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Sample records for organic ultraviolet photovoltaic

  1. Solution processable organic/inorganic hybrid ultraviolet photovoltaic detector

    NASA Astrophysics Data System (ADS)

    Guo, Xiaopeng; Tang, Libin; Xiang, Jinzhong; Ji, Rongbin; Zhang, Kai; Lai, Sin Ki; Zhao, Jun; Kong, Jincheng; Lau, Shu Ping

    2016-05-01

    Ultraviolet (UV) photodetector is a kind of important optoelectronic device which can be widely used in scientific and engineering fields including astronomical research, environmental monitoring, forest-fire prevention, medical analysis, and missile approach warning etc. The development of UV detector is hindered by the acquirement of stable p-type materials, which makes it difficult to realize large array, low-power consumption UV focal plane array (FPA) detector. Here, we provide a novel structure (Al/Poly(9,9-di-n-octylfuorenyl-2,7-diyl)(PFO)/ZnO/ITO) to demonstrate the UV photovoltaic (PV) response. A rather smooth surface (RMS roughness: 0.28 nm) may be reached by solution process, which sheds light on the development of large-array, light-weight and low-cost UV FPA detectors.

  2. Transparent ultraviolet photovoltaic cells.

    PubMed

    Yang, Xun; Shan, Chong-Xin; Lu, Ying-Jie; Xie, Xiu-Hua; Li, Bing-Hui; Wang, Shuang-Peng; Jiang, Ming-Ming; Shen, De-Zhen

    2016-02-15

    Photovoltaic cells have been fabricated from p-GaN/MgO/n-ZnO structures. The photovoltaic cells are transparent to visible light and can transform ultraviolet irradiation into electrical signals. The efficiency of the photovoltaic cells is 0.025% under simulated AM 1.5 illumination conditions, while it can reach 0.46% under UV illumination. By connecting several such photovoltaic cells in a series, light-emitting devices can be lighting. The photovoltaic cells reported in this Letter may promise the applications in glass of buildings to prevent UV irradiation and produce power for household appliances in the future. PMID:26872163

  3. Transparent ultraviolet photovoltaic cells.

    PubMed

    Yang, Xun; Shan, Chong-Xin; Lu, Ying-Jie; Xie, Xiu-Hua; Li, Bing-Hui; Wang, Shuang-Peng; Jiang, Ming-Ming; Shen, De-Zhen

    2016-02-15

    Photovoltaic cells have been fabricated from p-GaN/MgO/n-ZnO structures. The photovoltaic cells are transparent to visible light and can transform ultraviolet irradiation into electrical signals. The efficiency of the photovoltaic cells is 0.025% under simulated AM 1.5 illumination conditions, while it can reach 0.46% under UV illumination. By connecting several such photovoltaic cells in a series, light-emitting devices can be lighting. The photovoltaic cells reported in this Letter may promise the applications in glass of buildings to prevent UV irradiation and produce power for household appliances in the future.

  4. Organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Leo, Karl

    2016-08-01

    Organic photovoltaics are on the verge of revolutionizing building-integrated photovoltaics. For other applications, however, several basic open scientific questions need answering to, in particular, further improve energy-conversion efficiency and lifetime.

  5. Organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Krebs, Frederik C.; Chen, Hongzheng

    2013-12-01

    Energy inflation, the constant encouragement to economize on energy consumption and the huge investments in developing alternative energy resources might seem to suggest that there is a global shortage of energy. Far from it, the energy the Sun beams on the Earth each hour is equivalent to a year's supply, even at our increasingly ravenous rate of global energy consumption [1]. But it's not what you have got it's what you do with it. Hence the intense focus on photovoltaic research to find more efficient ways to harness energy from the Sun. Recently much of this research has centred on organic solar cells since they offer simple, low-cost, light-weight and large-area flexible photovoltaic structures. This issue with guest editors Frederik C Krebs and Hongzheng Chen focuses on some of the developments at the frontier of organic photovoltaic technology. Improving the power conversion efficiency of organic photovoltaic systems, while maintaining the inherent material, economic and fabrication benefits, has absorbed a great deal of research attention in recent years. Here significant progress has been made with reports now of organic photovoltaic devices with efficiencies of around 10%. Yet operating effectively across the electromagnetic spectrum remains a challenge. 'The trend is towards engineering low bandgap polymers with a wide optical absorption range and efficient hole/electron transport materials, so that light harvesting in the red and infrared region is enhanced and as much light of the solar spectrum as possible can be converted into an electrical current', explains Mukundan Thelakkat and colleagues in Germany, the US and UK. In this special issue they report on how charge carrier mobility and morphology of the active blend layer in thin film organic solar cells correlate with device parameters [2]. The work contributes to a better understanding of the solar-cell characteristics of polymer:fullerene blends, which form the material basis for some of the most

  6. Organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Krebs, Frederik C.; Chen, Hongzheng

    2013-12-01

    Energy inflation, the constant encouragement to economize on energy consumption and the huge investments in developing alternative energy resources might seem to suggest that there is a global shortage of energy. Far from it, the energy the Sun beams on the Earth each hour is equivalent to a year's supply, even at our increasingly ravenous rate of global energy consumption [1]. But it's not what you have got it's what you do with it. Hence the intense focus on photovoltaic research to find more efficient ways to harness energy from the Sun. Recently much of this research has centred on organic solar cells since they offer simple, low-cost, light-weight and large-area flexible photovoltaic structures. This issue with guest editors Frederik C Krebs and Hongzheng Chen focuses on some of the developments at the frontier of organic photovoltaic technology. Improving the power conversion efficiency of organic photovoltaic systems, while maintaining the inherent material, economic and fabrication benefits, has absorbed a great deal of research attention in recent years. Here significant progress has been made with reports now of organic photovoltaic devices with efficiencies of around 10%. Yet operating effectively across the electromagnetic spectrum remains a challenge. 'The trend is towards engineering low bandgap polymers with a wide optical absorption range and efficient hole/electron transport materials, so that light harvesting in the red and infrared region is enhanced and as much light of the solar spectrum as possible can be converted into an electrical current', explains Mukundan Thelakkat and colleagues in Germany, the US and UK. In this special issue they report on how charge carrier mobility and morphology of the active blend layer in thin film organic solar cells correlate with device parameters [2]. The work contributes to a better understanding of the solar-cell characteristics of polymer:fullerene blends, which form the material basis for some of the most

  7. Inverted organic photovoltaic cells.

    PubMed

    Wang, Kai; Liu, Chang; Meng, Tianyu; Yi, Chao; Gong, Xiong

    2016-05-21

    The advance in lifestyle, modern industrialization and future technological revolution are always at high expense of energy consumption. Unfortunately, there exist serious issues such as limited storage, high cost and toxic contamination in conventional fossil fuel energy sources. Instead, solar energy represents a renewable, economic and green alternative in the future energy market. Among the photovoltaic technologies, organic photovoltaics (OPVs) demonstrate a cheap, flexible, clean and easy-processing way to convert solar energy into electricity. However, OPVs with a conventional device structure are still far away from industrialization mainly because of their short lifetime and the energy-intensive deposition of top metal electrode. To address the stability and cost issue simultaneously, an inverted device structure has been introduced into OPVs, bridging laboratory research with practical application. In this review, recent progress in device structures, working mechanisms, functions and advances of each component layer as well their correlations with the efficiency and stability of inverted OPVs are reviewed and illustrated.

  8. Inverted organic photovoltaic cells.

    PubMed

    Wang, Kai; Liu, Chang; Meng, Tianyu; Yi, Chao; Gong, Xiong

    2016-05-21

    The advance in lifestyle, modern industrialization and future technological revolution are always at high expense of energy consumption. Unfortunately, there exist serious issues such as limited storage, high cost and toxic contamination in conventional fossil fuel energy sources. Instead, solar energy represents a renewable, economic and green alternative in the future energy market. Among the photovoltaic technologies, organic photovoltaics (OPVs) demonstrate a cheap, flexible, clean and easy-processing way to convert solar energy into electricity. However, OPVs with a conventional device structure are still far away from industrialization mainly because of their short lifetime and the energy-intensive deposition of top metal electrode. To address the stability and cost issue simultaneously, an inverted device structure has been introduced into OPVs, bridging laboratory research with practical application. In this review, recent progress in device structures, working mechanisms, functions and advances of each component layer as well their correlations with the efficiency and stability of inverted OPVs are reviewed and illustrated. PMID:27087582

  9. The Harvard organic photovoltaic dataset

    PubMed Central

    Lopez, Steven A.; Pyzer-Knapp, Edward O.; Simm, Gregor N.; Lutzow, Trevor; Li, Kewei; Seress, Laszlo R.; Hachmann, Johannes; Aspuru-Guzik, Alán

    2016-01-01

    The Harvard Organic Photovoltaic Dataset (HOPV15) presented in this work is a collation of experimental photovoltaic data from the literature, and corresponding quantum-chemical calculations performed over a range of conformers, each with quantum chemical results using a variety of density functionals and basis sets. It is anticipated that this dataset will be of use in both relating electronic structure calculations to experimental observations through the generation of calibration schemes, as well as for the creation of new semi-empirical methods and the benchmarking of current and future model chemistries for organic electronic applications. PMID:27676312

  10. Macromolecular architectures for organic photovoltaics.

    PubMed

    Popere, Bhooshan C; Della Pelle, Andrea M; Poe, Ambata; Thayumanavan, S

    2012-03-28

    Research in the field of organic photovoltaics has gained considerable momentum in the last two decades owing to the need for developing low-cost and efficient energy harvesting systems. Elegant molecular architectures have been designed, synthesized and employed as active materials for photovoltaic devices thereby leading to a better molecular structure-device property relationship understanding. In this perspective, we outline new macromolecular scaffolds that have been designed within the purview of each of the three fundamental processes involving light harvesting, charge separation and charge transport.

  11. Bimolecular recombination in organic photovoltaics.

    PubMed

    Lakhwani, Girish; Rao, Akshay; Friend, Richard H

    2014-01-01

    The recombination of electrons and holes is a major loss mechanism in photovoltaic devices that controls their performance. We review scientific literature on bimolecular recombination (BR) in bulk heterojunction organic photovoltaic devices to bring forward existing ideas on the origin and nature of BR and highlight both experimental and theoretical work done to quantify its extent. For these systems, Langevin theory fails to explain BR, and recombination dynamics turns out to be dependent on mobility, temperature, electric field, charge carrier concentration, and trapped charges. Relationships among the photocurrent, open-circuit voltage, fill factor, and morphology are discussed. Finally, we highlight the recent emergence of a molecular-level picture of recombination, taking into account the spin and delocalization of charges. Together with the macroscopic picture of recombination, these new insights allow for a comprehensive understanding of BR and provide design principles for future materials and devices.

  12. Energy Transport in Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Bergemann, Kevin J.

    Organic photovoltaics (OPV) have the potential to be a flexible and low-cost form of carbon-neutral energy production. However, many of the underlying physical mechanisms that dictate the behavior of OPVs remain frustratingly obscure in comparison to the well-understood physics of inorganic semiconductors. This dissertation centers around the development of new techniques to characterize the behavior of excitons in organic semiconductors, both in the bulk and at interfaces. We first examine the method of spectrally-resolved photoluminescence quenching (SR-PLQ), the most convenient and powerful current technique for measuring the exciton diffusion length (LD) of organic semiconductors, and extend it to work with optically thin films. This allows for its application to a much wider range of materials and physical systems. The second part of the dissertation presents a further extension of the method of PL quenching to characterize non-ideal interfaces, those which block or quench only a fraction of incident excitons. This is used to understand the operation of a novel fullerene:wide energy gap material buffer in OPVs. In combination with charge transport and morphological studies, it is shown that the mixed buffer shows disproportionate benefits from the two materials; blocking excitons superlinearly with wide energy gap material concentration and still conducting charges efficiently even at very small (10%) fullerene concentration. Finally, we extend the principles of PL quenching to characterize arbitrary interfaces, including those between materials with identical energy levels but different LD and exciton lifetime, and those between materials with small (˜20 meV) energy offsets. These techniques allow us to finally resolve the ambiguity in the spin state of the exciton which serves as the primary source of photocurrent in C60, one of the most important materials in current efficient OPVs.

  13. Two-layer organic photovoltaic cell

    SciTech Connect

    Tang, C.W.

    1986-01-13

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

  14. Classification of additives for organic photovoltaic devices.

    PubMed

    Machui, Florian; Maisch, Philipp; Burgués-Ceballos, Ignasi; Langner, Stefan; Krantz, Johannes; Ameri, Tayebeh; Brabec, Christoph J

    2015-04-27

    The use of additives to improve the performance of organic photovoltaic cells has been intensely researched in recent years. However, so far, no system has been reported for the classification of additives and their functions. In this report, a system for classifying additives according to the fundamental mechanism by which they influence microstructure formation for P3HT:PCBM is suggested. The major parameters used for their classification are solubility and drying kinetics. Both are discussed in detail and their consequences on processing are analyzed. Furthermore, a general mechanism to classify the impact of additives on structure formation is suggested and discussed for different materials relevant to organic photovoltaic devices.

  15. Monte carlo simulations of organic photovoltaics.

    PubMed

    Groves, Chris; Greenham, Neil C

    2014-01-01

    Monte Carlo simulations are a valuable tool to model the generation, separation, and collection of charges in organic photovoltaics where charges move by hopping in a complex nanostructure and Coulomb interactions between charge carriers are important. We review the Monte Carlo techniques that have been applied to this problem, and describe the results of simulations of the various recombination processes that limit device performance. We show how these processes are influenced by the local physical and energetic structure of the material, providing information that is useful for design of efficient photovoltaic systems.

  16. Ultraviolet radiation absorbing compounds in marine organisms

    SciTech Connect

    Chalker, B.E.; Dunlap, W.C. )

    1990-01-09

    Studies on the biological effects of solar ultraviolet radiations are becoming increasingly common, in part due to recent interest in the Antarctic ozone hole and in the perceived potential for global climate change. Marine organisms possess many strategies for ameliorating the potentially damaging effects of UV-B (280-320 nm) and the shorter wavelengths of UV-A (320-400nm). One mechanism is the synthesis of bioaccumulation of ultraviolet radiation absorbing compounds. Several investigators have noted the presence of absorbing compounds in spectrophotometer scans of extracts from a variety of marine organisms, particularly algae and coelenterates containing endosymbiotic algae. The absorbing compounds are often mycosporine-like amino acids. Thirteen mycosporine-like amino acids have already been described, and several others have recently been detected. Although, the mycosporine-like amino acids are widely distributed. these compounds are by no means the only type of UV-B absorbing compounds which has been identified. Coumarins from green algae, quinones from sponges, and indoles from a variety of sources are laternative examples which are documented in the natural products literature. When the biological impact of solar ultraviolet radiation is assessed, adequate attention must be devoted to the process of photoadaptation, including the accumulation of ultraviolet radiation absorbing compounds.

  17. Natural hybrid organic-inorganic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    De Padova, Paola; Lucci, Massimiliano; Olivieri, Bruno; Quaresima, Claudio; Priori, Sandro; Francini, Roberto; Grilli, Antonio; Hricovini, Karol; Davoli, Ivan

    2009-06-01

    Natural hybrid organic-inorganic photovoltaic devices based on TiO 2 have been realized. Chlorophyll A (from anacystis nidulans algae), chlorophyll B (from spinach), carmic acid (from insect Coccus cacti L.), synthetic trans- β-carotene, natural fresh picked Morus nigra, and their mixtures have been used as an organic photo active layer to fabricate photovoltaic prototypes. In order to reduce the charge's interfacial recombination, different thicknesses (5-45 nm) of Si layers, subsequently oxidized in air, were inserted between the TiO 2 and chlorophyll B. Scanning electron microscopy of TiO 2 and Si/TiO 2 systems shows the coexistence at least of four classes of nanoparticles of 60, 100, 150 and 250 nm in size. Auger electron spectroscopy of the Si L 2,3V V transition demonstrates the presence of silica and SiO x suboxides. Photocurrent measurements versus radiation wavelength in the range 300-800 nm exhibit different peaks according to the absorption spectra of the organic molecules. All realized photovoltaic devices are suitable for solar light electric energy conversion. Those made of a blend of all organic molecules achieved higher current and voltage output. The Si/TiO 2-based devices containing chlorophyll B exhibited an enhanced photocurrent response with respect to those with TiO 2 only.

  18. Organic bulk heterojunction photovoltaic structures: design, morphology and properties

    NASA Astrophysics Data System (ADS)

    Bulavko, G. V.; Ishchenko, A. A.

    2014-07-01

    Main approaches to the design of organic bulk heterojunction photovoltaic structures are generalized and systematized. Novel photovoltaic materials based on fullerenes, organic dyes and related compounds, graphene, conjugated polymers and dendrimers are considered. The emphasis is placed on correlations between the chemical structure and properties of materials. The effect of morphology of the photoactive layer on the photovoltaic properties of devices is analyzed. Main methods of optimization of the photovoltaic properties are outlined. The bibliography includes 338 references.

  19. Aluminum doped zinc oxide for organic photovoltaics

    SciTech Connect

    Murdoch, G. B.; Hinds, S.; Sargent, E. H.; Tsang, S. W.; Mordoukhovski, L.; Lu, Z. H.

    2009-05-25

    Aluminum doped zinc oxide (AZO) was grown via magnetron sputtering as a low-cost alternative to indium tin oxide (ITO) for organic photovoltaics (OPVs). Postdeposition ozone treatment resulted in devices with lower series resistance, increased open-circuit voltage, and power conversion efficiency double that of devices fabricated on untreated AZO. Furthermore, cells fabricated using ozone treated AZO and standard ITO displayed comparable performance.

  20. Computational assessment of organic photovoltaic candidate compounds

    NASA Astrophysics Data System (ADS)

    Borunda, Mario; Dai, Shuo; Olivares-Amaya, Roberto; Amador-Bedolla, Carlos; Aspuru-Guzik, Alan

    2015-03-01

    Organic photovoltaic (OPV) cells are emerging as a possible renewable alternative to petroleum based resources and are needed to meet our growing demand for energy. Although not as efficient as silicon based cells, OPV cells have as an advantage that their manufacturing cost is potentially lower. The Harvard Clean Energy Project, using a cheminformatic approach of pattern recognition and machine learning strategies, has ranked a molecular library of more than 2.6 million candidate compounds based on their performance as possible OPV materials. Here, we present a ranking of the top 1000 molecules for use as photovoltaic materials based on their optical absorption properties obtained via time-dependent density functional theory. This computational search has revealed the molecular motifs shared by the set of most promising molecules.

  1. Tube-based geometries for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Peterson, Eric D.; Huang, Huihui; Wang, Mingjun; Xue, Dan; Nie, Wanyi; Zhou, Wei; Carroll, David L.

    2010-06-01

    We demonstrate a waveguiding tube-based optical geometry that provides a general approach to improving organic photovoltaic performance. By fabricating bulk-heterojunction photovoltaics onto thin tubular light pipes, the optical energy can be effectively captured within the absorbing layer without associated reflective losses at the front and rear surfaces of the devices as is typical in planar structures. We have used a common absorber system: poly-3-hexyl-thiophene:phenyl-C61-butyric-acid-methyl-ester to demonstrate these tubular optical geometries result in very little overall radiative loss. Surprisingly, this also leads to an overall broadening of the absorption window for the device as indicated by the external quantum efficiency.

  2. Flexible, light trapping substrates for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Park, Yoonseok; Berger, Jana; Tang, Zheng; Müller-Meskamp, Lars; Lasagni, Andrés Fabián; Vandewal, Koen; Leo, Karl

    2016-08-01

    Micro-structured organic photovoltaic (OPV) devices on polyethylene terephthalate substrates are produced using direct laser interference patterning (DLIP). The performance of organic solar cells on these substrates is improved by a factor of 1.16, and a power conversion efficiency of 7.70% is achieved. We show that a shorter spatial period of the pattern allows for a stronger light trapping effect in solar cell, as it leads to a longer light path. Moreover, since the patterned structures are located on the outside of the fully encapsulated OPV devices, there are no problems with the roughness induced shunts.

  3. Systems chemistry approach in organic photovoltaics.

    PubMed

    Würthner, Frank; Meerholz, Klaus

    2010-08-16

    The common approach in organic materials science is dominated by the perception that the properties of the bulk materials are virtually determined by the properties of the molecular building blocks. In this Concept Article, we advocate for taking into account supramolecular organization principles for all kinds of organic solid-state materials, irrespective of them being crystalline, liquid crystalline, or amorphous, and discuss a showcase example, that is, the utilization of merocyanine dyes as p-type organic semiconductors in bulk heterojunction (BHJ) solar cells. Despite their extraordinarily large dipole moments, which are considered to be detrimental for efficient charge carrier transport, BHJ organic photovoltaic materials of these dyes with fullerenes have reached remarkable power conversion efficiencies of meanwhile nearly 5%. These at the first glance contradictory properties are, however, well-understandable on the systems chemistry level.

  4. Processes and Materials for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Cox, Marshall

    The field of organic photovoltaics is driven by the desire for better and cheaper solar cells. While showing much promise, current generations of organic photovoltaic (OPV) devices do not exhibit properties that are suited for wide scale commercialization. While much research has been dedicated towards this goal, more yet needs to be done before it can be clear whether this is an achievable goal. This thesis describes new materials investigations for higher efficiency better stability organic photovoltaics, as well as new processes that broaden the application and fabrication space for these devices. The application of electro-polymerization, a deposition process, towards organic thin-film fabrication is discussed. This novel process for OPVs is followed by an analysis of new and interesting materials for OPV devices, including a higher efficiency hole-transporting material, and two hole-transporting molecules that exhibit self-assembly during OPV fabrication. The results of these investigations indicate the possibility for increased fabrication freedom and control, molecular species design that could allow higher efficiency devices, as well as indications of the role that molecular interactions in OPV heterojunctions play. In addition, the possibilities of integrating graphene, the two-dimensional form of carbon, into OPV architectures is discussed. A new process for graphene transfer that allows the integration of graphene into chemically and physically more fragile systems including those composed of small molecule semiconductors is described and experimentally verified. Graphene is then integrated as a cathode in OPVs, and a modeling and experimental investigation is performed to evaluate the potential for integrating graphene as a recombination layer in tandem OPVs. Based on this investigation, the integration of graphene into tandem OPVs could enable higher efficiency devices and significantly broadened architectural freedom for tandem fabrication.

  5. Ultraviolet Absorption by Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Lee-Taylor, J. M.; Hodzic, A.; Aumont, B.

    2014-12-01

    Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.

  6. Is organic photovoltaics promising for indoor applications?

    NASA Astrophysics Data System (ADS)

    Lee, Harrison K. H.; Li, Zhe; Durrant, James R.; Tsoi, Wing C.

    2016-06-01

    This work utilizes organic photovoltaics (OPV) for indoor applications, such as powering small electronic devices or wireless connected Internet of Things. Three representative polymer-based OPV systems, namely, poly(3-hexylthiophene-2,5-diyl), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)], and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

  7. Functional substrates for flexible organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Niggemann, M.; Ruf, D.; Bläsi, B.; Glatthaar, M.; Riede, M.; Müller, C.; Zimmermann, B.; Gombert, A.

    2005-10-01

    Along with efficiency and lifetime, costs are one of the most important aspects for the commercialization of organic solar cells. Thinking of large scale production of organic solar cells by an efficient reel-to-reel process, the materials are expected to determine the costs of the final product. Our approach is to develop functional substrates for organic solar cells which have the potential for cost effective production. The functionality is obtained by combining periodically microstructured substrates with lamellar electrode structures. Such structured substrates were fabricated by cost effective replication from masterstructures that were generated by large area interference lithography. Two cell architectures were investigated - holographic microprisms and interdigital buried nanoelectrodes. A structure period of 20 μm in combination with a 2 μm wide metal grid was chosen for the microprism cells based on the results of electrical calculations. Current-voltage curves with reasonable fill factors were measured for these devices. A significant light trapping effect was predicted from optical simulations. Interdigital buried nanoelectrodes are embedded in the photoactive layer of the solar cell. Separated interdigital metal electrodes with a sufficiently high parallel resistance were manufactured despite a small electrode distance below 400 nm. Experimental results on first photovoltaic devices will be presented. We observe an insufficient rectification of the photovoltaic device which we attribute to partial electron injection into the gold anode.

  8. Efficient Computational Screening of Organic Polymer Photovoltaics.

    PubMed

    Kanal, Ilana Y; Owens, Steven G; Bechtel, Jonathon S; Hutchison, Geoffrey R

    2013-05-16

    There has been increasing interest in rational, computationally driven design methods for materials, including organic photovoltaics (OPVs). Our approach focuses on a screening "pipeline", using a genetic algorithm for first stage screening and multiple filtering stages for further refinement. An important step forward is to expand our diversity of candidate compounds, including both synthetic and property-based measures of diversity. For example, top monomer pairs from our screening are all donor-donor (D-D) combinations, in contrast with the typical donor-acceptor (D-A) motif used in organic photovoltaics. We also find a strong "sequence effect", in which the average HOMO-LUMO gap of tetramers changes by ∼0.2 eV as a function of monomer sequence (e.g., ABBA versus BAAB); this has rarely been explored in conjugated polymers. Beyond such optoelectronic optimization, we discuss other properties needed for high-efficiency organic solar cells, and applications of screening methods to other areas, including non-fullerene n-type materials, tandem cells, and improving charge and exciton transport. PMID:26282968

  9. Acetylene-based materials in organic photovoltaics.

    PubMed

    Silvestri, Fabio; Marrocchi, Assunta

    2010-04-08

    Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Organic photovoltaic systems hold the promise of a lightweight, flexible, cost-effective solar energy conversion platform, which could benefit from simple solution-processing of the active layer. The discovery of semiconductive polyacetylene by Heeger et al. in the late 1970s was a milestone towards the use of organic materials in electronics; the development of efficient protocols for the palladium catalyzed alkynylation reactions and the new conception of steric and conformational advantages of acetylenes have been recently focused the attention on conjugated triple-bond containing systems as a promising class of semiconductors for OPVs applications. We review here the most important and representative (poly)arylacetylenes that have been used in the field. A general introduction to (poly)arylacetylenes, and the most common synthetic approaches directed toward making these materials will be firstly given. After a brief discussion on working principles and critical parameters of OPVs, we will focus on molecular arylacetylenes, (co)polymers containing triple bonds, and metallopolyyne polymers as p-type semiconductor materials. The last section will deal with hybrids in which oligomeric/polymeric structures incorporating acetylenic linkages such as phenylene ethynylenes have been attached onto C(60), and their use as the active materials in photovoltaic devices.

  10. Endohedral fullerenes for organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel B.; Cardona, Claudia M.; Guldi, Dirk M.; Sankaranarayanan, Shankara Gayathri; Reese, Matthew O.; Kopidakis, Nikos; Peet, Jeff; Walker, Bright; Bazan, Guillermo C.; van Keuren, Edward; Holloway, Brian C.; Drees, Martin

    2009-03-01

    So far, one of the fundamental limitations of organic photovoltaic (OPV) device power conversion efficiencies (PCEs) has been the low voltage output caused by a molecular orbital mismatch between the donor polymer and acceptor molecules. Here, we present a means of addressing the low voltage output by introducing novel trimetallic nitride endohedral fullerenes (TNEFs) as acceptor materials for use in photovoltaic devices. TNEFs were discovered in 1999 by Stevenson et al. ; for the first time derivatives of the TNEF acceptor, Lu3N@C80, are synthesized and integrated into OPV devices. The reduced energy offset of the molecular orbitals of Lu3N@C80 to the donor, poly(3-hexyl)thiophene (P3HT), reduces energy losses in the charge transfer process and increases the open circuit voltage (Voc) to 260mV above reference devices made with [6,6]-phenyl-C61-butyric methyl ester (C60-PCBM) acceptor. PCEs >4% have been observed using P3HT as the donor material. This work clears a path towards higher PCEs in OPV devices by demonstrating that high-yield charge separation can occur with OPV systems that have a reduced donor/acceptor lowest unoccupied molecular orbital energy offset.

  11. Novel High Efficient Organic Photovoltaic Materials

    NASA Technical Reports Server (NTRS)

    Sun, Sam; Haliburton, James; Fan, Zben; Taft, Charles; Wang, Yi-Qing; Maaref, Shahin; Mackey, Willie R. (Technical Monitor)

    2001-01-01

    In man's mission to the outer space or a remote site, the most abundant, renewable, nonpolluting, and unlimited external energy source is light. Photovoltaic (PV) materials can convert light into electrical power. In order to generate appreciable electrical power in space or on the Earth, it is necessary to collect sunlight from large areas due to the low density of sunlight, and this would be very costly using current commercially available inorganic solar cells. Future organic or polymer based solar cells seemed very attractive due to several reasons. These include lightweight, flexible shape, ultra-fast optoelectronic response time (this also makes organic PV materials attractive for developing ultra-fast photo detectors), tunability of energy band-gaps via molecular design, versatile materials synthesis and device fabrication schemes, and much lower cost on large-scale industrial production. It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks will facilitate the charge separation and migration due to improved electronic ultrastructure and morphology in comparison to current polymer composite photovoltaic system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel donor-bridge-acceptor block copolymer system for potential high-efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene, the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene, and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes the holes, the acceptor block stabilizes the electrons. The bridge block is designed to hinder

  12. Bulk Heterojunction Organic Photovoltaic Devices Using Dendrimers

    SciTech Connect

    Kopidakis, N.; Mitchell, W. J.; Bozell, J. J.; Piris, J.; Ginley, D. S.; Rumbles, G.; Shaheen S. E.

    2005-11-01

    A family of prototype ..pi..-conjugated dendrimers has been synthesized and incorporated into solution-processable organic photovoltaic (OPV) devices. Bulk heterojunction devices were fabricated by blending the dendrimers with a solubilized fullerene. The best of these initial devices, which were not optimized for morphology, exhibited external quantum efficiencies of 22% at peak wavelength. It was found that 3-arm dendrimers, when sufficiently soluble, yielded higher photocurrents than their 4-arm counterparts. This was attributed to better planarity and intermolecular alignment of the 3-arm version. Device efficiency was seen to increase with increasing arm length. A reduced-band gap dendrimer was synthesized by attaching electron-withdrawing groups onto the core to yield an optical band gap of 1.82 eV.

  13. Organic photovoltaic cells with controlled polarization sensitivity

    SciTech Connect

    Awartani, Omar; O'Connor, Brendan T.; Kudenov, Michael W.

    2014-03-03

    In this study, we demonstrate linearly polarized organic photovoltaic cells with a well-controlled level of polarization sensitivity. The polarized devices were created through the application of a large uniaxial strain to the bulk heterojunction poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) film and printing the plastically deformed active layer onto a PEDOT:PSS and indium tin oxide coated glass substrate. The P3HT:PCBM layer is processed such that it is able to accommodate high strains (over 100%) without fracture. After printing the strained films, thermal annealing is used to optimize solar cell performance while maintaining polarization sensitivity. A dichroic ratio and short circuit current ratio of ≈6.1 and ≈1.6 were achieved, respectively.

  14. Utilizing Scanning Probe Microscopy to Study Organic Photovoltaic Materials

    NASA Astrophysics Data System (ADS)

    Kibel, Ashley; Bhattacharyya, Shreya; Liddell, Paul; Gust, Devens; Lindsay, Stuart

    2010-03-01

    Organic photovoltaics have the potential to provide cheaper alternatives to traditional silicon solar cells due to flexibility in design and engineering. Understanding how charge is transported in these materials is important for the future design and fabrication of efficient organic solar cells. We utilize scanning probe microscopy techniques to study the electrical properties of biomimetic organic molecules that have photovoltaic potential. We present results from conducting atomic force microscopy measurements performed on bare substrates commonly utilized in organic photovoltaic applications as well as measurements on organic thin films self assembled on these substrates. Furthermore, we present the results of single molecule conductivity experiments performed using a scanning tunneling microscope on novel donor-acceptor molecules. We discuss benefits, as well as challenges, to using scanning probe techniques on organic photovoltaic systems.

  15. Fullerene derivatives as electron acceptors for organic photovoltaic cells.

    PubMed

    Mi, Dongbo; Kim, Ji-Hoon; Kim, Hee Un; Xu, Fei; Hwang, Do-Hoon

    2014-02-01

    Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

  16. Reciprocal carrier collection in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Renshaw, C. Kyle; Schlenker, Cody W.; Thompson, Mark E.; Forrest, Stephen R.

    2011-07-01

    Buffer layers between the acceptor and cathode can perform several functions in organic photovoltaic devices, such as providing exciton blocking, protection of active layers against damage from cathode deposition, and optical spacing to maximize the electric field in the active device region. Here, we study electron collection by replacing the common buffer layer, bathocuproine, with a series of six, substituted tris(β-diketonato)Ru(III) analogues in the structure: indium-tin-oxide/copper phthalocyanine/C60/buffer/Ag. These buffer layers enable collection of photogenerated electrons by transporting holes from the cathode to the C60/buffer interface, followed by recombination with photogenerated electrons in the acceptor. We use a model for free-polaron and polaron-pair dynamics to describe device operation and the observed inflection in the current-voltage characteristics. The device characteristics are understood in terms of hole transfer from the highest occupied molecular orbital energy levels of several Ru-complexes to the acceptor.

  17. Reciprocal carrier collection in organic photovoltaics

    SciTech Connect

    Renshaw, C. Kyle; Schlenker, Cody W.; Thompson, Mark E.; Forrest, Stephen R.

    2011-07-18

    Buffer layers between the acceptor and cathode can perform several functions in organic photovoltaic devices, such as providing exciton blocking, protection of active layers against damage from cathode deposition, and optical spacing to maximize the electric field in the active device region. Here, we study electron collection by replacing the common buffer layer, bathocuproine, with a series of six, substituted tris(β-diketonato)Ru(III) analogues in the structure: indium-tin-oxide/copper phthalocyanine/C₆₀/buffer/Ag. These buffer layers enable collection of photogenerated electrons by transporting holes from the cathode to the C₆₀/buffer interface, followed by recombination with photogenerated electrons in the acceptor. We use a model for free-polaron and polaron-pair dynamics to describe device operation and the observed inflection in the current-voltage characteristics. The device characteristics are understood in terms of hole transfer from the highest occupied molecular orbital energy levels of several Ru-complexes to the acceptor.

  18. Modeling charge transport in organic photovoltaic materials.

    PubMed

    Nelson, Jenny; Kwiatkowski, Joe J; Kirkpatrick, James; Frost, Jarvist M

    2009-11-17

    The performance of an organic photovoltaic cell depends critically on the mobility of charge carriers within the constituent molecular semiconductor materials. However, a complex combination of phenomena that span a range of length and time scales control charge transport in disordered organic semiconductors. As a result, it is difficult to rationalize charge transport properties in terms of material parameters. Until now, efforts to improve charge mobilities in molecular semiconductors have proceeded largely by trial and error rather than through systematic design. However, recent developments have enabled the first predictive simulation studies of charge transport in disordered organic semiconductors. This Account describes a set of computational methods, specifically molecular modeling methods, to simulate molecular packing, quantum chemical calculations of charge transfer rates, and Monte Carlo simulations of charge transport. Using case studies, we show how this combination of methods can reproduce experimental mobilities with few or no fitting parameters. Although currently applied to material systems of high symmetry or well-defined structure, further developments of this approach could address more complex systems such anisotropic or multicomponent solids and conjugated polymers. Even with an approximate treatment of packing disorder, these computational methods simulate experimental mobilities within an order of magnitude at high electric fields. We can both reproduce the relative values of electron and hole mobility in a conjugated small molecule and rationalize those values based on the symmetry of frontier orbitals. Using fully atomistic molecular dynamics simulations of molecular packing, we can quantitatively replicate vertical charge transport along stacks of discotic liquid crystals which vary only in the structure of their side chains. We can reproduce the trends in mobility with molecular weight for self-organizing polymers using a cheap, coarse

  19. Novel High Efficient Organic Photovoltaic Materials

    NASA Technical Reports Server (NTRS)

    Sun, Sam; Haliburton, James; Wang, Yi-Qing; Fan, Zhen; Taft, Charles; Maaref, Shahin; Bailey, Sheila (Technical Monitor)

    2003-01-01

    Solar energy is a renewable, nonpolluting, and most abundant energy source for human exploration of a remote site or outer space. In order to generate appreciable electrical power in space or on the earth, it is necessary to collect sunlight from large areas and with high efficiency due to the low density of sunlight. Future organic or polymer (plastic) solar cells appear very attractive due to their unique features such as light weight, flexible shape, tunability of energy band-gaps via versatile molecular or supramolecular design, synthesis, processing and device fabrication schemes, and much lower cost on large scale industrial production. It has been predicted that supramolecular and nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration due to improved electronic ultrastructure and morphology in comparison to polymer composite system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel block copolymer system containing donor and acceptor blocks covalently attached. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (RO-PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (SF-PPV). The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block has a strong PL emission at around 560 nm, and acceptor block has a strong PL emission at around 520 nm, the PL emissions of final block copolymers are severely quenched. This verifies the expected electron transfer and charge separation due to interfaces of donor and acceptor nano phase separated blocks. The system therefore has potential for variety light harvesting applications, including high efficient photovoltaic applications.

