flow of dye-sensitized solar cells. The combined computational techniques yielded seven promising lead dyes each for all three chemical classes considered. Significant (130, 183, and 46%) increment in predicted %power conversion efficiency was observed comparing with the existing dye with highest experimental %power conversion efficiency value for tetrahydroquinoline, N,N'-dialkylaniline and indoline, respectively maintaining required electrochemical parameters.

Glucose buffer is suitable for blood group conversion with α-N acetylgalactosaminidase and α-galactosidase

PubMed Central

Gao, Hong-Wei; Li, Su-Bo; Bao, Guo-Qiang; Zhang, Xue; Li, Hui; Wang, Ying-Li; Tan, Ying-Xia; Ji, Shou-Ping; Gong, Feng

2014-01-01

Background It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by α-N-acetylgalactosaminidase or α-galactosidase. Materials and methods We compared the binding ability of α-N-acetylgalactosaminidase/α-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes’ ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. Results The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. Conclusion These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion. PMID:24333060

Coherent Microwave-to-Optical Conversion via Six-Wave Mixing in Rydberg Atoms

NASA Astrophysics Data System (ADS)

Han, Jingshan; Vogt, Thibault; Gross, Christian; Jaksch, Dieter; Kiffner, Martin; Li, Wenhui

2018-03-01

We present an experimental demonstration of converting a microwave field to an optical field via frequency mixing in a cloud of cold 87Rb atoms, where the microwave field strongly couples to an electric dipole transition between Rydberg states. We show that the conversion allows the phase information of the microwave field to be coherently transferred to the optical field. With the current energy level scheme and experimental geometry, we achieve a photon-conversion efficiency of ˜0.3 % at low microwave intensities and a broad conversion bandwidth of more than 4 MHz. Theoretical simulations agree well with the experimental data, and they indicate that near-unit efficiency is possible in future experiments.

Solar power from satellites

NASA Technical Reports Server (NTRS)

Glaser, P. E.

1977-01-01

Microwave beaming of satellite-collected solar energy to earth for conversion to useful industrial power is evaluated for feasibility, with attention given to system efficiencies and costs, ecological impact, hardware to be employed, available options for energy conversion and transmission, and orbiting and assembly. Advantages of such a power generation and conversion system are listed, plausible techniques for conversion of solar energy (thermionic, thermal electric, photovoltaic) and transmission to earth (lasers, arrays of mirrors, microwave beams) are compared. Structural fatigue likely to result from brief daily eclipses, 55% system efficiency at the present state of the art, present projections of system costs, and projected economic implications of the technology are assessed. Two-stage orbiting and assembly plans are described.

Comparison of oil refining and biodiesel production process between screw press and n-hexane techniques from beauty leaf feedstock

NASA Astrophysics Data System (ADS)

Bhuiya, M. M. K.; Rasul, M. G.; Khan, M. M. K.; Ashwath, N.

2016-07-01

The Beauty Leaf Tree (Callophylum inophyllum) is regarded as an alternative source of energy to produce 2nd generation biodiesel due to its potentiality as well as high oil yield content in the seed kernels. The treating process is indispensable during the biodiesel production process because it can augment the yield as well as quality of the product. Oil extracted from both mechanical screw press and solvent extraction using n-hexane was refined. Five replications each of 25 gm of crude oil for screw press and five replications each of 25 gm of crude oil for n-hexane were selected for refining as well as biodiesel conversion processes. The oil refining processes consists of degumming, neutralization as well as dewaxing. The degumming, neutralization and dewaxing processes were performed to remove all the gums (phosphorous-based compounds), free fatty acids, and waxes from the fresh crude oil before the biodiesel conversion process carried out, respectively. The results indicated that up to 73% and 81% of mass conversion efficiency of the refined oil in the screw press and n-hexane refining processes were obtained, respectively. It was also found that up to 88% and 90% of biodiesel were yielded in terms of mass conversion efficiency in the transesterification process for the screw press and n-hexane techniques, respectively. While the entire processes (refining and transesterification) were considered, the conversion of beauty leaf tree (BLT) refined oil into biodiesel was yielded up to 65% and 73% of mass conversion efficiency for the screw press and n-hexane techniques, respectively. Physico-chemical properties of crude and refined oil, and biodiesel were characterized according to the ASTM standards. Overall, BLT has the potential to contribute as an alternative energy source because of high mass conversion efficiency.

Theoretical analysis of improved efficiency of silicon-wafer solar cells with textured nanotriangular grating structure

NASA Astrophysics Data System (ADS)

Zhang, Yaoju; Zheng, Jun; Zhao, Xuesong; Ruan, Xiukai; Cui, Guihua; Zhu, Haiyong; Dai, Yuxing

2018-03-01

A practical model of crystalline silicon-wafer solar cells is proposed in order to enhance the light absorption and improve the conversion efficiency of silicon solar cells. In the model, the front surface of the silicon photovoltaic film is designed to be a textured-triangular-grating (TTG) structure, and the ITO contact film and the antireflection coating (ARC) of glass are coated on the TTG surface of silicon solar cells. The optical absorption spectrum of solar cells are simulated by applying the finite difference time domain method. Electrical parameters of the solar cells are calculated using two models with and without carrier loss. The effect of structure parameters on the performance of the TTG cell is discussed in detail. It is found that the thickness (tg) of the ARC, period (p) of grating, and base angle (θ) of triangle have a crucial influence on the conversion efficiency. The optimal structure of the TTG cell is designed. The TTG solar cell can produce higher efficiency in a wide range of solar incident angle and the average efficiency of the optimal TTG cell over 7:30-16:30 time of day is 8% higher than that of the optimal plane solar cell. In addition, the study shows that the bulk recombination of carriers has an influence on the conversion efficiency of the cell, the conversion efficiency of the actual solar cell with carrier recombination is reduced by 20.0% of the ideal cell without carrier recombination.

Comparison of holographic lens and filter systems for lateral spectrum splitting

NASA Astrophysics Data System (ADS)

Vorndran, Shelby; Chrysler, Benjamin; Kostuk, Raymond K.

2016-09-01

Spectrum splitting is an approach to increasing the conversion efficiency of a photovoltaic (PV) system. Several methods can be used to perform this function which requires efficient spatial separation of different spectral bands of the incident solar radiation. In this paper several of holographic methods for implementing spectrum splitting are reviewed along with the benefits and disadvantages associated with each approach. The review indicates that a volume holographic lens has many advantages for spectrum splitting in terms of both power conversion efficiency and energy yield. A specific design for a volume holographic spectrum splitting lens is discussed for use with high bandgap InGaP and low bandgap silicon PV cells. The holographic lenses are modeled using rigorous coupled wave analysis, and the optical efficiency is evaluated using non-sequential raytracing. A proof-of-concept off-axis holographic lens is also recorded in dichromated gelatin film and the spectral diffraction efficiency of the hologram is measured with multiple laser sources across the diffracted spectral band. The experimental volume holographic lens (VHL) characteristics are compared to an ideal spectrum splitting filter in terms of power conversion efficiency and energy yield in environments with high direct normal incidence (DNI) illumination and high levels of diffuse illumination. The results show that the experimental VHL can achieve 62.5% of the ideal filter power conversion efficiency, 64.8% of the ideal filter DNI environment energy yield, and 57.7% of the ideal diffuse environment energy yield performance.

Sulfide catalysts for reducing SO2 to elemental sulfur

DOEpatents

Jin, Yun; Yu, Qiquan; Chang, Shih-Ger

2001-01-01

A highly efficient sulfide catalyst for reducing sulfur dioxide to elemental sulfur, which maximizes the selectivity of elemental sulfur over byproducts and has a high conversion efficiency. Various feed stream contaminants, such as water vapor are well tolerated. Additionally, hydrogen, carbon monoxide, or hydrogen sulfides can be employed as the reducing gases while maintaining high conversion efficiency. This allows a much wider range of uses and higher level of feed stream contaminants than prior art catalysts.

Highly efficient continuous-wave Nd:YAG ceramic lasers at 946 nm

NASA Astrophysics Data System (ADS)

Zhu, H. Y.; Xu, C. W.; Zhang, J.; Tang, D. Y.; Luo, D. W.; Duan, Y. M.