  20. A Molecular Tetrapod for Organic Photovoltaics.

    PubMed

    Yang, Jianzhong; Zhang, Zhen; Qin, Yang

    2016-08-31

    The synthesis and characterization of a molecular tetrapod, SFBTD, featuring a tetraphenylsilane center and four identical conjugated arms, which structurally resembles breakwaters in common wave-reducing shore constructions, are reported. Cyclic voltammetry reveals that SFBTD has a medium band gap of ca. 2.0 eV and a low-lying HOMO energy level at ca. -5.2 eV. Absorption spectroscopy, X-ray diffraction, and differential scanning calorimetry experiments reveal a low degree of crystallinity in this compound and slow crystallization kinetics. Bulk heterojunction organic photovoltaics (OPVs) employing SFBTD and fullerene derivatives exhibit power conversion efficiencies (PCEs) up to 1.05% and open-circuit voltage (VOC) values as high as 1.02 V. To the best of our knowledge, this is the highest PCE obtained for OPVs employing molecular tetrapods as donor materials. These devices are relatively thermally stable due to the known ability of breakwater tetrapods to interlock, preventing dislodging and sliding. The lack of favorable phase separations and low hole mobilities of the blend films are the major factors limiting the device performance. Ternary blend devices by the addition of three low band gap poly(thienylene vinylene) (PTV) derivatives were fabricated and tested. We found that the added PTVs acted to be either the major hole conductor or a competing hole conduction channel depending on the HOMO level positions relative to that of SFBTD. Some of the ternary OPV devices out-performed the corresponding binary counterparts employing SFBTD or PTVs alone, suggesting cooperative effects in the ternary systems. PMID:27514435

  1. A Molecular Tetrapod for Organic Photovoltaics.

    PubMed

    Yang, Jianzhong; Zhang, Zhen; Qin, Yang

    2016-08-31

    The synthesis and characterization of a molecular tetrapod, SFBTD, featuring a tetraphenylsilane center and four identical conjugated arms, which structurally resembles breakwaters in common wave-reducing shore constructions, are reported. Cyclic voltammetry reveals that SFBTD has a medium band gap of ca. 2.0 eV and a low-lying HOMO energy level at ca. -5.2 eV. Absorption spectroscopy, X-ray diffraction, and differential scanning calorimetry experiments reveal a low degree of crystallinity in this compound and slow crystallization kinetics. Bulk heterojunction organic photovoltaics (OPVs) employing SFBTD and fullerene derivatives exhibit power conversion efficiencies (PCEs) up to 1.05% and open-circuit voltage (VOC) values as high as 1.02 V. To the best of our knowledge, this is the highest PCE obtained for OPVs employing molecular tetrapods as donor materials. These devices are relatively thermally stable due to the known ability of breakwater tetrapods to interlock, preventing dislodging and sliding. The lack of favorable phase separations and low hole mobilities of the blend films are the major factors limiting the device performance. Ternary blend devices by the addition of three low band gap poly(thienylene vinylene) (PTV) derivatives were fabricated and tested. We found that the added PTVs acted to be either the major hole conductor or a competing hole conduction channel depending on the HOMO level positions relative to that of SFBTD. Some of the ternary OPV devices out-performed the corresponding binary counterparts employing SFBTD or PTVs alone, suggesting cooperative effects in the ternary systems.

  2. Simple Analytic Description of Collection Efficiency in Organic Photovoltaics.

    PubMed

    Savoie, Brett M; Movaghar, Bijan; Marks, Tobin J; Ratner, Mark A

    2013-03-01

    The collection of charge carriers is a fundamental step in the photovoltaic conversion process. In disordered organic films, low mobility and disorder can make collection the performance-limiting step in energy conversion. We derive two analytic relationships for carrier collection efficiency in organic photovoltaics that account for the presence or absence of carrier-selective electrodes. These equations directly include drift and diffusive carrier transport in the device active layers and account for possible losses from Langevin and Shockley-Read-Hall recombination mechanisms. General relationships among carrier mobility, contact selectivity, recombination processes, and organic photovoltaic figures of merit are established. Our results suggest that device collection efficiency remains mobility-limited for many materials systems, and a renewed emphasis should be placed on materials' purity.

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

    PubMed Central

    2014-01-01

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

  4. Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

    SciTech Connect

    Lonergan, Mark

    2015-05-29

    Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been the polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.

  5. Single inorganic-organic hybrid photovoltaic nanorod

    NASA Astrophysics Data System (ADS)

    Yoo, Sang-Hoon; Liu, Lichun; Ku, Tea-Woong; Hong, Soonchang; Whang, Dongmok; Park, Sungho

    2013-09-01

    We demonstrate that single photovoltaic (PV) nanorods can be readily fabricated by electrochemical processing in solution-phase under ambient conditions. A porous Au nanorod electrode in the core of the PV nanorod was central to both its structural formation and superior performance. We examined an intrinsically conducting polymer (polypyrrole) and an inorganic semiconductor (cadmium selenide) as precursor materials. Through an extremely simple and cost-effective fashioning process (solution-phase, room temperature), unadorned PV nanorods with up to 1.1% power conversion efficiency were obtained.

  6. Ultraviolet Radiation Round-Robin Testing of Various Backsheets for Photovoltaic Modules

    SciTech Connect

    Koehl, Michael; Ballion, Amal; Lee, Yu-Hsien; Wu, Hung-Sen; Scott, Kurt; Glick, Stephen; Hacke, Peter; Koo, Hyun Jin

    2015-06-14

    Durability testing of materials exposed to natural weathering requires testing of the ultraviolet (UV) stability, especially for polymeric materials. The type approval testing of photovoltaic (PV) modules according to standards IEC 61215 and IEC 61646, which includes a so-called UV preconditioning test with a total UV dose of 15 kWh/m2, does not correspond to the real loads during lifetime. Between 3%-10% of the UV radiation has to be in the spectral range between 280 and 320 nm (UV-B) in the recent editions of the standards. However, the spectral distribution of the radiation source is very important because different samples show very individual spectral sensitivity for the radiation offered. Less than 6% of the intensity of solar radiation exists in the UV range. In the case of an increase of the intensity of the light source for accelerating the UV test, overheating of the samples would have to be prevented more rigorously and the temperature of the samples have to be measured to avoid misinterpretation of the test results.

  7. Photovoltaic effect in organic polymer-iodine complex

    NASA Technical Reports Server (NTRS)

    Hermann, A. M.; Rembaum, A.

    1967-01-01

    Certain charge transfer complexes formed from organic polymers and iodine generate appreciable voltages at relatively low impedances upon exposure to light. These films show promise in applications requiring chemically and electrically stable films as detectors of optical radiation and as energy converters in photovoltaic cells.

  8. Benefit and risk of organic ultraviolet filters.

    PubMed

    Nohynek, G J; Schaefer, H

    2001-06-01

    Modern sunscreen products provide broad-spectrum UV protection and may contain one or several UV filters. A modern UV filter should be heat and photostable, water resistant, nontoxic, and easy to formulate. Identification of a substance that meets these criteria is as difficult as discovering a new drug; hundreds of new molecules are synthesized and screened before a lead candidate is identified. The most important aspect in the development of a new UV filter is its safety. In our laboratories, the safety of new ultraviolet filters is assessed by an initial in vitro screen including photostability, cytotoxicity, photocytotoxicity, genotoxicity, and photogenotoxicity tests. These tests are performed in mammalian, yeast, and bacterial cell systems. Skin penetration potential is measured in vitro using human skin or, when required by regulations, in vivo. Because modern sunscreens are selected on the basis of their retention on and in the stratum corneum and are formulated as poorly penetrating emulsions, they generally have very low to negligible penetration rates. The safety and efficacy of UV filters are regulated and approved by national and international health authorities. Safety standards in the European Union, United States, or Japan stipulate that new filters pass a stringent toxicological safety evaluation prior to approval. The safety dossier of a new UV filter resembles that of a new drug and includes acute toxicity, irritation, sensitization, phototoxicity, photosensitization, subchronic and chronic toxicity, reproductive toxicity, genotoxicity, photogenotoxicity, carcinogenicity, and, in the United States, photocarcinogenicity testing. The margin of safety of new UV filters for application to humans is estimated by comparing the potential human systemic exposure with the no-effect level from in vivo toxicity studies. Only substances with a safe toxicological profile and a margin of safety of at least 100-fold are approved for human use. Finally, prior to

  9. Detailed balance limit of power conversion efficiency for organic photovoltaics

    SciTech Connect

    Seki, Kazuhiko; Furube, Akihiro; Yoshida, Yuji

    2013-12-16

    A fundamental difference between inorganic photovoltaic (IPV) and organic photovoltaic (OPV) cells is that charges are generated at the interface in OPV cells, while free charges can be generated in the bulk in IPV cells. In OPV cells, charge generation involves intrinsic energy losses to dissociate excitons at the interface between the donor and acceptor. By taking into account the energy losses, we show the theoretical limits of the power conversion efficiency set by radiative recombination of the carriers on the basis of the detailed balance relation between radiation from the cell and black-body radiation.

  10. Molecular Design of Benzodithiophene-Based Organic Photovoltaic Materials.

    PubMed

    Yao, Huifeng; Ye, Long; Zhang, Hao; Li, Sunsun; Zhang, Shaoqing; Hou, Jianhui

    2016-06-22

    Advances in the design and application of highly efficient conjugated polymers and small molecules over the past years have enabled the rapid progress in the development of organic photovoltaic (OPV) technology as a promising alternative to conventional solar cells. Among the numerous OPV materials, benzodithiophene (BDT)-based polymers and small molecules have come to the fore in achieving outstanding power conversion efficiency (PCE) and breaking 10% efficiency barrier in the single junction OPV devices. Remarkably, the OPV device featured by BDT-based polymer has recently demonstrated an impressive PCE of 11.21%, indicating the great potential of this class of materials in commercial photovoltaic applications. In this review, we offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship. We believe more exciting BDT-based photovoltaic materials and devices will be developed in the near future. PMID:27251307

  11. Molecular Design of Benzodithiophene-Based Organic Photovoltaic Materials.

    PubMed

    Yao, Huifeng; Ye, Long; Zhang, Hao; Li, Sunsun; Zhang, Shaoqing; Hou, Jianhui

    2016-06-22

    Advances in the design and application of highly efficient conjugated polymers and small molecules over the past years have enabled the rapid progress in the development of organic photovoltaic (OPV) technology as a promising alternative to conventional solar cells. Among the numerous OPV materials, benzodithiophene (BDT)-based polymers and small molecules have come to the fore in achieving outstanding power conversion efficiency (PCE) and breaking 10% efficiency barrier in the single junction OPV devices. Remarkably, the OPV device featured by BDT-based polymer has recently demonstrated an impressive PCE of 11.21%, indicating the great potential of this class of materials in commercial photovoltaic applications. In this review, we offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship. We believe more exciting BDT-based photovoltaic materials and devices will be developed in the near future.

  12. Current challenges in organic photovoltaic solar energy conversion.

    PubMed

    Schlenker, Cody W; Thompson, Mark E

    2012-01-01

    Over the last 10 years, significant interest in utilizing conjugated organic molecules for solid-state solar to electric conversion has produced rapid improvement in device efficiencies. Organic photovoltaic (OPV) devices are attractive for their compatibility with low-cost processing techniques and thin-film applicability to flexible and conformal applications. However, many of the processes that lead to power losses in these systems still remain poorly understood, posing a significant challenge for the future efficiency improvements required to make these devices an attractive solar technology. While semiconductor band models have been employed to describe OPV operation, a more appropriate molecular picture of the pertinent processes is beginning to emerge. This chapter presents mechanisms of OPV device operation, based on the bound molecular nature of the involved transient species. With the intention to underscore the importance of considering both thermodynamic and kinetic factors, recent progress in elucidating molecular characteristics that dictate photovoltage losses in heterojunction organic photovoltaics is also discussed.

  13. All solution processable organic photovoltaic cells using DMDCNQI as an organic N-type buffer layer.

    PubMed

    Yang, Eui Yeol; So, Byoung Min; Chung, Chan Moon; Oh, Se Young

    2012-01-01

    Organic photovoltaic cells consisting of ITO/PEDOT-PSS/P3HT:PCBM/TiO(x)/DMDCNQI/Al have been fabricated by using dip-coated DMDCNQI layer as a cathode buffer material. We have investigated the physical effects of charge transfer complex and wettability of DMDCNQI between TiO(x)/P3HT:PCBM layer and Al cathode electrode on the performance of organic photovoltaic cell. The photovoltaic cell fabricated with a dip-coated DMDCNQI layer exhibited almost similar performance compared to the device using conventional evaporated DMDCNQI layer. Especially, the power conversion efficiency of the prepared organic photovoltaic cell using TiO(x)/DMDCNQI layer was improved to 3.1%, which is mainly due to the decrease in the low contact resistance of organic-metal interface.

  14. Organic photovoltaic cells utilizing ultrathin sensitizing layer

    DOEpatents

    Rand, Barry P.; Forrest, Stephen R.

    2011-05-24

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

  15. Quantitative Tomography of Organic Photovoltaic Blends at the Nanoscale.

    PubMed

    Pfannmöller, M; Heidari, H; Nanson, L; Lozman, O R; Chrapa, M; Offermans, T; Nisato, G; Bals, S

    2015-10-14

    The success of semiconducting organic materials has enabled green technologies for electronics, lighting, and photovoltaics. However, when blended together, these materials have also raised novel fundamental questions with respect to electronic, optical, and thermodynamic properties. This is particularly important for organic photovoltaic cells based on the bulk heterojunction. Here, the distribution of nanoscale domains plays a crucial role depending on the specific device structure. Hence, correlation of the aforementioned properties requires 3D nanoscale imaging of materials domains, which are embedded in a multilayer device. Such visualization has so far been elusive due to lack of contrast, insufficient signal, or resolution limits. In this Letter, we introduce spectral scanning transmission electron tomography for reconstruction of entire volume plasmon spectra from rod-shaped specimens. We provide 3D structural correlations and compositional mapping at a resolution of approximately 7 nm within advanced organic photovoltaic tandem cells. Novel insights that are obtained from quantitative 3D analyses reveal that efficiency loss upon thermal annealing can be attributed to subtle, fundamental blend properties. These results are invaluable in guiding the design and optimization of future devices in plastic electronics applications and provide an empirical basis for modeling and simulation of organic solar cells.

  16. Quantitative Tomography of Organic Photovoltaic Blends at the Nanoscale.

    PubMed

    Pfannmöller, M; Heidari, H; Nanson, L; Lozman, O R; Chrapa, M; Offermans, T; Nisato, G; Bals, S

    2015-10-14

    The success of semiconducting organic materials has enabled green technologies for electronics, lighting, and photovoltaics. However, when blended together, these materials have also raised novel fundamental questions with respect to electronic, optical, and thermodynamic properties. This is particularly important for organic photovoltaic cells based on the bulk heterojunction. Here, the distribution of nanoscale domains plays a crucial role depending on the specific device structure. Hence, correlation of the aforementioned properties requires 3D nanoscale imaging of materials domains, which are embedded in a multilayer device. Such visualization has so far been elusive due to lack of contrast, insufficient signal, or resolution limits. In this Letter, we introduce spectral scanning transmission electron tomography for reconstruction of entire volume plasmon spectra from rod-shaped specimens. We provide 3D structural correlations and compositional mapping at a resolution of approximately 7 nm within advanced organic photovoltaic tandem cells. Novel insights that are obtained from quantitative 3D analyses reveal that efficiency loss upon thermal annealing can be attributed to subtle, fundamental blend properties. These results are invaluable in guiding the design and optimization of future devices in plastic electronics applications and provide an empirical basis for modeling and simulation of organic solar cells. PMID:26390367

  17. Organic photovoltaic cells utilizing ultrathin sensitizing layer

    DOEpatents

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

    2011-09-06

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

  18. Small molecule semiconductors for high-efficiency organic photovoltaics.

    PubMed

    Lin, Yuze; Li, Yongfang; Zhan, Xiaowei

    2012-06-01

    Organic photovoltaic cells (OPVs) are a promising cost-effective alternative to silicon-based solar cells, and possess light-weight, low-cost, and flexibility advantages. Significant progress has been achieved in the development of novel photovoltaic materials and device structures in the last decade. Nowadays small molecular semiconductors for OPVs have attracted considerable attention, due to their advantages over their polymer counterparts, including well-defined molecular structure, definite molecular weight, and high purity without batch to batch variations. The highest power conversion efficiencies of OPVs based on small molecular donor/fullerene acceptors or polymeric donor/fullerene acceptors are up to 6.7% and 8.3%, respectively, and meanwhile nonfullerene acceptors have also exhibited some promising results. In this review we summarize the developments in small molecular donors, acceptors (fullerene derivatives and nonfullerene molecules), and donor-acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs. We focus on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances. This structure-property relationship analysis may guide rational structural design and evaluation of photovoltaic materials (253 references).

  19. Spin-enhanced organic bulk heterojunction photovoltaic solar cells.

    PubMed

    Zhang, Ye; Basel, Tek P; Gautam, Bhoj R; Yang, Xiaomei; Mascaro, Debra J; Liu, Feng; Vardeny, Z Valy

    2012-01-01

    Recently, much effort has been devoted to improve the efficiency of organic photovoltaic solar cells based on blends of donors and acceptors molecules in bulk heterojunction architecture. One of the major losses in organic photovoltaic devices has been recombination of polaron pairs at the donor-acceptor domain interfaces. Here, we present a novel method to suppress polaron pair recombination at the donor-acceptor domain interfaces and thus improve the organic photovoltaic solar cell efficiency, by doping the device active layer with spin 1/2 radical galvinoxyl. At an optimal doping level of 3 wt%, the efficiency of a standard poly(3-hexylthiophene)/1-(3-(methoxycarbonyl)propyl)-1-1-phenyl)(6,6)C(61) solar cell improves by 18%. A spin-flip mechanism is proposed and supported by magneto-photocurrent measurements, as well as by density functional theory calculations in which polaron pair recombination rate is suppressed by resonant exchange interaction between the spin 1/2 radicals and charged acceptors, which convert the polaron pair spin state from singlet to triplet.

  20. Beyond fullerenes: design of nonfullerene acceptors for efficient organic photovoltaics.

    PubMed

    Li, Haiyan; Earmme, Taeshik; Ren, Guoqiang; Saeki, Akinori; Yoshikawa, Saya; Murari, Nishit M; Subramaniyan, Selvam; Crane, Matthew J; Seki, Shu; Jenekhe, Samson A

    2014-10-15

    New electron-acceptor materials are long sought to overcome the small photovoltage, high-cost, poor photochemical stability, and other limitations of fullerene-based organic photovoltaics. However, all known nonfullerene acceptors have so far shown inferior photovoltaic properties compared to fullerene benchmark [6,6]-phenyl-C60-butyric acid methyl ester (PC60BM), and there are as yet no established design principles for realizing improved materials. Herein we report a design strategy that has produced a novel multichromophoric, large size, nonplanar three-dimensional (3D) organic molecule, DBFI-T, whose π-conjugated framework occupies space comparable to an aggregate of 9 [C60]-fullerene molecules. Comparative studies of DBFI-T with its planar monomeric analogue (BFI-P2) and PC60BM in bulk heterojunction (BHJ) solar cells, by using a common thiazolothiazole-dithienosilole copolymer donor (PSEHTT), showed that DBFI-T has superior charge photogeneration and photovoltaic properties; PSEHTT:DBFI-T solar cells combined a high short-circuit current (10.14 mA/cm(2)) with a high open-circuit voltage (0.86 V) to give a power conversion efficiency of 5.0%. The external quantum efficiency spectrum of PSEHTT:DBFI-T devices had peaks of 60-65% in the 380-620 nm range, demonstrating that both hole transfer from photoexcited DBFI-T to PSEHTT and electron transfer from photoexcited PSEHTT to DBFI-T contribute substantially to charge photogeneration. The superior charge photogeneration and electron-accepting properties of DBFI-T were further confirmed by independent Xenon-flash time-resolved microwave conductivity measurements, which correctly predict the relative magnitudes of the conversion efficiencies of the BHJ solar cells: PSEHTT:DBFI-T > PSEHTT:PC60BM > PSEHTT:BFI-P2. The results demonstrate that the large size, multichromophoric, nonplanar 3D molecular design is a promising approach to more efficient organic photovoltaic materials.

  1. Boron Subphthalocyanines as Triplet Harvesting Materials within Organic Photovoltaics.

    PubMed

    Castrucci, Jeffrey S; Josey, David S; Thibau, Emmanuel; Lu, Zheng-Hong; Bender, Timothy P

    2015-08-01

    Singlet fission, the generation of two excited triplet states from a single absorbed photon, is currently an area of significant interest to photovoltaic researchers. In this Letter, we outline how a polychlorinated boron subphthalocyanine, previously hypothesized to be an effective harvester of singlet fission derived triplets from pentacene, is relatively efficient at facilitating the process. As expected, we found a major increase in photocurrent generation at the expense of device voltage. For a direct point of comparison, we also have paired the same polychlorinated boron subphthalocyanine with α-sexithiophene to probe the alternative technique of complementary absorption engineering. The sum of these efforts have let us present new guidelines for the molecular design of boron subphthalocyanine for organic photovoltaic applications.

  2. Interface Modifications for Applications in Organic and Hybrid Photovoltaics

    NASA Astrophysics Data System (ADS)

    Mazzio, Katherine A.

    Considerable research has been conducted in the area of organic photovoltaics due to several intrinsic advantages, including their high throughput solution processability, light weight, and their applicability on flexible substrates. Product development has been limited, however, due to the low mobilities and short exciton diffusion lengths of organic materials relative to inorganic materials used for photovoltaics. In this dissertation, we look at interfacial phenomena in attempt to control the charge transport dynamics in different parts of photovoltaic systems. The first chapter provides an overview of the field of organic photovoltaics, including their benefits, operating procedures, and a brief history of materials and device development. Chapter 2 examines some donor-acceptor small molecules as the electron donors in all organic bulk heterojunction solar cells with soluble fullerene derivatives as the electron acceptors. The donor-acceptor small molecules are unique because their energy levels agree well with the theoretical optimal HOMO and LUMO energy levels required for high efficiency organic photovoltaics. Even with energy level matching, however, we found that we were only able to obtain modest device efficiencies due to the formation of large domains that are greater than the exciton diffusion length and result in large interfacial areas. In chapter 3 we examine some of the optical, physical, and charge transport properties of a series of fully conjugated brush copolymers that are comprised of a carbazole-diketopyrrolorpyrrole donor-acceptor backbone copolymerized with different lengths of poly(3-hexylthiophene) pendant chains. It was found that there was a sufficient break in conjugation between the two copolymers such that the absorbance characteristics of both could be realized independently. In addition, the physical and charge transport properties could be tuned to primarily show influence from either the ambipolar low band gap backbone or the p

  3. Fabrication and Characterization of Organic/Inorganic Photovoltaic Device

    NASA Astrophysics Data System (ADS)

    Guvenc, Ali Bilge

    Energy is central to achieving the goals of sustainable development and will continue to be a primary engine for economic development. In fact, access to and consumption of energy is highly effective on the quality of life. The consumption of all energy sources have been increasing and the projections show that this will continue in the future. Unfortunately, conventional energy sources are limited and they are about to run out. Solar energy is one of the major alternative energy sources to meet the increasing demand. Photovoltaic devices are one way to harvest energy from sun and as a branch of photovoltaic devices organic bulk heterojunction photovoltaic devices have recently drawn tremendous attention because of their technological advantages for actualization of large-area and cost effective fabrication. The research in this dissertation focuses on both the mathematical modelling for better and more efficient characterization and the improvement of device power conversion efficiency. In the first part, we studied the effect of incident light power on the space charge regions of the Schottky barriers of the organic bulk heterojunction photovoltaic devices, the current-voltage characteristics and performance of the devices and built a current-voltage model for the devices that involves these effects. The incident light power showed an effect on the Schottky barriers of the devices by changing the width of the space charge regions. This change directly affects the reverse bias current-voltage curves by increasing the current values and the slope of the curves. But under excessive incident light power; the space charge regions merge, the devices break down and work as ohmic devices. In the second part, we combined the two improvement methods, improving the charge carrier transport and improving absorption of the organic bulk heterojunction photovoltaic devices. For charge carrier transport improvement, we presented deoxyribonucleic acid complexes as hole collecting

  4. 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

  5. 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

  6. Optical Properties of Photovoltaic Organic-Inorganic Lead Halide Perovskites.

    PubMed

    Green, Martin A; Jiang, Yajie; Soufiani, Arman Mahboubi; Ho-Baillie, Anita

    2015-12-01

    Over the last several years, organic-inorganic lead halide perovskites have rapidly emerged as a new photovoltaic contender. Although energy conversion efficiency above 20% has now been certified, improved understanding of the material properties contributing to these high performance levels may allow the progression to even higher efficiency, stable cells. The optical properties of these new materials are important not only to device design but also because of the insight they provide into less directly accessible properties, including energy-band structures, binding energies, and likely impact of excitons, as well as into absorption and inverse radiative recombination processes.

  7. Effects of solar ultraviolet radiation on coral reef organisms.

    PubMed

    Banaszak, Anastazia T; Lesser, Michael P

    2009-09-01

    Organisms living in shallow-water tropical coral reef environments are exposed to high UVR irradiances due to the low solar zenith angles (the angle of the sun from the vertical), the natural thinness of the ozone layer over tropical latitudes, and the high transparency of the water column. The hypothesis that solar ultraviolet radiation (UVR, 290-400 nm) is an important factor that affects the biology and ecology of coral reef organisms dates only to about 1980. It has been previously suggested that increased levels of biologically effective ultraviolet B radiation (UVB, 290-320 nm), which is the waveband primarily affected by ozone depletion, would have relatively small effects on corals and coral reefs and that these effects might be observed as changes in the minimum depths of occurrence of important reef taxa such as corals. This conclusion was based on predictions of increases in UVR as well as its attenuation with depth using the available data on UVR irradiances, ozone levels, and optical properties of the water overlying coral reefs. Here, we review the experimental evidence demonstrating the direct and indirect effects of UVR, both UVB and ultraviolet A (UVA, 320-400 nm) on corals and other reef associated biota, with emphasis on those studies conducted since 1996. Additionally, we re-examine the predictions made in 1996 for the increase in UVB on reefs with currently available data, assess whether those predictions were reasonable, and look at what changes might occur on coral reefs in the future as the multiple effects (i.e. increased temperature, hypercapnia, and ocean acidification) of global climate change continue.

  8. Surface-plasmon-enhanced photoconversion in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Morfa, Anthony John

    In this thesis, the benefits of including surface-plasmon-active materials into organic photovoltaics are investigated. First, the effect of discontinuous silver thin-films formed by physical vapor deposition at the transparent front electrode of the device is explored. A reproducible near doubling in efficiency is seen in these devices which arises from a near doubling of the short-circuit current. Analysis of the wavelength-dependence of the increase in current shows that the increase in current is due to surface-plasmon-enhanced optical absorption in the active layer of the devices. Additionally, these results are shown to be reproducible over several trials when using a fabrication routine that employs a low-temperature annealing step that retains the surface-plasmon activity of the substrate and prevents delamination of the active layers. The relative dielectric function of the active-layer material was determined at optical frequencies using variable-angle spectroscopic ellipsometry. A Huang-Rhys vibronic progression is used to model the peak energies of excitonic transitions in the film and the resulting parameters are found to be in excellent agreement with previously reported values. Theoretical calculations of the surface-plasmon enhancement are performed using the aforementioned dielectric function. The theoretical calculation of the skin depth of the surface plasmon is shown to be consistent with the observed wavelength dependence of the plasmonically enhanced current in organic photodiodes. In order to better understand the enhancement process and the fate of photogenerated holes and electrons, additional work was done to explore the electronic structure of the organic films using impedance spectroscopy. The results of this work indicate the presence of a Schottky diode at the metal/organic interface in standard device geometries. This result has several implications on charge extraction for standard devices and those including silver thin-films. It is

  9. Morphology-property insights into high-performance organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Darling, Seth

    2013-03-01

    Organic solar cells have attracted increasing attention as potential low-cost alternatives to traditional inorganic photovoltaic (PV) technologies. Additional advantages of OPVs include the use of earth-abundant materials, mechanical flexibility, light weight, rapid energy payback time, and the option for tunable coloring for aesthetic architectural installation. Key to their low-cost is solution-based high-throughput processing. Power conversion efficiency (PCE) of organic photovoltaics (OPVs) has steadily improved, with PTB series polymers exhibiting some of the highest PCEs. Using a suite of advanced characterization techniques, it is possible to decipher the morphology of OPV active layers across length scales from the molecular to the mesoscopic. Correlating these structural features with optoelectronic function leads to morphology-performance relationship insights, which in turn can be utilized as the foundation for a rational design of improved performance in OPV devices. Initial results from this methodology are encouraging, suggesting a viable alternative to the traditional Edisonian approach to device performance improvement. Use of the APS, EMC, and the Center for Nanoscale Materials (CNM) at Argonne National Laboratory was supported by the US DOE, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357

  10. Synthesis and characterization of ultraviolet light-emitting organic acids.

    PubMed

    An, Chun-Ai; Guo, Yanchao; Si, Zhenjun; Duan, Qian

    2014-05-01

    Three ultraviolet light-emitting organic acids of 3,3'-(4-phenyl-4H-1,2,4-triazole-3,5-diyl)dibenzoic acid (Tz-1), 4,4',4″-(4H-1,2,4-triazole-3,4,5-triyl)tribenzoic acid (Tz-2), and 4,4'-(4-(4'-carboxy-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazole-3,5-diyl)dibenzoic acid (Tz-3) were successfully synthesized and fully characterized by the (1)H NMR, the IR absorption spectra, and the X-ray single crystal diffraction. It was found that Tz-1, Tz-2, and Tz-3 could give out the ultraviolet photoluminescent spectra centered at 369 nm, 365 nm and 350 nm, respectively. The luminescence quantum yields of Tz-1 and Tz-2 were measured to be 0.20 and 0.14, respectively. Additionally, the density functional theory (DFT) and the time-dependent DFT calculations were also carried out for Tz-1, Tz-2, and Tz-3.

  11. Solution processed nickel oxide anodes for organic photovoltaic devices

    SciTech Connect

    Mustafa, Bestoon; Griffin, Jonathan; Alsulami, Abdullah S.; Lidzey, David G.; Buckley, Alastair R.

    2014-02-10

    Nickel oxide thin films have been prepared from a nickel acetylacetonate (Ni(acac)) precursor for use in bulk heterojunction organic photovoltaic devices. The conversion of Ni(acac) to NiO{sub x} has been investigated. Oxygen plasma treatment of the NiO layer after annealing at 400 °C affords solar cell efficiencies of 5.2%. Photoelectron spectroscopy shows that high temperature annealing converts the Ni(acac) to a reduced form of nickel oxide. Additional oxygen plasma treatment further oxidizes the surface layers and deepens the NiO work function from 4.7 eV for the annealed film, to 5.0 eV allowing for efficient hole extraction at the organic interface.

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

    SciTech Connect

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

    2010-09-01

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

  13. Thiophene-based oligomers, polymers and dendrimers for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Yong

    Demand for inexpensive renewable energy sources has stimulated new approaches for the production of efficient, low cost photovoltaic (PV) solar cell devices. This thesis research has focused on developing thiophene-based oligomers, polymers and dendrimers for this purpose. The key results are summarized as follows: First, three fully characterized polynorbornenes with electronically active pendant oligothiophene side chains have been synthesized and incorporated as active electronic components into single-layer photovoltaic cells. The device tests along with the electrochemical experiments demonstrate that incorporating chemically stable end-groups on the oligothiophene unit is responsible for the improvement of operation stability under ambient conditions. Second, in-situ surface-initiated polymerization of thiophene inside nanoporous networks has been realized. The resulting organic-inorganic hybrids with polythiophene covalently bound inside nanopores can achieve better interface contact, larger surface coverage and more complete filling of the pores. These result in more efficient photoinjection of electrons into the conduction band of nanocrystalline TiO2 than an analogous nanoporous structure infiltrated by polymer synthesized outside the network. The last part of this thesis covers the synthesis and characterization of a new series of semi-flexible oligothiophene-based dendrimers, which show pronounced solvatochromic and thermochromic properties. Microscopic fluorescence investigation of such surface adhered dendrimers provides the evidence that the intramolecular interactions inside these dendritic structures mainly account for the origin of the morphology-related chromism properties. This architecture is promising to make processable light harvesting structures having scaffolded donors covalently integrated with acceptors such as fullerenes in order to fabricate photovoltaics where phase segregation is suppressed.

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

    DOEpatents

    Marks, Tobin J.; Hains, Alexander W.

    2013-03-19

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

  15. Perylene Diimide Based ``Nanofabric'' Thin Films for Organic Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Carter, Austin; Park, June Hyoung; Min, Yong; Epstein, Arthur

    2011-03-01

    We report progress in using a perylene diimide (PDI) nanofabric as an effective electron accepting nanostructure for organic photovoltaics (OPV). A key challenge in OPV continues to be the recovery of electrons after charge separation due to the relatively poor mobility of C60 and related materials. A series of PDI compounds and complexes have been synthesized and used to fabricate nanofibers and thin films using solution and vacuum deposition techniques. Overlaping PDI-based nanofibers form a fast electron-transporting ``nanofabric'' that has been characterized (AFM, PL, UV-vis, etc.) and can be blended with electron donating materials. A solution-processible OPV configuration containing a nanofabric heterojunction (FHJ) of poly(3-hexylthiophene) and the PDI nanofabric was investigated. We observed a significant improvement in power-conversion efficiency due in part to expansion of the interfacial area and the presence of high mobility electron pathways to the LiF/Al electrode. This work is supported by the Wright Center for Photovoltaic Innovation and Commercialization, the Institute for Materials Research and the Center for Affordable Nanoengineering of Polymeric Biomedical Devices.

  16. Compatibilization of All-Conjugated Polymer Blends for Organic Photovoltaics.

    PubMed

    Lombeck, Florian; Sepe, Alessandro; Thomann, Ralf; Friend, Richard H; Sommer, Michael

    2016-08-23

    Compatibilization of an immiscible binary blend comprising a conjugated electron donor and a conjugated electron acceptor polymer with suitable electronic properties upon addition of a block copolymer (BCP) composed of the same building blocks is demonstrated. Efficient compatibilization during melt-annealing is feasible when the two polymers are immiscible in the melt, i.e. above the melting point of ∼250 °C of the semicrystalline donor polymer P3HT. To generate immiscibility at these high temperatures, the acceptor polymer PCDTBT is equipped with fluorinated side chains leading to an increased Flory-Huggins interaction parameter. Compatibilization in bulk and thin films is demonstrated, showing that the photovoltaic performance of pristine microphase separated and nanostructured BCPs can also be obtained for compatibilized blend films containing low contents of 10-20 wt % BCP. Thermodynamically stable domain sizes range between several tens of microns for pure blends and ∼10 nm for pure block copolymers. In addition to controlling domain size, the amount of block copolymer added dictates the ratio of edge-on and face-on P3HT crystals, with compatibilized films showing an increasing amount of face-on P3HT crystals with increasing amount of compatibilizer. This study demonstrates the prerequisites and benefits of compatibilizing all-conjugated semicrystalline polymer blends for organic photovoltaics. PMID:27482842

  17. Compatibilization of All-Conjugated Polymer Blends for Organic Photovoltaics.

    PubMed

    Lombeck, Florian; Sepe, Alessandro; Thomann, Ralf; Friend, Richard H; Sommer, Michael

    2016-08-23

    Compatibilization of an immiscible binary blend comprising a conjugated electron donor and a conjugated electron acceptor polymer with suitable electronic properties upon addition of a block copolymer (BCP) composed of the same building blocks is demonstrated. Efficient compatibilization during melt-annealing is feasible when the two polymers are immiscible in the melt, i.e. above the melting point of ∼250 °C of the semicrystalline donor polymer P3HT. To generate immiscibility at these high temperatures, the acceptor polymer PCDTBT is equipped with fluorinated side chains leading to an increased Flory-Huggins interaction parameter. Compatibilization in bulk and thin films is demonstrated, showing that the photovoltaic performance of pristine microphase separated and nanostructured BCPs can also be obtained for compatibilized blend films containing low contents of 10-20 wt % BCP. Thermodynamically stable domain sizes range between several tens of microns for pure blends and ∼10 nm for pure block copolymers. In addition to controlling domain size, the amount of block copolymer added dictates the ratio of edge-on and face-on P3HT crystals, with compatibilized films showing an increasing amount of face-on P3HT crystals with increasing amount of compatibilizer. This study demonstrates the prerequisites and benefits of compatibilizing all-conjugated semicrystalline polymer blends for organic photovoltaics.

  18. High performance organic photovoltaics with plasmonic-coupled metal nanoparticle clusters.

    PubMed

    Park, Hyung Il; Lee, Seunghoon; Lee, Ju Min; Nam, Soo Ah; Jeon, Taewoo; Han, Sang Woo; Kim, Sang Ouk

    2014-10-28

    Performance enhancement of organic photovoltaics using plasmonic nanoparticles has been limited without interparticle plasmon coupling. We demonstrate high performance organic photovoltaics employing gold nanoparticle clusters with controlled morphology as a plasmonic component. Near-field coupling at the interparticle gaps of nanoparticle clusters gives rise to strong enhancement in localized electromagnetic field, which led to the significant improvement of exciton generation and dissociation in the active layer of organic solar cells. A power conversion efficiency of 9.48% is attained by employing gold nanoparticle clusters at the bottom of the organic active layer. This is one of the highest efficiency values reported thus far for the single active layer organic photovoltaics.

  19. Coherent ultrafast charge transfer in an organic photovoltaic blend.

    PubMed

    Falke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, Christoph

    2014-05-30

    Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system. PMID:24876491

  20. Coherent ultrafast charge transfer in an organic photovoltaic blend.

    PubMed

    Falke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, Christoph

    2014-05-30

    Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system.

  1. Toward mass producible ordered bulk heterojunction organic photovoltaic devices.

    PubMed

    Kim, Taeyong; Yoon, Hyunsik; Song, Hyung-Jun; Haberkorn, Niko; Cho, Younghyun; Sung, Seung Hyun; Lee, Chang Hee; Char, Kookheon; Theato, Patrick

    2012-12-13

    A strategy to fabricate nanostructured poly(3-hexylthiophene) (P3HT) films for organic photovoltaic (OPV) cells by a direct transfer method from a reusable soft replica mold is presented. The flexible polyfluoropolyether (PFPE) replica mold allows low-pressure and low- temperature process condition for the successful transfer of nanostructured P3HT films onto PEDOT/PSS-coated ITO substrates. To reduce the fabrication cost of masters in large area, we employed well-ordered anodic aluminum oxide (AAO) as a template. Also, we provide a method to fabricate reversed nanostructures by exploiting the self-replication of replica molds. The concept of the transfer method in low temperature with a flexible and reusable replica mold obtained from an AAO template will be a firm foundation for a low-cost fabrication process of ordered OPVs.