2013-07-01

Highly efficient CW operation of diode-end-pumped Nd:YAG ceramic lasers at 946 nm is experimentally demonstrated. When a 5 mm long in-house fabricated Nd:YAG ceramic was used as the gain medium, a maximum output power of 10.5 W was obtained under an incident pump power of 35 W, corresponding to an optical conversion efficiency of 30%, while, when a 3 mm long ceramic sample was used, a maximum output power of 8.7 W was generated with a slope efficiency of 65% with respect to the absorbed pump power. Both the optical conversion efficiency and slope efficiency are the highest results reported so far for the diode-pumped 946 nm lasers.

A Linear Electromagnetic Piston Pump

NASA Astrophysics Data System (ADS)

Hogan, Paul H.

Advancements in mobile hydraulics for human-scale applications have increased demand for a compact hydraulic power supply. Conventional designs couple a rotating electric motor to a hydraulic pump, which increases the package volume and requires several energy conversions. This thesis investigates the use of a free piston as the moving element in a linear motor to eliminate multiple energy conversions and decrease the overall package volume. A coupled model used a quasi-static magnetic equivalent circuit to calculate the motor inductance and the electromagnetic force acting on the piston. The force was an input to a time domain model to evaluate the mechanical and pressure dynamics. The magnetic circuit model was validated with finite element analysis and an experimental prototype linear motor. The coupled model was optimized using a multi-objective genetic algorithm to explore the parameter space and maximize power density and efficiency. An experimental prototype linear pump coupled pistons to an off-the-shelf linear motor to validate the mechanical and pressure dynamics models. The magnetic circuit force calculation agreed within 3% of finite element analysis, and within 8% of experimental data from the unoptimized prototype linear motor. The optimized motor geometry also had good agreement with FEA; at zero piston displacement, the magnetic circuit calculates optimized motor force within 10% of FEA in less than 1/1000 the computational time. This makes it well suited to genetic optimization algorithms. The mechanical model agrees very well with the experimental piston pump position data when tuned for additional unmodeled mechanical friction. Optimized results suggest that an improvement of 400% of the state of the art power density is attainable with as high as 85% net efficiency. This demonstrates that a linear electromagnetic piston pump has potential to serve as a more compact and efficient supply of fluid power for the human scale.

Nanocrystal Size-Dependent Efficiency of Quantum Dot Sensitized Solar Cells in the Strongly Coupled CdSe Nanocrystals/TiO2 System.

PubMed

Yun, Hyeong Jin; Paik, Taejong; Diroll, Benjamin; Edley, Michael E; Baxter, Jason B; Murray, Christopher B

2016-06-15

Light absorption and electron injection are important criteria determining solar energy conversion efficiency. In this research, monodisperse CdSe quantum dots (QDs) are synthesized with five different diameters, and the size-dependent solar energy conversion efficiency of CdSe quantum dot sensitized solar cell (QDSSCs) is investigated by employing the atomic inorganic ligand, S(2-). Absorbance measurements and transmission electron microscopy show that the diameters of the uniform CdSe QDs are 2.5, 3.2, 4.2, 6.4, and 7.8 nm. Larger CdSe QDs generate a larger amount of charge under the irradiation of long wavelength photons, as verified by the absorbance results and the measurements of the external quantum efficiencies. However, the smaller QDs exhibit faster electron injection kinetics from CdSe QDs to TiO2 because of the high energy level of CBCdSe, as verified by time-resolved photoluminescence and internal quantum efficiency results. Importantly, the S(2-) ligand significantly enhances the electronic coupling between the CdSe QDs and TiO2, yielding an enhancement of the charge transfer rate at the interfacial region. As a result, the S(2-) ligand helps improve the new size-dependent solar energy conversion efficiency, showing best performance with 4.2-nm CdSe QDs, whereas conventional ligand, mercaptopropionic acid, does not show any differences in efficiency according to the size of the CdSe QDs. The findings reported herein suggest that the atomic inorganic ligand reinforces the influence of quantum confinement on the solar energy conversion efficiency of QDSSCs.

Integrating a dual-silicon photoelectrochemical cell into a redox flow battery for unassisted photocharging

PubMed Central

Liao, Shichao; Zong, Xu; Seger, Brian; Pedersen, Thomas; Yao, Tingting; Ding, Chunmei; Shi, Jingying; Chen, Jian; Li, Can

2016-01-01

Solar rechargeable flow cells (SRFCs) provide an attractive approach for in situ capture and storage of intermittent solar energy via photoelectrochemical regeneration of discharged redox species for electricity generation. However, overall SFRC performance is restricted by inefficient photoelectrochemical reactions. Here we report an efficient SRFC based on a dual-silicon photoelectrochemical cell and a quinone/bromine redox flow battery for in situ solar energy conversion and storage. Using narrow bandgap silicon for efficient photon collection and fast redox couples for rapid interface charge injection, our device shows an optimal solar-to-chemical conversion efficiency of ∼5.9% and an overall photon–chemical–electricity energy conversion efficiency of ∼3.2%, which, to our knowledge, outperforms previously reported SRFCs. The proposed SRFC can be self-photocharged to 0.8 V and delivers a discharge capacity of 730 mAh l−1. Our work may guide future designs for highly efficient solar rechargeable devices. PMID:27142885

Methods and analysis of factors impact on the efficiency of the photovoltaic generation

NASA Astrophysics Data System (ADS)

Tianze, Li; Xia, Zhang; Chuan, Jiang; Luan, Hou

2011-02-01

First of all, the thesis elaborates two important breakthroughs which happened In the field of the application of solar energy in the 1950s.The 21st century the development of solar photovoltaic power generation will have the following characteristics: the continued high growth of industrial development, the significantly reducing cost of the solar cell, the large-scale high-tech development of photovoltaic industries, the breakthroughs of the film battery technology, the rapid development of solar PV buildings integration and combined to the grids. The paper makes principles of solar cells the theoretical analysis. On the basis, we study the conversion efficiency of solar cells, find the factors impact on the efficiency of the photovoltaic generation, solve solar cell conversion efficiency of technical problems through the development of new technology, and open up new ways to improve the solar cell conversion efficiency. Finally, the paper connecting with the practice establishes policies and legislation to the use of encourage renewable energy, development strategy, basic applied research etc.

High-strength fermentable wastewater reclamation through a sequential process of anaerobic fermentation followed by microalgae cultivation.

PubMed

Qi, Wenqiang; Chen, Taojing; Wang, Liang; Wu, Minghong; Zhao, Quanyu; Wei, Wei

2017-03-01

In this study, the sequential process of anaerobic fermentation followed by microalgae cultivation was evaluated from both nutrient and energy recovery standpoints. The effects of different fermentation type on the biogas generation, broth metabolites' composition, algal growth and nutrients' utilization, and energy conversion efficiencies for the whole processes were discussed. When the fermentation was designed to produce hydrogen-dominating biogas, the total energy conversion efficiency (TECE) of the sequential process was higher than that of the methane fermentation one. With the production of hydrogen in anaerobic fermentation, more organic carbon metabolites were left in the broth to support better algal growth with more efficient incorporation of ammonia nitrogen. By applying the sequential process, the heat value conversion efficiency (HVCE) for the wastewater could reach 41.2%, if methane was avoided in the fermentation biogas. The removal efficiencies of organic metabolites and NH 4 + -N in the better case were 100% and 98.3%, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Power conversion efficiency exceeding the Shockley-Queisser limit in a ferroelectric insulator

NASA Astrophysics Data System (ADS)

Spanier, Jonathan E.; Fridkin, Vladimir M.; Rappe, Andrew M.; Akbashev, Andrew R.; Polemi, Alessia; Qi, Yubo; Gu, Zongquan; Young, Steve M.; Hawley, Christopher J.; Imbrenda, Dominic; Xiao, Geoffrey; Bennett-Jackson, Andrew L.; Johnson, Craig L.

2016-09-01

Ferroelectric absorbers, which promote carrier separation and exhibit above-gap photovoltages, are attractive candidates for constructing efficient solar cells. Using the ferroelectric insulator BaTiO3 we show how photogeneration and the collection of hot, non-equilibrium electrons through the bulk photovoltaic effect (BPVE) yields a greater-than-unity quantum efficiency. Despite absorbing less than a tenth of the solar spectrum, the power conversion efficiency of the BPVE device under 1 sun illumination exceeds the Shockley-Queisser limit for a material of this bandgap. We present data for devices that feature a single-tip electrode contact and an array with 24 tips (total planar area of 1 × 1 μm2) capable of generating a current density of 17 mA cm-2 under illumination of AM1.5 G. In summary, the BPVE at the nanoscale provides an exciting new route for obtaining high-efficiency photovoltaic solar energy conversion.