  2. Efficient organic photovoltaic cells with vertically ordered bulk heterojunctions.

    PubMed

    Yu, Bo; Wang, Haibo; Yan, Donghang

    2013-12-01

    Nanoscale morphology has been proved to be the key parameter deciding the exciton dissociation and charge transportation in bulk heterojunction (BHJ) solar cells. In this paper, we report a kind of small molecular organic photovoltaic cell (OPV) with a vertically ordered BHJ prepared by the weak epitaxial growth method. By this method, zinc phthalocyanine (ZnPc) can easily be formed into a highly ordered and continuous thin film and C60 is inclined to become dispersed crystalline grains in ZnPc film. Furthermore, we can control both the size and distribution density of C60 crystalline grains in ZnPc thin film without destroying the order of the ZnPc thin film. The OPVs with the vertically ordered BHJ show a high fill factor and a power conversion efficiency over 3% has been achieved.

  3. Graphene - a promising material for organic photovoltaic cells.

    PubMed

    Wan, Xiangjian; Long, Guankui; Huang, Lu; Chen, Yongsheng

    2011-12-01

    As a promising two-dimensional nanomaterial with outstanding electronic, optical, thermal, and mechanical properties, graphene has been proposed for many applications. In this Progress Report we summarize and discuss comprehensively the advances made so far for applications of graphene in organic photovoltaic (OPV) cells, including that for transparent electrodes, active layers and interfaces layer in OPV. It is concluded that graphene may very likely play a major role in new developments/improvements in OPVs. The future studies for this area are proposed to focus on the following: i) improving the conductivity without comprising the transparency as a transparent electrode material; ii) controlling the sheet sizes, band structure and surface morphology for use as a electron acceptor material, and iii) controlling and improving the functionalization and compatibility with other materials as interface layer material.

  4. Organic photovoltaic cells: from performance improvement to manufacturing processes.

    PubMed

    Youn, Hongseok; Park, Hui Joon; Guo, L Jay

    2015-05-20

    Organic photovoltaics (OPVs) have been pursued as a next generation power source due to their light weight, thin, flexible, and simple fabrication advantages. Improvements in OPV efficiency have attracted great attention in the past decade. Because the functional layers in OPVs can be dissolved in common solvents, they can be manufactured by eco-friendly and scalable printing or coating technologies. In this review article, the focus is on recent efforts to control nanomorphologies of photoactive layer and discussion of various solution-processed charge transport and extraction materials, to maximize the performance of OPV cells. Next, recent works on printing and coating technologies for OPVs to realize solution processing are reviewed. The review concludes with a discussion of recent advances in the development of non-traditional lamination and transfer method towards highly efficient and fully solution-processed OPV.

  5. Photoconductivity in donor-acceptor heterojunction organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Renshaw, C. K.; Zimmerman, J. D.; Lassiter, B. E.; Forrest, S. R.

    2012-08-01

    Organic photovoltaics (OPVs) differ from ideal inorganic solar cells due to their pronounced voltage dependence under reverse bias. This feature is commonly modeled in an ad hoc fashion by including a parallel junction resistance (Rp) that bypasses the heterojunction energy barrier between donor and acceptor. The existence of a finite Rp has variously been attributed to rough interfaces, pinhole defects, or to the electric field dependence of the dissociation of polaron pairs that are bound at the heterojunction. Here we show that the voltage dependence of the photocurrent can also arise from photoconductivity resulting from exciton generation followed by dissociation into free polarons within the bulk of the donor and acceptor layers. The presence of photoconductivity of the active layers does not result in an increase in power conversion efficiency, and places a constraint on the maximum fill factor that can be achieved in an OPV cell.

  6. Doping effects of fluorinated organic dyes on the open-circuit voltage of bulk-heterojunction photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomoki; Yamashita, Kenichi

    2015-08-01

    We have investigated photovoltaic properties of bulk-heterojunction (BHJ) organic absorption layer doped with fluorinated Coumarin dyes. By dilute doping of a fluorinated Coumarin dye, Coumarin 307, into poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) BHJ absorption layer, the open-circuit voltage of photovoltaic device increased by ∼90 mV without the significant degradation in the short-circuit current density. On the other hand, the doping of non-fluorinated Coumarin dye such as Coumarin 2 did not induce such the enhancement effect in the open-circuit voltage. In ultraviolet photoelectron spectroscopies, the doping of Coumarin 307 was found to have no impact on P3HT, but the density of state of PCBM was significantly modified by the doping. The change in the density of state was confirmed also in ultraviolet absorption measurement. Possible explanations for the enhancement in the open-circuit voltage are discussed from the experimental results, and a shift of the vacuum level by the doping can be considered as a direct origin.

  7. Stamping transfer of a quantum dot interlayer for organic photovoltaic cells.

    PubMed

    Jeon, Ji Hye; Wang, Dong Hwan; Park, Hyunmin; Park, Jong Hyeok; Park, O Ok

    2012-06-26

    An organophilic cadmium selenide (CdSe) quantum dot (QD) interlayer was prepared on the active layer in organic solar cells by a stamping transfer method. The mother substrate composed of a UV-cured film on a polycarbonate film with strong solvent resistance makes it possible to spin-coat QDs on it and dry transfer onto an active layer without damaging the active layer. The QD interlayers have been optimized by controlling the concentration of the QD solution. The coverage of QD particles on the active layer was verified by TEM analysis and fluorescence images. After insertion of the QD interlayer between the active layer and metal cathode, the photovoltaic performances of the organic solar cell were clearly enhanced. By ultraviolet photoelectron spectroscopy of CdSe QDs, it can be anticipated that the CdSe QD interlayer reduces charge recombination by blocking the holes moving to the cathode from the active layer and facilitating efficient collection of the electrons from the active layer to the cathode.

  8. Endohedral Fullerenes in Organic Thin Film Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel; Vankeuren, Edward; Drees, Martin; Cardona, Claudia; Holloway, Brian; Guldi, Dirk

    2008-03-01

    Cost factors in inorganic solar cells have opened up a new path to less expensive manufacturing techniques using bulk heterojunction polymer/fullerene based solar cells. Using empty cage fullerene derivatives as the acceptor material, state-of-the-art organic photovoltaics currently display ˜5% overall conversion efficiency. One of the main factors limiting the efficiency in organic solar cells is the low open circuit voltage. The open circuit voltage is governed by the molecular orbitals of the donor and acceptor material; therefore better matching of the orbitals will lead to improved voltages. We present a novel acceptor material based on TRIMETASPHERE^ carbon nanomaterials (TMS). TMS are endohedral metallofullerenes that consist of a trimetal nitride cluster enclosed in a C80 cage. First-generation TMS derivatives have been synthesized; electrochemical and photophysical studies show behavior consistent with C60 but with improved molecular orbitals. The electrochemical data suggests a maximum voltage increase of up to 280 mV over C60-PCBM-based devices. Organic solar cell devices are currently under construction and performance results will also be presented.

  9. Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Cacha, Brian Joseph Gonda

    Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

  10. ENGINEERED ELECTRODES AND ELECTRODE-ORGANIC INTERFACES FOR HIGH-EFFICIENCY ORGANIC PHOTOVOLTAICS

    SciTech Connect

    Tobin J. Marks; R.P.H. Chang; Tom Mason; Ken Poeppelmeier; Arthur J. Freeman

    2008-11-13

    Organic photovoltaic (OPV) cells offer the ultimate promise of low cost, readily manufacturable, and durable solar power. While recent advances have led to cells with impressive performance levels, OPV cells have yet to break the double-digit efficiency barrier. Further gains in efficiency and durability, to that competitive with high-performance inorganic photovoltaics will require breakthroughs in transparent electrode and interfacial materials science and engineering. This project involved an integrated basic research effort carried out by an experienced and highly collaborative interdisciplinary team to address in unconventional ways, critical electrode-interfacial issues underlying OPV performance--controlling band offsets between transparent electrodes and organics, addressing current loss/leakage problems at interfaces, enhancing adhesion, interfacial stability, and device durability while minimizing cost. It synergistically combined materials and interfacial reagent synthesis, nanostructural and photovoltaic characterization, and high level quantum theory. The research foci were: 1) understanding of/development of superior transparent electrode materials and materials morphologies--i.e., better matched electronically and chemically to organic active layers, 2) understanding-based development of inorganic interfacial current-collecting/charge-blocking layers, and 3) understanding-based development of self-assembled adhesion/current-collecting/charge-blocking/cross-linking layers for high-efficiency OPV interfaces. Pursing the goal of developing the fundamental scientific understanding needed to design, fabricate, prototype and ultimately test high-efficiency OPV cells incorporating these new concepts, we achieved a record power conversion efficiency of 5.2% for an organic bulk-heterjunction solar cell.

  11. Virtual screening of electron acceptor materials for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Halls, Mathew D.; Djurovich, Peter J.; Giesen, David J.; Goldberg, Alexander; Sommer, Jonathan; McAnally, Eric; Thompson, Mark E.

    2013-10-01

    Virtual screening involves the generation of structure libraries, automated analysis to predict properties related to application performance and subsequent screening to identify lead systems and estimate critical structure-property limits across a targeted chemical design space. This approach holds great promise for informing experimental discovery and development efforts for next-generation materials, such as organic semiconductors. In this work, the virtual screening approach is illustrated for nitrogen-substituted pentacene molecules to identify systems for development as electron acceptor materials for use in organic photovoltaic (OPV) devices. A structure library of tetra-azapentacenes (TAPs) was generated by substituting four nitrogens for CH at 12 sites on the pentacene molecular framework. Molecular properties (e.g. ELUMO, Eg and μ) were computed for each candidate structure using hybrid DFT at the B3LYP/6-311G** level of theory. The resulting TAPs library was then analyzed with respect to intrinsic properties associated with OPV acceptor performance. Marcus reorganization energies for charge transport for the most favorable TAP candidates were then calculated to further determine suitability as OPV electron acceptors. The synthesis, characterization and OPV device testing of TAP materials is underway, guided by these results.

  12. Lanthanides: new metallic cathode materials for organic photovoltaic cells.

    PubMed

    Nikiforov, Maxim P; Strzalka, Joseph; Jiang, Zhang; Darling, Seth B

    2013-08-21

    Organic photovoltaics (OPVs) are compliant with inexpensive, scalable, and environmentally benign manufacturing technologies. While substantial attention has been focused on optimization of active layer chemistry, morphology, and processing, far less research has been directed to understanding charge transport at the interfaces between the electrodes and the active layer. Electrical properties of these interfaces not only impact efficiency, but also play a central role in stability of organic solar cells. Low work function metals are the most widely used materials for the electron transport layer with Ca being the most common material. In bulk heterojunction OPV devices, low work function metals are believed to mirror the role they play in OLEDs, where such metals are used to control carrier selectivity, transport, extraction, and blocking, as well as interface band bending. Despite their advantages, low work function materials are generally prone to reactions with water, oxygen, nitrogen, and carbon dioxide from air leading to rapid device degradation. Here we discuss the search for a new metallic cathode interlayer material that increases device stability and still provides device efficiency similar to that achieved with a Ca interlayer.

  13. Exciton management in organic photovoltaic multidonor energy cascades.

    PubMed

    Griffith, Olga L; Forrest, Stephen R

    2014-05-14

    Multilayer donor regions in organic photovoltaics show improved power conversion efficiency when arranged in decreasing exciton energy order from the anode to the acceptor interface. These so-called "energy cascades" drive exciton transfer from the anode to the dissociating interface while reducing exciton quenching and allowing improved overlap with the solar spectrum. Here we investigate the relative importance of exciton transfer and blocking in a donor cascade employing diphenyltetracene (D1), rubrene (D2), and tetraphenyldibenzoperiflanthene (D3) whose optical gaps monotonically decrease from D1 to D3. In this structure, D1 blocks excitons from quenching at the anode, D2 accepts transfer of excitons from D1 and blocks excitons at the interface between D2 and D3, and D3 contributes the most to the photocurrent due to its strong absorption at visible wavelengths, while also determining the open circuit voltage. We observe singlet exciton Förster transfer from D1 to D2 to D3 consistent with cascade operation. The power conversion efficiency of the optimized cascade OPV with a C60 acceptor layer is 7.1 ± 0.4%, which is significantly higher than bilayer devices made with only the individual donors. We develop a quantitative model to identify the dominant exciton processes that govern the photocurrent generation in multilayer organic structures. PMID:24702468

  14. Exciton transport, charge extraction, and loss mechanisms in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Scully, Shawn Ryan

    Organic photovoltaics have attracted significant interest over the last decade due to their promise as clean low-cost alternatives to large-scale electric power generation such as coal-fired power, natural gas, and nuclear power. Many believe power conversion efficiency targets of 10-15% must be reached before commercialization is possible. Consequently, understanding the loss mechanisms which currently limit efficiencies to 4-5% is crucial to identify paths to reach higher efficiencies. In this work, we investigate the dominant loss mechanisms in some of the leading organic photovoltaic architectures. In the first class of architectures, which include planar heterojunctions and bulk heterojunctions with large domains, efficiencies are primarily limited by the distance photogenerated excitations (excitons) can be transported (termed the exciton diffusion length) to a heterojunction where the excitons may dissociate. We will discuss how to properly measure the exciton diffusion length focusing on the effects of optical interference and of energy transfer when using fullerenes as quenching layers and show how this explains the variety of diffusion lengths reported for the same material. After understanding that disorder and defects limit exciton diffusion lengths, we suggest some approaches to overcome this. We then extensively investigate the use of long-range resonant energy transfer to increase exciton harvesting. Using simulations and experiments as support, we discuss how energy transfer can be engineered into architectures to increase the distance excitons can be harvested. In an experimental model system, DOW Red/PTPTB, we will show how the distance excitons are harvested can be increased by almost an order of magnitude up to 27 nm from a heterojunction and give design rules and extensions of this concept for future architectures. After understanding exciton harvesting limitations we will look at other losses that are present in planar heterojunctions. One of

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

    PubMed

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

    2016-02-21

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

  16. Systematic investigation of organic photovoltaic cell charge injection/performance modulation by dipolar organosilane interfacial layers.

    PubMed

    Song, Charles Kiseok; White, Alicia C; Zeng, Li; Leever, Benjamin J; Clark, Michael D; Emery, Jonathan D; Lou, Sylvia J; Timalsina, Amod; Chen, Lin X; Bedzyk, Michael J; Marks, Tobin J

    2013-09-25

    With the goal of investigating and enhancing anode performance in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells, the glass/tin-doped indium oxide (ITO) anodes are modified with a series of robust silane-tethered bis(fluoroaryl)amines to form self-assembled interfacial layers (IFLs). The modified ITO anodes are characterized by contact angle measurements, X-ray reflectivity, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, atomic force microscopy, and cyclic voltammetry. These techniques reveal the presence of hydrophobic amorphous monolayers of 6.68 to 9.76 Å thickness, and modified anode work functions ranging from 4.66 to 5.27 eV. Two series of glass/ITO/IFL/active layer/LiF/Al BHJ OPVs are fabricated with the active layer = poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) or poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]thi-eno[3,4-b]thiophenediyl

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  19. Band-Tail Transport of CuSCN: Origin of Hole Extraction Enhancement in Organic Photovoltaics.

    PubMed

    Kim, Minju; Park, Soohyung; Jeong, Junkyeong; Shin, Dongguen; Kim, Jimin; Ryu, Sae Hee; Kim, Keun Su; Lee, Hyunbok; Yi, Yeonjin

    2016-07-21

    Copper thiocyanate (CuSCN) is known as a promising hole transport layer in organic photovoltaics (OPVs) due to its good hole conduction and exciton blocking abilities with high transparency. Despite its successful device applications, the origin of its hole extraction enhancement in OPVs has not yet been understood. Here, we investigated the electronic structure of CuSCN and the energy level alignment at the poly(3-hexylthiophene-2,5-diyl) (P3HT)/CuSCN/ITO interfaces using ultraviolet photoelectron spectroscopy. The band-tail states of CuSCN close to the Fermi level (EF) were observed at 0.25 eV below the EF, leading to good hole transport. The CuSCN interlayer significantly reduces the hole transport barrier between ITO and P3HT due to its high work function and band-tail states. The barrier reduction leads to enhanced current density-voltage characteristics of hole-dominated devices. These results provide the origin of hole-extraction enhancement by CuSCN and insights for further application.

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

    PubMed

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

    2016-02-21

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

  1. Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters.

    PubMed

    Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas; Jagals, Paul; Stuetz, Richard

    2014-09-15

    For many decades, populations in rural and remote developing regions will be unable to access centralised piped potable water supplies, and indeed, decentralised options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, ultraviolet (UV) light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technology is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). Our review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technology (e.g. UV-A, visible light, Advanced Oxidation), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technology should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities especially UV-A, photocatalyst/photosensitiser use and pulsed emission options. PMID:24946032

  2. Photovoltaic powered ultraviolet and visible light-emitting diodes for sustainable point-of-use disinfection of drinking waters.

    PubMed

    Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas; Jagals, Paul; Stuetz, Richard

    2014-09-15

    For many decades, populations in rural and remote developing regions will be unable to access centralised piped potable water supplies, and indeed, decentralised options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, ultraviolet (UV) light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technology is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). Our review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technology (e.g. UV-A, visible light, Advanced Oxidation), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technology should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities especially UV-A, photocatalyst/photosensitiser use and pulsed emission options.

  3. Enhanced Performance and Stability in Polymer Photovoltaic Cells Using Ultraviolet-Treated PEDOT:PSS

    NASA Astrophysics Data System (ADS)

    Xu, Xue-Jian; Yang, Li-Ying; Tian, Hui; Qin, Wen-Jing; Yin, Shou-Gen; Zhang, Fengling

    2013-07-01

    We investigate the effects of ultraviolet (UV) irradiation treatment with varying irradiation intensities for different treatment times of poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film on the performance and stability of polymer solar cells (PSCs) based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend. Ultraviolet-visible transmission spectra, x-ray photoelectron spectroscopy, contact angle measurement, atomic force microscopy and the Kelvin probe method are conducted to characterize the UV-treated PEDOT:PSS film. The results demonstrate that UV treatment can improve the power conversion efficiency (PCE) and stability of PSCs effectively. The best performance is achieved under 1200 μW/cm2 UV treatment for 50 min. Compared to the control device, the optimized device exhibits enhanced performance with a Voc of 0.59 V, Jsc of 12.3 mA/cm2, fill factor of 51%, and PCE of 3.64%, increased by 3.5%, 33%, 8.7% and 50%, respectively. The stability of the PSCs is enhanced by 2.5 times simply through the UV treatment on the PEDOT:PSS buffer layer. The improvement in the device performance and stability is attributed to the improvement in the wettability property and the increase in the work function of the PEDOT:PSS film by UV treatment, while the impact of UV treatment on the transparency of the PEDOT:PSS film is negligible. The strategy of using UV treatment to improve device performance and stability is attractive due to its simplicity, cost-effectiveness, and because it is suitable for large-scale commercial production.

  4. Optical Spintronics in Organic-Inorganic Perovskite Photovoltaics

    PubMed Central

    Li, Junwen; Haney, Paul M.

    2016-01-01

    Organic-inorganic halide CH3NH3PbI3 solar cells have attracted enormous attention in recent years due to their remarkable power conversion efficiency. When inversion symmetry is broken, these materials should exhibit interesting spin-dependent properties as well, owing to their strong spin-orbit coupling. In this work, we consider the spin-dependent optical response of CH3NH3PbI3. We first use density functional theory to compute the ballistic spin current generated by absorption of unpolarized light. We then consider diffusive transport of photogenerated charge and spin for a thin CH3NH3PbI3 layer with a passivated surface and an Ohmic, non-selective contact. The spin density and spin current are evaluated by solving the drift-diffusion equations for a simplified 3-dimensional Rashba model of the electronic structure of the valence and conduction bands. We provide analytic expressions for the photon flux required to induce measurable spin densities, and propose that these spin densities can provide useful information about the role of grain boundaries in the photovoltaic behavior of these materials. We also discuss the prospects for measuring the optically generated spin current with the inverse spin Hall effect. PMID:27453958

  5. Intrinsic coincident linear polarimetry using stacked organic photovoltaics.

    PubMed

    Roy, S Gupta; Awartani, O M; Sen, P; O'Connor, B T; Kudenov, M W

    2016-06-27

    Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter.

  6. Computational Design of Photovoltaic Materials with Self Organized Nano Structures

    NASA Astrophysics Data System (ADS)

    Sato, Kazunori; Katayama-Yoshida, Hiroshi

    2013-03-01

    Chalcopyrite and II-VI semiconductors, such as Cu(In, Ga)Se2, Cu2ZnSn(S, Se)4 and Cd(S, Te), are one of the most promising materials for low cost photovoltaic solar-cells. In this paper, based on first-principles calculations, we propose that self-organized nano-structures in these compounds will enhance the conversion efficiency. Our calculations are based on the KKR-CPA-LDA with the self-interaction correction. We also use VASP package for calculating mixing energy and effective interactions of the systems by using the cluster expansion method. For phase separating systems, we simulate nano-structure formation by using the Monte Carlo method. It is expected that the photo-generated electron-hole pairs are efficiently separated by the type-II interface and then effectively transferred along the quasi-one-dimensional structures. Moreover, we can expect multiplication of generated carriers due to the multi-exciton effects in nano-structures.

  7. Fullerene derivatives as electron donor for organic photovoltaic cells

    SciTech Connect

    Zhuang, Taojun; Wang, Xiao-Feng E-mail: ziruo@yz.yamagata-u.ac.jp; Sano, Takeshi; Kido, Junji; Hong, Ziruo E-mail: ziruo@yz.yamagata-u.ac.jp; Yang, Yang

    2013-11-11

    We demonstrated the performance of unconventional, all-fullerene-based, planar heterojunction (PHJ) organic photovoltaic (OPV) cells using fullerene derivatives indene-C{sub 60} bisadduct (ICBA) and phenyl C{sub 61}-butyric acid methyl ester as the electron donors with fullerene C{sub 70} as the electron acceptor. Two different charge generation processes, including charge generation in the fullerene bulk and exciton dissociation at the donor-acceptor interface, have been found to exist in such all-fullerene-based PHJ cells and the contribution to the total photocurrent from each process is strongly dependent on the thickness of fullerene donor. The optimized 5 nm ICBA/40 nm C{sub 70} PHJ cell gives clear external quantum efficiency responses for the long-wavelength photons corresponding to the dissociation of strongly bound Frenkel excitons, which is hardly observed in fullerene-based single layer reference devices. This approach using fullerene as a donor material provides further possibilities for developing high performance OPV cells.

  8. Selective Interlayers and Contacts in Organic Photovoltaic Cells

    SciTech Connect

    Ratcliff, Erin L.; Zacher, Brian; Armstrong, Neal R.

    2011-06-02

    Organic photovoltaic cells (OPVs) are promising solar electric energy conversion systems with impressive recent optimization of active layers. OPV optimization must now be accompanied by the development of new charge-selective contacts and interlayers. This Perspective considers the role of interface science in energy harvesting using OPVs, looking back at early photoelectrochemical (photogalvanic) energy conversion platforms, which suffered from a lack of charge carrier selectivity. We then examine recent platforms and the fundamental aspects of selective harvesting of holes and electrons at opposite contacts. For blended heterojunction OPVs, contact/interlayer design is especially critical because charge harvesting competes with recombination at these same contacts. New interlayer materials can modify contacts to both control work function and introduce selectivity and chemical compatibility with nonpolar active layers and add thermodynamic and kinetic selectivity to charge harvesting. We briefly discuss the surface and interface science required for the development of new interlayer materials and take a look ahead at the challenges yet to be faced in their optimization

  9. Selective Interlayers and Contacts in Organic Photovoltaic Cells.

    PubMed

    Ratcliff, Erin L; Zacher, Brian; Armstrong, Neal R

    2011-06-01

    Organic photovoltaic cells (OPVs) are promising solar electric energy conversion systems with impressive recent optimization of active layers. OPV optimization must now be accompanied by the development of new charge-selective contacts and interlayers. This Perspective considers the role of interface science in energy harvesting using OPVs, looking back at early photoelectrochemical (photogalvanic) energy conversion platforms, which suffered from a lack of charge carrier selectivity. We then examine recent platforms and the fundamental aspects of selective harvesting of holes and electrons at opposite contacts. For blended heterojunction OPVs, contact/interlayer design is especially critical because charge harvesting competes with recombination at these same contacts. New interlayer materials can modify contacts to both control work function and introduce selectivity and chemical compatibility with nonpolar active layers and add thermodynamic and kinetic selectivity to charge harvesting. We briefly discuss the surface and interface science required for the development of new interlayer materials and take a look ahead at the challenges yet to be faced in their optimization. PMID:26295432

  10. Selective Interlayers and Contacts in Organic Photovoltaic Cells.

    PubMed

    Ratcliff, Erin L; Zacher, Brian; Armstrong, Neal R

    2011-06-01

    Organic photovoltaic cells (OPVs) are promising solar electric energy conversion systems with impressive recent optimization of active layers. OPV optimization must now be accompanied by the development of new charge-selective contacts and interlayers. This Perspective considers the role of interface science in energy harvesting using OPVs, looking back at early photoelectrochemical (photogalvanic) energy conversion platforms, which suffered from a lack of charge carrier selectivity. We then examine recent platforms and the fundamental aspects of selective harvesting of holes and electrons at opposite contacts. For blended heterojunction OPVs, contact/interlayer design is especially critical because charge harvesting competes with recombination at these same contacts. New interlayer materials can modify contacts to both control work function and introduce selectivity and chemical compatibility with nonpolar active layers and add thermodynamic and kinetic selectivity to charge harvesting. We briefly discuss the surface and interface science required for the development of new interlayer materials and take a look ahead at the challenges yet to be faced in their optimization.

  11. Performance limits of plasmon-enhanced organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Karatay, Durmus U.; Salvador, Michael; Yao, Kai; Jen, Alex K.-Y.; Ginger, David S.

    2014-07-01

    We use a combination of experiment and modeling to explore the promise and limitations of using plasmon-resonant metal nanoparticles to enhance the device performance of organic photovoltaics (OPVs). We focus on optical properties typical of the current generation of low-bandgap donor polymers blended with the fullerene (6,6)-phenyl C71-butyric acid methyl ester (PC71BM) and use the polymer poly(indacenodithiophene-co-phenanthro[9,10-b]quinoxaline) (PIDT-PhanQ) as our test case. We model the optical properties and performance of these devices both in the presence and absence of a variety of colloidal silver nanoparticles. We show that for these materials, device performance is sensitive to the relative z-position and the density of nanoparticles inside the active layer. Using conservative estimates of the internal quantum efficiency for the PIDT-PhanQ/PC71BM blend, we calculate that optimally placed silver nanoparticles could yield an enhancement in short-circuit current density of over 31% when used with ˜ 80-nm-thick active layers, resulting in an absolute increase in power conversion efficiency of up to ˜2% for the device based on optical engineering.

  12. Quantitative bimolecular recombination in organic photovoltaics through triplet exciton formation.

    PubMed

    Chow, Philip C Y; Gélinas, Simon; Rao, Akshay; Friend, Richard H

    2014-03-01

    The nanoscale morphology and high charge densities in organic photovoltaics (OPVs) lead to a high rate of bimolecular encounters between spin-uncorrelated electrons and holes. This process can lead to the formation of low-energy triplet excitons on the donor polymer that decay nonradiatively and limit the device performance. We use time-resolved optical spectroscopy to characterize the effect of morphology through the use of solvent additives such as 1,8-octanedithiol (ODT) on triplet dynamics and charge recombination in blends of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] and [6,6]-phenyl-C71-butyric acid methyl ester. This is an attractive OPV system since the extended absorption of the polymer into the near-infrared gives good coverage of the solar spectrum, but nevertheless, the internal quantum efficiency (IQE) has not been reported to be higher than ~65% under short circuit conditions. We find that, without ODT, the IQE is 48% and 16% of excitations decay via bimolecular triplet formation. With ODT treatment, which improves crystallinity and carrier mobility, the IQE increases to 65%, but bimolecular triplet formation significantly increases and now accounts for all of the recombination (35% of charges). PMID:24521399

  13. Optical spintronics in organic-inorganic perovskite photovoltaics

    NASA Astrophysics Data System (ADS)

    Li, Junwen; Haney, Paul M.

    2016-04-01

    Organic-inorganic halide CH3NH3PbI3 solar cells have attracted enormous attention in recent years due to their remarkable power conversion efficiency. When inversion symmetry is broken, these materials should exhibit interesting spin-dependent properties as well, owing to their strong spin-orbit coupling. In this work, we consider the spin-dependent optical response of CH3NH3PbI3 . We first use density functional theory to compute the ballistic spin current generated by absorption of unpolarized light. We then consider diffusive transport of photogenerated charge and spin for a thin CH3NH3PbI3 layer with a passivated surface and an Ohmic, nonselective contact. The spin density and spin current are evaluated by solving the drift-diffusion equations for a simplified three-dimensional Rashba model of the electronic structure of the valence and conduction bands. We provide analytic expressions for the photon flux required to induce measurable spin densities, and propose that these spin densities can provide useful information about the role of grain boundaries in the photovoltaic behavior of these materials. We also discuss the prospects for measuring the optically generated spin current with the inverse spin Hall effect.

  14. Complete intrinsic coincident polarimetry using stacked organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Gupta Roy, S.; Awartani, O. M.; Sen, P.; O'Connor, B. T.; Kudenov, M. W.

    2015-09-01

    Measuring the 2 dimensional Stokes vector, to determine the polarization state of light, finds application in multiple areas, including the characterization of aerosol size distributions, target identification, quality control by evaluating the distribution of stress birefringence, resolving data channels in telecommunications, and for evaluating biological tissues in medical imaging. Conventional methods, such as channeled and division of focal plane polarimeters, usually limit spatial resolution, while others, like division of aperture or division of amplitude polarimeters, have higher complexity and less compactness. To help solve these issues, we have developed a system that uses semitransparent organic photovoltaics (OPVs) as photodetectors. The active area of the devices consist of biaxially oriented polymer films, which enables the device to preferentially absorb certain polarized states of incident light, depending on the orientation of the polymer chains. Taking advantage of the cells' transparency and ease of processing, compared to inorganic materials, enables multiple devices to be "stacked" along the optical axis. Presently, experiments have been conducted to detect linear polarization states of light. We use three stacked OPVs, where each device can measure one of the first three Stokes parameters simultaneously, thereby ensuring high spatial and temporal resolution with inherent spatial registration. In this paper, the fabrication of the OPVs and the design and calibration technique is documented, along with experimental data, supporting the hypothesis.

  15. Computational screening of organic materials towards improved photovoltaic properties

    NASA Astrophysics Data System (ADS)

    Dai, Shuo; Olivares-Amaya, Roberto; Amador-Bedolla, Carlos; Aspuru-Guzik, Alan; Borunda, Mario

    2015-03-01

    The world today faces an energy crisis that is an obstruction to the development of the human civilization. One of the most promising solutions is solar energy harvested by economical solar cells. Being the third generation of solar cell materials, organic photovoltaic (OPV) materials is now under active development from both theoretical and experimental points of view. In this study, we constructed a parameter to select the desired molecules based on their optical spectra performance. We applied it to investigate a large collection of potential OPV materials, which were from the CEPDB database set up by the Harvard Clean Energy Project. Time dependent density functional theory (TD-DFT) modeling was used to calculate the absorption spectra of the molecules. Then based on the parameter, we screened out the top performing molecules for their potential OPV usage and suggested experimental efforts toward their synthesis. In addition, from those molecules, we summarized the functional groups that provided molecules certain spectrum capability. It is hoped that useful information could be mined out to provide hints to molecular design of OPV materials.

  16. Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics.

    PubMed

    Salim, Teddy; Lek, Jun Yan; Bräuer, Björn; Fichou, Denis; Lam, Yeng Ming

    2014-11-21

    The morphology of donor-acceptor blends holds the key to good performance through the balancing of good exciton dissociation efficiency and interconnectivity for good charge collection. In this work, the good morphology is preserved in ternary blend systems through the use of poly(3-hexylthiophene) (P3HT) nanofibers. The iridium(III)-based metal complex is incorporated in P3HT-PCBM blends as a triplet exciton sensitizer in the bulk heterojunction (BHJ) organic photovoltaics (OPV). The devices using triplet-sensitized ternary blends of P3HT experience a significant degradation in performance, a tendency further aggravated by thermal treatment. This is due to disruption in the morphology thus affecting charge generation and collection. In order to overcome these morphological issues and to circumvent the restriction due to the crystallization of the polymers, here we demonstrate the use of pre-assembled nanofibers in these ternary blends. The concept of stabilizing the nanomorphology of the blend material through the use of nanofibers can also be applied to other ternary systems.

  17. Molecular materials for organic photovoltaics: small is beautiful.

    PubMed

    Roncali, Jean; Leriche, Philippe; Blanchard, Philippe

    2014-06-18

    An overview of some recent developments of the chemistry of molecular donor materials for organic photovoltaics (OPV) is presented. Although molecular materials have been used for the fabrication of OPV cells from the very beginning of the field, the design of molecular donors specifically designed for OPV is a relatively recent research area. In the past few years, molecular donors have been used in both vacuum-deposited and solution-processed OPV cells and both fields have witnessed impressive progress with power conversion efficiencies crossing the symbolic limit of 10 %. However, this progress has been achieved at the price of an increasing complexity of the chemistry of active materials and of the technology of device fabrication. This evolution probably inherent to the progress of research is difficult to reconcile with the necessity for OPV to demonstrate a decisive economic advantage over existing silicon technology. In this short review various classes of molecular donors are discussed with the aim of defining possible basic molecular structures that can combine structural simplicity, low molecular weight, synthetic accessibility, scalability and that can represent possible starting points for the development of simple and cost-effective OPV materials.

  18. Performance limits of plasmon-enhanced organic photovoltaics

    SciTech Connect

    Karatay, Durmus U.; Ginger, David S.; Salvador, Michael; Yao, Kai; Jen, Alex K.-Y.

    2014-07-21

    We use a combination of experiment and modeling to explore the promise and limitations of using plasmon-resonant metal nanoparticles to enhance the device performance of organic photovoltaics (OPVs). We focus on optical properties typical of the current generation of low-bandgap donor polymers blended with the fullerene (6,6)-phenyl C{sub 71}-butyric acid methyl ester (PC{sub 71}BM) and use the polymer poly(indacenodithiophene-co-phenanthro[9,10-b]quinoxaline) (PIDT-PhanQ) as our test case. We model the optical properties and performance of these devices both in the presence and absence of a variety of colloidal silver nanoparticles. We show that for these materials, device performance is sensitive to the relative z-position and the density of nanoparticles inside the active layer. Using conservative estimates of the internal quantum efficiency for the PIDT-PhanQ/PC{sub 71}BM blend, we calculate that optimally placed silver nanoparticles could yield an enhancement in short-circuit current density of over 31% when used with ∼ 80-nm-thick active layers, resulting in an absolute increase in power conversion efficiency of up to ∼2% for the device based on optical engineering.

  19. Intrinsic coincident linear polarimetry using stacked organic photovoltaics.

    PubMed

    Roy, S Gupta; Awartani, O M; Sen, P; O'Connor, B T; Kudenov, M W

    2016-06-27

    Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter. PMID:27410627

  20. Self-organized discotic liquid crystals for high-efficiency organic photovoltaics.

    PubMed

    Schmidt-Mende, L; Fechtenkötter, A; Müllen, K; Moons, E; Friend, R H; MacKenzie, J D

    2001-08-10

    Self-organization of liquid crystalline and crystalline-conjugated materials has been used to create, directly from solution, thin films with structures optimized for use in photodiodes. The discotic liquid crystal hexa-peri-hexabenzocoronene was used in combination with a perylene dye to produce thin films with vertically segregated perylene and hexabenzocoronene, with large interfacial surface area. When incorporated into diode structures, these films show photovoltaic response with external quantum efficiencies of more than 34 percent near 490 nanometers. These efficiencies result from efficient photoinduced charge transfer between the hexabenzocoronene and perylene, as well as from effective transport of charges through vertically segregated perylene and hexabenzocoronene pi systems. This development demonstrates that complex structures can be engineered from novel materials by means of simple solution-processing steps and may enable inexpensive, high-performance, thin-film photovoltaic technology.

  1. Formation of organic crystalline nanopillar arrays and their application to organic photovoltaic cells.

    PubMed

    Hirade, Masaya; Nakanotani, Hajime; Yahiro, Masayuki; Adachi, Chihaya

    2011-01-01

    To enhance the performance of organic photovoltaic (OPV) cells, preparation of organic nanometer-sized pillar arrays is fascinating because a significantly large area of a donor/acceptor heterointerface having continuous conduction path to both anode and cathode electrodes can be realized. In this study, we grew cupper phthalocyanine (CuPc) crystalline nanopillar arrays by conventional thermal gradient sublimation technique using a few-nanometer-sized trigger seeds composed of a CuPc and 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) stacked layer. We optimized the pillar density by tuning crystal growth condition in order to apply it to OPV cells.

  2. Organic photovoltaics: potential fate and effects in the environment.

    PubMed

    Zimmermann, Yannick-Serge; Schäffer, Andreas; Hugi, Christoph; Fent, Karl; Corvini, Philippe F-X; Lenz, Markus

    2012-11-15

    In times of dwindling fossil fuels it is particularly crucial to develop novel "green" technologies in order to cover the increasing worldwide demand for energy. Organic photovoltaic solar cells (OPVs) are promising as a renewable energy source due to low energy requirement for production, low resource extraction, and no emission of greenhouse gasses during use. In contrast to silicium-based solar cells, OPVs offer the advantages of light-weight, semi-transparency and mechanical flexibility. As to a possible forthcoming large-scale production, the environmental impact of such OPVs should be assessed and compared to currently best available technologies. For the first time, this review compiles the existing knowledge and identifies gaps regarding the environmental impact of such OPVs in a systematic manner. In this regard, we discuss the components of a typical OPV layer by layer. We discuss the probability of enhanced release of OPV-borne components into the environment during use-phase (e.g. UV- and biodegradation) and end-of-life phase (e.g. incineration and waste disposal). For this purpose, we compiled available data on bioavailability, bioaccumulation, biodegradation, and ecotoxicity. Whereas considerable research has already been carried out concerning the ecotoxicity of certain OPV components (e.g. nanoparticles and fullerenes), others have not been investigated at all so far. In conclusion, there is a general lack of information about fate, behavior as well as potential ecotoxicity of most of the main OPV components and their degradation/transformation products. So far, there is no evidence for a worrying threat coming from OPVs, but since at present, no policy and procedures regarding recycling of OPVs are in action, in particular improper disposal upon end-of-life might result in an adverse effect of OPVs in the environment when applied in large-scale.

  3. Distance distributions of photogenerated charge pairs in organic photovoltaic cells.

    PubMed

    Barker, Alex J; Chen, Kai; Hodgkiss, Justin M

    2014-08-27

    Strong Coulomb interactions in organic photovoltaic cells dictate that charges must separate over relatively long distances in order to circumvent geminate recombination and produce photocurrent. In this article, we measure the distance distributions of thermalized charge pairs by accessing a regime at low temperature where charge pairs are frozen out following the primary charge separation step and recombine monomolecularly via tunneling. The exponential attenuation of tunneling rate with distance provides a sensitive probe of the distance distribution of primary charge pairs, reminiscent of electron transfer studies in proteins. By fitting recombination dynamics to distributions of recombination rates, we identified populations of charge-transfer states and well-separated charge pairs. For the wide range of materials we studied, the yield of separated charges in the tunneling regime is strongly correlated with the yield of free charges measured via their intensity-dependent bimolecular recombination dynamics at room temperature. We therefore conclude that populations of free charges are established via long-range charge separation within the thermalization time scale, thus invoking early branching between free and bound charges across an energetic barrier. Subject to assumed values of the electron tunneling attenuation constant, we estimate critical charge separation distances of ∼3-4 nm in all materials. In some blends, large fullerene crystals can enhance charge separation yields; however, the important role of the polymers is also highlighted in blends that achieved significant charge separation with minimal fullerene concentration. We expect that our approach of isolating the intrinsic properties of primary charge pairs will be of considerable value in guiding new material development and testing the validity of proposed mechanisms for long-range charge separation.

  4. A critical test of organic P-N photovoltaic cells

    SciTech Connect

    Bird, G.R.

    1996-09-01

    We present an urgent view of the field of organic solid state photovoltaic cells. This is a proper time to select the most promising materials from the Electrophotographic Industry, materials long tried in terms of stability, high quantum yield of charge carriers, but set apart by unusually high quantum yields at low applied fields. Our experience with the candidate dyes has covered new tests for identifiable impurities and removal of these impurities by verifiable methods. A new method of purification, reactive train sublimation, has been developed for DNT, one of the simplest of the outstanding perylene dyes, and the method seems applicable to some of the other promising perylene derivatives. It removes the offending impurity by converting it into the desired pure product. The role of water of hydration in the {open_quotes}wine cellar effect{close_quotes}, the slowly rising performance of newly made phthalocyanine containing cells has been analyzed. Under the concept of feasibility testing before a final refinement for practicality of materials and production methods, the hydration can be controlled for high level testing. At the same time, efforts go forward to eliminate the need. At least one of the best phthalocyanine components, X-H{sub 2}Pc, does not require water for peak performance. Finally, we have attacked BBIP (bis-benzimidazole perylene) one of the best and most enigmatic of the near infrared sensors. It has long been known and used as a mixture of synthetic isomers, and we hypothesize that either of these would be better than the uncontrolled mixture. A partial success in the form of isolating highly enriched crystals for an X-ray structure of the trans-molecule, is first presented here. A simple optical analysis method has been developed to follow enrichment procedures. For all of its difficult history, this material seems closest to a state of readiness for critical feasibility testing.

  5. Porphyrin Based Near Infrared-Absorbing Materials for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhong, Qiwen

    The conservation and transformation of energy is essential to the survival of mankind, and thus concerns every modern society. Solar energy, as an everlasting source of energy, holds one of the key solutions to some of the most urgent problems the world now faces, such as global warming and the oil crisis. Advances in technologies utilizing clean, abundant solar energy, could be the steering wheel of our societies. Solar cells, one of the major advances in converting solar energy into electricity, are now capturing people's interest all over the globe. While solar cells have been commercially available for many years, the manufacturing of solar cells is quite expensive, limiting their broad based implementation. The cost of solar cell based electricity is 15-50 cents per kilowatt hour (¢/kwh), depending on the type of solar cell, compared to 0.7 ¢/kwh for fossil fuel based electricity. Clearly, decreasing the cost of electricity from solar cells is critical for their wide spread deployment. This will require a decrease in the cost of light absorbing materials and material processing used in fabricating the cells. Organic photovoltaics (OPVs) utilize organic materials such as polymers and small molecules. These devices have the advantage of being flexible and lower cost than conventional solar cells built from inorganic semiconductors (e.g. silicon). The low cost of OPVs is tied to lower materials and fabrication costs of organic cells. However, the current power conversion efficiencies of OPVs are still below 15%, while convention crystalline Si cells have efficiencies of 20-25%. A key limitation in OPVs today is their inability to utilize the near infrared (NIR) portion of the solar spectrum. This part of the spectrum comprises nearly half of the energy in sunlight that could be used to make electricity. The first and foremost step in conversion solar energy conversion is the absorption of light, which nature has provided us optimal model of, which is

  6. Charge extraction from nanostructured hybrid organic-inorganic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Goh, Chiatzun

    Conjugated polymers are attractive for use in photovoltaic (PV) cells because they are highly absorptive, their absorption spectrum can be tuned to match various regions of the solar spectrum and their solubility in common solvents enables the use of low-cost printing technique to mass produce PV panels. Photoexcitation of conjugated polymers forms excitons, which are bound electron-hole pairs. In order to convert these excitons into free carriers, the polymers have to be blended with an electron acceptor in close promixity of ˜10 nm. The charge transfer process at the donor-acceptor interface provides the necessary driving force to split excitons, while the close proximity guarantees excitons reaching an interface before decaying. Once the carriers are split, they have to be transported to their respective electrodes before recombining. Ordered nanostructured titania (TiO2) matrix infiltrated with conjugated polymers is a promising acceptor-donor system, which can potentially meet these requirements. In this work, several optimizations are shown to be essential for increasing the performance of TiO2/polymer cells. First, we measure the hole mobility of poly(3-hexylthiophene) (P3HT) in a thin film diode in the space-charge limited regime. We show that the mobility increases with the polymer molecular weight and can be correlated to the film morphology. The anisotropy in P3HT chain packing suggests that its diode mobility of 10-4 cm 2/Vs can be further enhanced upon chain alignment in straight nanopores. Second, we investigate the use of molecular surface modification to control the interfacial energetics and charge transfer dynamics. By introducing dipoles at the TiO2/P3HT interface, the interfacial energy offset can be changed resulting in a concomitant change in the open circuit voltage. In addition, certain modifiers improve exciton harvesting by mediating charge transfer from the polymer to TiO2. We further show that the use of an amphiphilic molecule

  7. Comparison of graphene oxide with reduced graphene oxide as hole extraction layer in organic photovoltaic cells.

    PubMed

    Choi, Kyoung Soon; Park, Yensil; Kim, Soo Young

    2013-05-01

    A comparison was performed between the use of graphene oxide (GO) and reduced graphene oxide (rGO) as a hole extraction layer (HEL) in organic photovoltaic (OPV) cells with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester. Hydrazine hydrate (HYD) and the thermal method (Thermal) were adopted to change the GO to rGO. The GO HEL was deposited on an indium tin oxide electrode by spin coating, followed by the reduction process to form the rGO HELs. The success of the reduction processes was confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoemission spectroscopy, transmittance, and 2-point probe method. The OPV cell with the GO (-3 nm) HEL exhibits an increased power conversion efficiency (PCE) as high as 2.5% under 100 mW/cm2 illumination under air mass conditions, which is higher than that of the OPV cell without HEL, viz. 1.78%. However, the PCE of the OPV cell with rGO HEL is not high as the values of 1.8% for the HYD-rGO and 1.9% for the Thermal-rGO. The ultraviolet photoemission spectroscopy results showed that the work function of GO was 4.7 eV, but those of HYD-rGO and Thermal-rGO were 4.2 eV and 4.5 eV, respectively. Therefore, it is considered that GO is adequate to extract the holes from the active layer, but HYD-rGO and Thermal-rGO are not appropriate to use as HELs in OPV cells from the viewpoint of the energy alignment.

  8. Tetracene dicarboxylic imide and its disulfide: synthesis of ambipolar organic semiconductors for organic photovoltaic cells.

    PubMed

    Okamoto, Toshihiro; Suzuki, Tsuyoshi; Tanaka, Hideyuki; Hashizume, Daisuke; Matsuo, Yutaka

    2012-01-01

    We have designed and synthesized a new donor/acceptor-type tetracene derivative by the introduction of dicarboxylic imide and disulfide groups as electron-withdrawing and -donating units, respectively. The prepared compounds, tetracene dicarboxylic imide (TI) and its disulfide (TIDS) have high chemical and electrochemical stability as well as long-wavelength absorptions of up to 886 nm in the thin films. The crystal packing structure of TIDS molecules features face-to-face π-stacking, derived from dipole-dipole interactions. Notably, TIDS exhibited ambipolar properties of both electron-donating and -accepting natures in p-n and p-i-n heterojunction organic thin-film photovoltaic devices. Accordingly, TI and TIDS are expected to be promising compounds for designing new organic semiconductors.

  9. End-group-directed self-assembly of organic compounds useful for photovoltaic applications

    DOEpatents

    Beaujuge, Pierre M.; Lee, Olivia P.; Yiu, Alan T.; Frechet, Jean M.J.

    2016-05-31

    The present invention provides for an organic compound comprising electron deficient unit covalently linked to two or more electron rich units. The present invention also provides for a device comprising the organic compound, such as a light-emitting diode, thin-film transistor, chemical biosensor, non-emissive electrochromic, memory device, photovoltaic cells, or the like.

  10. Dominant effects of first monolayer energetics at donor/acceptor interfaces on organic photovoltaics.

    PubMed

    Izawa, Seiichiro; Nakano, Kyohei; Suzuki, Kaori; Hashimoto, Kazuhito; Tajima, Keisuke

    2015-05-20

    Energy levels of the first monolayer are manipulated at donor/acceptor interfaces in planar heterojunction organic photovoltaics by using molecular self-organization. A "cascade" energy landscape allows thermal-activation-free charge generation by photoirradiation, destabilizes the energy of the interfacial charge-transfer state, and suppresses bimolecular charge recombination, resulting in a higher open-circuit voltage and fill factor.

  11. Design of donor-acceptor star-shaped oligomers for efficient solution-processible organic photovoltaics.

    PubMed

    Ponomarenko, S A; Luponosov, Y N; Min, J; Solodukhin, A N; Surin, N M; Shcherbina, M A; Chvalun, S N; Ameri, T; Brabec, C

    2014-01-01

    This contribution describes recent progress in the design, synthesis and properties of solution-processible star-shaped oligomers and their application in organic photovoltaics. Even though alternative chemistry has been used to design such oligomers, the most successful approach is based on a triphenylamine donor branching center, (oligo)thiophene conjugated spacers and dicyanovinyl acceptor groups. These are mainly amorphous low band-gap organic semiconductors, though crystalline or liquid crystalline ordering can sometimes be realized. It was shown that the solubility, thermal behavior and structure of such molecules in the bulk strongly depend on the presence and position of alkyl groups, as well as on their length. The photovoltaic properties of solution-processed molecules of this type are now approaching 5% which exceeds those of vacuum-sublimed devices. The design rules and future perspectives of this class of organic photovoltaic molecules are discussed. PMID:25277550

  12. Design of donor-acceptor star-shaped oligomers for efficient solution-processible organic photovoltaics.

    PubMed

    Ponomarenko, S A; Luponosov, Y N; Min, J; Solodukhin, A N; Surin, N M; Shcherbina, M A; Chvalun, S N; Ameri, T; Brabec, C

    2014-01-01

    This contribution describes recent progress in the design, synthesis and properties of solution-processible star-shaped oligomers and their application in organic photovoltaics. Even though alternative chemistry has been used to design such oligomers, the most successful approach is based on a triphenylamine donor branching center, (oligo)thiophene conjugated spacers and dicyanovinyl acceptor groups. These are mainly amorphous low band-gap organic semiconductors, though crystalline or liquid crystalline ordering can sometimes be realized. It was shown that the solubility, thermal behavior and structure of such molecules in the bulk strongly depend on the presence and position of alkyl groups, as well as on their length. The photovoltaic properties of solution-processed molecules of this type are now approaching 5% which exceeds those of vacuum-sublimed devices. The design rules and future perspectives of this class of organic photovoltaic molecules are discussed.

  13. Diarylindenotetracenes via a selective cross-coupling/C-H functionalization: electron donors for organic photovoltaic cells.

    PubMed

    Gu, Xingxian; Luhman, Wade A; Yagodkin, Elisey; Holmes, Russell J; Douglas, Christopher J

    2012-03-16

    A direct synthesis of new donor materials for organic photovoltaic cells is reported. Diaryindenotetracenes were synthesized utilizing a Kumada-Tamao-Corriu cross-coupling of peri-substituted tetrachlorotetracene with spontaneous indene annulation via C-H activation. Vacuum deposited planar heterojunction organic photovoltaic cells incorporating these molecules as electron donors exhibit power conversion efficiencies exceeding 1.5% with open-circuit voltages ranging from 0.7 to 1.1 V when coupled with C(60) as an electron acceptor.

  14. Singlet Fission of Non-polycyclic Aromatic Molecules in Organic Photovoltaics.

    PubMed

    Kawata, So; Pu, Yong-Jin; Saito, Ayaka; Kurashige, Yuki; Beppu, Teruo; Katagiri, Hiroshi; Hada, Masaki; Kido, Junji

    2016-02-24

    Singlet fission of thienoquinoid compounds in organic photovoltaics is demonstrated. The escalation of the thienoquinoid length of the compounds realizes a suitable packing structure and energy levels for singlet fission. The magnetic-field dependence of the photocurrent and the external quantum efficiency of the devices reveal singlet fission of the compounds and dissociation of triplet excitons into charges.

  15. Rhodanine dye-based small molecule acceptors for organic photovoltaic cells.

    PubMed

    Kim, Yujeong; Song, Chang Eun; Moon, Sang-Jin; Lim, Eunhee

    2014-08-01

    The solution-processable small molecules based on carbazole or fluorene containing rhodanine dyes at both ends were synthesized and introduced as acceptors in organic photovoltaic cells. The high energy levels of their lowest unoccupied molecular orbitals resulted in a power conversion efficiency of 3.08% and an open circuit voltage of up to 1.03 V.

  16. Material structure-composite morphology-photovoltaic performance relationship for organic bulk heterojunction solar cells.

    PubMed

    Troshin, Pavel A; Mukhacheva, Olga A; Goryachev, Andrey E; Dremova, Nadezhda N; Voylov, Dmitry; Ulbricht, Christoph; Egbe, Daniel A M; Sariciftci, Niyazi Serdar; Razumov, Vladimir F

    2012-10-01

    Conjugated PPV-PPE copolymer has been investigated in organic solar cells in combination with twelve different fullerene derivatives. It was shown that the length of solubilizing alkyl chains in the fullerene derivative structures correlates well with the performance of photovoltaic cells.

  17. Monolithic Parallel Tandem Organic Photovoltaic Cell with Transparent Carbon Nanotube Interlayer

    NASA Technical Reports Server (NTRS)

    Tanaka, S.; Mielczarek, K.; Ovalle-Robles, R.; Wang, B.; Hsu, D.; Zakhidov, A. A.

    2009-01-01

    We demonstrate an organic photovoltaic cell with a monolithic tandem structure in parallel connection. Transparent multiwalled carbon nanotube sheets are used as an interlayer anode electrode for this parallel tandem. The characteristics of front and back cells are measured independently. The short circuit current density of the parallel tandem cell is larger than the currents of each individual cell. The wavelength dependence of photocurrent for the parallel tandem cell shows the superposition spectrum of the two spectral sensitivities of the front and back cells. The monolithic three-electrode photovoltaic cell indeed operates as a parallel tandem with improved efficiency.

  18. EMERGING TECHNOLOGY REPORT: DESTRUCTION OF ORGANIC CONTAMINANTS IN AIR USING ADVANCED ULTRAVIOLET FLASHLAMPS

    EPA Science Inventory

    This paper describes a new process for photo-oxidation of volatile organic compounds (VOCs) in air using an advanced ultraviolet source, a Purus xenon flashlamp. The flashlamps have greater output at 200-250 nm than medium-pressure mercury lamps at the same power and therefore ca...

  19. Solution-processed organic photovoltaic cells based on a squaraine dye.

    PubMed

    Chen, Guo; Sasabe, Hisahiro; Wang, Zhongqiang; Wang, Xiaofeng; Hong, Ziruo; Kido, Junji; Yang, Yang

    2012-11-14

    In this work, 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) was systematically studied as an electron donor in solution processed photovoltaic cells, showing power conversion efficiency of >4.0% under AM1.5G 1 sun illumination at room temperature. Low mobilities were found to limit charge transport in the bulk heterojunctions. Efficiency was thus improved to 5.1% at 80 °C mainly due to improvement of photocurrent extraction. We also demonstrated that the SQ compound synthesized via a simple method has high purity, and thus can be used in photovoltaic cells without further purification. Our results suggest the huge potential of SQ and its analogs in organic photovoltaic applications.

  20. The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Chyba, C.

    1997-01-01

    Atmospheric mixing ratios of approximately 10(-5 +/- 1) for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing.

  1. Solution-grown organic single-crystalline donor-acceptor heterojunctions for photovoltaics.

    PubMed

    Li, Hanying; Fan, Congcheng; Fu, Weifei; Xin, Huolin L; Chen, Hongzheng

    2015-01-12

    Organic single crystals are ideal candidates for high-performance photovoltaics due to their high charge mobility and long exciton diffusion length; however, they have not been largely considered for photovoltaics due to the practical difficulty in making a heterojunction between donor and acceptor single crystals. Here, we demonstrate that extended single-crystalline heterojunctions with a consistent donor-top and acceptor-bottom structure throughout the substrate can be simply obtained from a mixed solution of C60 (acceptor) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (donor). 46 photovoltaic devices were studied with the power conversion efficiency of (0.255±0.095)% under 1 sun, which is significantly higher than the previously reported value for a vapor-grown organic single-crystalline donor-acceptor heterojunction (0.007%). As such, this work opens a practical avenue for the study of organic photovoltaics based on single crystals.

  2. A-D-A small molecules for solution-processed organic photovoltaic cells.

    PubMed

    Ni, Wang; Wan, Xiangjian; Li, Miaomiao; Wang, Yunchuang; Chen, Yongsheng

    2015-03-25

    A-D-A small molecules have drawn more and more attention in solution-processed organic solar cells due to the advantages of a diversity of structures, easy control of energy levels, etc. Recently, a power conversion efficiency of nearly 10% has been achieved through careful material design and device optimization. This feature article reviews recent representative progress in the design and application of A-D-A small molecules in organic photovoltaic cells.

  3. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics.

    PubMed

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.

  4. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics

    NASA Astrophysics Data System (ADS)

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G.; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.

  5. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics.

    PubMed

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells. PMID:27603960

  6. Magnetic Studies of Photovoltaic Processes in Organic Solar Cells

    SciTech Connect

    Zang, Huidong; Ivanov, Ilia N; Hu, Bin

    2010-01-01

    In this paper, we use magnetic field effects of photocurrent (MFEPC ) to study the photovoltaic processes in pristine conjugated polymer, bulk heterojunction, and double-layer solar cells, respectively, based on poly(3-alkylthiophene) (P3HT). The MFEPC reveals that the photocurrent generation undergoes the dissociation in polaron pair states and the charge reaction in excitonic states in pristine conjugated polymers. As for the bulk-heterojunction solar cells consisting of electron donor P3HT and electron acceptor [6,6]-phenyl C61-butyric acid methyl ester (PCBM), the MFEPC indicates that the dissociated electrons and holes inevitably form the intermolecular charge-transfer (CT) complexes at donor and acceptor interfaces. Essentially, the photocurrent generation relies on the further dissociation of intermolecular CT complexes. Moreover, we use double-layer solar cell to further study the intermolecular CT complexes with well-controlled donor acceptor interfaces based on double-layer P3HT/TiOx design. We find that the increase in free energies can significantly reduce the density of CT complexes upon thermal annealing.

  7. Novel High Efficient Organic Photovoltaic Materials: Final Summary of Research

    NASA Astrophysics Data System (ADS)

    Sun, Sam

    2002-07-01

    The objectives and goals of this project were to investigate and develop high efficient, lightweight, and cost effective materials for potential photovoltaic applications, such as solar energy conversion or photo detector devices. Specifically, as described in the original project proposal, the target material to be developed was a block copolymer system containing an electron donating (or p-type) conjugated polymer block coupled to an electron withdrawing (or n-type) conjugated polymer block through a non-conjugated bridge unit. Due to several special requirements of the targeted block copolymer systems, such as electron donating and withdrawing substituents, conjugated block structures, processing requirement, stability requirement, size controllability, phase separation and self ordering requirement, etc., many traditional or commonly used block copolymer synthetic schemes are not suitable for this system. Therefore, the investigation and development of applicable and effective synthetic protocols became the most critical and challenging part of this project. During the entire project period, and despite the lack of a proposed synthetic polymer postdoctoral research associate due to severe shortage of qualified personnel in the field, several important accomplishments were achieved in this project and are briefly listed and elaborated. A more detailed research and experimental data is listed in the Appendix.

  8. Novel High Efficient Organic Photovoltaic Materials: Final Summary of Research

    NASA Technical Reports Server (NTRS)

    Sun, Sam

    2002-01-01

    The objectives and goals of this project were to investigate and develop high efficient, lightweight, and cost effective materials for potential photovoltaic applications, such as solar energy conversion or photo detector devices. Specifically, as described in the original project proposal, the target material to be developed was a block copolymer system containing an electron donating (or p-type) conjugated polymer block coupled to an electron withdrawing (or n-type) conjugated polymer block through a non-conjugated bridge unit. Due to several special requirements of the targeted block copolymer systems, such as electron donating and withdrawing substituents, conjugated block structures, processing requirement, stability requirement, size controllability, phase separation and self ordering requirement, etc., many traditional or commonly used block copolymer synthetic schemes are not suitable for this system. Therefore, the investigation and development of applicable and effective synthetic protocols became the most critical and challenging part of this project. During the entire project period, and despite the lack of a proposed synthetic polymer postdoctoral research associate due to severe shortage of qualified personnel in the field, several important accomplishments were achieved in this project and are briefly listed and elaborated. A more detailed research and experimental data is listed in the Appendix.

  9. First principles investigations of vinazene molecule and molecular crystal: a prospective candidate for organic photovoltaic applications.

    PubMed

    Mohamad, Mazmira; Ahmed, Rashid; Shaari, Amirudin; Goumri-Said, Souraya

    2015-02-01

    Escalating demand for sustainable energy resources, because of the rapid exhaustion of conventional energy resources as well as to maintain the environmental level of carbon dioxide (CO2) to avoid its adverse effect on the climate, has led to the exploitation of photovoltaic technology manifold more than ever. In this regard organic materials have attracted great attention on account of demonstrating their potential to harvest solar energy at an affordable rate for photovoltaic technology. 2-vinyl-4,5-dicyanoimidazole (vinazene) is considered as a suitable material over the fullerenes for photovoltaic applications because of its particular chemical and physical nature. In the present study, DFT approaches are employed to provide an exposition of optoelectronic properties of vinazene molecule and molecular crystal. To gain insight into its properties, different forms of exchange correlation energy functional/potential such as LDA, GGA, BLYP, and BL3YP are used. Calculated electronic structure of vinazene molecule has been displayed via HOMO-LUMO isosurfaces, whereas electronic structure of the vinazene molecular crystal, via electronic band structure, is presented. The calculated electronic and optical properties were analyzed and compared as well. Our results endorse vinazene as a suitable material for organic photovoltaic applications.

  10. Organic photovoltaic cells based on ZnO thin film electrodes.

    PubMed

    Ghica, C; Ion, L; Epurescu, G; Nistor, L; Antohe, S; Dinescu, M

    2010-02-01

    Due to its wide band-gap (ca. 3.4 eV), ZnO is a possible candidate material to be used as transparent electrode for a new class of photovoltaic (PV) cells. Also, an increased interest for the photovoltaic properties of several organic monomers and polymers (merocyanines, phthalocyanines and porphyrins) was noticed, because of their high optical absorption in the visible region of the spectrum allowing them to be used as potential inexpensive materials for solar cells. Preparation and properties of CuPc (copper phthalocyanine) based photovoltaic cells using ZnO thin films as transparent conductor electrodes are presented in this paper. ZnO layers are grown by pulsed laser deposition, while the organic layers are obtained by thermal evaporation. Structural characterization is performed by electron microscopy. Optical and transport properties of the mutilayered structures are obtained by electrical and spectro-photometric measurements. The influence of the ZnO-polymer interface on the external quantum efficiency (EQE) of the photovoltaic cell is clearly evidenced by our measurements.

  11. Theoretical description of structural and electronic properties of organic photovoltaic materials.

    PubMed

    Zhugayevych, Andriy; Tretiak, Sergei

    2015-04-01

    We review recent progress in the modeling of organic solar cells and photovoltaic materials, as well as discuss the underlying theoretical methods with an emphasis on dynamical electronic processes occurring in organic semiconductors. The key feature of the latter is a strong electron-phonon interaction, making the evolution of electronic and structural degrees of freedom inseparable. We discuss commonly used approaches for first-principles modeling of this evolution, focusing on a multiscale framework based on the Holstein-Peierls Hamiltonian solved via polaron transformation. A challenge for both theoretical and experimental investigations of organic solar cells is the complex multiscale morphology of these devices. Nevertheless, predictive modeling of photovoltaic materials and devices is attainable and is rapidly developing, as reviewed here. PMID:25580623

  12. Theoretical description of structural and electronic properties of organic photovoltaic materials.

    PubMed

    Zhugayevych, Andriy; Tretiak, Sergei

    2015-04-01

    We review recent progress in the modeling of organic solar cells and photovoltaic materials, as well as discuss the underlying theoretical methods with an emphasis on dynamical electronic processes occurring in organic semiconductors. The key feature of the latter is a strong electron-phonon interaction, making the evolution of electronic and structural degrees of freedom inseparable. We discuss commonly used approaches for first-principles modeling of this evolution, focusing on a multiscale framework based on the Holstein-Peierls Hamiltonian solved via polaron transformation. A challenge for both theoretical and experimental investigations of organic solar cells is the complex multiscale morphology of these devices. Nevertheless, predictive modeling of photovoltaic materials and devices is attainable and is rapidly developing, as reviewed here.

  13. The electrodeposition of multilayers on a polymeric substrate in flexible organic photovoltaic solar cells

    NASA Astrophysics Data System (ADS)

    Guedes, Andre F. S.; Guedes, Vilmar P.; Souza, Monica L.; Tartari, Simone; Cunha, Idaulo J.

    2015-09-01

    Flexible organic photovoltaic solar cells have drawn intense attention due to their advantages over competing solar cell technologies. The method utilized to deposit as well as to integrate solutions and processed materials, manufacturing organic solar cells by the Electrodeposition System, has been presented in this research. In addition, we have demonstrated a successful integration of a process for manufacturing the flexible organic solar cell prototype and we have discussed on the factors that make this process possible. The maximum process temperature was 120°C, which corresponds to the baking of the active polymeric layer. Moreover, the new process of the Electrodeposition of complementary active layer is based on the application of voltage versus time in order to obtain a homogeneous layer with thin film. This thin film was not only obtained by the electrodeposition of PANI-X1 on P3HT/PCBM Blend, but also prepared in perchloric acid solution. Furthermore, these flexible organic photovoltaic solar cells presented power conversion efficiency of 12% and the inclusion of the PANI-X1 layer reduced the effects of degradation on these organic photovoltaic panels induced by solar irradiation. Thus, in the Scanning Electron Microscopy (SEM), these studies have revealed that the surface of PANI-X1 layers is strongly conditioned by the dielectric surface morphology.

  14. Systematic Analysis of Polymer Molecular Weight Influence on the Organic Photovoltaic Performance.

    PubMed

    Katsouras, Athanasios; Gasparini, Nicola; Koulogiannis, Chrysanthos; Spanos, Michael; Ameri, Tayebeh; Brabec, Christoph J; Chochos, Christos L; Avgeropoulos, Apostolos

    2015-10-01

    The molecular weight of an electron donor-conjugated polymer is as essential as other well-known parameters in the chemical structure of the polymer, such as length and the nature of any side groups (alkyl chains) positioned on the polymeric backbone, as well as their placement, relative strength, the ratio of the donor and acceptor moieties in the backbone of donor-acceptor (D-A)-conjugated polymers, and the arrangement of their energy levels for organic photovoltaic performance. Finding the "optimal" molecular weight for a specific conjugated polymer is an important aspect for the development of novel photovoltaic polymers. Therefore, it is evident that the chemistry of functional conjugated polymers faces major challenges and materials have to adopt a broad range of specifications in order to be established for high photovoltaic performance. In this review, the approaches followed for enhancing the molecular weight of electron-donor polymers are presented in detail, as well as how this influences the optoelectronic properties, charge transport properties, structural conformation, morphology, and the photovoltaic performance of the active layer.

  15. Organic photovoltaic cells based on unconventional electron donor fullerene and electron acceptor copper hexadecafluorophthalocyanine

    NASA Astrophysics Data System (ADS)

    Yang, J. L.; Sullivan, P.; Schumann, S.; Hancox, I.; Jones, T. S.

    2012-01-01

    We demonstrate organic discrete heterojunction photovoltaic cells based on fullerene (C60) and copper hexadecafluorophthalocyanine (F16CuPc), in which the C60 and F16CuPc act as the electron donor and the electron acceptor, respectively. The C60/F16CuPc cells fabricated with conventional and inverted architectures both exhibit comparable power conversion efficiencies. Furthermore, we show that the photocurrent in both cells is generated by a conventional exciton dissociation mechanism rather than the exciton recombination mechanism recently proposed for a similar C60/F16ZnPc system [Song et al., J. Am. Chem. Soc. 132, 4554 (2010)]. These results demonstrate that new unconventional material systems are a potential way to fabricate organic photovoltaic cells with inverted as well as conventional architectures.

  16. Effect of ZnO:Cs2CO3 on the performance of organic photovoltaics

    PubMed Central

    2014-01-01

    We demonstrate a new solution-processed electron transport layer (ETL), zinc oxide doped with cesium carbonate (ZnO:Cs2CO3), for achieving organic photovoltaics (OPVs) with good operational stability at ambient air. An OPV employing the ZnO:Cs2CO3 ETL exhibits a fill factor of 62%, an open circuit voltage of 0.90 V, and a short circuit current density of −6.14 mA/cm2 along with 3.43% power conversion efficiency. The device demonstrated air stability for a period over 4 weeks. In addition, we also studied the device structure dependence on the performance of organic photovoltaics. Thus, we conclude that ZnO:Cs2CO3 ETL could be employed in a suitable architecture to achieve high-performance OPV. PMID:25045340

  17. Fine structures of organic photovoltaic thin films probed by frequency-shift electrostatic force microscopy

    NASA Astrophysics Data System (ADS)

    Araki, Kento; Ie, Yutaka; Aso, Yoshio; Matsumoto, Takuya

    2016-07-01

    The localized charge and electrostatic properties of organic photovoltaic thin films are predominating factors for controlling energy conversion efficiency. The surface potential and electrostatic structures of organic photovoltaic thin films were investigated by frequency shift mode Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The KFM images of a poly[2-methoxy-5-(3‧,7‧-dimethyloctyloxy)-1,4-phenylene vinylene]/phenyl-C61-butyric-acid-methyl ester (PCBM) blend thin film reveals that the PCBM domains precipitate as the topmost layer on the thin films. We find fine structures that were not observed in the topography and KFM images. The bias dependence of the EFM images suggests that the EFM contrast reflects the field-induced polarization, indicating the presence of charge trapping sites.

  18. Fast printing and in situ morphology observation of organic photovoltaics using slot-die coating.

    PubMed

    Liu, Feng; Ferdous, Sunzida; Schaible, Eric; Hexemer, Alexander; Church, Matthew; Ding, Xiaodong; Wang, Cheng; Russell, Thomas P

    2015-02-01

    The mini-slot-die coater offers a simple, convenient, materials-efficient route to print bulk-heterojunction (BHJ) organic photovoltaics (OPVs) that show efficiencies similar to spin-coating. Grazing-incidence X-ray diffraction (GIXD) and GI small-angle X-ray scattering (GISAXS) methods are used in real time to characterize the active-layer formation during printing. A polymer-aggregation-phase-separation-crystallization mechanism for the evolution of the morphology describes the observations.

  19. Robust carrier formation process in low-band gap organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Yonezawa, Kouhei; Kamioka, Hayato; Yasuda, Takeshi; Han, Liyuan; Moritomo, Yutaka

    2013-10-01

    By means of femto-second time-resolved spectroscopy, we investigated the carrier formation process against film morphology and temperature (T) in highly-efficient organic photovoltaic, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b '] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophenediyl

  20. Controlling surface enrichment in polymeric hole extraction layers to achieve high-efficiency organic photovoltaic cells.

    PubMed

    Kim, Dong-Hun; Lim, Kyung-Geun; Park, Jong Hyeok; Lee, Tae-Woo

    2012-10-01

    Hole extraction in organic photovoltaic cells (OPVs) can be modulated by a surface-enriched layer formed on top of the conducting polymer-based hole extraction layer (HEL). This tunes the surface work function of the HEL to better align with the ionization potential of the polymeric photoactive layer. Results show noticeable improvement in device power conversion efficiencies (PCEs) in OPVs. We achieved a 6.1 % PCE from the OPV by optimizing the surface-enriched layer.

  1. Effect of mixed layer crystallinity on the performance of mixed heterojunction organic photovoltaic cells.

    PubMed

    Song, Byeongseop; Rolin, Cedric; Zimmerman, Jeramy D; Forrest, Stephen R

    2014-05-01

    Organic vapor-phase deposition (OVPD) is used to grow tetraphenyldibenzoperiflanthen (DBP):C70 mixed heterojunction photovoltaic devices. Compared with vacuum thermal evaporation (VTE), the OVPD-grown film develops nanocrystalline domains of C70. Optimized OVPD-grown OPVs have a 61% fill factor for a 100 nm active layer thickness, whereas VTE-grown devices have a 47% fill factor at the same thickness.

  2. Nanosecond intersystem crossing times in fullerene acceptors: implications for organic photovoltaic diodes.

    PubMed

    Chow, Philip C Y; Albert-Seifried, Sebastian; Gélinas, Simon; Friend, Richard H

    2014-07-23

    Triplet-exciton formation through intersystem crossing of photogenerated singlet excitons in fullerene acceptors can compete with charge generation in organic photovoltaic diodes. This article reports the intersystem crossing timescale (τISC ) of the most commonly used fullerene acceptors, PC60 BM and PC70 BM, in solutions and in spin-coated films. These times are on the nanosecond timescale, and are longer than the characteristic times for charge generation (τd ).

  3. Universal formation of compositionally graded bulk heterojunction for efficiency enhancement in organic photovoltaics.

    PubMed

    Xiao, Zhengguo; Yuan, Yongbo; Yang, Bin; VanDerslice, Jeremy; Chen, Jihua; Dyck, Ondrej; Duscher, Gerd; Huang, Jinsong

    2014-05-21

    A universal method is reported to form graded bulk heterojunction (BHJ) organic photovoltaic devices (OPVs) by a simple solvent-fluxing process. Donors are enriched at the anode and acceptors are enriched at cathode side, matching the gradient electron and hole current across the film. Efficiency enhancements by 15-50% are achieved for all BHJ systems tested compared with the optimized regular BHJ OPVs.

  4. A hybrid organic semiconductor/silicon photodiode for efficient ultraviolet photodetection.

    PubMed

    Levell, J W; Giardini, M E; Samuel, I D W

    2010-02-15

    A method employing conjugated polymer thin film blends is shown to provide a simple and convenient way of greatly enhancing the ultraviolet response of silicon photodetectors. Hybrid organic semiconductor/silicon photodetectors are demonstrated using fluorene copolymers and give a quantum efficiency of 60% at 200 nm. The quantum efficiency is greater than 34% over the entire 200-620 nm range. These devices show promise for use in high sensitivity, low cost UV-visible photodetection and imaging applications.

  5. The photoirradiation induced p-n junction in naphthylamine-based organic photovoltaic cells.

    PubMed

    Bai, Linyi; Gao, Qiang; Xia, Youyi; Ang, Chung Yen; Bose, Purnandhu; Tan, Si Yu; Zhao, Yanli

    2015-09-21

    The bulk heterojunction (BHJ) plays an indispensable role in organic photovoltaics, and thus has been investigated extensively in recent years. While a p-n heterojunction is usually fabricated using two different donor and acceptor materials such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), it is really rare that such a BHJ is constructed by a single entity. Here, we presented a photoirradiation-induced p-n heterojunction in naphthylamine-based organic photovoltaic cells, where naphthylamine as a typical p-type semiconductor could be oxidized under photoirradiation and transformed into a new semiconductor with the n-type character. The p-n heterojunction was realized using both the remaining naphthylamine and its oxidative product, giving rise to the performance improvement in organic photovoltaic devices. The experimental results show that the power conversion efficiency (PCE) of the devices could be achieved up to 1.79% and 0.43% in solution and thin film processes, respectively. Importantly, this technology using naphthylamine does not require classic P3HT and PCBM to realize the p-n heterojunction, thereby simplifying the device fabrication process. The present approach opens up a promising route for the development of novel materials applicable to the p-n heterojunction.

  6. An indium-free low work function window electrode for organic photovoltaics which improves with in-situ oxidation.

    PubMed

    Hutter, Oliver S; Stec, Helena M; Hatton, Ross A

    2013-01-11

    A low-cost window electrode for organic photovoltaics that simultaneously removes the requirement for conducting oxide and conventional low work function electrodes and functions as a sink for oxygen/water in the heart of the device. Remarkably the functionality of this electrode, which is based on a 7.8 nm nanostructured Cu:Al film, improves upon in situ oxidation as demonstrated in bulk heterojunction organic photovoltaics. PMID:23108998

  7. Controlling the Solidification of Organic Photovoltaic Blends with Nucleating Agents

    NASA Astrophysics Data System (ADS)

    Nekuda Malik, Jennifer A.; Treat, Neil D.; Abdelsamie, Maged; Yu, Liyang; Li, Ruipeng; Smilgies, Detlef-M.; Amassian, Aram; Hawker, Craig J.; Chabinyc, Michael L.; Stingelin, Natalie

    2014-11-01

    Blending fullerenes with a donor polymer for the fabrication of organic solar cells often leads to at least partial vitrification of one, if not both, components. For prototypical poly(3-hexylthiophene):fullerene blend, we show that the addition of a commercial nucleating agent, di(3,4-dimethyl benzylidene)sorbitol, to such binary blends accelerates the crystallization of the donor, resulting in an increase in its degree of crystallinity in as-cast structures. This allows manipulation of the extent of intermixing/ phase separation of the donor and acceptor directly from solution, offering a tool to improve device characteristics such as power conversion efficiency.