Al-/Ga-Doped ZnO Window Layers for Highly Efficient Cu₂ZnSn(S,Se)₄ Thin Film Solar Cells.

PubMed

Seo, Se Won; Seo, Jung Woo; Kim, Donghwan; Cheon, Ki-Beom; Lee, Doh-Kwon; Kim, Jin Young

2018-09-01

The successful use of Al-/Ga-doped ZnO (AGZO) thin films as a transparent conducting oxide (TCO) layer of a Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell is demonstrated. The AGZO thin films were prepared by radio frequency (RF) sputtering. The structural, crystallographic, electrical, and optical properties of the AGZO thin films were systematically investigated. The photovoltaic properties of CZTSSe thin film solar cells incorporating the AGZO-based TCO layer were also reported. It has been found that the RF power and substrate temperature of the AGZO thin film are important factors determining the electrical, optical, and structural properties. The optimization process involving the RF power and the substrate temperature leads to good electrical and optical transmittance of the AGZO thin films. Finally, the CZTSSe solar cell with the AGZO TCO layer demonstrated a high conversion efficiency of 9.68%, which is higher than that of the conventional AZO counterpart by 12%.

LiNbO3 coating on concrete surface: a new and environmentally friendly route for artificial photosynthesis.

PubMed

Nath, Ranjit K; Zain, M F M; Kadhum, Abdul Amir H

2013-01-01

The addition of a photocatalyst to ordinary building materials such as concrete creates environmentally friendly materials by which air pollution or pollution of the surface can be diminished. The use of LiNbO3 photocatalyst in concrete material would be more beneficial since it can produce artificial photosynthesis in concrete. In these research photoassisted solid-gas phases reduction of carbon dioxide (artificial photosynthesis) was performed using a photocatalyst, LiNbO3, coated on concrete surface under illumination of UV-visible or sunlight and showed that LiNbO3 achieved high conversion of CO2 into products despite the low levels of band-gap light available. The high reaction efficiency of LiNbO3 is explained by its strong remnant polarization (70 µC/cm(2)), allowing a longer lifetime of photoinduced carriers as well as an alternative reaction pathway. Due to the ease of usage and good photocatalytic efficiency, the research work done showed its potential application in pollution prevention.

The improved photovoltaic performance of phenothiazine-dithienopyrrole based dyes with auxiliary acceptors

NASA Astrophysics Data System (ADS)

Han, Ming-Liang; Zhu, Yi-Zhou; Liu, Shuang; Liu, Qing-Long; Ye, Dan; Wang, Bing; Zheng, Jian-Yu

2018-05-01

Incorporating alkyl chain decorated dithienopyrrole π-spacer with phenothiazine donor has proven to be efficient strategy for constructing novel dyes, which can achieve both large short-circuit current (Jsc) and high open-circuit voltage (Voc) in dye-sensitized solar cells (DSSCs). To promote the light harvesting capability, auxiliary acceptors including benzotriazole (BTZ), benzothiadiazole (BTD), and quinoxaline (Qu) have been inserted into the skeleton of dyes, and much improved Jsc have been realized. Meantime, the rational design of alkyl chains endows dyes JY53 and JY55 a good shielding effect from the penetration of electrolyte, guaranteeing a high Voc (over 810 mV) through retarding unwanted interfacial charge recombination. As a result, with the assistance of introduced auxiliary acceptors and alkyl chains, the photovoltaic performance of devices have been significantly improved, and dye JY55 has achieved an excellent power conversion efficiency (PCE) of 10.06% with Jsc of 19.18 mA cm-2, Voc of 829 mV, and FF of 0.63 under AM 1.5 G irradiation.

Passive Q-switching of a Tm,Ho:KLu(WO₄)₂ microchip laser by a Cr:ZnS saturable absorber.

PubMed

Serres, J M; Loiko, P; Mateos, X; Jambunathan, V; Yasukevich, A S; Yumashev, K V; Petrov, V; Griebner, U; Aguiló, M; Díaz, F

2016-05-10

A diode-pumped Tm,Ho:KLu(WO₄)₂ microchip laser passively Q-switched with a Cr:ZnS saturable absorber generated an average output power of 131 mW at 2063.6 nm with a slope efficiency of 11% and a Q-switching conversion efficiency of 58%. The pulse characteristics were 14  ns/9  μJ at a pulse repetition frequency of 14.5 kHz. With higher modulation depth of the saturable absorber, 9  ns/10.4  μJ/8.2  kHz pulses were generated at 2061.1 nm, corresponding to a record peak power extracted from a passively Q-switched Tm,Ho laser of 1.15 kW. A theoretical model is presented, predicting the pulse energy and duration. The simulations are in good agreement with the experimental results.

Bio hydrogen production from cassava starch by anaerobic mixed cultures: Multivariate statistical modeling

NASA Astrophysics Data System (ADS)

Tien, Hai Minh; Le, Kien Anh; Le, Phung Thi Kim

2017-09-01

Bio hydrogen is a sustainable energy resource due to its potentially higher efficiency of conversion to usable power, high energy efficiency and non-polluting nature resource. In this work, the experiments have been carried out to indicate the possibility of generating bio hydrogen as well as identifying effective factors and the optimum conditions from cassava starch. Experimental design was used to investigate the effect of operating temperature (37-43 °C), pH (6-7), and inoculums ratio (6-10 %) to the yield hydrogen production, the COD reduction and the ratio of volume of hydrogen production to COD reduction. The statistical analysis of the experiment indicated that the significant effects for the fermentation yield were the main effect of temperature, pH and inoculums ratio. The interaction effects between them seem not significant. The central composite design showed that the polynomial regression models were in good agreement with the experimental results. This result will be applied to enhance the process of cassava starch processing wastewater treatment.

Highly Efficient Photothermal Semiconductor Nanocomposites for Photothermal Imaging of Latent Fingerprints.

PubMed

Cui, Jiabin; Xu, Suying; Guo, Chang; Jiang, Rui; James, Tony D; Wang, Leyu

2015-11-17

Optical imaging of latent fingerprints (LFPs) has been widely used in forensic science and for antiterrorist applications, but it suffers from interference from autofluorescence and the substrates background color. Cu7S4 nanoparticles (NPs), with excellent photothermal properties, were synthesized using a new strategy and then fabricated into amphiphilic nanocomposites (NCs) via polymerization of allyl mercaptan coated on Cu7S4 NPs to offer good affinities toward LFPs. Here, we develop a facile and versatile photothermal LFP imaging method based on the high photothermal conversion efficiency (52.92%, 808 nm) of Cu7S4 NCs, indicating its effectiveness for imaging LFPs left on different substrates (with various background colors), which will be extremely useful for crime scene investigations. Furthermore, by fabricating Cu7S4-CdSe@ZnS NCs, a fluorescent-photothermal dual-mode imaging strategy was used to detect trinitrotoluene (TNT) in LFPs while still maintaining a complete photothermal image of LFP.

Improved ambient-stable perovskite solar cells enabled by a hybrid polymeric electron-transporting layer

DOE PAGES

Zhu, Zonglong; Chueh, Chu -Chen; Zhang, Guangye; ...

2016-08-26

In this study, an efficient inverted perovskite solar cell with decent ambient stability is successfully demonstrated by employing an n-type polymer, poly{[ N,N’-bis(2-octyldodecyl)- 1,4,5,8-naphthalene diimide-2,6-diyl]- alt-5,5’-(2,2’-bithiophene)} (N2200), as the electron-transporting layer (ETL). The device performance can be further enhanced from a power conversion efficiency (PCE) of 15 to 16.8% by tailoring the electronic properties of N2200 with a polymeric additive, poly[9,9-bis(6’- ( N,N’-diethylamino)propyl)-fluorene- alt-9,9-bis(3-ethyl(oxetane- 3-ethyloxy)-hexyl) fluorene] (PFN-Ox). More importantly, the device derived from this hybrid ETL can maintain good ambient stability inherent from the pristine N2200 ETL, for which 60–70% of initial PCE can be retained after being stored inmore » air with 10–20% humidity for 45 days.« less

Spectrophotometry near the atmospheric cutoff of the strongest Bowen resonance fluorescence lines of O III in two planetary nebulae

NASA Technical Reports Server (NTRS)

O'Dell, C. R.; Opal, Chet B.