  8. The role of spin in the kinetic control of recombination in organic photovoltaics.

    PubMed

    Rao, Akshay; Chow, Philip C Y; Gélinas, Simon; Schlenker, Cody W; Li, Chang-Zhi; Yip, Hin-Lap; Jen, Alex K-Y; Ginger, David S; Friend, Richard H

    2013-08-22

    In biological complexes, cascade structures promote the spatial separation of photogenerated electrons and holes, preventing their recombination. In contrast, the photogenerated excitons in organic photovoltaic cells are dissociated at a single donor-acceptor heterojunction formed within a de-mixed blend of the donor and acceptor semiconductors. The nanoscale morphology and high charge densities give a high rate of electron-hole encounters, which should in principle result in the formation of spin-triplet excitons, as in organic light-emitting diodes. Although organic photovoltaic cells would have poor quantum efficiencies if every encounter led to recombination, state-of-the-art examples nevertheless demonstrate near-unity quantum efficiency. Here we show that this suppression of recombination arises through the interplay between spin, energetics and delocalization of electronic excitations in organic semiconductors. We use time-resolved spectroscopy to study a series of model high-efficiency polymer-fullerene systems in which the lowest-energy molecular triplet exciton (T1) for the polymer is lower in energy than the intermolecular charge transfer state. We observe the formation of T1 states following bimolecular recombination, indicating that encounters of spin-uncorrelated electrons and holes generate charge transfer states with both spin-singlet ((1)CT) and spin-triplet ((3)CT) characters. We show that the formation of triplet excitons can be the main loss mechanism in organic photovoltaic cells. But we also find that, even when energetically favoured, the relaxation of (3)CT states to T1 states can be strongly suppressed by wavefunction delocalization, allowing for the dissociation of (3)CT states back to free charges, thereby reducing recombination and enhancing device performance. Our results point towards new design rules both for photoconversion systems, enabling the suppression of electron-hole recombination, and for organic light-emitting diodes

  9. Rapid and Checkable Electrical Post-Treatment Method for Organic Photovoltaic Devices

    PubMed Central

    Park, Sangheon; Seo, Yu-Seong; Shin, Won Suk; Moon, Sang-Jin; Hwang, Jungseek

    2016-01-01

    Post-treatment processes improve the performance of organic photovoltaic devices by changing the microscopic morphology and configuration of the vertical phase separation in the active layer. Thermal annealing and solvent vapor (or chemical) treatment processes have been extensively used to improve the performance of bulk-heterojunction (BHJ) organic photovoltaic (OPV) devices. In this work we introduce a new post-treatment process which we apply only electrical voltage to the BHJ-OPV devices. We used the commercially available P3HT [Poly(3-hexylthiophene)] and PC61BM (Phenyl-C61-Butyric acid Methyl ester) photovoltaic materials as donor and acceptor, respectively. We monitored the voltage and current applied to the device to check for when the post-treatment process had been completed. This electrical treatment process is simpler and faster than other post-treatment methods, and the performance of the electrically treated solar cell is comparable to that of a reference (thermally annealed) device. Our results indicate that the proposed treatment process can be used efficiently to fabricate high-performance BHJ-OPV devices. PMID:26932767

  10. Rapid and Checkable Electrical Post-Treatment Method for Organic Photovoltaic Devices.

    PubMed

    Park, Sangheon; Seo, Yu-Seong; Shin, Won Suk; Moon, Sang-Jin; Hwang, Jungseek

    2016-03-02

    Post-treatment processes improve the performance of organic photovoltaic devices by changing the microscopic morphology and configuration of the vertical phase separation in the active layer. Thermal annealing and solvent vapor (or chemical) treatment processes have been extensively used to improve the performance of bulk-heterojunction (BHJ) organic photovoltaic (OPV) devices. In this work we introduce a new post-treatment process which we apply only electrical voltage to the BHJ-OPV devices. We used the commercially available P3HT [Poly(3-hexylthiophene)] and PC61BM (Phenyl-C61-Butyric acid Methyl ester) photovoltaic materials as donor and acceptor, respectively. We monitored the voltage and current applied to the device to check for when the post-treatment process had been completed. This electrical treatment process is simpler and faster than other post-treatment methods, and the performance of the electrically treated solar cell is comparable to that of a reference (thermally annealed) device. Our results indicate that the proposed treatment process can be used efficiently to fabricate high-performance BHJ-OPV devices.

  11. Rapid and Checkable Electrical Post-Treatment Method for Organic Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Park, Sangheon; Seo, Yu-Seong; Shin, Won Suk; Moon, Sang-Jin; Hwang, Jungseek

    2016-03-01

    Post-treatment processes improve the performance of organic photovoltaic devices by changing the microscopic morphology and configuration of the vertical phase separation in the active layer. Thermal annealing and solvent vapor (or chemical) treatment processes have been extensively used to improve the performance of bulk-heterojunction (BHJ) organic photovoltaic (OPV) devices. In this work we introduce a new post-treatment process which we apply only electrical voltage to the BHJ-OPV devices. We used the commercially available P3HT [Poly(3-hexylthiophene)] and PC61BM (Phenyl-C61-Butyric acid Methyl ester) photovoltaic materials as donor and acceptor, respectively. We monitored the voltage and current applied to the device to check for when the post-treatment process had been completed. This electrical treatment process is simpler and faster than other post-treatment methods, and the performance of the electrically treated solar cell is comparable to that of a reference (thermally annealed) device. Our results indicate that the proposed treatment process can be used efficiently to fabricate high-performance BHJ-OPV devices.

  12. Nature-inspired light-harvesting liquid crystalline porphyrins for organic photovoltaics

    SciTech Connect

    Li, Lanfang; Kang, Shin-Woong; Harden, John; Sun, Qingjiang; Zhou, Xiaoli; Dai, Liming; Jakli, Antal; Kumar, Satyendra; Li, Quan

    2008-12-22

    A new class of nanoscale light-harvesting discotic liquid crystalline porphyrins, with the same basic structure of the best photoreceptor in nature (chlorophyll), was synthesized. These materials can be exceptionally aligned into a highly ordered architecture in which the columns formed by intermolecular {pi}-{pi} stacking are spontaneously perpendicular to the substrate. The homeotropic alignment, well confirmed by synchrotron X-ray diffraction, could not only provide the most efficient pathway for hole conduction along the columnar axis crossing the device thickness, but also offer the largest area to the incident light for optimized light harvesting. Their preliminary photocurrent generation and photovoltaic performances were also demonstrated. The results provide new and efficient pathways to the development of organic photovoltaics by using homeotropically aligned liquid crystal thin films.

  13. Improved efficiency of hybrid organic photovoltaics by pulsed laser sintering of silver nanowire network transparent electrode.

    PubMed

    Spechler, Joshua A; Nagamatsu, Ken A; Sturm, James C; Arnold, Craig B

    2015-05-20

    In this Research Article, we demonstrate pulsed laser processing of a silver nanowire network transparent conductor on top of an otherwise complete solar cell. The macroscopic pulsed laser irradiation serves to sinter nanowire-nanowire junctions on the nanoscale, leading to a much more conductive electrode. We fabricate hybrid silicon/organic heterojunction photovoltaic devices, which have ITO-free, solution processed, and laser processed transparent electrodes. Furthermore, devices which have high resistive losses show up to a 35% increase in power conversion efficiency after laser processing. We perform this study over a range of laser fluences, and a range of nanowire area coverage to investigate the sintering mechanism of nanowires inside of a device stack. The increase in device performance is modeled using a simple photovoltaic diode approach and compares favorably to the experimental data.

  14. TOPICAL REVIEW Organic photovoltaics: principles and techniques for nanometre scale characterization

    NASA Astrophysics Data System (ADS)

    Nicholson, Patrick G.; Castro, Fernando A.

    2010-12-01

    The photoconversion efficiency of state-of-the-art organic solar cells has experienced a remarkable increase in the last few years, with reported certified efficiency values of up to 8.3%. This increase has been due to an improved understanding of the underlying physics, synthetic discovery and the realization of the pivotal role that morphological optimization plays. Advances in nanometre scale characterization have underpinned all three factors. Here we give an overview of the current understanding of the fundamental processes in organic photovoltaic devices, on optimization considerations and on recent developments in nanometre scale measuring techniques. Finally, recommendations for future developments from the perspective of characterization techniques are set forth.

  15. Molecular design and photovoltaic performance of organic dyes containing phenothiazine for dye-sensitized solar cells.

    PubMed

    Jo, Hyo Jeong; Nam, Jung Eun; Sim, Kyoseung; Kim, Dae-Hwan; Kim, Jae Hong; Kang, Jin-Kyu

    2014-10-01

    We synthesized novel organic photosensitizers based on fluorine-substituted phenothiazine with thiophene bridge units in the chromophore for application in dye-sensitized solar cells (DSSCs). Furthermore, organic dyes with different acceptors exhibited higher molar extinction coefficients, and better light absorption at longer wavelengths. The photovoltaic properties of organic dyes composed of different acceptors in their chromophores were measured to identify their effects on the DSSC performance. The organic dye, PFSCN2 containing multi-cyanoacrylic acid as the electron acceptor, showed a power conversion efficiency of 4.67% under AM 1.5 illumination (100 mW/cm2). The retarded recombination kinetics from TiO2 electrode to electrolyte enhanced the electron life time of the organic dye, PFSCN2 in the photoanode of the DSSC. This was confirmed with impedance analysis.

  16. Morphology optimization for enhanced performance in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wodo, Olga; Zola, Jaroslaw; Ganapathysubramanian, Baskar

    2015-03-01

    Organic solar cells have the potential for widespread usage due to their low cost-per-watt and mechanical flexibility. Their wide spread use, however, is bottlenecked primarily by their low solar efficiencies. Experimental evidence suggests that a key property determining the solar efficiency of such devices is the final morphological distribution of the electron-donor and electron-acceptor constituents. By carefully designing the morphology of the device, one could potentially significantly enhance their performance. This is an area of intense experimental effort that is mostly trial-and-error based, and serves as a fertile area for introducing mechanics and computational thinking. In this work, we use optimization techniques coupled with computational modeling to identify the optimal structures for high efficiency solar cells. In particular, we use adaptive population-based incremental learning method linked to graph-based surrogate model to evaluate properties for given structure. We study several different criterions and find optimal structure that that improve the performance of currently hypothesized optimal structures by 29%.

  17. The preparation of a Eu3+-doped ZnO bi-functional layer and its application in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wu, Na; Luo, Qun; Qiao, Xvsheng; Ma, Chang-Qi

    2015-12-01

    Recently, spectra conversion has been used to minimize energy loss in photovoltaic devices. In this work, we explore the development of a novel Eu3+-doped ZnO bi-functional layer for use in organic solar cells. The bi-functional layer acts as both a spectra conversion and an electron transporting layer. Compared to conventional spectra conversion layers, it has a simpler device structure, is easier to fabricate, and has a wider spectrum-sensitized region. A series of Eu3+-doped ZnO nanocrystals were synthesized using the simple solution route. X-ray powder diffraction patterns (XRD), transmission electron microscopy (TEM), and UV-visible absorbance spectra were used to characterize the obtained ZnO nanocrystals. The results reveal that the size and bandgap of ZnO nanocrystals can be controlled through regulation of the doping concentration of Eu3+ ions. The energy transfer of ZnO → Eu3+ is observed by photoluminescence (PL) spectra. At a bandgap excitation of around 300-400 nm, a typical emission band from the Eu3+ is obtained. By employing the Eu3+- doped ZnO nanocrystals as a buffer layer in a P3HT:PC61BM bulk heterojunction device, the obtained performance is similar to the undoped ZnO device, indicating that the electrical properties of ZnO are not affected by Eu3+ doping. Due to the down-conversion energy transfer between ZnO and Eu3+, the external quantum efficiency of the ZnO:Eu3+ device at 300-400 nm is higher than that of the pure ZnO device, which subsequently leads to an increase in short circuit current density (J SC). This work proves that it is possible to improve the solar spectrum response in the ultraviolet region of organic solar cells effectively by incorporating the bi-functional layer.

  18. Self-assembled, aligned ZnO nanorod buffer layers for high-current-density, inverted organic photovoltaics.

    PubMed

    Rao, Arun D; Karalatti, Suresh; Thomas, Tiju; Ramamurthy, Praveen C

    2014-10-01

    Two different soft-chemical, self-assembly-based solution approaches are employed to grow zinc oxide (ZnO) nanorods with controlled texture. The methods used involve seeding and growth on a substrate. Nanorods with various aspect ratios (1-5) and diameters (15-65 nm) are grown. Obtaining highly oriented rods is determined by the way the substrate is mounted within the chemical bath. Furthermore, a preheat and centrifugation step is essential for the optimization of the growth solution. In the best samples, we obtain ZnO nanorods that are almost entirely oriented in the (002) direction; this is desirable since electron mobility of ZnO is highest along this crystallographic axis. When used as the buffer layer of inverted organic photovoltaics (I-OPVs), these one-dimensional (1D) nanostructures offer: (a) direct paths for charge transport and (b) high interfacial area for electron collection. The morphological, structural, and optical properties of ZnO nanorods are studied using scanning electron microscopy, X-ray diffraction, and ultraviolet-visible light (UV-vis) absorption spectroscopy. Furthermore, the surface chemical features of ZnO films are studied using X-ray photoelectron spectroscopy and contact angle measurements. Using as-grown ZnO, inverted OPVs are fabricated and characterized. For improving device performance, the ZnO nanorods are subjected to UV-ozone irradiation. UV-ozone treated ZnO nanorods show: (i) improvement in optical transmission, (ii) increased wetting of active organic components, and (iii) increased concentration of Zn-O surface bonds. These observations correlate well with improved device performance. The devices fabricated using these optimized buffer layers have an efficiency of ∼3.2% and a fill factor of 0.50; this is comparable to the best I-OPVs reported that use a P3HT-PCBM active layer.

  19. Fabrication of ordered bulk heterojunction organic photovoltaic cells using nanopatterning and electrohydrodynamic spray deposition methods.

    PubMed

    Park, Sung-Eun; Kim, Sehwan; Kim, Kangmin; Joe, Hang-Eun; Jung, Buyoung; Kim, Eunkyoung; Kim, Woochul; Min, Byung-Kwon; Hwang, Jungho

    2012-12-21

    Organic photovoltaic cells with an ordered heterojunction (OHJ) active layer are expected to show increased performance. In the study described here, OHJ cells were fabricated using a combination of nanoimprinting and electrohydrodynamic (EHD) spray deposition methods. After an electron donor material was nanoimprinted with a PDMS stamp (valley width: 230 nm, period: 590 nm) duplicated from a Si nanomold, an electron acceptor material was deposited onto the nanoimprinted donor layer using an EHD spray deposition method. The donor-acceptor interface layer was observed by obtaining cross-sectional images with a focused ion beam (FIB) microscope. The photocurrent generation performance of the OHJ cells was evaluated with the current density-voltage curve under air mass (AM) 1.5 conditions. It was found that the surface morphology of the electron acceptor layer affected the current and voltage outputs of the photovoltaic cells. When an electron acceptor layer with a smooth thin (250 nm above the valley of the electron donor layer) surface morphology was obtained, power conversion efficiency was as high as 0.55%. The electrohydrodynamic spray deposition method used to produce OHJ photovoltaic cells provides a means for the adoption of large area, high throughput processes.

  20. Promising Strategy To Improve Charge Separation in Organic Photovoltaics: Installing Permanent Dipoles in PCBM Analogues.

    PubMed

    de Gier, Hilde D; Jahani, Fatemeh; Broer, Ria; Hummelen, Jan C; Havenith, Remco W A

    2016-07-14

    A multidisciplinary approach involving organic synthesis and theoretical chemistry was applied to investigate a promising strategy to improve charge separation in organic photovoltaics: installing permanent dipoles in fullerene derivatives. First, a PCBM analogue with a permanent dipole in the side chain (PCBDN) and its reference analogue without a permanent dipole (PCBBz) were successfully synthesized and characterized. Second, a multiscale modeling approach was applied to investigate if a PCBDN environment around a central donor-acceptor complex indeed facilitates charge separation. Alignment of the embedding dipoles in response to charges present on the central donor-acceptor complex enhances charge separation. The good correspondence between experimentally and theoretically determined electronic and optical properties of PCBDN, PCBBz, and PCBM indicates that the theoretical analysis of the embedding effects of these molecules gives a reliable expectation for their influence on the charge separation process at a microscopic scale in a real device. This work suggests the following strategies to improve charge separation in organic photovoltaics: installing permanent dipoles in PCBM analogues and tuning the concentration of these molecules in an organic donor/acceptor blend.

  1. Architectures and criteria for the design of high efficiency organic photovoltaic cells

    DOEpatents

    Rand, Barry; Forrest, Stephen R; Pendergrast Burk, Diane

    2015-03-31

    A method for fabricating an organic photovoltaic cell includes providing a first electrode; depositing a series of at least seven layers onto the first electrode, each layer consisting essentially of a different organic semiconductor material, the organic semiconductor material of at least an intermediate layer of the sequence being a photoconductive material; and depositing a second electrode onto the sequence of at least seven layers. One of the first electrode and the second electrode is an anode and the other is a cathode. The organic semiconductor materials of the series of at least seven layers are arranged to provide a sequence of decreasing lowest unoccupied molecular orbitals (LUMOs) and a sequence of decreasing highest occupied molecular orbitals (HOMOs) across the series from the anode to the cathode.

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

    PubMed

    Su, Zisheng; Wang, Lidan; Li, Yantao; Zhao, Haifeng; Chu, Bei; Li, Wenlian

    2012-08-17

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

  3. Exciton-to-Carrier Conversion Processes in a Low-Band-Gap Organic Photovoltaic

    NASA Astrophysics Data System (ADS)

    Yonezawa, Kouhei; Kamioka, Hayato; Yasuda, Takeshi; Han, Liyuan; Moritomo, Yutaka

    2013-06-01

    A bulk heterojunction (BHJ) based on a donor (D) polymer and an acceptor (A) fullerene derivative is a promising organic photovoltaic (OPV). We investigated femtosecond charge dynamics after D (at 633 nm) and A (at 400 nm) excitations in a prototypical low-band-gap and highly efficient OPV, i.e., poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

  4. Organic photovoltaic solar cells with cathode modified by ZnO.

    PubMed

    Kim, Hyeong Pil; Yusoff, Abd Rashid Bin Mohd; Jang, Jin

    2013-07-01

    Solution processed cathode organic photovoltaic cells (OPVs) utilizing thin layer of ZnO with 27% increase in power conversion efficiency (PCE) to control devices have been demonstrated. Devices without the presence of ZnO layer have much lower PCE than the ones with ZnO layer. Cathode modification layer can be used to reduce photogenerated excitions and finally improve the performance of the OPVs. The successful demonstrations of OPVs with an introduction of ZnO cathode layer give promise of further device progresses.

  5. Effects on Organic Photovoltaics Using Femtosecond-Laser-Treated Indium Tin Oxides.

    PubMed

    Chen, Mei-Hsin; Tseng, Ya-Hsin; Chao, Yi-Ping; Tseng, Sheng-Yang; Lin, Zong-Rong; Chu, Hui-Hsin; Chang, Jan-Kai; Luo, Chih-Wei

    2016-09-28

    The effects of femtosecond-laser-induced periodic surface structures (LIPSS) on an indium tin oxide (ITO) surface applied to an organic photovoltaic (OPV) system were investigated. The modifications of ITO induced by LIPPS in OPV devices result in more than 14% increase in power conversion efficiency (PCE) and short-circuit current density relative to those of the standard device. The basic mechanisms for the enhanced short-circuit current density are attributed to better light harvesting, increased scattering effects, and more efficient charge collection between the ITO and photoactive layers. Results show that higher PCEs would be achieved by laser-pulse-treated electrodes. PMID:27618510

  6. Effects on Organic Photovoltaics Using Femtosecond-Laser-Treated Indium Tin Oxides.

    PubMed

    Chen, Mei-Hsin; Tseng, Ya-Hsin; Chao, Yi-Ping; Tseng, Sheng-Yang; Lin, Zong-Rong; Chu, Hui-Hsin; Chang, Jan-Kai; Luo, Chih-Wei

    2016-09-28

    The effects of femtosecond-laser-induced periodic surface structures (LIPSS) on an indium tin oxide (ITO) surface applied to an organic photovoltaic (OPV) system were investigated. The modifications of ITO induced by LIPPS in OPV devices result in more than 14% increase in power conversion efficiency (PCE) and short-circuit current density relative to those of the standard device. The basic mechanisms for the enhanced short-circuit current density are attributed to better light harvesting, increased scattering effects, and more efficient charge collection between the ITO and photoactive layers. Results show that higher PCEs would be achieved by laser-pulse-treated electrodes.

  7. Intrinsic and extrinsic parameters for controlling the growth of organic single-crystalline nanopillars in photovoltaics.

    PubMed

    Zhang, Yue; Diao, Ying; Lee, Hyunbok; Mirabito, Timothy J; Johnson, Richard W; Puodziukynaite, Egle; John, Jacob; Carter, Kenneth R; Emrick, Todd; Mannsfeld, Stefan C B; Briseno, Alejandro L

    2014-10-01

    The most efficient architecture for achieving high donor/acceptor interfacial area in organic photovoltaics (OPVs) would employ arrays of vertically interdigitated p- and n- type semiconductor nanopillars (NPs). Such morphology could have an advantage in bulk heterojunction systems; however, precise control of the dimension morphology in a crystalline, interpenetrating architecture has not yet been realized. Here we present a simple, yet facile, crystallization technique for the growth of vertically oriented NPs utilizing a modified thermal evaporation technique that hinges on a fast deposition rate, short substrate-source distance, and ballistic mass transport. A broad range of organic semiconductor materials is beneficial from the technique to generate NP geometries. Moreover, this technique can also be generalized to various substrates, namely, graphene, PEDOT-PSS, ZnO, CuI, MoO3, and MoS2. The advantage of the NP architecture over the conventional thin film counterpart is demonstrated with an increase of power conversion efficiency of 32% in photovoltaics. This technique will advance the knowledge of organic semiconductor crystallization and create opportunities for the fabrication and processing of NPs for applications that include solar cells, charge storage devices, sensors, and vertical transistors.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  9. Induced genetic deficiency of the nucleolar organizer in rat kangaroo cells (PTK1) by ultraviolet laser microirradiation.

    PubMed

    Liang, H; Berns, M W

    1983-03-01

    An ultraviolet laser microbeam was used to irradiate one of the two nucleolar organizer regions of PTK1 cells in early prophase. The directed nucleolar deficiency induced by ultraviolet laser irradiation was maintained in the daughter cells through subsequent cell generations. However, the frequent occurrence of spontaneous cell fusion in low density cells following the cloning procedure facilitated a recovery of cells to two or more nucleoli.

  10. Correlating Molecular Structures with Transport Dynamics in High-Efficiency Small-Molecule Organic Photovoltaics.

    PubMed

    Peng, Jiajun; Chen, Yani; Wu, Xiaohan; Zhang, Qian; Kan, Bin; Chen, Xiaoqing; Chen, Yongsheng; Huang, Jia; Liang, Ziqi

    2015-06-24

    Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport.

  11. Correlating Molecular Structures with Transport Dynamics in High-Efficiency Small-Molecule Organic Photovoltaics.

    PubMed

    Peng, Jiajun; Chen, Yani; Wu, Xiaohan; Zhang, Qian; Kan, Bin; Chen, Xiaoqing; Chen, Yongsheng; Huang, Jia; Liang, Ziqi

    2015-06-24

    Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport. PMID:26066398

  12. Activation of Organic Photovoltaic Light Detectors Using Bend Leakage from Optical Fibers.

    PubMed

    Griffith, Matthew J; Willis, Matthew S; Kumar, Pankaj; Holdsworth, John L; Bezuidenhout, Henco; Zhou, Xiaojing; Belcher, Warwick; Dastoor, Paul C

    2016-03-01

    This work investigates the detection and subsequent utilization of leaked light from bends in a silica optical fiber using organic photovoltaic detectors. The optic power lost by single mode and multimode silica optical fibers was calibrated for bend radii between 1 and 7 mm for 532 and 633 nm light, exhibiting excellent agreement with previous theoretical solutions. The spatial location of maximum power leakage on the exterior of the fiber was found to exist in the same plane as the fiber, with a 10° offset from the normal. Two different organic photovoltaic detectors fabricated using a poly(3-hexylthiophene):indene-C60-bisadduct donor-acceptor blend cast from chloroform and chlorobenzene were fabricated to detect the leaked light. The two detectors exhibited different photovoltaic performances, predominantly due to different active layer thicknesses. Both devices showed sensitivity to leakage light, exhibiting voltages between 200 and 300 mV in response to leaked light from the fiber. The temporal responses of the devices were observed to differ, with a rise time from 10% to 90% of maximum voltage of 1430 μs for the chlorobenzene device, and a corresponding rise time of 490 μs for the higher performing chloroform device. The two OPVs were used to simultaneously detect leaked light from induced bends in the optical fiber, with the differing temporal profiles employed to create a unique time-correlated detection signal with enhanced security. The delay between detection of each OPV voltage could be systematically varied, allowing for either a programmable and secure single detection signal or triggering of multiple events with variable time resolution. The results reported in this study present exciting avenues toward the deployment of this simple and noninvasive optical detection system in a range of different applications. PMID:26891938

  13. Activation of Organic Photovoltaic Light Detectors Using Bend Leakage from Optical Fibers.

    PubMed

    Griffith, Matthew J; Willis, Matthew S; Kumar, Pankaj; Holdsworth, John L; Bezuidenhout, Henco; Zhou, Xiaojing; Belcher, Warwick; Dastoor, Paul C

    2016-03-01

    This work investigates the detection and subsequent utilization of leaked light from bends in a silica optical fiber using organic photovoltaic detectors. The optic power lost by single mode and multimode silica optical fibers was calibrated for bend radii between 1 and 7 mm for 532 and 633 nm light, exhibiting excellent agreement with previous theoretical solutions. The spatial location of maximum power leakage on the exterior of the fiber was found to exist in the same plane as the fiber, with a 10° offset from the normal. Two different organic photovoltaic detectors fabricated using a poly(3-hexylthiophene):indene-C60-bisadduct donor-acceptor blend cast from chloroform and chlorobenzene were fabricated to detect the leaked light. The two detectors exhibited different photovoltaic performances, predominantly due to different active layer thicknesses. Both devices showed sensitivity to leakage light, exhibiting voltages between 200 and 300 mV in response to leaked light from the fiber. The temporal responses of the devices were observed to differ, with a rise time from 10% to 90% of maximum voltage of 1430 μs for the chlorobenzene device, and a corresponding rise time of 490 μs for the higher performing chloroform device. The two OPVs were used to simultaneously detect leaked light from induced bends in the optical fiber, with the differing temporal profiles employed to create a unique time-correlated detection signal with enhanced security. The delay between detection of each OPV voltage could be systematically varied, allowing for either a programmable and secure single detection signal or triggering of multiple events with variable time resolution. The results reported in this study present exciting avenues toward the deployment of this simple and noninvasive optical detection system in a range of different applications.

  14. Spatially-resolved in-situ structural study of organic electronic devices with nanoscale resolution: the plasmonic photovoltaic case study.

    PubMed

    Paci, B; Bailo, D; Albertini, V Rossi; Wright, J; Ferrero, C; Spyropoulos, G D; Stratakis, E; Kymakis, E

    2013-09-14

    A novel high spatial resolution synchrotron X-ray diffraction stratigraphy technique has been applied in-situ to an integrated plasmonic nanoparticle-based organic photovoltaic device. This original approach allows for the disclosure of structure-property relations linking large scale organic devices to length scales of local nano/hetero structures and interfaces between the different components.

  15. Research in the Field of Organic Photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences

    NASA Astrophysics Data System (ADS)

    Troshin, Pavel A.

    2015-08-01

    In the present review we highlight the main research activities in the field of organic photonics and photovoltaics at the Institute for Problems of Chemical Physics of Russian Academy of Sciences (IPCP RAS). Extensive investigation of optical and electrical properties of π-conjugated organic compounds performed at IPCP RAS since 1960's resulted in design of many exciting materials representing organic semiconductors, metals and superconductors. Organic Schottky barrier and p/n junction photovoltaic devices constructed at IPCP RAS in 1960's and 1970's were among the first examples of reasonably efficient organic solar cells at that time. These early discoveries inspired younger generations of the researchers to continue the work of their mentors and explore the world of organic materials and photonic devices such as molecular photonic switches, organic light emitting diodes, solar cells, photodetectors, photoswitchable organic field-effect transistors and memory elements.

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

    PubMed Central

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

    2015-01-01

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

  17. Architectures and criteria for the design of high efficiency organic photovoltaic cells

    DOEpatents

    Rand, Barry; Forrest, Stephen R; Burk, Diana Pendergrast

    2015-03-24

    An organic photovoltaic cell includes an anode and a cathode, and a plurality of organic semiconductor layers between the anode and the cathode. At least one of the anode and the cathode is transparent. Each two adjacent layers of the plurality of organic semiconductor layers are in direct contact. The plurality of organic semiconductor layers includes an intermediate layer consisting essentially of a photoconductive material, and two sets of at least three layers. A first set of at least three layers is between the intermediate layer and the anode. Each layer of the first set consists essentially of a different organic semiconductor material having a higher LUMO and a higher HOMO, relative to the material of an adjacent layer of the plurality of organic semiconductor layers closer to the cathode. A second set of at least three layers is between the intermediate layer and the cathode. Each layer of the second set consists essentially of a different organic semiconductor material having a lower LUMO and a lower HOMO, relative to the material of an adjacent layer of the plurality of organic semiconductor layers closer to the anode.

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

    PubMed

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

    2015-06-30

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

  19. 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%.

  20. Perylenediimide functionalized bridged-siloxane nanoparticles for bulk heterojunction organic photovoltaics.

    PubMed

    Rathnayake, Hemali; Binion, Jenna; McKee, Aaron; Scardino, Debra Jo; Hammer, Nathan I

    2012-08-01

    Perylenediimide functionalized bridged siloxane nanoparticles were prepared by direct hydrolysis and condensation of a perylenediimide silane precursor in the presence of a catalytic amount of tetraethoxysilane (TEOS). The sizes of the particles were controlled by adjusting organotrialkoxysilane, base, and TEOS concentrations. Using this modified Stöber method, we were able to incorporate a higher load of organic content (∼70%) into the siloxane core compared to typical organically modified Stöber silica nanoparticles. The size, shape, and surface morphology of these functionalized particles were visualized using transmission electron microscopy. Their compositions were confirmed by FTIR, thermogravimetric analysis, and elemental analysis. The photovoltaic performance of these nanohybrids in the poly(3-hexylthiophene) polymer matrix was evaluated. The device made from a sample annealed at 150 °C showed reasonably good photovoltaic performance with a power conversion efficiency of 1.56% under standard test conditions of AM 1.5G spectra at an illumination intensity of 100 mW cm(-2).

  1. Can Computational Approaches Aid in Untangling the Inherent Complexity of Practical Organic Photovoltaic Systems?

    SciTech Connect

    Sumpter, Bobby G; Meunier, Vincent

    2012-01-01

    Organic materials, in particular conjugated polymers, have recently become the subject of extensive research for photovoltaic device applications. This increase of interest is primarily the result of their potentially low manufacturing cost, compatibility with flexible substrates, diverse chemical tunability, scalability, and ease of processing currently available for suitable bulk heterojunction (BHJ) construction. However, to-date, these materials have not been able to exceed power conversion efficiencies (PCE) beyond 5-9%, values shy of those considered commercially viable. The shortfall in PCE appears to derive from a combination of physicochemical and device complexities associated with inadequate hole transport mobility, solubility and miscibility with an appropriate acceptor, narrow electronic band gap for efficient solar light harvesting, appropriate HOMO and LUMO energies to maximize the open circuit voltage (Voc) and electron transfer to the acceptor, and in particular the control of the multidimensional problem of BHJ morphology. In this review article we provide an overview of some of the recent progress towards implementing theory, modeling and simulation approaches in combination with results from precision synthesis, characterization and device fabrication as a means to overcome/understand the inherent issues that limit practical applications of organic photovoltaics (OPVs).

  2. Tilted bulk heterojunction organic photovoltaic cells grown by oblique angle deposition

    NASA Astrophysics Data System (ADS)

    Li, Ning; Forrest, Stephen R.

    2009-09-01

    We demonstrate small molecule bulk heterojunction organic photovoltaic cells using oblique angle vacuum deposition. Obliquely deposited donor chloroaluminum phthalocyanine (ClAlPc) films on indium tin oxide have surface feature sizes of ˜30 nm, resulting in ClAlPc/C60 donor-acceptor heterojunctions (HJs) with approximately twice the interface area of HJs grown at normal incidence. This results in nearly twice the external quantum efficiency in the ClAlPc absorption band compared with analogous, planar HJs. The efficiency increase is attributed to the increased surface area presented by the donor-acceptor junction to the incident illumination by ClAlPc protrusions lying obliquely to the substrate plane formed during deposition. The power conversion efficiency improves from (2.0±0.1)% to (2.8±0.1)% under 1 sun, AM 1.5G simulated solar illumination. Similarly, the power efficiency of copper phthalocyanine/C60 organic photovoltaic cells is increased from (1.3±0.1)% to (1.7±0.1)%.

  3. High efficiency air stable organic photovoltaics with an aqueous inorganic contact

    NASA Astrophysics Data System (ADS)

    Jayawardena, K. D. G. Imalka; Li, Siying; Sam, Laurent F.; Smith, Christopher T. G.; Beliatis, Michail J.; Gandhi, Keyur K.; Prabhath, M. R. Ranga; Pozegic, Thomas R.; Chen, Sujie; Xu, Xiaoli; Dabera, G. Dinesha M. R.; Rozanski, Lynn J.; Sporea, Radu A.; Mills, Christopher A.; Guo, Xiaojun; Silva, S. Ravi P.

    2015-08-01

    We report a ZnO interfacial layer based on an environmentally friendly aqueous precursor for organic photovoltaics. Inverted PCDTBT devices based on this precursor show power conversion efficiencies of 6.8-7%. Unencapsulated devices stored in air display prolonged lifetimes extending over 200 hours with less than 20% drop in efficiency compared to devices based on the standard architecture.We report a ZnO interfacial layer based on an environmentally friendly aqueous precursor for organic photovoltaics. Inverted PCDTBT devices based on this precursor show power conversion efficiencies of 6.8-7%. Unencapsulated devices stored in air display prolonged lifetimes extending over 200 hours with less than 20% drop in efficiency compared to devices based on the standard architecture. Electronic supplementary information (ESI) available: Experimental methods, performance of standard architecture, inverted architecture with TiOx interlayer, onset of s-curves for the standard architecture, photoluminescence of the ZnO film, field effect characteristics of the ZnO thin films, thermogravimetric analysis of ZnO. See DOI: 10.1039/c5nr01239b

  4. Organic photovoltaic cells with stable top metal electrodes modified with polyethylenimine.

    PubMed

    Khan, Talha M; Zhou, Yinhua; Dindar, Amir; Shim, Jae Won; Fuentes-Hernandez, Canek; Kippelen, Bernard

    2014-05-14

    Efficient organic photovoltaic cells (OPV) often contain highly reactive low-work-function calcium electron-collecting electrodes. In this work, efficient OPV are demonstrated in which calcium electrodes were avoided by depositing a thin layer of the amine-containing nonconjugated polymer, polyethylenimine (PEIE), between the photoactive organic semiconductor layer and stable metal electrodes such as aluminum, silver, or gold. Devices with structure ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(3-hexylthiophene):indene-C60-bis-adduct (P3HT:ICBA)/PEIE/Al demonstrated overall photovoltaic device performance comparable to devices containing calcium electron-collecting electrodes, ITO/PEDOT:PSS/P3HT:ICBA/Ca/Al, with open-circuit voltage of 775±6 mV, short-circuit current density of 9.1±0.5 mA cm(-2), fill factor of 0.65±0.01, and power conversion efficiency of 4.6±0.3%, averaged over 5 devices at 1 sun.

  5. Fullerene C{sub 70} as a p-type donor in organic photovoltaic cells

    SciTech Connect

    Zhuang, Taojun; Wang, Xiao-Feng E-mail: zrhong@ucla.edu Sano, Takeshi; Kido, Junji E-mail: zrhong@ucla.edu; Hong, Ziruo E-mail: zrhong@ucla.edu; Li, Gang; Yang, Yang

    2014-09-01

    Fullerenes and their derivatives have been widely used as n-type materials in organic transistor and photovoltaic devices. Though it is believed that they shall be ambipolar in nature, there have been few direct experimental proofs for that. In this work, fullerene C{sub 70}, known as an efficient acceptor, has been employed as a p-type electron donor in conjunction with 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile as an electron acceptor in planar-heterojunction (PHJ) organic photovoltaic (OPV) cells. High fill factors (FFs) of more than 0.70 were reliably achieved with the C{sub 70} layer even up to 100 nm thick in PHJ cells, suggesting the superior potential of fullerene C{sub 70} as the p-type donor in comparison to other conventional donor materials. The optimal efficiency of these unconventional PHJ cells was 2.83% with a short-circuit current of 5.33 mA/cm{sup 2}, an open circuit voltage of 0.72 V, and a FF of 0.74. The results in this work unveil the potential of fullerene materials as donors in OPV devices, and provide alternative approaches towards future OPV applications.