1989-01-01

Spectrophotometric results are presented for the stronger, well-resolved Bowen O III resonance fluorescence emission lines in the planetary nebulae 7027 and NGC 7662 down to and including the intrinsically strong line at 3133 A. These data are combined with results from the IUE atlas of spectra and similar results for the longer wavelength lines by Likkel and Aller (1986) to give the first full coverage of the Bowen lines. Good agreement is found with fluorescence theory for the primary cascade lines, except for the Likkel and Aller results. The efficiency of conversion of the exciting He II Ly-alpha into O III lines is determined, and values comparable to other planetary nebulae are found.

Cross-linked chitosan aerogel modified with Au: Synthesis, characterization and catalytic application.

PubMed

Keshipour, Sajjad; Mirmasoudi, Seyyedeh Sahra

2018-09-15

Dimercaprol as the chelating agent of Au(III) was loaded on chitosan aerogel. Dimercaprol supported on chitosan aerogel efficiently was complexed with Au(III). The new organometallic compound showed good catalytic activity in the oxidation reaction of some aliphatic alcohols, benzyl alcohol, and ethylbenzene. High conversions and excellent selectivities were obtained in the solvent-free oxidation reactions under mild reaction conditions. Also, turnover numbers were calculated for the oxidation reactions with 203, 134, 308, 282, 392, and 153 for 1-pentanol, 1-octanol, 2-propanol, 2-butanol, benzyl alcohol, and ethylbenzene, respectively. The organometallic compound is applicable as a heterogeneous Au(III) catalyst with high chemical stabilityand recyclability up to 6 times. Copyright © 2018 Elsevier Ltd. All rights reserved.

Solvent effects of a dimethyldicyanoquinonediimine buffer layer as N-type material on the performance of organic photovoltaic cells.

PubMed

Yang, Eui Yeol; Oh, Se Young

2014-08-01

In the present work, we have fabricated organic photovoltaic cells consisting of ITO/PEDOT:PSS/P3HT:PCBM/DMDCNQI/Al using a dip-coating method with various solvent systems. We have investigated solvent effects (such as solubility, viscosity and vapor pressure) in deposition of a thin DMDCNQI buffer layer on the performance of organic photovoltaic cells. The solvent system which had low viscosity and good solubility properties, made a dense and uniform DMDCNQI ultra thin film, resulting in a high performance device. In particular, a prepared organic photovoltaic cell was fabricated using a cosolvent system (methanol:methylenechloride = 3:1) and showed a maximum power conversion efficiency of 4.53%.

Impedance matched thin metamaterials make metals absorbing.

PubMed

Mattiucci, N; Bloemer, M J; Aközbek, N; D'Aguanno, G

2013-11-13

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.

Design and experiment of a cross-shaped mode converter for high-power microwave applications.

PubMed

Peng, Shengren; Yuan, Chengwei; Zhong, Huihuang; Fan, Yuwei

2013-12-01

A compact mode converter, which is capable of converting a TM01 mode into a circularly polarized TE11 mode, was developed and experimentally studied with high-power microwaves. The converter, consisting of two turnstile junctions, is very short along the wave propagation direction, and therefore is suitable for designing compact and axially aligned high-power microwave radiation systems. In this paper, the principle of a converter working at 1.75 GHz is demonstrated, as well as the experimental results. The experimental and simulation results are in good agreement. At the center frequency, the conversion efficiency is more than 95%, the measured axial ratio is about 0.4 dB, and the power-handing capacity is excess of 1.9 GW.

Performance Enhancement of Small Molecular Solar Cells by Bilayer Cathode Buffer.

PubMed

Sun, Qinjun; Zhao, Huanbin; Zhou, Miao; Gao, Liyan; Hao, Yuying

2016-04-01

An effective composite bilayer cathode buffer structure is proposed for use in small molecular solar cells. CsF was doped in Alq3 to form the first cathode buffer, leading to small serial resistances. BCP was used as the second cathode buffer to block the holes to the electrode. The optimized bilayer cathode buffer significantly increased the short circuit and fill factor of devices. By integrating this bilayer cathode buffer, the CuPc/C60 small molecular heterojunction cell exhibited a power conversion efficiency of up to 0.8%, which was an improvement of 56% compared to a device with only the Alq3 cathode buffer. Meanwhile, the bilayer cathode buffer still has a good protective effect on the performance of the device.

Designing perfect linear polarization converters using perfect electric and magnetic conducting surfaces

PubMed Central

Zhou, Gaochao; Tao, Xudong; Shen, Ze; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

2016-01-01

We propose a kind of general framework for the design of a perfect linear polarization converter that works in the transmission mode. Using an intuitive picture that is based on the method of bi-directional polarization mode decomposition, it is shown that when the device under consideration simultaneously possesses two complementary symmetry planes, with one being equivalent to a perfect electric conducting surface and the other being equivalent to a perfect magnetic conducting surface, linear polarization conversion can occur with an efficiency of 100% in the absence of absorptive losses. The proposed framework is validated by two design examples that operate near 10 GHz, where the numerical, experimental and analytic results are in good agreements. PMID:27958313

Modifying Yeast Tolerance to Inhibitory Conditions of Ethanol Production Processes

PubMed Central

Caspeta, Luis; Castillo, Tania; Nielsen, Jens

2015-01-01

Saccharomyces cerevisiae strains having a broad range of substrate utilization, rapid substrate consumption, and conversion to ethanol, as well as good tolerance to inhibitory conditions are ideal for cost-competitive ethanol production from lignocellulose. A major drawback to directly design S. cerevisiae tolerance to inhibitory conditions of lignocellulosic ethanol production processes is the lack of knowledge about basic aspects of its cellular signaling network in response to stress. Here, we highlight the inhibitory conditions found in ethanol production processes, the targeted cellular functions, the key contributions of integrated -omics analysis to reveal cellular stress responses according to these inhibitors, and current status on design-based engineering of tolerant and efficient S. cerevisiae strains for ethanol production from lignocellulose. PMID:26618154

Electrical properties of graphene film for counter electrode in dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Khalifa, Ali; Shafie, S.; Hasan, W. Z. W.; Lim, H. N.; Rusop, M.; Samaila, Buda

2018-05-01

A graphene counter electrode for dye-sensitized solar cell was prepared simply by drop casting method on a conducting FTO glass at room temperature. Raman spectroscopy was used to study the defection in the graphene films. The sheet resistance was also measured and recoded minimum value of 7.04 Ω/□ at 22.19µm thickness. The casted films show good adhesion to substrates with low defects. A DSSC based on graphene counter electrode demonstrates reasonable conversion efficiency of 2.78% with short circuit current of 7.60mA, open circuit voltage of 0.69V and fill factor of 0.52. The high conductivity and low defects render the prepared graphene dispersion for DSSCs' CE application.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion

NASA Astrophysics Data System (ADS)

Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

2016-07-01

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area. Electronic supplementary information (ESI) available: XRD patterns of the fs laser structured Cu surface as produced and after the photothermal conversion test, directly measured temperature values on Cu surfaces, temperature rise on Cu surfaces at varied solar irradiation angles, comparison of the white light and IR images of the structured Cu surface with the polished Cu surface, temperature rise on the peripheral zones of the blue coating surface. See DOI: 10.1039/c6nr03662g

Condenser design for AMTEC power conversion

NASA Technical Reports Server (NTRS)

Crowley, Christopher J.

1991-01-01

The condenser and the electrodes are the two elements of an alkali metal thermal-to-electric conversion (AMTEC) cell which most greatly affect the energy conversion performance. A condenser is described which accomplishes two critical functions in an AMTEC cell: management of the fluid under microgravity conditions and optimization of conversion efficiency. The first function is achieved via the use of a controlled surface shape, along with drainage grooves and arteries to collect the fluid. Capillary forces manage the fluid in microgravity and dominate hydrostatic effects on the ground so the device is ground-testable. The second function is achieved via a smooth film of highly reflective liquid sodium on the condensing surface, resulting in minimization of parasitic heat losses due to radiation heat transfer. Power conversion efficiencies of 25 percent to 30 percent are estimated with this condenser using present technology for the electrodes.

Potential for Increasing the Output of Existing Hydroelectric Plants.

DTIC Science & Technology

1981-06-01

existing units to higher generating capacity by rehabilitating, modifying or replacing turbines and/or generators; increasing the effective...loss in converting fluid energy (flow and head) to mechanical energy ( turbine output) to electrical energy (generator output). The significant practical...opportunity is improvement of the energy conversion efficiency of the hydraulic turbine since the energy conversion efficiency of electrical

Coherent Beam Combining of Fiber Amplifiers via LOCSET (Postprint)

DTIC Science & Technology

2012-07-10

load on final optics , and atmospheric turbulence compensation [20]. More importantly, tiled array systems are being investigated for extension to...compactness, near diffraction limited beam quality, superior thermal- optical properties, and high optical to optical conversion efficiencies. Despite...including: compactness, near diffraction limited beam quality, superior thermal- optical properties, and high optical to optical conversion efficiencies

Imidazolium salt-modified porous hypercrosslinked polymers for synergistic CO2 capture and conversion.

PubMed

Wang, Jinquan; Sng, Waihong; Yi, Guangshun; Zhang, Yugen

2015-08-04

A new type of imidazolium salt-modified porous hypercrosslinked polymer (BET surface area up to 926 m(2) g(-1)) was reported. These porous materials exhibited good CO2 capture capacities (14.5 wt%) and catalytic activities for the conversion of CO2 into various cyclic carbonates under metal-free conditions. The synergistic effect of CO2 capture and conversion was observed.

The effect of the DSSC photoanode area based on TiO2/Ag on the conversion efficiency of solar energy into electrical energy

NASA Astrophysics Data System (ADS)

Ibrayev, N.; Serikov, T.; Zavgorodniy, A.; Sadykova, A.

2018-01-01

A module based on dye-sensitized solar cells with Ag/TiO2 structure was developed. It is shown that the addition of the core-shell structure to the semiconductor film of titanium dioxide, where the nanoparticle Ag serves as the core, and the TiO2 is shell, increases the coefficient of solar energy conversion into electrical energy. The effect of the photoanode area on the efficiency of conversion of solar energy into electrical energy is studied. It is shown that the density of the photocurrent decreases with increasing of the photoanode area, which leads to a drop in the efficiency of solar cells.

The influence of cellular uptake on gold nanorods photostability and photoacoustic conversion efficiency

NASA Astrophysics Data System (ADS)

Cavigli, Lucia; Ratto, Fulvio; Tatini, Francesca; Matteini, Paolo; Cini, Alberto; Giovannelli, Ilaria; de Angelis, Marella; Rossi, Francesca; Centi, Sonia; Pini, Roberto

2015-03-01

Their intense optical absorbance in the near-infrared window and chemical versatility make gold nanorods attractive for biomedical applications, such as photothermal therapies and photoacoustic imaging. However, their limited photostability remains a drawback of practical concern. In fact, when gold nanorods are irradiated with nanosecond laser pulses in resonance with their plasmon oscillations, there may occur reshaping into spherical particles or even fragmentation at higher optical fluences, which cause substantial modifications of their optical features with a loss of photoacoustic conversion efficiency. In this contribution, we focus on how the gold nanorods photostability is affected when these particles are modified for cellular uptake, by investigating their stability and photoacoustic conversion efficiency under near infrared pulsed irradiation at different laser fluences.

An efficient copper phthalocyanine additive of perovskite precursor for improving the photovoltaic performance of planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Wu, Shufang; Liu, Qingwei; Zheng, Ya; Li, Renjie; Peng, Tianyou

2017-08-01

Solution processable planar heterojunction perovskite solar cell has drawn much attention as a promising low-cost photovoltaic device, and much effort has been made to improve its power conversion efficiency by choosing appropriate additives for the perovskite precursor solution. Different to those additives reported, a soluble and thermal stable tert-butyl substituted copper phthalocyanine (CuPc(tBu)4) as additive is first introduced into the perovskite precursor solution of a planar perovskite solar cell that is fabricated via the one-step solution process. It is found that the pristine device without CuPc(tBu)4 additive exhibits a power conversion efficiency of 15.3%, while an extremely low concentration (4.4 × 10-3 mM) of CuPc(tBu)4 in the precursor solution leads to the corresponding device achieving an enhanced power conversion efficiency of 17.3%. CuPc(tBu)4 as an additive can improve the quality of perovskite layer with higher crystallinity and surface coverage, then resulting in enhanced light absorption and reduced charge recombination, and thus the better power conversion efficiency. The finding presented here provides a new choice for improving the quality of perovskite layer and the photovoltaic performance of the planar heterojunction perovskite solar cells.

Applications of novel effects derived from Si ingot growth inside Si melt without contact with crucible wall using noncontact crucible method to high-efficiency solar cells

NASA Astrophysics Data System (ADS)

Nakajima, Kazuo; Ono, Satoshi; Kaneko, Yuzuru; Murai, Ryota; Shirasawa, Katsuhiko; Fukuda, Tetsuo; Takato, Hidetaka; Jensen, Mallory A.; Youssef, Amanda; Looney, Erin E.; Buonassisi, Tonio; Martel, Benoit; Dubois, Sèbastien; Jouini, Anis

2017-06-01

The noncontact crucible (NOC) method was proposed for obtaining Si single bulk crystals with a large diameter and volume using a cast furnace and solar cells with high conversion efficiency and yield. This method has several novel characteristics that originate from its key feature that ingots can be grown inside a Si melt without contact with a crucible wall. Si ingots for solar cells were grown by utilizing the merits resulting from these characteristics. Single ingots with high quality were grown by the NOC method after furnace cleaning, and the minority carrier lifetime was measured to investigate reduction of the number of impurities. A p-type ingot with a convex growth interface in the growth direction was also grown after furnace cleaning. For p-type solar cells prepared using wafers cut from the ingot, the highest and average conversion efficiencies were 19.14% and 19.0%, respectively, which were obtained using the same solar cell structure and process as those employed to obtain a conversion efficiency of 19.1% for a p-type Czochralski (CZ) wafer. Using the cast furnace, solar cells with a conversion efficiency and yield as high as those of CZ solar cells were obtained by the NOC method.

Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Gur, Emre; Kocak, Yusuf

2018-01-01

Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires' layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm2 under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%) . The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.

Effect of Copper Oxide Nanoparticles as a barrier for Efficiency Improvement in ZnO Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Sonthila, A.; Ruankham, P.; Choopun, S.; Wongratanaphisan, D.; Phadungdhitidhada, S.; Gardchareon, A.

2017-09-01

CuO nanoparticles (CuO NPs) were used as a barrier layer in ZnO dye-sensitized solar cells (DSSCs) to obtain high power conversion efficiency. The barrier layer was investigated in terms of the size of CuO NPs by varying power of pulsed Nd:YAG (1064 nm) laser ablation. Morphological and optical properties of CuO NPs were characterized by transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis) and dynamic light scattering (DLS). It was found that the CuO NPs are rather spherical in shape with diameter in between 20 - 132 nm. In addition, the energy gap of CuO decreases with the increase of CuO NPs size. The power conversion efficiency of ZnO DSSCs was measured under illumination of simulated sunlight obtained from a solar simulator with the radiant power of 100 mW/cm2. The results showed that the ZnO DSSC with the CuO NPs with size of 37 nm exhibits the optimum power conversion efficiency of 1.01% which is higher than that of one without CuO NPs. Moreover, the power conversion efficiency of the ZnO DSSCs decreases with the increase of CuO NPs size.

Efficient and Selective Electrochemical and Photoelectrochemical Reduction of 5-Hydroxymethylfurfural to 2,5-Bis(hydroxymethyl)furan using Water as the Hydrogen Source

DOE PAGES

Roylance, John J.; Kim, Tae Woo; Choi, Kyoung-Shin

2016-02-17

Reductive biomass conversion has been conventionally conducted using H 2 gas under high-temperature and-pressure conditions. Here, efficient electrochemical reduction of 5-hydroxymethylfurfural (HMF), a key intermediate for biomass conversion, to 2,5-bis(hydroxymethyl)furan (BHMF), an important monomer for industrial processes, was demonstrated using Ag catalytic electrodes. This process uses water as the hydrogen source under ambient conditions and eliminates the need to generate and consume H 2 for hydrogenation, providing a practical and efficient route for BHMF production. By systematic investigation of HMF reduction on the Ag electrode surface, BHMF production was achieved with the Faradaic efficiency and selectivity nearing 100%, and plausiblemore » reduction mechanisms were also elucidated. Furthermore, construction of a photoelectrochemical cell (PEC) composed of an n-type BiVO 4 semiconductor anode, which uses photogenerated holes for water oxidation, and a catalytic Ag cathode, which uses photoexcited electrons from BiVO 4 for the reduction of HMF to BHMF, was demonstrated to utilize solar energy to significantly decrease the external voltage necessary for HMF reduction. This shows the possibility of coupling electrochemical HMF reduction and solar energy conversion, which can provide more efficient and environmentally benign routes for reductive biomass conversion.« less

Modelling and optimization of Mn/activate carbon nanocatalysts for NO reduction: comparison of RSM and ANN techniques.