  6. Negative differential resistance and photovoltaic phenomena observed in nanostructured organic heterojunction.

    PubMed

    Chowdhury, Avijit; Biswas, Bipul; Mallik, Biswanath

    2013-06-01

    Single layer organic photovoltaic devices based on copper phthalocyanine (CuPc) sandwiched between indium tin oxide (ITO) coated glass substrate and aluminum (Al) electrode have been fabricated. The interface dipoles formed at the metal/organic interface play a key role in determining the barrier for charge (electron or hole) injection between the metal electrode and significantly affects the efficiency of organic based electronic and optoelectronic devices. The origin of interface dipoles formed at the metal/organic (Al/CuPc) interface is assumed to be the charge transfer process between the organics (CuPc) and the metal (Al) electrode. Such a device shows forward rectifying property under dark condition when ITO kept at positive bias and Al kept at negative bias. Negative differential resistance (NDR) effect has been observed at high reverse bias voltage. Under white light excitation the device shows reverse rectifying property with a high open circuit voltage. It appears that the interface dipoles formed at the Al/CuPc junction act as exciton dissociation centers. NDR effect can be explained due to charge accumulation layer at the AI/CuPc interface and hence interface dipoles and/or band bending in CuPc. Asymmetry in dark current-voltage (I-V) characteristics has been explained due to strengthening or weakening the dipole field on the application of reverse bias or forward bias at the junction interface, respectively. Various photovoltaic parameters have been calculated from the I-V characteristics of the devices under illumination through ITO electrode. PMID:23862461

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

    PubMed

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

    2013-10-01

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

  8. Evaluation of the charge transfer efficiency of organic thin-film photovoltaic devices fabricated using a photoprecursor approach.

    PubMed

    Masuo, Sadahiro; Sato, Wataru; Yamaguchi, Yuji; Suzuki, Mitsuharu; Nakayama, Ken-ichi; Yamada, Hiroko

    2015-05-01

    Recently, a unique 'photoprecursor approach' was reported as a new option to fabricate a p-i-n triple-layer organic photovoltaic device (OPV) through solution processes. By fabricating the p-i-n architecture using two kinds of photoprecursors and a [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the donor and the acceptor, the p-i-n OPVs afforded a higher photovoltaic efficiency than the corresponding p-n devices and i-devices, while the photovoltaic efficiency of p-i-n OPVs depended on the photoprecursors. In this work, the charge transfer efficiency of the i-devices composed of the photoprecursors and PC71BM was investigated using high-sensitivity fluorescence microspectroscopy combined with a time-correlated single photon counting technique to elucidate the photovoltaic efficiency depending on the photoprecursors and the effects of the p-i-n architecture. The spatially resolved fluorescence images and fluorescence lifetime measurements clearly indicated that the compatibility of the photoprecursors with PC71BM influences the charge transfer and the photovoltaic efficiencies. Although the charge transfer efficiency of the i-device was quite high, the photovoltaic efficiency of the i-device was much lower than that of the p-i-n device. These results imply that the carrier generation and carrier transportation efficiencies can be increased by fabricating the p-i-n architecture.

  9. Photovoltaic properties and morphology of organic solar cells based on liquid-crystal semiconducting polymer with additive

    SciTech Connect

    Suzuki, Atsushi; Zushi, Masahito; Suzuki, Hisato; Ogahara, Shinichi; Akiyama, Tsuyoshi; Oku, Takeo

    2014-02-20

    Bulk heterojunction organic solar cell based on liquid crystal semiconducting polymers of poly[9,9-dioctylfluorene-co-bithiophene] (F8T2) as p-type semiconductors and fullerenes (C{sub 60}) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron donor and acceptor has been fabricated and characterized for improving photovoltaic and optical properties. The photovoltaic performance including current voltage curves in the dark and illumination of the F8T2/C{sub 60} conventional and inverted bulk heterojunction solar cells were investigated. Relationship between the photovoltaic properties and morphological behavior was focused on tuning for optimization of photo-voltaic performance under annealing condition near glass transition temperature. Additive-effect of diiodooctane (DIO) and poly(3-hexylthiophene-2,5-diyl) (P3HT) on the photovoltaic performance and optical properties was investigated. Mechanism of the photovoltaic properties of the conventional and inverted solar cells will be discussed by the experimental results.

  10. Interface engineering of graphene for universal applications as both anode and cathode in organic photovoltaics

    PubMed Central

    Park, Hyesung; Chang, Sehoon; Smith, Matthew; Gradečak, Silvija; Kong, Jing

    2013-01-01

    The high transparency of graphene, together with its good electrical conductivity and mechanical robustness, enable its use as transparent electrodes in optoelectronic devices such as solar cells. While initial demonstrations of graphene-based organic photovoltaics (OPV) have been promising, realization of scalable technologies remains challenging due to their performance and, critically, poor device reproducibility and yield. In this work, we demonstrate by engineering the interface between graphene and organic layers, device performance and yield become close to devices using indium tin oxide. Our study confirms that the key issue leading to the poor performance or irreproducibility in graphene-based OPV originates from the graphene interface, and can be addressed by a simple interface modification method introduced in this work. We also show similar approach allows graphene to be used as cathode in inverted OPV geometry, thereby demonstrating the universal application of graphene as transparent conductors for both the anode and cathode. PMID:23545570

  11. Performance enhancement of organic photovoltaic devices enabled by Au nanoarrows inducing surface plasmonic resonance effect.

    PubMed

    Li, Shujun; Li, Zhiqi; Zhang, Xinyuan; Zhang, Zhihui; Liu, Chunyu; Shen, Liang; Guo, Wenbin; Ruan, Shengping

    2016-09-21

    The surface plasmon resonance (SPR) effect of metal nanoparticles is widely employed in organic solar cells to enhance device performance. However, the light-harvesting improvement is highly dependent on the shape of the metal nanoparticles. In this study, the significantly enhanced performance upon incorporation of Au nanoarrows in solution-processed organic photovoltaic devices is demonstrated. Incorporating Au nanoarrows into the ZnO cathode buffer layer results in superior broadband optical absorption improvement and a power conversion efficiency of 7.82% is realized with a 27.3% enhancement compared with the control device. The experimental and theoretical results indicate that the introduction of Au nanoarrows not only increases optical trapping by the SPR effect but also facilitates exciton generation, dissociation, and charge transport inside the thin film device. PMID:27531663

  12. Effective variables to control the fill factor of organic photovoltaic cells.

    PubMed

    Kim, Myung-Su; Kim, Bong-Gi; Kim, Jinsang

    2009-06-01

    Effective cell design variables having a large impact on the fill factor (FF) of organic photovoltaic cells (OPVCs) were systematically identified using a general device structure of ITO/PEDOT:PSS/P3HT + PCBM/LiF/Al. The results show that the characteristic properties of the organic layer, such as morphology and thickness, the regioregularity of the conjugated polymer, and the two interfaces between the electrodes and the blend layer have a large influence on the FF by affecting the series resistance (R(s)) and the shunt resistance (R(sh)). The systematic investigation described in this contribution provides a comprehensive understanding of the correlation between the device variables and R(s) and R(sh) and a way to control FF, which is critically important to achieving a high-performance OPVC.

  13. Interface engineering of graphene for universal applications as both anode and cathode in organic photovoltaics.

    PubMed

    Park, Hyesung; Chang, Sehoon; Smith, Matthew; Gradečak, Silvija; Kong, Jing

    2013-01-01

    The high transparency of graphene, together with its good electrical conductivity and mechanical robustness, enable its use as transparent electrodes in optoelectronic devices such as solar cells. While initial demonstrations of graphene-based organic photovoltaics (OPV) have been promising, realization of scalable technologies remains challenging due to their performance and, critically, poor device reproducibility and yield. In this work, we demonstrate by engineering the interface between graphene and organic layers, device performance and yield become close to devices using indium tin oxide. Our study confirms that the key issue leading to the poor performance or irreproducibility in graphene-based OPV originates from the graphene interface, and can be addressed by a simple interface modification method introduced in this work. We also show similar approach allows graphene to be used as cathode in inverted OPV geometry, thereby demonstrating the universal application of graphene as transparent conductors for both the anode and cathode.

  14. Performance enhancement of organic photovoltaic devices enabled by Au nanoarrows inducing surface plasmonic resonance effect.

    PubMed

    Li, Shujun; Li, Zhiqi; Zhang, Xinyuan; Zhang, Zhihui; Liu, Chunyu; Shen, Liang; Guo, Wenbin; Ruan, Shengping

    2016-09-21

    The surface plasmon resonance (SPR) effect of metal nanoparticles is widely employed in organic solar cells to enhance device performance. However, the light-harvesting improvement is highly dependent on the shape of the metal nanoparticles. In this study, the significantly enhanced performance upon incorporation of Au nanoarrows in solution-processed organic photovoltaic devices is demonstrated. Incorporating Au nanoarrows into the ZnO cathode buffer layer results in superior broadband optical absorption improvement and a power conversion efficiency of 7.82% is realized with a 27.3% enhancement compared with the control device. The experimental and theoretical results indicate that the introduction of Au nanoarrows not only increases optical trapping by the SPR effect but also facilitates exciton generation, dissociation, and charge transport inside the thin film device.

  15. Directing energy transport in organic photovoltaic cells using interfacial exciton gates.

    PubMed

    Menke, S Matthew; Mullenbach, Tyler K; Holmes, Russell J

    2015-04-28

    Exciton transport in organic semiconductors is a critical, mediating process in many optoelectronic devices. Often, the diffusive and subdiffusive nature of excitons in these systems can limit device performance, motivating the development of strategies to direct exciton transport. In this work, directed exciton transport is achieved with the incorporation of exciton permeable interfaces. These interfaces introduce a symmetry-breaking imbalance in exciton energy transfer, leading to directed motion. Despite their obvious utility for enhanced exciton harvesting in organic photovoltaic cells (OPVs), the emergent properties of these interfaces are as yet uncharacterized. Here, directed exciton transport is conclusively demonstrated in both dilute donor and energy-cascade OPVs where judicious optimization of the interface allows exciton transport to the donor-acceptor heterojunction to occur considerably faster than when relying on simple diffusion. Generalized systems incorporating multiple exciton permeable interfaces are also explored, demonstrating the ability to further harness this phenomenon and expeditiously direct exciton motion, overcoming the diffusive limit.

  16. Enhanced photovoltaic performance of organic/silicon nanowire hybrid solar cells by solution-evacuated method.

    PubMed

    Wang, Wei-Li; Zou, Xian-Shao; Zhang, Bin; Dong, Jun; Niu, Qiao-Li; Yin, Yi-An; Zhang, Yong

    2014-06-01

    A method has been developed to fabricate organic-inorganic hybrid heterojunction solar cells based on n-type silicon nanowire (SiNW) and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) hybrid structures by evacuating the PEDOT:PSS solution with dip-dropping on the top of SiNWs before spin-coating (solution-evacuating). The coverage and contact interface between PEDOT:PSS and SiNW arrays can be dramatically enhanced by optimizing the solution-evacuated time. The maximum power conversion efficiency (PCE) reaches 9.22% for a solution-evacuated time of 2 min compared with 5.17% for the untreated pristine device. The improvement photovoltaic performance is mainly attributed to better organic coverage and contact with an n-type SiNW surface.

  17. Determining the optimum morphology in high-performance polymer-fullerene organic photovoltaic cells.

    PubMed

    Hedley, Gordon J; Ward, Alexander J; Alekseev, Alexander; Howells, Calvyn T; Martins, Emiliano R; Serrano, Luis A; Cooke, Graeme; Ruseckas, Arvydas; Samuel, Ifor D W

    2013-01-01

    The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM. We show that optimized blends consist of elongated fullerene-rich and polymer-rich fibre-like domains, which are 10-50 nm wide and 200-400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion that helps in the extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene domains show a much lower efficiency of charge extraction of ~45%, which is attributed to poor electron and hole transport. Our results show that the formation of narrow and elongated domains is desirable for efficient bulk heterojunction solar cells.

  18. Materials for the active layer of organic photovoltaics: ternary solar cell approach.

    PubMed

    Chen, Yung-Chung; Hsu, Chih-Yu; Lin, Ryan Yeh-Yung; Ho, Kuo-Chuan; Lin, Jiann T

    2013-01-01

    Power conversion efficiencies in excess of 7% have been achieved with bulk heterojunction (BHJ)-type organic solar cells using two components: p- and n-doped materials. The energy level and absorption profile of the active layer can be tuned by introduction of an additional component. Careful design of the additional component is required to achieve optimal panchromatic absorption, suitable energy-level offset, balanced electron and hole mobility, and good light-harvesting efficiency. This article reviews the recent progress on ternary organic photovoltaic systems, including polymer/small molecule/functional fullerene, polymer/polymer/functional fullerene, small molecule/small molecule/functional fullerene, polymer/functional fullerene I/functional fullerene II, and polymer/quantum dot or metal/functional fullerene systems.

  19. Spin-dependent charge transfer state design rules in organic photovoltaics.

    PubMed

    Chang, Wendi; Congreve, Daniel N; Hontz, Eric; Bahlke, Matthias E; McMahon, David P; Reineke, Sebastian; Wu, Tony C; Bulović, Vladimir; Van Voorhis, Troy; Baldo, Marc A

    2015-01-01

    Charge transfer states play a crucial role in organic photovoltaics, mediating both photocurrent generation and recombination losses. In this work, we examine recombination losses as a function of the electron-hole spacing in fluorescent charge transfer states, including direct monitoring of both singlet and triplet charge transfer state dynamics. Here we demonstrate that large donor-acceptor separations minimize back transfer from the charge transfer state to a low-lying triplet exciton 'drain' or the ground state by utilizing external pressure to modulate molecular spacing. The triplet drain quenches triplet charge transfer states that would otherwise be spin protected against recombination, and switches the most efficient origin of the photocurrent from triplet to singlet charge transfer states. Future organic solar cell designs should focus on raising the energy of triplet excitons to better utilize triplet charge transfer mediated photocurrent generation or increasing the donor-acceptor spacing to minimize recombination losses. PMID:25762410

  20. Solution-Processed Metal Oxides as Efficient Carrier Transport Layers for Organic Photovoltaics.

    PubMed

    Choy, Wallace C H; Zhang, Di

    2016-01-27

    Carrier (electron and hole) transport layers (CTLs) are essential components for boosting the performance of various organic optoelectronic devices such as organic solar cells and organic light-emitting diodes. Considering the drawbacks of conventional CTLs (easily oxidized/unstable, demanding/costly fabrication, etc.), transition metal oxides with good carrier transport/extraction and superior stability have drawn extensive research interest as CTLs for next-generation devices. In recent years, many research efforts have been made toward the development of solution-based metal oxide CTLs with the focus on low- or even room-temperature processes, which can potentially be compatible with the deposition processes of organic materials and can significantly contribute to the low-cost and scale-up of organic devices. Here, the recent progress of different types of solution-processed metal oxide CTLs are systematically reviewed in the context of organic photovoltaics, from synthesis approaches to device performance. Different approaches for further enhancing the performance of solution-based metal oxide CTLs are also discussed, which may push the future development of this exciting field.

  1. Organic MEMS/NEMS-based high-efficiency 3D ITO-less flexible photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Kassegne, Sam; Moon, Kee; Martín-Ramos, Pablo; Majzoub, Mohammad; Őzturk, Gunay; Desai, Krishna; Parikh, Mihir; Nguyen, Bao; Khosla, Ajit; Chamorro-Posada, Pedro

    2012-11-01

    A novel approach based on three-dimensional (3D) architecture for polymeric photovoltaic cells made up of an array of sub-micron and nano-pillars which not only increase the area of the light absorbing surface, but also improve the carrier collection efficiency of bulk-heterojunction organic solar cells is presented. The approach also introduces coating of 3D anodes with a new solution-processable highly conductive transparent polymer (Orgacon™) that replaces expensive vacuum-deposited ITO (indium tin oxide) as well as the additional hole-collecting layer of conventional PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)). In addition, the described procedure is well suited to roll-to-roll high-throughput manufacturing. The high aspect-ratio 3D pillars which form the basis for this new architecture are patterned through micro-electromechanical-system- and nano-electromechanical-system-based processes. For the particular case of P3HT (poly(3-hexylthiophene)) and PCBM (phenyl-C61-butyric acid methyl ester) active material, efficiencies in excess of 6% have been achieved for these photovoltaic cells of 3D architecture using ITO-less flexible PET (polyethylene terephthalate) substrates. This increase in efficiency turns out to be more than twice higher than those achieved for their 2D counterparts.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  3. A molecular nematic liquid crystalline material for high-performance organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Sun, Kuan; Xiao, Zeyun; Lu, Shirong; Zajaczkowski, Wojciech; Pisula, Wojciech; Hanssen, Eric; White, Jonathan M.; Williamson, Rachel M.; Subbiah, Jegadesan; Ouyang, Jianyong; Holmes, Andrew B.; Wong, Wallace W. H.; Jones, David J.

    2015-01-01

    Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.

  4. A molecular nematic liquid crystalline material for high-performance organic photovoltaics.

    PubMed

    Sun, Kuan; Xiao, Zeyun; Lu, Shirong; Zajaczkowski, Wojciech; Pisula, Wojciech; Hanssen, Eric; White, Jonathan M; Williamson, Rachel M; Subbiah, Jegadesan; Ouyang, Jianyong; Holmes, Andrew B; Wong, Wallace W H; Jones, David J

    2015-01-14

    Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.

  5. A molecular nematic liquid crystalline material for high-performance organic photovoltaics

    PubMed Central

    Sun, Kuan; Xiao, Zeyun; Lu, Shirong; Zajaczkowski, Wojciech; Pisula, Wojciech; Hanssen, Eric; White, Jonathan M.; Williamson, Rachel M.; Subbiah, Jegadesan; Ouyang, Jianyong; Holmes, Andrew B.; Wong, Wallace W.H.; Jones, David J.

    2015-01-01

    Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs. PMID:25586307

  6. High-Performance Silver Window Electrodes for Top-Illuminated Organic Photovoltaics Using an Organo-molybdenum Oxide Bronze Interlayer.

    PubMed

    Tyler, Martin S; Walker, Marc; Hatton, Ross A

    2016-05-18

    We report an organo-molybdenumn oxide bronze that enables the fabrication of high-performance silver window electrodes for top-illuminated solution processed organic photovoltaics without complicating the process of device fabrication. This hybrid material combines the function of wide-band-gap interlayer for efficient hole extraction with the role of metal electrode seed layer, enabling the fabrication of highly transparent, low-sheet-resistance silver window electrodes. Additionally it is also processed from ethanol, which ensures orthogonality with a large range of solution processed organic semiconductors. The key organic component is the low cost small molecule 3-mercaptopropionic acid, which (i) promotes metal film formation and imparts robustness at low metal thickness, (ii) reduces the contact resistance at the Ag/molybdenumn oxide bronze interface, (iii) and greatly improves the film forming properties. Silver electrodes with a thickness of 8 nm deposited by simple vacuum evaporation onto this hybrid interlayer have a sheet resistance as low as 9.7 Ohms per square and mean transparency ∼80% over the wavelength range 400-900 nm without the aid of an antireflecting layer, which makes them well-matched to the needs of organic photovoltaics and applicable to perovskite photovoltaics. The application of this hybrid material is demonstrated in two types of top-illuminated organic photovoltaic devices.

  7. Water Based Inkjet Material Deposition Of Donor-Acceptor Nanoparticles For Usage In Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Penmetcha, Anirudh Raju

    Significant efficiency increases are being made for bulk heterojunction organic photovoltaic prototype devices with world records at 11%. However the chlorinated solvents most frequently used in prototype manufacture would cause local health and safety concerns or large scale environmental pollution upon expansion of these techniques for commercialization. Moreover, research to bridge prototype and large-scale production of these solar cells is still in its infancy. Most prototype devices are made in inert glove box environments using spin-coating. There is a need to develop a non-toxic ink and incorporate it into a material deposition system that can be used in mass production. In this thesis, P3HT:PCBM organic photovoltaic devices were fabricated with the help of inkjet printing. P3HT:PCBM blends were dissolved in organic solvent systems, and this solution was used as the ink for the printer. The "coffee-ring effect" as well as the effect of inkjet printing parameters on film formation were highlighted - thus the inkjet printing method was validated as a stepping stone between lab-scale production of OPVs and large-scale roll-to-roll manufacturing. To address the need of a non-toxic ink, P3HT:PCBM blends were then dispersed in water, using the miniemulsion method. The nanoparticles were characterized for their size, as well as the blending between the P3HT and PCBM within the nanoparticle. These dispersions were then converted into inks. Finally, these nanoparticle inks were inkjet-printed to fabricate OPV devices. Based on the results obtained here, tentative "next steps" have been outlined in order to improve upon this research work, in the future.

  8. Motivating California organic farmers to go solar: Economics may trump philosophy in deciding to adopt photovoltaics

    NASA Astrophysics Data System (ADS)

    Fata, Johnathon A.

    Organic farmers who have adopted solar photovoltaic (PV) systems to generate electricity are leaders in agricultural energy sustainability, yet research on their culture and motivations is largely incomplete. These farmers share economic and logistical constraints, but they may differ in their underlying worldviews. To better understand what motivates San Francisco Bay Area organic farmers to install solar PV systems, 14 in-depth interviews and short surveys were conducted and included a "frontier mentality" rubric. Additionally, nine online surveys were administered. In this study's sample, financial concerns turned out to provide the greatest motivation for farmers to adopt solar PV. Concern for the environment followed closely. Among farms that did not have solar, the overwhelming prohibiting factor was upfront cost. Climate change was not cited directly as a driving force for adoption of solar PV by any of the participants. A wide range of differences among organic farmers existed in environmental attitudes. This reflected the diversity of views held by organic farmers in California today. For example, certified organic farmers had less strongly held environmental values than did those that eschew third-party certification in favor of a trust-based connection to the consumer. Understanding this group of highly involved environmental players provides insight into environmental behavior of other farmers as well as broader categories of consumers and businesses.

  9. Mesoporous silicate MCM-41 containing organic ultraviolet ray absorbents: Preparation, photostability and in vitro release

    NASA Astrophysics Data System (ADS)

    Ambrogi, V.; Perioli, L.; Marmottini, F.; Latterini, L.; Rossi, C.; Costantino, U.

    2007-05-01

    The mesoporous silicate MCM-41 was studied for its properties to adsorb and to influence the photostability and the release of three organic ultraviolet (UV) ray absorbents, namely benzophenone-3 (B3), benzophenone-2 (B2) and p-aminobenzoic acid (PABA). MCM-41 microcrystals have been loaded with the UV absorbents obtaining a good loading w/w percentage. The loaded samples have been characterized by chemical and thermal analyses, X-ray diffraction, N2 adsorption isotherms. Photochemical studies demonstrated that the UV-shielding properties of B2 were maintained whereas in other cases a small reduction of sunscreen protection range was noticed. B3 and B2 release from loaded MCM-41 formulations were studied and compared to those obtained from formulations containing free UV ray absorbent; no remarkable differences were observed in the release profiles.

  10. 25th anniversary article: a decade of organic/polymeric photovoltaic research.

    PubMed

    Dou, Letian; You, Jingbi; Hong, Ziruo; Xu, Zheng; Li, Gang; Street, Robert A; Yang, Yang

    2013-12-10

    Organic photovoltaic (OPV) technology has been developed and improved from a fancy concept with less than 1% power conversion efficiency (PCE) to over 10% PCE, particularly through the efforts in the last decade. The significant progress is the result of multidisciplinary research ranging from chemistry, material science, physics, and engineering. These efforts include the design and synthesis of novel compounds, understanding and controlling the film morphology, elucidating the device mechanisms, developing new device architectures, and improving large-scale manufacture. All of these achievements catalyzed the rapid growth of the OPV technology. This review article takes a retrospective look at the research and development of OPV, and focuses on recent advances of solution-processed materials and devices during the last decade, particular the polymer version of the materials and devices. The work in this field is exciting and OPV technology is a promising candidate for future thin film solar cells. PMID:24105687

  11. Bulk heterojunction organic photovoltaics from water-processable nanomaterials and their facile fabrication approaches.

    PubMed

    Subianto, Surya; Dutta, Naba; Andersson, Mats; Choudhury, Namita Roy

    2016-09-01

    Organic thin film photovoltaics based on bulk-heterojunction donor-acceptor combinations have received significant interest due to their potential for low-cost, large-scale solution processing. However, current state-of-the-art cells utilise materials soluble mainly in halogenated solvents which pose processing challenges due to their toxicity and thus environmental hazards. In this contribution, we look at various nanomaterials, and alternative processing of these solar cells using environmentally friendly solvents, and review recently reported different strategies and approaches that are making inroads in this field. Specifically, we focus on the use of water-dispersible donors and acceptors, use of aqueous solvents for fabrication and discuss the merits of the two main approaches of water-processable solar cells; namely, through the use of water-soluble materials and the use of aqueous dispersion rather than a solution, as well as review some of the recent advances in alternative fabrication techniques.

  12. Evidence of Delocalization in Charge-Transfer State Manifold for Donor:Acceptor Organic Photovoltaics.

    PubMed

    Guan, Zhiqiang; Li, Ho-Wa; Zhang, Jinfeng; Cheng, Yuanhang; Yang, Qingdan; Lo, Ming-Fai; Ng, Tsz-Wai; Tsang, Sai-Wing; Lee, Chun-Sing

    2016-08-24

    How charge-transfer states (CTSs) assist charge separation of a Coulombically bound exciton in organic photovoltaics has been a hot topic. It is believed that the delocalization feature of a CTS plays a crucial role in the charge separation process. However, the delocalization of the "hot" and the "relaxed" CTSs is still under debate. Here, with a novel frequency dependent charge-modulated electroabsorption spectroscopy (CMEAS) technique, we elucidate clearly that both "hot" and "relaxed" CTSs are loosely bound and delocalized states. This is confirmed by comparing the CMEAS results of CTSs with those of localized polaron states. Our results reveal the role of CTS delocalization on charge separation and indicate that no substantial delocalization gradient exists in CTSs.

  13. Methods for improving the lifetime performance of organic photovoltaics with low-costing encapsulation.

    PubMed

    Giannouli, Myrsini; Drakonakis, Vasileios M; Savva, Achilleas; Eleftheriou, Polyvios; Florides, Georgios; Choulis, Stelios A

    2015-04-27

    Recent years have seen considerable advances in organic photovoltaics (OPVs), most notably a significant increase in their efficiency, from around 4 % to over 10 %. The stability of these devices, however, continues to remain an issue that needs to be resolved to enable their commercialization. This review discusses the main degradation processes of OPVs and recent methods that help to increase device stability and lifetime. One of the most effective steps that can be taken to increase the lifetime of OPVs is their encapsulation, which protects them from atmospheric degradation. Efficient encapsulation is essential for long-term device performance, but it is equally important for the commercialization of OPVs to strike a balance between achieving the maximum device protection possible and using low-cost processing for their encapsulation. Various encapsulation techniques are discussed herein, with emphasis on their cost effectiveness and their overall suitability for commercial applications.

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

    SciTech Connect

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

    2015-07-06

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

  15. Assessment of Hybrid Organic-Inorganic Antimony Sulfides for Earth-Abundant Photovoltaic Applications.

    PubMed

    Yang, Ruo Xi; Butler, Keith T; Walsh, Aron

    2015-12-17

    Hybrid organic-inorganic solar absorbers are currently the subject of intense interest; however, the highest-performing materials contain Pb. Here we assess the potential of three Sb-based semiconductors: (i) Sb2S3, (ii) Cs2Sb8S13, and (iii) (CH3NH3)2Sb8S13. While the crystal structure of Sb2S3 is composed of 1D chains, 2D layers are formed in the ternary cesium and hybrid methylammonium antimony sulfide compounds. In each case, a stereochemically active Sb 5s(2) lone pair is found, resulting in a distorted coordination environment for the Sb cations. The bandgap of the binary sulfide is found to increase, while the ionization potential also changes, upon transition to the more complex compounds. Based on the predicted electronic structure, device configurations are suggested to be suitable for photovoltaic applications. PMID:26624204

  16. Influence of the morphology of organic heterojunction on the photovoltaic cell performance

    NASA Astrophysics Data System (ADS)

    Podhájecká, K.; Pfleger, J.

    2006-12-01

    We present a series of organic photovoltaic (PV) cells based on the bulk-distributed heterojunction where π -conjugated polymer poly[1-(4-trimethylsilylphenyl)-2-phenylvinylene], PSDPhV, acts as the donor upon photoexcitation and the substituted perylene based low-molecular-weight compound: N,N`-di(pent-3-yl)-perylene-3,4:9,10-bis(dicarboximide), DPe-PTCDI, as the acceptor of photogenerated electrons. According to both absorption spectra and AFM images of the thin films spin-coated from solution of DPe-PTCDI and PSDPhV in toluene, the DPe-PTCDI is molecularly dissolved in conjugated polymer matrix. Upon exposition of layers to toluene vapors, microcrystals of DPe-PTCDI are progressively formed. The influence of the morphology of DPe-PTCDI inside the polymer matrix on PV cell performance is investigated. This paper has been presented at “ECHOS06”, Paris, 28 30 juin 2006.

  17. Delocalization and dielectric screening of charge transfer states in organic photovoltaic cells.

    PubMed

    Bernardo, B; Cheyns, D; Verreet, B; Schaller, R D; Rand, B P; Giebink, N C

    2014-01-01

    Charge transfer (CT) states at a donor-acceptor heterojunction have a key role in the charge photogeneration process of organic solar cells, however, the mechanism by which these states dissociate efficiently into free carriers remains unclear. Here we explore the nature of these states in small molecule-fullerene bulk heterojunction photovoltaics with varying fullerene fraction and find that the CT energy scales with dielectric constant at high fullerene loading but that there is a threshold C60 crystallite size of ~4 nm below which the spatial extent of these states is reduced. Electroabsorption measurements indicate an increase in CT polarizability when C60 crystallite size exceeds this threshold, and that this change is correlated with increased charge separation yield supported by CT photoluminescence transients. These results support a model of charge separation via delocalized CT states independent of excess heterojunction offset driving energy and indicate that local fullerene crystallinity is critical to the charge separation process.

  18. Effect of temperature on carrier formation efficiency in organic photovoltaic cells

    SciTech Connect

    Moritomo, Yutaka Yonezawa, Kouhei; Yasuda, Takeshi

    2014-08-18

    The internal quantum efficiency (ϕ{sub IQ}) of an organic photovoltaic cell is governed by plural processes. Here, we propose that ϕ{sub IQ} can be experimentally decomposed into carrier formation (ϕ{sub CF}) and carrier transfer (ϕ{sub CT}) efficiencies. By combining femtosecond time-resolved and electrochemical spectroscopy, we clarified the effect of temperature on ϕ{sub CF} in a regioregular poly(3-hexylthiophene) (rr-P3HT)/[6,6]-phenyl C{sub 61}-butyric acid methyl ester blend film. We found that ϕ{sub CF} (=0.55) at 80 K is the same as that (=0.55) at 300 K. The temperature insensitivity of ϕ{sub CF} indicates that the electron-hole pairs at the D/A interface are seldom subjected to coulombic binding energy.

  19. Assessment of Hybrid Organic-Inorganic Antimony Sulfides for Earth-Abundant Photovoltaic Applications.

    PubMed

    Yang, Ruo Xi; Butler, Keith T; Walsh, Aron

    2015-12-17

    Hybrid organic-inorganic solar absorbers are currently the subject of intense interest; however, the highest-performing materials contain Pb. Here we assess the potential of three Sb-based semiconductors: (i) Sb2S3, (ii) Cs2Sb8S13, and (iii) (CH3NH3)2Sb8S13. While the crystal structure of Sb2S3 is composed of 1D chains, 2D layers are formed in the ternary cesium and hybrid methylammonium antimony sulfide compounds. In each case, a stereochemically active Sb 5s(2) lone pair is found, resulting in a distorted coordination environment for the Sb cations. The bandgap of the binary sulfide is found to increase, while the ionization potential also changes, upon transition to the more complex compounds. Based on the predicted electronic structure, device configurations are suggested to be suitable for photovoltaic applications.

  20. Electric field measurement of organic photovoltaic cell model using electrooptic probe

    NASA Astrophysics Data System (ADS)

    Saito, Ryo; Yabe, Yoko; Suzuki, Akito; Shinagawa, Mitsuru; Sugino, Hiroyuki; Katsuyama, Jun; Matsumoto, Yoshinori

    2016-09-01

    In this paper, we describe the use of a transverse electrooptic probe to measure the electric field of an organic photovoltaic (OPV) cell model. It is necessary to measure the voltage of each OPV cell in order to diagnose failure of the OPV. An electric field is generated by the OPV cell voltage, so measuring the electric field is effective for obtaining a failure diagnosis of the OPV. We use a transverse electrooptic probe as an instrumentation tool for measuring the electric field over the OPV. We confirmed the principle of superposition for the electric field strength from each OPV cell model. These results show that the calibration of each OPV cell voltage can be accomplished by measuring the electric field strength over the OPV cells.

  1. Correlation between the Open-Circuit Voltage and Charge Transfer State Energy in Organic Photovoltaic Cells.

    PubMed

    Zou, Yunlong; Holmes, Russell J

    2015-08-26

    In order to further improve the performance of organic photovoltaic cells (OPVs), it is essential to better understand the factors that limit the open-circuit voltage (VOC). Previous work has sought to correlate the value of VOC in donor-acceptor (D-A) OPVs to the interface energy level offset (EDA). In this work, measurements of electroluminescence are used to extract the charge transfer (CT) state energy for multiple small molecule D-A pairings. The CT state as measured from electroluminescence is found to show better correlation to the maximum VOC than EDA. The difference between EDA and the CT state energy is attributed to the Coulombic binding energy of the CT state. This correlation is demonstrated explicitly by inserting an insulating spacer layer between the donor and acceptor materials, reducing the binding energy of the CT state and increasing the measured VOC. These results demonstrate a direct correlation between maximum VOC and CT state energy.

  2. Organic photovoltaics: elucidating the ultra-fast exciton dissociation mechanism in disordered materials.

    PubMed

    Heitzer, Henry M; Savoie, Brett M; Marks, Tobin J; Ratner, Mark A

    2014-07-14

    Organic photovoltaics (OPVs) offer the opportunity for cheap, lightweight and mass-producible devices. However, an incomplete understanding of the charge generation process, in particular the timescale of dynamics and role of exciton diffusion, has slowed further progress in the field. We report a new Kinetic Monte Carlo model for the exciton dissociation mechanism in OPVs that addresses the origin of ultra-fast (<1 ps) dissociation by incorporating exciton delocalization. The model reproduces experimental results, such as the diminished rapid dissociation with increasing domain size, and also lends insight into the interplay between mixed domains, domain geometry, and exciton delocalization. Additionally, the model addresses the recent dispute on the origin of ultra-fast exciton dissociation by comparing the effects of exciton delocalization and impure domains on the photo-dynamics.This model provides insight into exciton dynamics that can advance our understanding of OPV structure-function relationships.

  3. Monte Carlo Simulations of Charge Transport in 2D Organic Photovoltaics.

    PubMed

    Gagorik, Adam G; Mohin, Jacob W; Kowalewski, Tomasz; Hutchison, Geoffrey R

    2013-01-01

    The effect of morphology on charge transport in organic photovoltaics is assessed using Monte Carlo. In isotopic two-phase morphologies, increasing the domain size from 6.3 to 18.3 nm improves the fill factor by 11.6%, a result of decreased tortuosity and relaxation of Coulombic barriers. Additionally, when small aggregates of electron acceptors are interdispersed into the electron donor phase, charged defects form in the system, reducing fill factors by 23.3% on average, compared with systems without aggregates. In contrast, systems with idealized connectivity show a 3.31% decrease in fill factor when domain size was increased from 4 to 64 nm. We attribute this to a decreased rate of exciton separation at donor-acceptor interfaces. Finally, we notice that the presence of Coulomb interactions increases device performance as devices become smaller. The results suggest that for commonly found isotropic morphologies the Coulomb interactions between charge carriers dominates exciton separation effects.

  4. Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes.

    PubMed

    Gélinas, Simon; Rao, Akshay; Kumar, Abhishek; Smith, Samuel L; Chin, Alex W; Clark, Jenny; van der Poll, Tom S; Bazan, Guillermo C; Friend, Richard H

    2014-01-31

    Understanding the charge-separation mechanism in organic photovoltaic cells (OPVs) could facilitate optimization of their overall efficiency. Here we report the time dependence of the separation of photogenerated electron hole pairs across the donor-acceptor heterojunction in OPV model systems. By tracking the modulation of the optical absorption due to the electric field generated between the charges, we measure ~200 millielectron volts of electrostatic energy arising from electron-hole separation within 40 femtoseconds of excitation, corresponding to a charge separation distance of at least 4 nanometers. At this separation, the residual Coulomb attraction between charges is at or below thermal energies, so that electron and hole separate freely. This early time behavior is consistent with charge separation through access to delocalized π-electron states in ordered regions of the fullerene acceptor material.

  5. Nanophotonics for Optoelectronic Devices: Extrinsic Silicon Photonic Receivers and Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Grote, Richard R.

    The demand for high data rate communications and renewable energy sources has led to new materials and platforms for optoelectronic devices, which require nanometer scale feature sizes. Devices that operate in the visible and near-infrared commonly have active areas with dimensions on the order of the diffraction limit ( l2n , where lambda is the free space wavelength and n is the index of refraction), for which the ray optics modeling techniques and bulk focusing optics traditionally used in optoelectronic device design are no longer applicable. In this subwavelength regime, nanophotonic light-trapping strategies are required to localize electromagnetic fields in the active area. This dissertation details the application of nanophotonics to two optoelectronic systems: extrinsic photodetectors for silicon photonics and light-trapping in organic photovoltaics. Error-free reception of 10 Gb/s data at lambda = 1.55 mum is demonstrated with a Si+ ion-implanted silicon waveguide photodiode. To mitigate the relatively small absorption coefficient of ion-implanted silicon, resonant cavity enhancement using in-line Fabry-Perot and 1D photonic crystal cavities, as well as slow light enhancement using a coupled resonator optical waveguide are discussed. The extension of these photodiodes to the mid-infrared is demonstrated using Zn+ implantation to detect over a range of lambda = 2.2-2.4 mum, and a new method for modulation and switching in integrated optics by using interference in a resonant cavity, termed coherent perfect loss (CPL), is presented. Finally, the upper limit of nanophotonic light trapping is derived for organic photovoltaics with material anisotropy included.