PubMed

Mousavi, Seyed Mahdi; Niaei, Aligholi; Salari, Dariush; Panahi, Parvaneh Nakhostin; Samandari, Masoud

2013-01-01

A response surface methodology (RSM) involving a central composite design was applied to the modelling and optimization of a preparation of Mn/active carbon nanocatalysts in NH3-SCR of NO at 250 degrees C and the results were compared with the artificial neural network (ANN) predicted values. The catalyst preparation parameters, including metal loading (wt%), calcination temperature and pre-oxidization degree (v/v% HNO3) were selected as influence factors on catalyst efficiency. In the RSM model, the predicted values of NO conversion were found to be in good agreement with the experimental values. Pareto graphic analysis showed that all the chosen parameters and some of the interactions were effective on response. The optimization results showed that maximum NO conversion was achieved at the optimum conditions: 10.2 v/v% HNO3, 6.1 wt% Mn loading and calcination at 480 degrees C. The ANN model was developed by a feed-forward back propagation network with the topology 3, 8 and 1 and a Levenberg-Marquardt training algorithm. The mean square error for the ANN and RSM models were 0.339 and 1.176, respectively, and the R2 values were 0.991 and 0.972, respectively, indicating the superiority of ANN in capturing the nonlinear behaviour of the system and being accurate in estimating the values of the NO conversion.

Carbon nanotube/metal-sulfide composite flexible electrodes for high-performance quantum dot-sensitized solar cells and supercapacitors

NASA Astrophysics Data System (ADS)

Muralee Gopi, Chandu V. V.; Ravi, Seenu; Rao, S. Srinivasa; Eswar Reddy, Araveeti; Kim, Hee-Je

2017-04-01

Carbon nanotubes (CNT) and metal sulfides have attracted considerable attention owing to their outstanding properties and multiple application areas, such as electrochemical energy conversion and energy storage. Here we describes a cost-effective and facile solution approach to the preparation of metal sulfides (PbS, CuS, CoS, and NiS) grown directly on CNTs, such as CNT/PbS, CNT/CuS, CNT/CoS, and CNT/NiS flexible electrodes for quantum dot-sensitized solar cells (QDSSCs) and supercapacitors (SCs). X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy confirmed that the CNT network was covered with high-purity metal sulfide compounds. QDSSCs equipped with the CNT/NiS counter electrode (CE) showed an impressive energy conversion efficiency (η) of 6.41% and remarkable stability. Interestingly, the assembled symmetric CNT/NiS-based polysulfide SC device exhibited a maximal energy density of 35.39 W h kg-1 and superior cycling durability with 98.39% retention after 1,000 cycles compared to the other CNT/metal-sulfides. The elevated performance of the composites was attributed mainly to the good conductivity, high surface area with mesoporous structures and stability of the CNTs and the high electrocatalytic activity of the metal sulfides. Overall, the designed composite CNT/metal-sulfide electrodes offer an important guideline for the development of next level energy conversion and energy storage devices.

Carbon nanotube/metal-sulfide composite flexible electrodes for high-performance quantum dot-sensitized solar cells and supercapacitors.

PubMed

Muralee Gopi, Chandu V V; Ravi, Seenu; Rao, S Srinivasa; Eswar Reddy, Araveeti; Kim, Hee-Je

2017-04-19

Carbon nanotubes (CNT) and metal sulfides have attracted considerable attention owing to their outstanding properties and multiple application areas, such as electrochemical energy conversion and energy storage. Here we describes a cost-effective and facile solution approach to the preparation of metal sulfides (PbS, CuS, CoS, and NiS) grown directly on CNTs, such as CNT/PbS, CNT/CuS, CNT/CoS, and CNT/NiS flexible electrodes for quantum dot-sensitized solar cells (QDSSCs) and supercapacitors (SCs). X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy confirmed that the CNT network was covered with high-purity metal sulfide compounds. QDSSCs equipped with the CNT/NiS counter electrode (CE) showed an impressive energy conversion efficiency (η) of 6.41% and remarkable stability. Interestingly, the assembled symmetric CNT/NiS-based polysulfide SC device exhibited a maximal energy density of 35.39 W h kg -1 and superior cycling durability with 98.39% retention after 1,000 cycles compared to the other CNT/metal-sulfides. The elevated performance of the composites was attributed mainly to the good conductivity, high surface area with mesoporous structures and stability of the CNTs and the high electrocatalytic activity of the metal sulfides. Overall, the designed composite CNT/metal-sulfide electrodes offer an important guideline for the development of next level energy conversion and energy storage devices.

Elucidating the Irreversible Mechanism and Voltage Hysteresis in Conversion Reaction for High-Energy Sodium-Metal Sulfide Batteries

DOE PAGES

Wang, Jiajun; Wang, Liguang; Eng, Christopher; ...

2017-03-03

We present that irreversible electrochemical behavior and large voltage hysteresis are commonly observed in battery materials, in particular for materials reacting through conversion reaction, resulting in undesirable round-trip energy loss and low coulombic efficiency. Seeking solutions to these challenges relies on the understanding of the underlying mechanism and physical origins. Here, this study combines in operando 2D transmission X-ray microscopy with X-ray absorption near edge structure, 3D tomography, and galvanostatic intermittent titration techniques to uncover the conversion reaction in sodium–metal sulfide batteries, a promising high-energy battery system. This study shows a high irreversible electrochemistry process predominately occurs at first cycle,more » which can be largely linked to Na ion trapping during the first desodiation process and large interfacial ion mobility resistance. Subsequently, phase transformation evolution and electrochemical reaction show good reversibility at multiple discharge/charge cycles due to materials' microstructural change and equilibrium. The origin of large hysteresis between discharge and charge is investigated and it can be attributed to multiple factors including ion mobility resistance at the two-phase interface, intrinsic slow sodium ion diffusion kinetics, and irreversibility as well as ohmic voltage drop and overpotential. In conclusion, this study expects that such understandings will help pave the way for engineering design and optimization of materials microstructure for future-generation batteries.« less

Review of solar fuel-producing quantum conversion processes

NASA Technical Reports Server (NTRS)

Peterson, D. B.; Biddle, J. R.; Fujita, T.

1984-01-01

The status and potential of fuel-producing solar photochemical processes are discussed. Research focused on splitting water to produce dihydrogen and is at a relatively early stage of development. Current emphasis is primarily directed toward understanding the basic chemistry underlying such quantum conversion processes. Theoretical analyses by various investigators predict a limiting thermodynamic efficiency of 31% for devices with a single photosystem operating with unfocused sunlight at 300 K. When non-idealities are included, it appears unlikely that actual devices will have efficiencies greater than 12 to 15%. Observed efficiencies are well below theoretical limits. Cyclic homogeneous photochemical processes for splitting water have efficiencies considerably less than 1%. Efficiency can be significantly increased by addition of a sacrificial reagent; however, such systems are no longer cyclic and it is doubtful that they would be economical on a commercial scale. The observed efficiencies for photoelectrochemical processes are also low but such systems appear more promising than homogeneous photochemical systems. Operating and systems options, including operation at elevated temperature and hybrid and coupled quantum-thermal conversion processes, are also considered.

Long vertically aligned titania nanotubes on transparent conducting oxide for highly efficient solar cells.

PubMed

Varghese, Oomman K; Paulose, Maggie; Grimes, Craig A

2009-09-01

Dye-sensitized solar cells consist of a random network of titania nanoparticles that serve both as a high-surface-area support for dye molecules and as an electron-transporting medium. Despite achieving high power conversion efficiencies, their performance is limited by electron trapping in the nanoparticle film. Electron diffusion lengths can be increased by transporting charge through highly ordered nanostructures such as titania nanotube arrays. Although titania nanotube array films have been shown to enhance the efficiencies of both charge collection and light harvesting, it has not been possible to grow them on transparent conducting oxide glass with the lengths needed for high-efficiency device applications (tens of micrometres). Here, we report the fabrication of transparent titania nanotube array films on transparent conducting oxide glass with lengths between 0.3 and 33.0 microm using a novel electrochemistry approach. Dye-sensitized solar cells containing these arrays yielded a power conversion efficiency of 6.9%. The incident photon-to-current conversion efficiency ranged from 70 to 80% for wavelengths between 450 and 650 nm.