  6. Elucidating the Role of Conjugated Polyelectrolyte Interlayers for High-Efficiency Organic Photovoltaics.

    PubMed

    Lim, Kyung-Geun; Park, Sung Min; Woo, Han Young; Lee, Tae-Woo

    2015-09-21

    Despite the promising function of conjugated polyelectrolytes (CPEs) as an interfacial layer in organic photovoltaics (OPVs), the underlying mechanism of dipole orientation and the electrical characteristics of CPE interlayers remain unclear. Currently, the ionic functionality of CPEs (i.e., whether they are cationic or anionic) is believed to determine the interfacial dipole alignment and the resulting electron or hole extraction properties at the interface between an organic photoactive layer and a metal electrode. In this research, we find that in contrast to this common belief, the photovoltaic efficiency can be improved significantly by both cationic and anionic CPE layers regardless of the ion functionality of the CPE. This improvement occurs because the interfacial dipoles of cationic and anionic CPEs are realigned in the identical direction despite the different ionic functionality. The net dipole is determined not by the intrinsic molecular dipole of the CPE but by the ionic redistribution in the CPE layer and the resulting interfacial dipole at the intimate contact with adjacent layers. We also demonstrated that the energy level alignment and performance parameters of OPVs can be controlled systematically by the electrically poled CPE layers with the oriented interfacial dipoles; the distribution of positive and negative ions in the CPE layer was adjusted by applying an appropriate external electric field, and the energy alignment was reversible by changing the electric field direction. The anionic and cationic CPEs (PSBFP-Na and PAHFP-Br) based on the same π-conjugated backbone of fluorene-phenylene were each used as the electron extraction layer on a photoactive layer. Both anionic and cationic CPE interlayers improved the energy level alignment at the interface between the photoactive layer and the electrode and the resulting performance parameters, which thereby increased the power conversion efficiency to 8.3 %.

  7. Synthesis and characterization of organic semiconducting polymers containing dithienylfluorenone for use in organic photovoltaic cells.

    PubMed

    Byun, Yun-Sun; Kim, Ji-Hoon; Park, Jong Baek; Hwang, Do-Hoon

    2014-08-01

    2,7-Bis(5-bromo-4-hexylthiophen-2-yl)-9H-fluoren-9-one (DTFO) was synthesized as a new electron-accepting material in semiconducting polymers for use in photovoltaic devices. The synthesized DTFO was polymerized with two different electron-donating counter monomers: 2,7-dibromo-9,9-dioctyl-9H-fluorene (DOF) and 2,6-bis(trimethyltin)-4,8-di(2-ethylhexyloxyl)benzo [1,2-b:4,5-b']dithiophene (BDT). Two alternating copolymers, poly(DTFO-alt-DOF) and poly(DTFO-alt-BDT), were synthesized through the Suzuki and Stille coupling polymerizations, respectively. The synthesized polymers exhibited good solubility in common solvents and show good thermal stability up to 350 °C. The optical band gap energies of poly(DTFO-alt-DOF) and poly(DTFO-alt-BDT) were determined to be 2.44 and 2.23 eV, respectively. The positions of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the polymers were determined by cyclic voltammetry (CV). One of these devices showed a power conversion efficiency of 0.50%, with an open-circuit voltage of 0.67 V, a short-circuit current of 2.34 mA/cm2, and a fill factor of 0.30 under air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW/cm2).

  8. Characteristics of dissolved organic carbon revealed by ultraviolet/visible absorbance and fluorescence spectroscopy: The current status and future exploration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dissolved organic carbon (DOC) is an important research subject for various disciplines. The objectives of this chapter are to review and summarize recent advancement in characterization of DOC by ultraviolet/visible (UV/Vis) and fluorescence spectroscopies and to identify the information gaps for ...

  9. Optical studies of the charge transfer complex in polythiophene/fullerene blends for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Drori, T.; Holt, J.; Vardeny, Z. V.

    2010-08-01

    We studied the photophysics of regioregular polythiophene/ C61 (RR-P3HT/PCBM) blend films utilized for organic photovoltaic applications using the femtosecond transient and steady-state photomodulation techniques with above-gap and below-gap pump excitations and electroabsorption spectroscopy. We provide strong evidence for the existence of charge transfer complex (CTC) state in the blend that is formed deep inside the optical gap of the polymer and fullerene constituents, which is clearly revealed in the electroabsorption spectrum with an onset at 1.2 eV. We identify this “midgap” band as the lowest lying CTC state formed at the interfaces separating the polymer and fullerene phases. With above-gap pump excitation the primary photoexcitations in the blend are excitons and polarons in the polymer domains that are generated within the experimental time resolution (150 fs), having distinguishable photoinduced absorption (PA) bands in the mid-IR. The photogenerated excitons subsequently decay within ˜10ps , consistent with the polymer weak photoluminescence in the blend. In contrast, with below-gap pump excitation, a new PA band in the mid-IR is generated within our time resolution, which is associated with photogenerated species that decay into polarons at much later times; also no PA of excitons is observed. We interpret the photoexcitations as CT excitons, which with below-gap pump excitation are resonantly generated on the CTC states at the interfaces, as the first step for polaron generation, without involving intrachain excitons in the polymer phase. We found that the polarons generated with below-gap pump excitation are trapped at the interfaces with relatively long lifetime, and thus may generate polarons on the polymer chains and fullerene molecules with a different mechanism than with above-gap excitation. In any case the interfacial polarons generated with below-gap excitation do not substantially contribute to the photocurrent density in photovoltaic

  10. Aggregation of a dibenzo[b,def]chrysene based organic photovoltaic material in solution.

    PubMed

    Simonov, Alexandr N; Kemppinen, Peter; Pozo-Gonzalo, Cristina; Boas, John F; Bilic, Ante; Scully, Andrew D; Attia, Adel; Nafady, Ayman; Mashkina, Elena A; Winzenberg, Kevin N; Watkins, Scott E; Bond, Alan M

    2014-06-19

    Detailed electrochemical studies have been undertaken on molecular aggregation of the organic semiconductor 7,14-bis((triisopropylsilyl)-ethynyl)dibenzo[b,def]chrysene (TIPS-DBC), which is used as an electron donor material in organic solar cells. Intermolecular association of neutral TIPS-DBC molecules was established by using (1)H NMR spectroscopy as well as by the pronounced dependence of the color of TIPS-DBC solutions on concentration. Diffusion limited current data provided by near steady-state voltammetry also reveal aggregation. Furthermore, variation of concentration produces large changes in shapes of transient DC and Fourier transformed AC (FTAC) voltammograms for oxidation of TIPS-DBC in dichloromethane. Subtle effects of molecular aggregation on the reduction of TIPS-DBC are also revealed by the highly sensitive FTAC voltammetric method. Simulations of FTAC voltammetric data provide estimates of the kinetic and thermodynamic parameters associated with oxidation and reduction of TIPS-DBC. Significantly, aggregation of TIPS-DBC facilitates both one-electron oxidation and reduction by shifting the reversible potentials to less and more positive values, respectively. EPR spectroscopy is used to establish the identity of one-electron oxidized and reduced forms of TIPS-DBC. Implications of molecular aggregation on the HOMO energy level in solution are considered with respect to efficiency of organic photovoltaic devices utilizing TIPS-DBC as an electron donor material.

  11. Study on electrical and thermal behavior of organic photovoltaic (OPV) cells

    NASA Astrophysics Data System (ADS)

    Dobre, Robert Alexandru; Ionescu, Ciprian; Vlǎdescu, Marian; NiÅ£ǎ, Valentin Adrian

    2015-02-01

    Organic photovoltaic cells represent a major application of Flexible Organic and Large Area Electronics (FOLAE) field. The advantages of these cells are represented by flexibility and reduced thickness, making them easy to be integrated in electronics designs, removing the necessity of having a large, flat, heavy surface for energy harvesting. Although many studies about the structure1 and chemical reactions that occur exist, not a large amount of information is available about the characteristics that would be useful for an electronics engineer designing an electronic system. This paper presents the investigations of the electrical2 and thermal behavior of OPV cells, offering as results the optimal operating conditions and their evaluation using a comparison with the standard, semiconductor-based cells. Thermal characterization is very important because the targeted light source is the sun. By exposing the panels to sunlight in a summer day will greatly increase the working temperature of the cells, implying the necessity of knowing the impact on their electrical characteristics. The response of the cells at different wavelengths of the incident light, voltage vs. current and output voltage diagrams for different light intensities and different temperatures will be determined. In addition, the behavior of the cell as a light sensor will be investigated and a system that uses organic electronics at both ends: for sensing light intensity and also displaying this information will be built, using an electrochromic display.

  12. Intensity-modulated scanning Kelvin probe microscopy for probing recombination in organic photovoltaics.

    PubMed

    Shao, Guozheng; Glaz, Micah S; Ma, Fei; Ju, Huanxin; Ginger, David S

    2014-10-28

    We study surface photovoltage decays on sub-millisecond time scales in organic solar cells using intensity-modulated scanning Kelvin probe microscopy (SKPM). Using polymer/fullerene (poly[N-9"-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]/[6,6]-phenyl C71-butyric acid methyl ester, PCDTBT/PC71BM) bulk heterojunction devices as a test case, we show that the decay lifetimes measured by SKPM depend on the intensity of the background illumination. We propose that this intensity dependence is related to the well-known carrier-density-dependent recombination kinetics in organic bulk heterojunction materials. We perform transient photovoltage (TPV) and charge extraction (CE) measurements on the PCDTBT/PC71BM blends to extract the carrier-density dependence of the recombination lifetime in our samples, and we find that the device TPV and CE data are in good agreement with the intensity and frequency dependence observed via SKPM. Finally, we demonstrate the capability of intensity-modulated SKPM to probe local recombination rates due to buried interfaces in organic photovoltaics (OPVs). We measure the differences in photovoltage decay lifetimes over regions of an OPV cell fabricated on an indium tin oxide electrode patterned with two different phosphonic acid monolayers known to affect carrier lifetime.

  13. Organic molecules and nanoparticles in inorganic crystals: Vitamin C in CaCO3 as an ultraviolet absorber

    NASA Astrophysics Data System (ADS)

    Sato, H.; Ikeya, M.

    2004-03-01

    Organic molecules and nanoparticles embedded in inorganic crystalline lattices have been studied to add different properties and functions to composite materials. Calcium carbonate was precipitated by dropping an aqueous solution of CaCl2 into that of Na2CO3 containing dissolved vitamin C (ascorbic acid). The optical absorption ascribed to divalent ascorbate anions in the lattice was observed in the ultraviolet B (wavelength: 280-315 nm) region, while solid vitamin C exhibited absorption in the ultraviolet C (100-280 nm) region. The divalent ascorbate anion is only stable in CaCO3 due to the absence of oxygen molecules. Doping CaCO3 with nanoparticles of ZnO also enhanced the absorption in the ultraviolet A (315-380 nm) region. These composite materials are suggested for use as UV absorbers.

  14. Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light.

    PubMed

    Wu, Qianyuan; Li, Chao; Wang, Wenlong; He, Tao; Hu, Hongying; Du, Ye; Wang, Ting

    2016-05-01

    Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter (DOM) was investigated in this study. Solar light significantly decreased the UV254 absorbance and fluorescence (FLU) intensity of reclaimed water. However, its effect on the dissolved organic carbon (DOC) value of reclaimed water was very limited. The decrease in the UV254 absorbance intensity and FLU excitation-emission matrix regional integration volume (FLU volume) of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV254 absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV254 absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV254 and FLU intensity were independent of light intensity. The peaks of the UV254 absorbance and FLU intensity with an apparent molecular weight (AMW) of 100Da to 2000Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.

  15. Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light.

    PubMed

    Wu, Qianyuan; Li, Chao; Wang, Wenlong; He, Tao; Hu, Hongying; Du, Ye; Wang, Ting

    2016-05-01

    Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter (DOM) was investigated in this study. Solar light significantly decreased the UV254 absorbance and fluorescence (FLU) intensity of reclaimed water. However, its effect on the dissolved organic carbon (DOC) value of reclaimed water was very limited. The decrease in the UV254 absorbance intensity and FLU excitation-emission matrix regional integration volume (FLU volume) of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV254 absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV254 absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV254 and FLU intensity were independent of light intensity. The peaks of the UV254 absorbance and FLU intensity with an apparent molecular weight (AMW) of 100Da to 2000Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change. PMID:27155416

  16. Exciplex formation and electroluminescent absorption in ultraviolet organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Zhang, Hao; Zhang, Xiao-Wen; Xu, Tao; Wei, Bin

    2015-02-01

    We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes (UV OLEDs) using different heterojunction structures. It is found that an energy barrier of over 0.3 eV between the emissive layer (EML) and adjacent transport layer facilitates exciplex formation. The electron blocking layer effectively confines electrons in the EML, which contributes to pure UV emission and enhances efficiency. The change in EML thickness generates tunable UV emission from 376 nm to 406 nm. In addition, the UV emission excites low-energy organic function layers and produces photoluminescent emission. In UV OLED, avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency. A maximum external quantum efficiency of 1.2% with a UV emission peak of 376 nm is realized. Project supported by the National Natural Science Foundation of China (Grant Nos. 61136003 and 61275041) and the Guangxi Provincial Natural Science Foundation, China (Grant No. 2012GXNSFBA053168).

  17. [Determination of organic acids in cane vinasse by micellar electrokinetic capillary chromatography with indirect ultraviolet detection].

    PubMed

    Xu, Yuanjin; Xu, Guiping; Wei, Yuanan

    2006-01-01

    Micellar electrokinetic capillary chromatography (MECC) with indirect ultraviolet (UV) detection method for the separation and determination of several organic acids in cane vinasse, including malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acids, were developed. Electrophoretic conditions were as follows: uncoated fused silica capillary (56 cm/ 64 cm (effective/total length), 50 microm i. d. ), 7.5 mmol/L potassium acid phthalate-1. 5 mmol/L cetyltrimethyl-ammonium bromide (CTAB) at pH = 6.50 as buffer solution, applied voltage -25 kV, temperature 25 degrees C, detection wavelength 300 nm, reference wavelength 210 nm. Good linearities were obtained for nine organic acids, and the detection limits were 0.5 mg/L, 0.3 mg/L, 1.5 mg/L, 1.5 mg/L, 0.3 mg/L, 0.3 mg/L, 0.4 mg/L, 0.4 mg/L, 0.4 mg/L for malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acid, respectively. The relative standard deviations (RSDs) for migration times and peak areas of nine organic acids within a day were 0.4% - 0.6% and 2.3% - 4.8%, respectively. The corresponding data for five days were 0.5% -0.7% and 3.3% - 5.2%. The recoveries of acid standards were above 93%. The method can be applied to determine the organic acids in cane vinasse with satisfactory results. PMID:16827307

  18. Beyond Fullerenes: Designing Alternative Molecular Electron Acceptors for Solution-Processable Bulk Heterojunction Organic Photovoltaics.

    PubMed

    Sauvé, Geneviève; Fernando, Roshan

    2015-09-17

    Organic photovoltaics (OPVs) are promising candidates for providing a low cost, widespread energy source by converting sunlight into electricity. Solution-processable active layers have predominantly consisted of a conjugated polymer donor blended with a fullerene derivative as the acceptor. Although fullerene derivatives have been the acceptor of choice, they have drawbacks such as weak visible light absorption and poor energy tuning that limit overall efficiencies. This has recently fueled new research to explore alternative acceptors that would overcome those limitations. During this exploration, one question arises: what are the important design principles for developing nonfullerene acceptors? It is generally accepted that acceptors should have high electron affinity, electron mobility, and absorption coefficient in the visible and near-IR region of the spectra. In this Perspective, we argue that alternative molecular acceptors, when blended with a conjugated polymer donor, should also have large nonplanar structures to promote nanoscale phase separation, charge separation and charge transport in blend films. Additionally, new material design should address the low dielectric constant of organic semiconductors that have so far limited their widespread application.

  19. Magneto-photocurrent in organic photovoltaic cells; the effect of short-lived charge transfer states

    NASA Astrophysics Data System (ADS)

    Ehrenfreund, Eitan; Devir-Wolfman, A.; Khachatryan, B.; Gautam, B.; Tessler, N.; Vardeny, Z. V.

    2014-03-01

    The spin degrees of freedom are responsible for the magnetic field effects in organic devices at low magnetic fields. The MFE is formed via a variety of spin-mixing mechanisms, such as the hyperfine (typical strength: Bhf<0.003 T), triplet-polaron or triplet-triplet (Btrip<0.1 T) interactions, that limit the response by their respective strength. We report on magneto-photocurrent (MPC) response of bulk hetero-junction organic photovoltaic cells in an extended field range B =0.00005 - 8 Tesla, and found that spin mixing mechanisms are still operative even at the highest fields. In fact, the response MPC(B) can be divided into three main regions, each with a different sign: sharp response that increases with B up to B1 ~ 0.04 T; broad response that decreases with B in the range from B1 to B2 ~ 0.3-0.7 T; and even broader response that increases above B2; this response does not saturate even at 8.5 T. We attribute the latter MPC component to short-lived charge transfer excitons (CTE) where spin-mixing is caused by the difference of the donor/acceptor g factors; a mechanism that is increasingly more effective at high magnetic field. Supported by the US-Israel BSF.

  20. Recent Advances in Organic Photovoltaics: Device Structure and Optical Engineering Optimization on the Nanoscale.

    PubMed

    Luo, Guoping; Ren, Xingang; Zhang, Su; Wu, Hongbin; Choy, Wallace C H; He, Zhicai; Cao, Yong

    2016-03-23

    Organic photovoltaic (OPV) devices, which can directly convert absorbed sunlight to electricity, are stacked thin films of tens to hundreds of nanometers. They have emerged as a promising candidate for affordable, clean, and renewable energy. In the past few years, a rapid increase has been seen in the power conversion efficiency of OPV devices toward 10% and above, through comprehensive optimizations via novel photoactive donor and acceptor materials, control of thin-film morphology on the nanoscale, device structure developments, and interfacial and optical engineering. The intrinsic problems of short exciton diffusion length and low carrier mobility in organic semiconductors creates a challenge for OPV designs for achieving optically thick and electrically thin device structures to achieve sufficient light absorption and efficient electron/hole extraction. Recent advances in the field of OPV devices are reviewed, with a focus on the progress in device architecture and optical engineering approaches that lead to improved electrical and optical characteristics in OPV devices. Successful strategies are highlighted for light wave distribution, modulation, and absorption promotion inside the active layer of OPV devices by incorporating periodic nanopatterns/nanostructures or incorporating metallic nanomaterials and nanostructures. PMID:26856789

  1. Tandem organic photovoltaics incorporating two solution-processed small molecule donor layers

    NASA Astrophysics Data System (ADS)

    Lassiter, B. E.; Zimmerman, J. D.; Forrest, S. R.

    2013-09-01

    We develop a partially solution-processed small molecule tandem organic photovoltaic cell using an organic/inorganic interlayer structure that provides efficient charge recombination while protecting underlying layers from degradation due to attack from solvents applied during the deposition of subsequent sub-cells. Each sub-cell consists of a functionalized squaraine (fSQ) blend donor that is cast from solution, followed by evaporation of other functional layers. The first fSQ layer is cast from chloroform, while the second is cast from a tetrahydrofuran, thereby minimizing dissolution of the relatively insoluble, underlying fullerene layer that acts to protect the first donor layer. Solvent vapor annealing increases the sub-cell performance while decreasing the damage caused by spin-coating of the second fSQ layer, both of which result from increased film crystallinity that reduces the rate of solvent penetration. The tandem cell has a power conversion efficiency of 6.2% ± 0.3% and an open circuit voltage nearly equal to the sum of the constituent sub-cells.

  2. Recent Advances in Organic Photovoltaics: Device Structure and Optical Engineering Optimization on the Nanoscale.

    PubMed

    Luo, Guoping; Ren, Xingang; Zhang, Su; Wu, Hongbin; Choy, Wallace C H; He, Zhicai; Cao, Yong

    2016-03-23

    Organic photovoltaic (OPV) devices, which can directly convert absorbed sunlight to electricity, are stacked thin films of tens to hundreds of nanometers. They have emerged as a promising candidate for affordable, clean, and renewable energy. In the past few years, a rapid increase has been seen in the power conversion efficiency of OPV devices toward 10% and above, through comprehensive optimizations via novel photoactive donor and acceptor materials, control of thin-film morphology on the nanoscale, device structure developments, and interfacial and optical engineering. The intrinsic problems of short exciton diffusion length and low carrier mobility in organic semiconductors creates a challenge for OPV designs for achieving optically thick and electrically thin device structures to achieve sufficient light absorption and efficient electron/hole extraction. Recent advances in the field of OPV devices are reviewed, with a focus on the progress in device architecture and optical engineering approaches that lead to improved electrical and optical characteristics in OPV devices. Successful strategies are highlighted for light wave distribution, modulation, and absorption promotion inside the active layer of OPV devices by incorporating periodic nanopatterns/nanostructures or incorporating metallic nanomaterials and nanostructures.

  3. Interface control in organic heterojunction photovoltaic cells by phase separation processes

    NASA Astrophysics Data System (ADS)

    Heier, Jakob; Castro, Fernando A.; Nüesch, Frank; Hany, Roland

    2007-09-01

    Significant progress is being made in the photovoltaic energy conversion using organic semiconducting materials. One of the focuses of attention is the nanoscale morphology of the donor-acceptor mixture, to ensure efficient charge generation and loss-free charge transport at the same time. Using small molecule and polymer blend systems, recent efforts highlight the problems to ensure an optimized relationship between molecular structure, morphology and device properties. Here, we present two examples using a host/guest mixture approach for the controlled, sequential design of bilayer organic solar cell architectures that consist of a large interface area with connecting paths to the respective electrodes at the same time. In the first example, we employed polymer demixing during spin coating to produce a rough interface: surface directed spinodal decomposition leads to a 2-dimensional spinodal pattern with submicrometer features at the polymer-polymer interface. The second system consists of a solution of a blend of small molecules, where phase separation into a bilayer during spin coating is followed by dewetting. For both cases, the guest can be removed using a selective solvent after the phase separation process, and the rough host surface can be covered with a second active, semiconducting component. We explain the potential merits of the resulting interdigitated bilayer films, and explore to which extent polymer-polymer and surface interactions can be employed to create surface features in the nanometer range.

  4. Ultrafast charge-transfer in organic photovoltaic interfaces: geometrical and functionalization effects.

    PubMed

    Santos, Elton J G; Wang, W L

    2016-09-21

    Understanding the microscopic mechanisms of electronic excitation in organic photovoltaic cells is a challenging problem in the design of efficient devices capable of performing sunlight harvesting. Here we develop and apply an ab initio approach based on time-dependent density functional theory and Ehrenfest dynamics to investigate photoinduced charge transfer in small organic molecules. Our calculations include mixed quantum-classical dynamics with ions moving classically and electrons quantum mechanically, where no experimental external parameter other than the material geometry is required. We show that the behavior of photocarriers in zinc phthalocyanine (ZnPc) and C60 systems, an effective prototype system for organic solar cells, is sensitive to the atomic orientation of the donor and the acceptor units as well as the functionalization of covalent molecules at the interface. In particular, configurations with the ZnPc molecules facing on C60 facilitate charge transfer between substrate and molecules that occurs within 200 fs. In contrast, configurations where ZnPc is tilted above C60 present extremely low carrier injection efficiency even at longer times as an effect of the larger interfacial potential level offset and higher energetic barrier between the donor and acceptor molecules. An enhancement of charge injection into C60 at shorter times is observed as binding groups connect ZnPc and C60 in a dyad system. Our results demonstrate a promising way of designing and controlling photoinduced charge transfer on the atomic level in organic devices that would lead to efficient carrier separation and maximize device performance. PMID:27314747

  5. Ultrafast charge-transfer in organic photovoltaic interfaces: geometrical and functionalization effects.

    PubMed

    Santos, Elton J G; Wang, W L

    2016-09-21

    Understanding the microscopic mechanisms of electronic excitation in organic photovoltaic cells is a challenging problem in the design of efficient devices capable of performing sunlight harvesting. Here we develop and apply an ab initio approach based on time-dependent density functional theory and Ehrenfest dynamics to investigate photoinduced charge transfer in small organic molecules. Our calculations include mixed quantum-classical dynamics with ions moving classically and electrons quantum mechanically, where no experimental external parameter other than the material geometry is required. We show that the behavior of photocarriers in zinc phthalocyanine (ZnPc) and C60 systems, an effective prototype system for organic solar cells, is sensitive to the atomic orientation of the donor and the acceptor units as well as the functionalization of covalent molecules at the interface. In particular, configurations with the ZnPc molecules facing on C60 facilitate charge transfer between substrate and molecules that occurs within 200 fs. In contrast, configurations where ZnPc is tilted above C60 present extremely low carrier injection efficiency even at longer times as an effect of the larger interfacial potential level offset and higher energetic barrier between the donor and acceptor molecules. An enhancement of charge injection into C60 at shorter times is observed as binding groups connect ZnPc and C60 in a dyad system. Our results demonstrate a promising way of designing and controlling photoinduced charge transfer on the atomic level in organic devices that would lead to efficient carrier separation and maximize device performance.

  6. Combinatorial fabrication and studies of intense efficient ultraviolet--violet organic light-emitting device arrays

    SciTech Connect

    Zou, L.; Savvate'ev, V.; Booher, J.; Kim, C.-H.; Shinar, J.

    2001-10-01

    Arrays of ultraviolet--violet (indium tin oxide)/[copper phthalocyanine (CuPc)]/[4,4'-bis(9-carbazolyl)biphenyl (CBP)]/[2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole (Bu-PBD)]/CsF/Al organic light-emitting devices, fabricated combinatorially using a sliding shutter technique, are described. Comparison of the OLED electroluminescence and CBP photoluminescence spectra indicates that the emission originates from the bulk of that layer. In arrays of devices in which the thickness of the CuPc and Bu--PBD were varied, but that of CBP was fixed at 50 nm, the optimal radiance R was obtained at CuPc and Bu--PBD thicknesses of 15 and 18 nm, respectively. At 10 mA/cm{sup 2}, R was 0.38 mW/cm{sup 2}, i.e., the external quantum efficiency was 1.25%; R increased to {approx}1.2 mW/cm{sup 2} at 100 mA/cm{sup 2}.

  7. Rapid determination of nonaromatic organic acids in honey by capillary zone electrophoresis with direct ultraviolet detection.

    PubMed

    Mato, Inés; Huidobro, José F; Simal-Lozano, Jesús; Sancho, M Teresa

    2006-03-01

    A rapid capillary zone electrophoresis (CZE) method with direct ultraviolet (UV) detection has been set up and developed to determine the most important nonaromatic organic acids in honey with a really simple treatment of the sample. The determination of oxalic, formic, malic, succinic, pyruvic, acetic, lactic, citric, and gluconic acids has been carried out in 4 min. The electrolyte composition was phosphate as the carrier buffer (7.5 mM NaH(2)PO(4) and 2.5 mM Na(2)HPO(4)), 2.5 mM tetradecyltrimethylammonium hydroxide (TTAOH) as electroosmotic flow modifier, and 0.24 mM CaCl(2) as selectivity modifier, with the pH adjusted at 6.40 constant value. The running voltage was -25 kV at a thermostated temperature of 25 degrees C. The injections were performed in hydrodynamic mode (30 s), and the detection mode was UV direct at 185 nm. Validation parameters of the method as detection and quantification limits, linearity, precision (repeatability and reproducibility), and recovery were also studied. The advantages related to the technique such as simplicity, short analysis times, and low consumption of chemicals as well as the good validation parameters obtained for this method permit it to be considered as adequate for routine analysis in honey.

  8. Determination of organic mercury species in soils by high-performance liquid chromatography with ultraviolet detection.

    PubMed

    Hempel, M; Hintelmann, H; Wilken, R D

    1992-03-01

    Reversed-phase high-performance liquid chromatography with ultraviolet detection was optimized for the simultaneous separation and quantification of nine organic mercury compounds: methyl-, ethyl-, phenyl-, methoxyethyl-, ethoxyethyl-, benzoic and tolylmercury, mersalylic acid and nitromersol. The nine compounds were successfully separated on octadecylsilane columns (200 x 3 mm i.d.) by gradient elution with a methanol-water mixture ranging from 30 to 50% v/v. The detection limits for the various compounds are in the range 7.0-95.1 micrograms dm-3. For the extraction of five organomercurials from spiked soils, eight different extraction solutions were tested to differentiate between the total content and the available/soluble fraction of the analytes. Ammonium acetate solutions (1 mol dm-3) and water proved to be suitable agents for the estimation of the available and soluble fractions of methyl-, ethyl-, benzoic, methoxyethyl- and ethoxyethylmercury. For the determination of the total content of methyl- and benzoic mercury in soils, solutions of potassium iodide (1 mol dm-3)-ascorbic acid (0.1 mol dm-3) and oxalic acid (1 mol dm-3) provided recoveries in the ranges 53-81%. None of the solutions tested is suitable for the extraction of ethyl-, methoxyethyl- and ethoxyethylmercury.

  9. Consequences of anode interfacial layer deletion. HCl-treated ITO in P3HT:PCBM-based bulk-heterojunction organic photovoltaic devices.

    PubMed

    Irwin, Michael D; Liu, Jun; Leever, Benjamin J; Servaites, Jonathan D; Hersam, Mark C; Durstock, Michael F; Marks, Tobin J

    2010-02-16

    In studies to simplify the fabrication of bulk-heterojunction organic photovoltaic (OPV) devices, it was found that when glass/tin-doped indium oxide (ITO) substrates are treated with dilute aqueous HCl solutions, followed by UV ozone (UVO), and then used to fabricate devices of the structure glass/ITO/P3HT:PCBM/LiF/Al, device performance is greatly enhanced. Light-to-power conversion efficiency (Eff) increases from 2.4% for control devices in which the ITO surface is treated only with UVO to 3.8% with the HCl + UVO treatment--effectively matching the performance of an identical device having a PEDOT:PSS anode interfacial layer. The enhancement originates from increases in V(OC) from 463 to 554 mV and FF from 49% to 66%. The modified-ITO device also exhibits a 4x enhancement in thermal stability versus an identical device containing a PEDOT:PSS anode interfacial layer. To understand the origins of these effects, the ITO surface is analyzed as a function of treatment by ultraviolet photoelectron spectroscopy work function measurements, X-ray photoelectron spectroscopic composition analysis, and atomic force microscopic topography and conductivity imaging. Additionally, a diode-based device model is employed to further understand the effects of ITO surface treatment on device performance.

  10. Rational design and preparation of organic semiconductors for use in field effect transistors and photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Mauldin, Clayton Edward

    The goal of this research was to develop methods to control the material properties of organic semiconductors, like solubility, stability, charge mobility, and self-assembly, through structural design. Investigations of structure-property relationships were conducted to optimize the properties of organic semiconductors for applications in organic field effect transistors (OFETs) and organic photovoltaics (OPVs). Chapter 1 gives an introduction to charge transport in organic semiconductors, and describes how the structure of conjugated molecules can affect their electrical performance and facilitate facile solution deposition. Furthermore, factors that can affect the stability of organic semiconductors to ambient conditions are discussed. Also, the device characteristics of OFETs and OPVs are summarized as a reference for subsequent chapters. Chapter 2 discusses the investigation of the air stability of distyryl oligothiophenes in OFETs. This work made use of thermally labile solubilizing groups to facilitate solution deposition of the oligothiophenes. In addition to device characterization, an extensive analysis of the thin film morphology using AFM, NEXAFS and GIXD is presented. This work revealed the general stability of distyryl oligothiophenes to oxidative degradation, and the high degree of crystallinity in our thin films. In Chapter 3, the charge transporting properties of pentathiophene monolayer islands is analyzed using current sensing AFM. The pentathiophenes were prepared with carboxylic acid moieties for self assembly, and the sub-monolayer films were transferred onto conductive substrates using the Langmuir-Blodgett technique. The morphology of the monolayers was observed to be sensitive to the alkyl substitution pattern of the pentathiophenes, which in turn affected charge transport. Hierarchical supramolecular assemblies of oligothiophenes and block copolymers are studied in Chapter 4. The structure of the assemblies is studied by TEM and small angle

  11. Optical, electrical, and magnetic field studies of organic materials for light emitting diodes and photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Basel, Tek Prasad

    We studied optical, electrical, and magnetic field responses of films and devices based on organic semiconductors that are used for organic light emitting diodes (OLEDs) and photovoltaic (OPV) solar cell applications. Our studies show that the hyperfine interaction (HFI)-mediated spin mixing is the key process underlying various magnetic field effects (MFE) and spin transport in aluminum tris(8-hydroxyquinoline)[Alq3]-based OLEDs and organic spin-valve (OSV). Conductivity-detected magnetic resonance in OLEDs and magneto-resistance (MR) in OSVs show substantial isotope dependence. In contrast, isotope-insensitive behavior in the magneto-conductance (MC) of same devices is explained by the collision of spin ½ carriers with triplet polaron pairs. We used steady state optical spectroscopy for studying the energy transfer dynamics in films and OLEDs based on host-guest blends of the fluorescent polymer and phosphorescent molecule. We have also studied the magnetic-field controlled color manipulation in these devices, which provide a strong proof for the `polaron-pair' mechanism underlying the MFE in organic devices. The critical issue that hampers organic spintronics device applications is significant magneto-electroluminescence (MEL) at room temperature (RT). Whereas inorganic spin valves (ISVs) show RT magneto-resistance, MR>80%, however, the devices do not exhibit electroluminescence (EL). In contrast, OLEDs show substantive EL emission, and are particularly attractive because of their flexibility, low cost, and potential for multicolor display. We report a conceptual novel hybrid organic/inorganic spintronics device (h-OLED), where we employ both ISV with large MR at RT, and OLED that has efficient EL emission. We investigated the charge transfer process in an OPV solar cell through optical, electrical, and magnetic field measurements of thin films and devices based on a low bandgap polymer, PTB7 (fluorinated poly-thienothiophene-benzodithiophene). We found that

  12. Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells.

    PubMed

    Brun, Nadja Rebecca; Wehrli, Bernhard; Fent, Karl

    2016-02-01

    Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583 μg L(-1) molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219 μg L(-1). From OPV, copper (14 μg L(-1)), zinc (87 μg L(-1)) and silver (78 μg L(-1)) leached. Zebrafish embryos were exposed until 120 h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk. PMID:26615488

  13. Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells.

    PubMed

    Brun, Nadja Rebecca; Wehrli, Bernhard; Fent, Karl

    2016-02-01

    Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583 μg L(-1) molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219 μg L(-1). From OPV, copper (14 μg L(-1)), zinc (87 μg L(-1)) and silver (78 μg L(-1)) leached. Zebrafish embryos were exposed until 120 h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk.

  14. Dependence of light-emitting and photovoltaic properties of dual-function organic diodes on carrier-transporting layers

    NASA Astrophysics Data System (ADS)

    Lee, Ho-Nyeon; Choi, Mun Soo

    2013-10-01

    Dual-function photovoltaic organic light-emitting diodes (PVOEDs) have been investigated in this work. The PVOLEDs emit light when forward biased and generate electricity when backward biased. This dual function is based on the half-gap junction composed of 5,6,11,12-tetraphenylnaphthacene (rubrene) and C 60. The device structure was optimized through experiments using various organic materials for the electron-transporting layer (ETL) and electron-injection layer (EIL). Through this work, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), C 60 and LiF were selected as the ETL, electron-accepting layer and EIL, respectively. Using this device structure, we obtained a current efficiency of 0.27 cd/A for the light-emitting mode and a power-conversion efficiency of 1.95% for the photovoltaic mode.

  15. Ultraviolet irradiation effects incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter.

    PubMed

    Thorn, Kevin A; Cox, Larry G

    2012-01-01

    One of the concerns regarding the safety and efficacy of ultraviolet radiation for treatment of drinking water and wastewater is the fate of nitrate, particularly its photolysis to nitrite. In this study, N NMR was used to establish for the first time that UV irradiation effects the incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter (NOM). Irradiation of (15)N-labeled nitrate in aqueous solution with an unfiltered medium pressure mercury lamp resulted in the incorporation of nitrogen into Suwannee River NOM (SRNOM) via nitrosation and other reactions over a range of pH from approximately 3.2 to 8.0, both in the presence and absence of bicarbonate, confirming photonitrosation of the NOM. The major forms of the incorporated label include nitrosophenol, oxime/nitro, pyridine, nitrile, and amide nitrogens. Natural organic matter also catalyzed the reduction of nitrate to ammonia on irradiation. The nitrosophenol and oxime/nitro nitrogens were found to be susceptible to photodegradation on further irradiation when nitrate was removed from the system. At pH 7.5, unfiltered irradiation resulted in the incorporation of (15)N-labeled nitrite into SRNOM in the form of amide, nitrile, and pyridine nitrogen. In the presence of bicarbonate at pH 7.4, Pyrex filtered (cutoff below 290-300 nm) irradiation also effected incorporation of nitrite into SRNOM as amide nitrogen. We speculate that nitrosation of NOM from the UV irradiation of nitrate also leads to production of nitrogen gas and nitrous oxide, a process that may be termed photo-chemodenitrification. Irradiation of SRNOM alone resulted in transformation or loss of naturally abundant heterocyclic nitrogens.

  16. Ultraviolet irradiation effects incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter

    USGS Publications Warehouse

    Thorn, Kevin A.; Cox, Larry G.

    2012-01-01

    One of the concerns regarding the safety and efficacy of ultraviolet radiation for treatment of drinking water and wastewater is the fate of nitrate, particularly its photolysis to nitrite. In this study, 15N NMR was used to establish for the first time that UV irradiation effects the incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter (NOM). Irradiation of 15N-labeled nitrate in aqueous solution with an unfiltered medium pressure mercury lamp resulted in the incorporation of nitrogen into Suwannee River NOM (SRNOM) via nitrosation and other reactions over a range of pH from approximately 3.2 to 8.0, both in the presence and absence of bicarbonate, confirming photonitrosation of the NOM. The major forms of the incorporated label include nitrosophenol, oxime/nitro, pyridine, nitrile, and amide nitrogens. Natural organic matter also catalyzed the reduction of nitrate to ammonia on irradiation. The nitrosophenol and oxime/nitro nitrogens were found to be susceptible to photodegradation on further irradiation when nitrate was removed from the system. At pH 7.5, unfiltered irradiation resulted in the incorporation of 15N-labeled nitrite into SRNOM in the form of amide, nitrile, and pyridine nitrogen. In the presence of bicarbonate at pH 7.4, Pyrex filtered (cutoff below 290–300 nm) irradiation also effected incorporation of nitrite into SRNOM as amide nitrogen. We speculate that nitrosation of NOM from the UV irradiation of nitrate also leads to production of nitrogen gas and nitrous oxide, a process that may be termed photo-chemodenitrification. Irradiation of SRNOM alone resulted in transformation or loss of naturally abundant heterocyclic nitrogens.