Silicon Nanowire/Polymer Hybrid Solar Cell-Supercapacitor: A Self-Charging Power Unit with a Total Efficiency of 10.5.

PubMed

Liu, Ruiyuan; Wang, Jie; Sun, Teng; Wang, Mingjun; Wu, Changsheng; Zou, Haiyang; Song, Tao; Zhang, Xiaohong; Lee, Shuit-Tong; Wang, Zhong Lin; Sun, Baoquan

2017-07-12

An integrated self-charging power unit, combining a hybrid silicon nanowire/polymer heterojunction solar cell with a polypyrrole-based supercapacitor, has been demonstrated to simultaneously harvest solar energy and store it. By efficiency enhancement of the hybrid nanowire solar cells and a dual-functional titanium film serving as conjunct electrode of the solar cell and supercapacitor, the integrated system is able to yield a total photoelectric conversion to storage efficiency of 10.5%, which is the record value in all the integrated solar energy conversion and storage system. This system may not only serve as a buffer that diminishes the solar power fluctuations from light intensity, but also pave its way toward cost-effective high efficiency self-charging power unit. Finally, an integrated device based on ultrathin Si substrate is demonstrated to expand its feasibility and potential application in flexible energy conversion and storage devices.

Highly efficient frequency conversion with bandwidth compression of quantum light

PubMed Central

Allgaier, Markus; Ansari, Vahid; Sansoni, Linda; Eigner, Christof; Quiring, Viktor; Ricken, Raimund; Harder, Georg; Brecht, Benjamin; Silberhorn, Christine

2017-01-01

Hybrid quantum networks rely on efficient interfacing of dissimilar quantum nodes, as elements based on parametric downconversion sources, quantum dots, colour centres or atoms are fundamentally different in their frequencies and bandwidths. Although pulse manipulation has been demonstrated in very different systems, to date no interface exists that provides both an efficient bandwidth compression and a substantial frequency translation at the same time. Here we demonstrate an engineered sum-frequency-conversion process in lithium niobate that achieves both goals. We convert pure photons at telecom wavelengths to the visible range while compressing the bandwidth by a factor of 7.47 under preservation of non-classical photon-number statistics. We achieve internal conversion efficiencies of 61.5%, significantly outperforming spectral filtering for bandwidth compression. Our system thus makes the connection between previously incompatible quantum systems as a step towards usable quantum networks. PMID:28134242

Single component Mn-doped perovskite-related CsPb2ClxBr5-x nanoplatelets with a record white light quantum yield of 49%: a new single layer color conversion material for light-emitting diodes.

PubMed

Wu, Hao; Xu, Shuhong; Shao, Haibao; Li, Lang; Cui, Yiping; Wang, Chunlei

2017-11-09

Single component nanocrystals (NCs) with white fluorescence are promising single layer color conversion media for white light-emitting diodes (LED) because the undesirable changes of chromaticity coordinates for the mixture of blue, green and red emitting NCs can be avoided. However, their practical applications have been hindered by the relative low photoluminescence (PL) quantum yield (QY) for traditional semiconductor NCs. Though Mn-doped perovskite nanocube is a potential candidate, it has been unable to realize a white-light emission to date. In this work, the synthesis of Mn-doped 2D perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets with a pure white emission from a single component is reported. Unlike Mn-doped perovskite nanocubes with insufficient energy transfer efficiency, the current reported Mn-doped 2D perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets show a 10 times higher energy transfer efficiency from perovskite to Mn impurities at the required emission wavelengths (about 450 nm for perovskite emission and 580 nm for Mn emission). As a result, the Mn/perovskite dual emission intensity ratio surprisingly elevates from less than 0.25 in case of Mn-doped nanocubes to 0.99 in the current Mn-doped CsPb 2 Cl x Br 5-x nanoplatelets, giving rise to a pure white light emission with Commission Internationale de l'Eclairage (CIE) color coordinates of (0.35, 0.32). More importantly, the highest PL QY for Mn-doped perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets is up to 49%, which is a new record for white-emitting nanocrystals with single component. These highly luminescent nanoplatelets can be blended with polystyrene (PS) without changing the white light emission but dramatically improving perovskite stability. The perovskite-PS composites are available not only as a good solution processable coating material for assembling LED, but also as a superior conversion material for achieving white light LED with a single conversion layer.

Mn-doped quantum dot sensitized solar cells: a strategy to boost efficiency over 5%.

PubMed

Santra, Pralay K; Kamat, Prashant V

2012-02-08

To make Quantum Dot Sensitized Solar Cells (QDSC) competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies. By employing Mn(2+) doping of CdS, we have now succeeded in significantly improving QDSC performance. QDSC constructed with Mn-doped-CdS/CdSe deposited on mesoscopic TiO(2) film as photoanode, Cu(2)S/Graphene Oxide composite electrode, and sulfide/polysulfide electrolyte deliver power conversion efficiency of 5.4%.

Enhanced efficiency of the second harmonic inhomogeneous component in an opaque cavity.

PubMed

Roppo, V; Raineri, F; Raj, R; Sagnes, I; Trull, J; Vilaseca, R; Scalora, M; Cojocaru, C

2011-05-15

In this Letter, we experimentally demonstrate the enhancement of the inhomogeneous second harmonic conversion in the opaque region of a GaAs cavity with efficiencies of the order of 0.1% at 612 nm, using 3 ps pump pulses having peak intensities of the order of 10 MW/cm(2). We show that the conversion efficiency of the inhomogeneous, phase-locked second harmonic component is a quadratic function of the cavity factor Q. © 2011 Optical Society of America

Absorber for solar power.

PubMed

Powell, W R

1974-10-01

A simple, economical absorber utilizing a new principle of operation to achieve very low reradiation losses while generating temperatures limited by material properties of quartz is described. Its performance is analyzed and indicates approximately 90% thermal efficiency and 73% conversion efficiency for an earth based unit with moderately concentrated (~tenfold) sunlight incident. It is consequently compatible with the most economic of concentrator mirrors (stamped) or mirrors deployable in space. Space applications are particularly attractive, as temperatures significantly below 300 K are possible and permit even higher conversion efficiency.

Tailoring perovskite compounds for broadband light absorption

NASA Astrophysics Data System (ADS)

Lu, Hengchang; Guo, Xiaowei; Yang, Cheng; Li, Shaorong

2018-01-01

Perovskite solar cells have experienced an outstanding advance in power conversion efficiency (PCE) by optimizing the perovskite layer morphology, composition, interfaces, and charge collection efficiency. To enhance PCE, the mixed perovskites were proposed in recent years. In this study, optoelectronic performance of pure perovskites and mixed ones were investigated. It was demonstrated that the mixed perovskites exhibit superior to the pure ones. The mixed material can absorb broadband light absorption and result in increased short circuit current density and power conversion efficiency.

Quantum mechanical study of the proton exchange in the ortho-para H2 conversion reaction at low temperature.

PubMed

Honvault, P; Jorfi, M; González-Lezana, T; Faure, A; Pagani, L

2011-11-14

Ortho-para H(2) conversion reactions mediated by the exchange of a H(+) proton have been investigated at very low energy for the first time by means of a time independent quantum mechanical (TIQM) approach. State-to-state probabilities and cross sections for H(+) + H(2) (v = 0, j = 0,1) processes have been calculated for a collision energy, E(c), ranging between 10(-6) eV and 0.1 eV. Differential cross sections (DCSs) for H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) for very low energies only start to develop a proper global minimum around the sideways scattering direction (θ≈ 90°) at E(c) = 10(-3) eV. Rate coefficients, a crucial information required for astrophysical models, are provided between 10 K and 100 K. The relaxation ortho-para process j = 1 → j' = 0 is found to be more efficient than the j = 0 → j' = 1 conversion at low temperatures, in line with the extremely small ratio between the ortho and para species of molecular hydrogen predicted at the temperature of interstellar cold molecular clouds. The results obtained by means of a statistical quantum mechanical (SQM) model, which has previously proved to provide an adequate description of the dynamics of the title reactions at a higher collision energy regime, have been compared with the TIQM results. A reasonable good agreement has been found with the only exception of the DCSs for the H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) process at very low energy. SQM cross sections are also slightly below the quantum results. Estimates for the rate coefficients, in good accord with the TIQM values, are a clear improvement with respect to pioneering statistical studies on the reaction.

High efficiency GaP power conversion for Betavoltaic applications

NASA Astrophysics Data System (ADS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-09-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

Dual-Function Au@Y2O3:Eu3+ Smart Film for Enhanced Power Conversion Efficiency and Long-Term Stability of Perovskite Solar Cells.

PubMed

Kim, Chang Woo; Eom, Tae Young; Yang, In Seok; Kim, Byung Su; Lee, Wan In; Kang, Yong Soo; Kang, Young Soo

2017-07-28

In the present study, a dual-functional smart film combining the effects of wavelength conversion and amplification of the converted wave by the localized surface plasmon resonance has been investigated for a perovskite solar cell. This dual-functional film, composed of Au nanoparticles coated on the surface of Y 2 O 3 :Eu 3+ phosphor (Au@Y 2 O 3 :Eu 3+ ) nanoparticle monolayer, enhances the solar energy conversion efficiency to electrical energy and long-term stability of photovoltaic cells. Coupling between the Y 2 O 3 :Eu 3+ phosphor monolayer and ultraviolet solar light induces the latter to be converted into visible light with a quantum yield above 80%. Concurrently, the Au nanoparticle monolayer on the phosphor nanoparticle monolayer amplifies the converted visible light by up to 170%. This synergy leads to an increased solar light energy conversion efficiency of perovskite solar cells. Simultaneously, the dual-function film suppresses the photodegradation of perovskite by UV light, resulting in long-term stability. Introducing the hybrid smart Au@Y 2 O 3 :Eu 3+ film in perovskite solar cells increases their overall solar-to-electrical energy conversion efficiency to 16.1% and enhances long-term stability, as compared to the value of 15.2% for standard perovskite solar cells. The synergism between the wavelength conversion effect of the phosphor nanoparticle monolayer and the wave amplification by the localized surface plasmon resonance of the Au nanoparticle monolayer in a perovskite solar cell is comparatively investigated, providing a viable strategy of broadening the solar spectrum utilization.

High efficiency GaP power conversion for Betavoltaic applications

NASA Technical Reports Server (NTRS)

Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

1994-01-01

AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

Luminescent and transparent nanopaper based on rare-earth up-converting nanoparticle grafted nanofibrillated cellulose derived from garlic skin.

PubMed

Zhao, Jingpeng; Wei, Zuwu; Feng, Xin; Miao, Miao; Sun, Lining; Cao, Shaomei; Shi, Liyi; Fang, Jianhui

2014-09-10

Highly flexible, transparent, and luminescent nanofibrillated cellulose (NFC) nanopaper with heterogeneous network, functionalized by rare-earth up-converting luminescent nanoparticles (UCNPs), was rapidly synthesized by using a moderate pressure extrusion paper-making process. NFC was successfully prepared from garlic skin using an efficient extraction approach combined with high frequency ultrasonication and high pressure homogenization after removing the noncellulosic components. An efficient epoxidation treatment was carried out to enhance the activity of the UCNPs (NaYF4:Yb,Er) with oleic acid ligand capped on the surface. The UCNPs after epoxidation then reacted with NFC in aqueous medium to form UCNP-grafted NFC nanocomposite (NFC-UCNP) suspensions at ambient temperature. Through the paper-making process, the assembled fluorescent NFC-UCNP hybrid nanopaper exhibits excellent properties, including high transparency, strong up-conversion luminescence, and good flexibility. The obtained hybrid nanopaper was characterized by transmission electron microscopy (TEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), field emission-scanning electron microscope (FE-SEM), up-conversion luminescence (UCL) spectrum, and ultraviolet and visible (UV-vis) spectrophotometer. The experimental results demonstrate that the UCNPs have been successfully grafted to the NFC matrix with heterogeneous network. And the superiorly optical transparent and luminescent properties of the nanopaper mainly depend on the ratio of UCNPs to NFC. Of importance here is that, NFC and UCNPs afford the nanopaper a prospective candidate for multimodal anti-counterfeiting, sensors, and ion probes applications.

General Conversion for Obtaining Strongly Existentially Unforgeable Signatures

NASA Astrophysics Data System (ADS)

Teranishi, Isamu; Oyama, Takuro; Ogata, Wakaha

We say that a signature scheme is strongly existentially unforgeable (SEU) if no adversary, given message/signature pairs adaptively, can generate a signature on a new message or a new signature on a previously signed message. We propose a general and efficient conversion in the standard model that transforms a secure signature scheme to SEU signature scheme. In order to construct that conversion, we use a chameleon commitment scheme. Here a chameleon commitment scheme is a variant of commitment scheme such that one can change the committed value after publishing the commitment if one knows the secret key. We define the chosen message security notion for the chameleon commitment scheme, and show that the signature scheme transformed by our proposed conversion satisfies the SEU property if the chameleon commitment scheme is chosen message secure. By modifying the proposed conversion, we also give a general and efficient conversion in the random oracle model, that transforms a secure signature scheme into a SEU signature scheme. This second conversion also uses a chameleon commitment scheme but only requires the key only attack security for it.

Conversion of evanescent Lamb waves into propagating waves via a narrow aperture edge.

PubMed

Yan, Xiang; Yuan, Fuh-Gwo

2015-06-01

This paper presents a quantitative study of conversion of evanescent Lamb waves into propagating in isotropic plates. The conversion is substantiated by prescribing time-harmonic Lamb displacements/tractions through a narrow aperture at an edge of a semi-infinite plate. Complex-valued dispersion and group velocity curves are employed to characterize the conversion process. The amplitude coefficient of the propagating Lamb modes converted from evanescent is quantified based on the complex reciprocity theorem via a finite element analysis. The power flow generated into the plate can be separated into radiative and reactive parts made on the basis of propagating and evanescent Lamb waves, where propagating Lamb waves are theoretically proved to radiate pure real power flow, and evanescent Lamb waves carry reactive pure imaginary power flow. The propagating power conversion efficiency is then defined to quantitatively describe the conversion. The conversion efficiency is strongly frequency dependent and can be significant. With the converted propagating waves from evanescent, sensors at far-field can recapture some localized damage information that is generally possessed in evanescent waves and may have potential application in structural health monitoring.

Enhanced Power Conversion Efficiency of Perovskite Solar Cells with an Up-Conversion Material of Er3+-Yb3+-Li+ Tri-doped TiO2

NASA Astrophysics Data System (ADS)

Zhang, Zhenlong; Qin, Jianqiang; Shi, Wenjia; Liu, Yanyan; Zhang, Yan; Liu, Yuefeng; Gao, Huiping; Mao, Yanli

2018-05-01

In this paper, Er3+-Yb3+-Li+ tri-doped TiO2 (UC-TiO2) was prepared by an addition of Li+ to Er3+-Yb3+ co-doped TiO2. The UC-TiO2 presented an enhanced up-conversion emission compared with Er3+-Yb3+ co-doped TiO2. The UC-TiO2 was applied to the perovskite solar cells. The power conversion efficiency (PCE) of the solar cells without UC-TiO2 was 14.0%, while the PCE of the solar cells with UC-TiO2 was increased to 16.5%, which presented an increase of 19%. The results suggested that UC-TiO2 is an effective up-conversion material. And this study provided a route to expand the spectral absorption of perovskite solar cells from visible light to near-infrared using up-conversion materials.

Statistical thermodynamics foundation for photovoltaic and photothermal conversion. II. Application to photovoltaic conversion

NASA Astrophysics Data System (ADS)

Badescu, Viorel; Landsberg, Peter T.

1995-08-01

The general theory developed in part I was applied to build up two models of photovoltaic conversion. To this end two different systems were analyzed. The first system consists of the whole absorber (converter), for which the balance equations for energy and entropy are written and then used to derive an upper bound for solar energy conversion. The second system covers a part of the absorber (converter), namely the valence and conduction electronic bands. The balance of energy is used in this case to derive, under additional assumptions, another upper limit for the conversion efficiency. This second system deals with the real location where the power is generated. Both models take into consideration the radiation polarization and reflection, and the effects of concentration. The second model yields a more accurate upper bound for the conversion efficiency. A generalized solar cell equation is derived. It is proved that other previous theories are particular cases of the present more general formalism.