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

    PubMed

    Kulbak, Michael; Cahen, David; Hodes, Gary

    2015-07-01

    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.

  18. Efficient Organic Photovoltaics Utilizing Nanoscale Heterojunctions in Sequentially Deposited Polymer/fullerene Bilayer

    NASA Astrophysics Data System (ADS)

    Seok, Jeesoo; Shin, Tae Joo; Park, Sungmin; Cho, Changsoon; Lee, Jung-Yong; Yeol Ryu, Du; Kim, Myung Hwa; Kim, Kyungkon

    2015-02-01

    A highly efficient sequentially deposited bilayer (SD-bilayer) of polymer/fullerene organic photovoltaic (OPV) device is developed via the solution process. Herein, we resolve two essential problems regarding the construction of an efficient SD-bilayer OPV. First, the solution process fabrication of the SD-bilayer is resolved by incorporating an ordering agent (OA) to the polymer solution, which improves the ordering of the polymer chain and prevents the bottom-layer from dissolving into the top-layer solution. Second, a non-planar heterojunction with a large surface area is formed by the incorporation of a heterojunction agent (HA) to the top-layer solution. Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) is used for the bottom-layer and phenyl-C71-butyric-acid-methyl ester (PC70BM) is used for the top-layer. The SD-bilayer OPV produced utilizing both an OA and HA exhibits a power conversion efficiency (PCE) of 7.12% with a high internal quantum efficiency (IQE). We believe our bilayer system affords a new way of forming OPVs distinct from bulk heterojunction (BHJ) systems and offers a chance to reconsider the polymers that have thus far shown unsatisfactory performance in BHJ systems.

  19. A silver-free, reflective substrate electrode for electron extraction in top-illuminated organic photovoltaics.

    PubMed

    Tyler, Martin S; Hutter, Oliver S; Walker, Marc; Hatton, Ross A

    2015-04-27

    The choice of metals suitable as the reflective substrate electrode for top-illuminated organic photovoltaics (OPVs) is extremely limited. Herein, we report a novel substrate electrode for this class of OPV architecture based on an Al | Cu | AlOx triple-layer structure, which offers a reflectivity comparable to that of Al over the wavelength range 400-900 nm, a work function suitable for efficient electron extraction in OPVs and high stability towards oxidation. In addition to demonstrating the advantage of this composite electrode over Al in model top-illuminated OPVs, we also present the results of a photoelectron spectroscopy study, which show that an oxidised 0.8 nm Al layer deposited by thermal evaporation onto an Al | Cu reflective substrate electrode is sufficient to block oxidation of the underlying Cu by air or during deposition of a ZnO1-x electron-transport layer. This is remarkable given that the self-limiting oxide thickness on Al metal is greater than 2 nm.

  20. Rapidly Thermal Annealed Si-Doped In2O3 Films for Organic Photovoltaics.

    PubMed

    Lee, Hye-Min; Kim, Han-Ki

    2015-10-01

    We report the electrical, optical, and structural properties of Si-doped In2O3 (ISO) films prepared using co-sputtering system with multi cathode guns for use in organic photovoltaics (OPVs). We investigated the effect of Si doping power on the electrical, optical, and structural properties of ISO film that was rapidly thermally annealed at a temperature of 400 °C. Due to the high Lewis acid strength (8.096) of the Si dopant, the ISO films showed high mobility and low resistivity despite the low Si doping concentration. Low resistivity of the annealed ISO films indicated that Si(4+) acts as an effective dopant of an In2O3 matrix by substitution with the In(3+) site. At a Si doping power of 50 W, ISO film showed a sheet resistance of 19.7 Ohm/square and optical transparency of 76.7%, which are acceptable values for fabrication of OPVs. Successful operation of OPV cells fabricated on transparent ISO film indicates that ISO is a promising high mobility transparent electrode material and alternative to conventional ITO films.

  1. Oligomeric Dithienopyrrole-Thienopyrrolodione (DTP-TPD) Donor-Acceptor Copolymer for Organic Photovoltaics: Preprint

    SciTech Connect

    Hammond, S. R.; Braunecker, W.; Garcia, A.; Larsen, R.; Owczarczyk, Z.; Olson, D.; Ginley, D.

    2011-07-01

    A new donor-acceptor copolymer system based upon a dithienopyrrole (DTP) donor moiety and a thienopyrrolodione (TPD) accepting moiety has been designed and synthesized for organic photovoltaic (OPV) applications. The TPD accepting moiety has recently gained significant attention in the OPV community and is being incorporated into a number of different polymer systems. In contrast, the DTP donor moiety has received only limited attention, likely due in part to synthetic difficulties relating to the monomer. In our hands, the bis(trimethyltin)-DTP monomer was indelibly contaminated with ~5% of the mono-destannylated DTP, which limited the Stille polymerization with the dibromo-TPD monomer (>99% pure) to produce material with Mn ~ 4130 g/mol (PDI = 1.10), corresponding to around eight repeat units. Despite this limitation, UV-visible absorption spectroscopy demonstrates strong absorption for this material with a band gap of ~1.6 eV. Cyclic voltammetry indicates a highest occupied molecular orbital (HOMO) energy level of -5.3 eV, which is much lower than calculations predicted. Initial bulk heterojunction OPV devices fabricated with the fullerene acceptor phenyl C61 butyric acid methyl ester (PCBM) exhibit Voc ~ 700 mV, which supports the deep HOMO value obtained from CV. These results suggest the promise of this copolymer system.

  2. Site-specific probing of charge transfer dynamics in organic photovoltaics

    SciTech Connect

    Arion, Tiberiu; Roth, Friedrich; Hussain, Zahid; Eberhardt, Wolfgang

    2015-03-23

    We report the site-specific probing of charge-transfer dynamics in a prototype system for organic photovoltaics (OPVs) by picosecond time-resolved X-ray photoelectron spectroscopy. A layered system consisting of approximately two monolayers of C{sub 60} deposited on top of a thin film of Copper-Phthalocyanine (CuPC) is excited by an optical pump pulse and the induced electronic dynamics are probed with 590 eV X-ray pulses. Charge transfer from the electron donor (CuPC) to the acceptor (C{sub 60}) and subsequent charge carrier dynamics are monitored by recording the time-dependent C 1s core level photoemission spectrum of the system. The arrival of electrons in the C{sub 60} layer is readily observed as a completely reversible, transient shift of the C{sub 60} associated C 1s core level, while the C 1s level of the CuPC remains unchanged. The capability to probe charge transfer and recombination dynamics in OPV assemblies directly in the time domain and from the perspective of well-defined domains is expected to open additional pathways to better understand and optimize the performance of this emerging technology.

  3. Optical properties of low bandgap copolymer PTB7 for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Huynh, Uyen; Basel, Tek; Xu, Tao; Lu, Luyao; Zheng, Tianyue; Yu, Luping; Vardeny, Valy

    2014-09-01

    We used both cw and transient spectroscopies for studying the optical properties and photoexcitations in the low bandgap copolymer PTB7 that has been used in organic photovoltaic applications (OPV). Surprisingly we observed two primary photoexcitations that are generated within ~150 fs (our time resolution); we identify them as singlet exciton (S1) and triplet-pair (1TT). The singlet exciton has been considered to be the only primary photoexcitation in regular π-conjugated polymers and is related with a transient absorption band that peaks at an energy value close to the exciton binding energy (~0.4 eV in PTB7). The TT pair is a novel photoexcitation species in low band-gap π-conjugated copolymers. It has an absorption band close to that of isolated triplet exciton, and may readily dissociate at the donoracceptor interfaces in the PTB7/fullerene blend. This finding may explain the underlying mechanism for the high obtained power conversion efficiency in OPV devices based on the PTB7 copolymer.

  4. Enhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles

    SciTech Connect

    Nalwa, Kanwar; Carr, John; Mahadevapuram, Rakesh; Kodali, Hari; Bose, Sayantan; Chen, Yuqing; Petrich, Jacob; Ganapathysubramanian, Baskar; Chaudhary, Sumit

    2012-02-23

    A key requirement for realizing efficient organic photovoltaic (OPV) cells is the dissociation of photogenerated electron-hole pairs (singlet-excitons) in the donor polymer, and charge-transfer-excitons at the donor–acceptor interface. However, in modern OPVs, these excitons are typically not sufficiently harnessed due to their high binding energy. Here, we show that doping the OPV active-layers with a ferroelectric polymer leads to localized enhancements of electric field, which in turn leads to more efficient dissociation of singlet-excitons and charge-transfer-excitons. Bulk-heterojunction OPVs based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester are fabricated. Upon incorporating a ferroelectric polymer as additive in the active-layer, power conversion efficiencies increase by nearly 50%, and internal quantum efficiencies approach 100% – indicating complete exciton dissociation at certain photon energies. Similar enhancements in bilayer-heterojunctions, and direct influence of ferroelectric poling on device behavior show that improved dissociation is due to ferroelectric dipoles rather than any morphological change. Enhanced singlet-exciton dissociation is also revealed by photoluminescence lifetime measurements, and predicted by simulations using a numerical device model.

  5. Lithography-Free Broadband Ultrathin-Film Absorbers with Gap-Plasmon Resonance for Organic Photovoltaics.

    PubMed

    Choi, Minjung; Kang, Gumin; Shin, Dongheok; Barange, Nilesh; Lee, Chang-Won; Ko, Doo-Hyun; Kim, Kyoungsik

    2016-05-25

    Strategies to confine electromagnetic field within ultrathin film emerge as essential technologies for applications from thin-film solar cells to imaging and sensing devices. We demonstrate a lithography-free, low-cost, large-scale method to realize broadband ultrathi-film metal-dielectric-metal (MDM) absorbers, by exploiting gap-plasmon resonances for strongly confined electromagnetic field. A two-steps method, first organizing Au nanoparticles via thermal dewetting and then transferring the nanoparticles to a spacer-reflector substrate, is used to achieve broader absorption bandwidth by manipulating geometric shapes of the top metallic layer into hemiellipsoids. A fast-deposited nominal Au film, instead of a conventional slow one, is employed in the Ostwald ripening process to attain hemiellipsoidal nanoparticles. A polymer supported transferring step allows a wider range of dewetting temperature to manipulate the nanoparticles' shape. By incorporating circularity with ImageJ software, the geometries of hemiellipsoidal nanoparticles are quantitatively characterized. Controlling the top geometry of MDM structure from hemisphere to hemiellipsoid increases the average absorption at 500-900 nm from 23.1% to 43.5% in the ultrathin film and full width at half-maximum of 132-324 nm, which is consistently explained by finite-difference time-domain simulation. The structural advantages of our scheme are easily applicable to thin-film photovoltaic devices because metal electrodes can act as metal reflectors and semiconductor layers as dielectric spacers. PMID:27160410

  6. Lithography-Free Broadband Ultrathin-Film Absorbers with Gap-Plasmon Resonance for Organic Photovoltaics.

    PubMed

    Choi, Minjung; Kang, Gumin; Shin, Dongheok; Barange, Nilesh; Lee, Chang-Won; Ko, Doo-Hyun; Kim, Kyoungsik

    2016-05-25

    Strategies to confine electromagnetic field within ultrathin film emerge as essential technologies for applications from thin-film solar cells to imaging and sensing devices. We demonstrate a lithography-free, low-cost, large-scale method to realize broadband ultrathi-film metal-dielectric-metal (MDM) absorbers, by exploiting gap-plasmon resonances for strongly confined electromagnetic field. A two-steps method, first organizing Au nanoparticles via thermal dewetting and then transferring the nanoparticles to a spacer-reflector substrate, is used to achieve broader absorption bandwidth by manipulating geometric shapes of the top metallic layer into hemiellipsoids. A fast-deposited nominal Au film, instead of a conventional slow one, is employed in the Ostwald ripening process to attain hemiellipsoidal nanoparticles. A polymer supported transferring step allows a wider range of dewetting temperature to manipulate the nanoparticles' shape. By incorporating circularity with ImageJ software, the geometries of hemiellipsoidal nanoparticles are quantitatively characterized. Controlling the top geometry of MDM structure from hemisphere to hemiellipsoid increases the average absorption at 500-900 nm from 23.1% to 43.5% in the ultrathin film and full width at half-maximum of 132-324 nm, which is consistently explained by finite-difference time-domain simulation. The structural advantages of our scheme are easily applicable to thin-film photovoltaic devices because metal electrodes can act as metal reflectors and semiconductor layers as dielectric spacers.

  7. Broad spectral sensitivity and improved efficiency in CuPc/Sub-Pc organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Kumar, Hemant; Kumar, Pankaj; Bhardwaj, Ramil; Sharma, G. D.; Chand, Suresh; Jain, S. C.; Kumar, Vikram

    2009-01-01

    We demonstrate organic photovoltaic devices incorporating two donors, namely, copper phthalocyanine (CuPc) and boron sub-phthalocyanine chloride (Sub-Pc) in association with single acceptor fullerene (C60) with sensitivity extending across the visible solar spectrum. It has been found that the absorption in different spectral regions in CuPc and Sub-Pc results in efficient harvesting of incident light photons which leads to enhanced power conversion efficiency (η). An enhancement in η from 0.64%, in the device architecture indium-tin-oxide (ITO)/CuPc(20 nm)/C60(40 nm)/bathophenanthroline (BPhen) (8 nm)/Al(150 nm), to ~1.3% in the optimized device having a 2 nm layer of Sub-Pc in the geometry ITO/CuPc(18 nm)/Sub-Pc(2 nm)/C60 (40 nm)/BPhen (8 nm)/Al(150 nm) has been observed. This enhancement in η is dominantly attributed to the increment in short circuit current density (Jsc) due to efficient photon harvesting by incorporation of dual donors.

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

    SciTech Connect

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

    2014-06-16

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

  9. On Absorption-Enhanced Organic Photovoltaic By Incorporating Metallic Nano Pyramid Particles

    NASA Astrophysics Data System (ADS)

    Qasem, Hussamaldeen Saif

    A lattice structure of metallic Nano pyramids (NPY) particles was planted on the interface between hole transport layer (HTL) and the transparent conductive layer (TCL) of an organic photovoltaic (OPV) cell. Standard metal evaporation along with Nano sphere lithography was used to grow the metallic NPY mesh structure. Silver (Ag) and Gold (Au) were the primary choice of the NPY mesh structure due to the excellent overlap of their peak localized surface Plasmon resonance (LSPR) frequency with the active layer absorption wavelengths. The current-voltage curve displayed an improvement in the efficiency and fill factor values of OPVs that used NPY lattice structure over devices that used regular sphere-shaped Nano particles. Despite the better-shaped and strong (LSPR) peak frequency of the Ag NPY lattice structure, Au NPY lattice structure exhibited an enhanced absorption and overall efficiency, which was owed to the wider (LSPR) frequency peak that Au possesses. The effect of NPY lattice structure could be further investigated with several approaches such as using different NPY materials, using core-shill approach, and growing the NPY on different layers or interfaces.

  10. Detailed analysis of ultrathin fluorescent red dye interlayer for organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Zang, Yue; Yu, Jun-Sheng; Wang, Na-Na; Jiang, Ya-Dong

    2011-01-01

    The influence of an ultrathin 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) fluorescent dye layer at donor/acceptor heterojunction on the performance of small-molecule organic photovoltaic (OPV) cell is studied. The structure of OPV cell is of indium-tin oxide (ITO)/copper phthalocyanine (CuPc)/DCJTB/fullerene (C60)/bathophenanthroline (Bphen)/Ag. The results show that open circuit voltage (VOC) increases to 0.57 V as the film thickness of DCJTB layer increases from 0.2 to 2.0 nm. By using an equivalent circuit model, the enhancement of VOC is found to be attributed to the reduced reverse saturation current density (JS) which is due to the lower highest occupied molecular orbital (HOMO) level in DCJTB than that in CuPc. Also, the short circuit current density (JSC) is affected when the DCJTB layer becomes thicker, resulting from the high series resistance RSA due to the low charge carrier mobility of fluorescent red dye.

  11. Roll-to-roll embedded conductive structures integrated into organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    van de Wiel, H. J.; Galagan, Y.; van Lammeren, T. J.; de Riet, J. F. J.; Gilot, J.; Nagelkerke, M. G. M.; Lelieveld, R. H. C. A. T.; Shanmugam, S.; Pagudala, A.; Hui, D.; Groen, W. A.

    2013-12-01

    Highly conductive screen printed metallic (silver) structures (current collecting grids) combined with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are a viable replacement for indium tin oxide (ITO) and inkjet printed silver as transparent electrode materials. To provide successful integration into organic photovoltaic (OPV) devices, screen printed silver current collecting grids should be embedded into a substrate to avoid topology issues. In this study micron-thick conductive structures are embedded and integrated into OPV devices. The embedded structures are produced roll-to-roll with optimized process settings and materials. Topology measurements show that the embedded grids are well suited for integration into OPV devices since the surface is almost without spikes and has low surface roughness. JV measurements of OPV devices with embedded structures on a polyethylene terephthalate/silicon nitride (PET/SiN) substrate show an efficiency of 2.15%, which is significantly higher than identical flexible devices with ITO (1.02%) and inkjet printed silver (1.48%). The use of embedded screen printed silver instead of ITO and inkjet printed silver in OPV devices will allow for higher efficiency devices which can be produced with larger design and process freedom.

  12. Multichromophoric energy sensitization of C{sub 60} for organic photovoltaics

    SciTech Connect

    Bartynski, Andrew N.; Trinh, Cong; Kirlikovali, Kent O.; Thompson, Mark E.

    2014-09-15

    In organic photovoltaics (OPVs), photocurrent generation is limited by absorption and exciton diffusion in the active layer. In this work, we describe the energy sensitization of C{sub 60} simultaneously by two chromophores at high volume concentrations (50%). This sensitization strategy takes advantage of the intense absorption of the sensitizers and the exceptional electron conduction and exciton diffusion length of C{sub 60} resulting in a 30% increase in photoresponse of the C{sub 60}-based sensitized acceptor layer between λ = 450 nm and 670 nm and power conversion efficiency under simulated AM 1.5 G illumination. In (2,4-bis[4-(N,N-diphenylamino)-2,6-dihydroxyphenyl] squaraine)/C{sub 60} devices, sensitization results in an increase in J{sub SC} from 6.5 ± 0.2 mA/cm{sup 2} to 8.6 ± 0.2 mA/cm{sup 2} without compromising V{sub OC} or FF. These results demonstrate the robust nature of this sensitization scheme and its broad potential for application in OPVs.

  13. Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

    DOE PAGES

    Dyck, Ondrej; Hu, Sheng; Das, Sanjib; Keum, Jong; Xiao, Kai; Khomami, Bamin; Duscher, Gerd

    2015-11-24

    Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. Our paper outlines the application of two electron energy-loss spectroscopic (EELS) imaging techniques that can complement and enhance current phase detection techniques. Specifically, the bulk plasmon peak position, often used to produce contrast between phases in energy filtered transmission electron microscopy (EFTEM), is quantitatively mapped across a sample cross section. One complementary spectrum image capturing the carbon and sulfur core loss edges is compared with themore » plasmon peak map and found to agree quite well, indicating that carbon and sulfur density differences between the two phases also allows phase discrimination. Additionally, an analytical technique for determining absolute atomic areal density is used to produce an absolute carbon and sulfur areal density map. We also show how these maps may be re-interpreted as a phase ratio map, giving quantitative information about the purity of the phases within the junction.« less

  14. Doped Interlayers for Improved Selectivity in Bulk Herterojunction Organic Photovoltaic Devices

    DOE PAGES

    Mauger, Scott A.; Glasser, Melodie P.; Tremolet de Villers, Bertrand J.; Duong, Vincent V.; Ayzner, Alexander L.; Olson, Dana C.

    2016-01-21

    Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is less selective for holes in inverted-architecture organic photovoltaic (OPV) than it is in a conventional-architecture OPV device due differences between the interfacial-PSS concentration at the top and bottom of the PEDOT:PSS layer. In this work, thin layers of polysulfonic acids are inserted between the P3HT:ICBA bulk heterojunction (BHJ) active layer and PEDOT:PSS to create a higher concentration of acid at this interface and, therefore, mimic the distribution of materials present in a conventional device. Upon thermal annealing, this acid layer oxidizes P3HT, creating a thin p-type interlayer of P3HT+/acid- on top of the BHJ. Using x-raymore » absorption spectroscopy, Kelvin probe and ellipsometry measurements, this P3HT+/acid- layer is shown to be insoluble in water, indicating it remains intact during the subsequent deposition of PEDOT:PSS. Current density - voltage measurements show this doped interlayer reduces injected dark current while increasing both open-circuit voltage and fill factor through the creation of a more hole selective BHJ-PEDOT:PSS interface.« less

  15. Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics

    PubMed Central

    Kingsley, James W.; Marchisio, Pier Paolo; Yi, Hunan; Iraqi, Ahmed; Kinane, Christy J.; Langridge, Sean; Thompson, Richard L.; Cadby, Ashley J.; Pearson, Andrew J.; Lidzey, David G.; Jones, Richard A. L.; Parnell, Andrew J.

    2014-01-01

    We have used Soxhlet solvent purification to fractionate a broad molecular weight distribution of the polycarbazole polymer PCDTBT into three lower polydispersity molecular weight fractions. Organic photovoltaic devices were made using a blend of the fullerene acceptor PC71BM with the molecular weight fractions. An average power conversion efficiency of 5.89% (peak efficiency of 6.15%) was measured for PCDTBT blend devices with a number average molecular weight of Mn = 25.5 kDa. There was significant variation between the molecular weight fractions with low (Mn = 15.0 kDa) and high (Mn = 34.9 kDa) fractions producing devices with average efficiencies of 5.02% and 3.70% respectively. Neutron reflectivity measurements on these polymer:PC71BM blend layers showed that larger molecular weights leads to an increase in the polymer enrichment layer thickness at the anode interface, this improves efficiency up to a limiting point where the polymer solubility causes a reduction of the PCDTBT concentration in the active layer. PMID:24924096

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    The addition of spacing layers in organic photovoltaic cells (OPVs) can enhance light absorption by optimizing the spatial distribution of the incident optical field in the multilayer structure. We explore the optical spacing effect in OPVs achieved using a diluted electron acceptor layer of C60. While optical spacing is often realized by optimizing buffer layer thickness, we find that optical spacing via dilution leads to cells with similar or enhanced photocurrent. This is observed despite a smaller quantity of absorbing molecules, suggesting a more efficient use of absorbed photons. In fact, dilution is found to concentrate optical absorption near the electron donor-acceptor interface, resulting in a marked increase in the exciton diffusion efficiency. Contrasting the use of changes in thickness to engineer optical absorption, the use of dilution does not significantly alter the overall thickness of the OPV. Optical spacing via dilution is shown to be a viable alternative to more traditional optical spacing techniques and may be especially useful in the continued optimization of next-generation, tandem OPVs where it is important to minimize competition for optical absorption between individual sub-cells.

  17. Elucidating the Factors that Determine the Open Circuit Voltage in Discrete Heterojunction Organic Photovoltaic Cells

    SciTech Connect

    Chauhan, V.; Hatton, R; Sullivan, P; Jones, T; Cho, S; Piper, L; DeMasi, A; Smith, K

    2010-01-01

    The operation of discrete heterojunction organic photovoltaic (OPV) cells employing chloro-aluminium phthalocyanine (ClAlPc) as the electron donor and C{sub 60} as the electron acceptor is reported and the characteristics are correlated with the energy level structure of the devices determined using X-ray photoelectron spectroscopy. The results give new insight into the origin of the open circuit voltage (V{sub oc}) in discrete heterojunction OPVs. The measured V{sub oc} in this system is found to be determined by: (i) the frontier orbital energy offsets between the donor and acceptor materials, accounting for the likely formation of an abrupt vacuum level shift at the heterojunction interface and (ii) the degree of alignment between the hole-extracting electrode Fermi level and the highest occupied molecular orbital energy of the electron donor material. The generality of the findings is demonstrated by rationalising the V{sub oc} in OPVs employing the archetypal electron donor, copper phthalocyanine.

  18. Electroabsorption and oppositely directed built-in fields in a photovoltaic organic heterostructure

    SciTech Connect

    Blinov, L. M. Lazarev, V. V.; Yudin, S. G.

    2013-11-15

    The directions and intensities of local electric fields spontaneously built into organic nanoscale structures of Schottky-diode type, indium tin oxide (ITO)-CuPc-Al and ITO-C{sub 60}-Al, with donor and acceptor layers of copper phthalocyanine (CuPc) and fullerene (C{sub 60}) have been investigated using an improved spectral electroabsorption technique. It is established that, in the absence of external field and illumination, the built-in fields in the bulk of these structures are directed differently: from Al to ITO in the case of CuPc and from ITO to Al in the case of C{sub 6}0. The best studied photovoltaic heterostructure ITO-CuPc-C{sub 6}0-Al contains simultaneously strong built-in fields in CuPc and C{sub 60} layers, with strengths of about 15 and -22 V/{mu}m, respectively. A high (on the order of 10{sup -3} C/m{sup 2}) positive space charge arises at the donor-acceptor interface, and the oppositely directed fields may either increase or reduce the efficiency of light-energy converters, depending on the heterostructure parameters.

  19. High-Performance Inverted Organic Photovoltaics Without Hole-Selective Contact

    PubMed Central

    2015-01-01

    A detailed investigation of the functionality of inverted organic photovoltaics (OPVs) using bare Ag contacts as the top electrode is presented. The inverted OPVs without a hole-transporting layer (HTL) exhibit a significant gain in hole-carrier selectivity and power-conversion efficiency (PCE) after exposure in ambient conditions. Inverted OPVs comprised of ITO–ZnO–poly(3-hexylthiophene-2,5-diyl)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)–Ag demonstrate over 3.5% power conversion efficiency only if the devices are exposed in air for over 4 days. As concluded through a series of measurements, the oxygen presence is essential to obtaining fully operational solar cell devices without HTL. Moreover, accelerated stability tests under damp heat conditions (RH = 85% and T = 65 °C) performed to nonencapsulated OPVs demonstrate that HTL-free inverted OPVs exhibit comparable stability to the reference inverted OPVs. Importantly, it is shown that bare Ag top electrodes can be efficiently used in inverted OPVs using various high-performance polymer–fullerene bulk heterojunction material systems demonstrating 6.5% power-conversion efficiencies. PMID:26468993

  20. Dual use of tantalum disulfides as hole and electron extraction layers in organic photovoltaic cells.

    PubMed

    Le, Quyet Van; Nguyen, Thang Phan; Choi, Kyoung Soon; Cho, Yoon-Ho; Hong, Young Joon; Kim, Soo Young

    2014-12-14

    UV/ozone treated (UVO-treated) TaS2 and non-treated TaS2 nanosheets are introduced into organic photovoltaic cells (OPVs) as hole extraction layers (HEL) and electron extraction layers (EEL). TaS2 nanosheets are obtained via ultrasonic vibration and size-controlled by centrifugation. Atomic force microscopy (AFM) images reveal that the thickness and lateral size of TaS2 nanosheets are approximately 1 and 70 nm, indicating that uniform and ultrathin TaS2 nanosheets are obtained. The work function of TaS2 increases from 4.4 eV to 4.9-5.1 eV after applying UVO treatment by forming Ta2O5. In addition, the power conversion efficiencies of normal OPV with UVO-treated TaS2 and inverted OPV with TaS2 are 3.06 and 2.73%, which are higher than those of OPV without TaS2 (1.56% for normal OPV and 0.22% for inverted OPV). These results indicate that TaS2 is a promising material for HEL and EEL layers in OPVs.

  1. 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.

  2. Electrosprayed molybdenum trioxide aqueous solution and its application in organic photovoltaic cells.

    PubMed

    Suzuki, Katsumi; Fukuda, Takeshi; Liao, Yingjie

    2014-01-01

    A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer.

  3. Magnetophotocurrent in Organic Bulk Heterojunction Photovoltaic Cells at Low Temperatures and High Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Khachatryan, B.; Devir-Wolfman, A. H.; Tzabari, L.; Tessler, N.; Vardeny, Z. V.; Ehrenfreund, E.

    2016-04-01

    We study high-field (up to B ˜8.5 T ) magnetophotocurrent (MPC) related to photogenerated polaron pairs (PPs) in the temperature range T =10 - 320 K in organic bulk heterojunction photovoltaic cells. We find that in the high-field regime (B >1 T ), MPC (B ) response increases with B for temperature T >200 K but decreases with B at T <200 K . MPC (B ) response does not saturate even at the highest field studied, at all T . We attribute the observed high-field MPC (B ) response to two competing mechanisms within the PP spin states: (a) a spin-mixing mechanism caused by the difference in the donor-acceptor (or positive-negative polarons) g factors (the so-called "Δ g mechanism"), and (b) the spin polarization induced by thermal population of the PP Zeeman split levels. The nonsaturating MPC (B ) response at high fields and high temperatures indicates that there exist charge-transfer excitons (CTEs) with decay time in the subnanosecond time domain. With decreasing temperature, the CTE decay time sharply increases, thereby promoting an increase of the thermal spin-polarization contribution to the MPC (B ) response.

  4. Degradation/oxidation susceptibility of organic photovoltaic cells in aqueous solutions.

    PubMed

    Habib, K; Husain, A; Al-Hazza, A

    2015-12-01

    A criterion of the degradation/oxidation susceptibility of organic photovoltaic (OPV) cells in aqueous solutions was proposed for the first time. The criterion was derived based on calculating the limit of the ratio value of the polarization resistance of an OPV cell in aqueous solution (Rp(s)) to the polarization resistance of the OPV cell in air (Rp(air)). In other words, the criterion lim(Rp(s)/Rp(air)) = 1 was applied to determine the degradation/oxidation of the OPV cell in the aqueous solution when Rp(air) became equal (increased) to Rp(s) as a function of time of the exposure of the OPV cell to the aqueous solution. This criterion was not only used to determine the degradation/oxidation of different OPV cells in a simulated operational environment but also it was used to determine the electrochemical behavior of OPV cells in deionized water and a polluted water with fine particles of sand. The values of Rp(s) were determined by the electrochemical impedance spectroscopy at low frequency. In addition, the criterion can be applied under diverse test conditions with a predetermined period of OPV operations.

  5. Basic aspects for improving the energy conversion efficiency of hetero-junction organic photovoltaic cells.

    PubMed

    Ryuzaki, Sou; Onoe, Jun

    2013-01-01

    Hetero-junction organic photovoltaic (OPV) cells consisting of donor (D) and acceptor (A) layers have been regarded as next-generation PV cells, because of their fascinating advantages, such as lightweight, low fabrication cost, resource free, and flexibility, when compared to those of conventional PV cells based on silicon and semiconductor compounds. However, the power conversion efficiency (η) of the OPV cells has been still around 8%, though more than 10% efficiency has been required for their practical use. To fully optimize these OPV cells, it is necessary that the low mobility of carriers/excitons in the OPV cells and the open circuit voltage (V OC), of which origin has not been understood well, should be improved. In this review, we address an improvement of the mobility of carriers/excitons by controlling the crystal structure of a donor layer and address how to increase the V OC for zinc octaethylporphyrin [Zn(OEP)]/C60 hetero-junction OPV cells [ITO/Zn(OEP)/C60/Al]. It was found that crystallization of Zn(OEP) films increases the number of inter-molecular charge transfer (IMCT) excitons and enlarges the mobility of carriers and IMCT excitons, thus significantly improving the external quantum efficiency (EQE) under illumination of the photoabsorption band due to the IMCT excitons. Conversely, charge accumulation of photo-generated carriers in the vicinity of the donor/acceptor (D/A) interface was found to play a key role in determining the V OC for the OPV cells.

  6. Tailored exciton diffusion in organic photovoltaic cells for enhanced power conversion efficiency.

    PubMed

    Menke, S Matthew; Luhman, Wade A; Holmes, Russell J

    2013-02-01

    Photoconversion in planar-heterojunction organic photovoltaic cells (OPVs) is limited by a short exciton diffusion length (L(D)) that restricts migration to the dissociating electron donor/acceptor interface. Consequently, bulk heterojunctions are often used to realize high efficiency as these structures reduce the distance an exciton must travel to be dissociated. Here, we present an alternative approach that seeks to directly engineer L(D) by optimizing the intermolecular separation and consequently, the photophysical parameters responsible for excitonic energy transfer. By diluting the electron donor boron subphthalocyanine chloride into a wide-energy-gap host material, we optimize the degree of interaction between donor molecules and observe a ~50% increase in L(D). Using this approach, we construct planar-heterojunction OPVs with a power conversion efficiency of (4.4 ± 0.3)%, > 30% larger than the case of optimized devices containing an undiluted donor layer. The underlying correlation between L(D) and the degree of molecular interaction has wide implications for the design of both OPV active materials and device architectures.

  7. Morphology change and improved efficiency in organic photovoltaics via hexa-peri-hexabenzocoronene templates.

    PubMed

    Dam, Henk H; Sun, Kuan; Hanssen, Eric; White, Jonathan M; Marszalek, Tomasz; Pisula, Wojciech; Czolk, Jens; Ludwig, Jens; Colsmann, Alexander; Pfaff, Marina; Gerthsen, Dagmar; Wong, Wallace W H; Jones, David J

    2014-06-11

    The morphology of the active layer in organic photovoltaics (OPVs) is of crucial importance as it greatly influences charge generation and transport. A templating interlayer between the electrode and the active layer can change active layer morphology and influence the domain orientation. A series of amphiphilic interface modifiers (IMs) combining a hydrophilic polyethylene-glycol (PEG) oligomer and a hydrophobic hexabenzocoronene (HBC) were designed to be soluble in PEDOT:PSS solutions, and surface accumulate on drying. These IMs are able to self-assemble in solution. When IMs are deposited on top of a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) film, they induce a morphology change of the active layer consisting of discotic fluorenyl-substituted HBC (FHBC) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). However, when only small amounts (0.2 wt %) of IMs are blended into PEDOT:PSS, a profound change of the active layer morphology is also observed. Morphology changes were monitored by grazing incidence wide-angle X-ray scattering (GIWAXS), transmission electron microscopy (TEM), TEM tomography, and low-energy high-angle angular dark-field scanning transmission electron microscopy (HAADF STEM). The interface modification resulted in a 20% enhancement of power conversion efficiency. PMID:24848983

  8. Small optical gap molecules and polymers: using theory to design more efficient materials for organic photovoltaics.

    PubMed

    Risko, Chad; Brédas, Jean-Luc

    2014-01-01

    Recent improvements in the power conversion efficiencies of organic solar cells have been derived through a combination of new materials, processing, and device designs. A key factor has also been quantum-chemical studies that have led to a better understanding not only of the intrinsic electronic and optical properties of the materials but also of the physical processes that take place during the photovoltaic effect. In this chapter we review some recent quantum-chemical investigations of donor-acceptor copolymers, systems that have found wide use as the primary absorbing and hole-transport materials in bulk-heterojunction solar cells. We underline a number of current limitations with regard to available electronic structure methods and in terms of the understanding of the processes involved in solar cell operation. We conclude with a brief outlook that discusses the need to develop multiscale simulation methods that combine quantum-chemical techniques with large-scale classically-based simulations to provide a more complete picture.

  9. Theoretical study of phenyl-substituted indacenodithiophene copolymers for high performance organic photovoltaics.

    PubMed

    Chochos, Christos L; Avgeropoulos, Apostolos; Lidorikis, Elefterios

    2013-02-14

    The theoretical estimation of energy levels and energy gaps of conjugated polymers for organic photovoltaics (OPVs) represents in principle a useful tool for the prescreening of new donor systems as a suitable pair for the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). In this study, ten tetraphenyl-substituted indacenodithiophene (IDT) copolymers (eight in the form of donor-acceptor), whose energy gaps vary in the range of 1.48-2.11 eV have been selected and their highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs), and gap energies have been calculated by applying density functional theory (DFT) and/or time-dependent density functional theory (TD-DFT) methods. In spite of the examined molecular structure variety, nice correlations (theoretical models) between experimental and theoretical electronic parameters were found. It is shown that the theoretical band gap estimated by the TD-DFT using dimer model compounds and DFT using tetramer model compounds provide in good agreement the optical band gap of these polymers. Finally, the optimum theoretical limits of the LUMO offset between the fullerene and the IDT tetramer model compounds, for which high performance OPVs (efficiency > 6%) are obtained, is presented for the first time.

  10. Efficient organic photovoltaics utilizing nanoscale heterojunctions in sequentially deposited polymer/fullerene bilayer.

    PubMed

    Seok, Jeesoo; Shin, Tae Joo; Park, Sungmin; Cho, Changsoon; Lee, Jung-Yong; Yeol Ryu, Du; Kim, Myung Hwa; Kim, Kyungkon

    2015-02-11

    A highly efficient sequentially deposited bilayer (SD-bilayer) of polymer/fullerene organic photovoltaic (OPV) device is developed via the solution process. Herein, we resolve two essential problems regarding the construction of an efficient SD-bilayer OPV. First, the solution process fabrication of the SD-bilayer is resolved by incorporating an ordering agent (OA) to the polymer solution, which improves the ordering of the polymer chain and prevents the bottom-layer from dissolving into the top-layer solution. Second, a non-planar heterojunction with a large surface area is formed by the incorporation of a heterojunction agent (HA) to the top-layer solution. Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) is used for the bottom-layer and phenyl-C71-butyric-acid-methyl ester (PC70BM) is used for the top-layer. The SD-bilayer OPV produced utilizing both an OA and HA exhibits a power conversion efficiency (PCE) of 7.12% with a high internal quantum efficiency (IQE). We believe our bilayer system affords a new way of forming OPVs distinct from bulk heterojunction (BHJ) systems and offers a chance to reconsider the polymers that have thus far shown unsatisfactory performance in BHJ systems.

  11. High-Performance Inverted Organic Photovoltaics Without Hole-Selective Contact.

    PubMed

    Savva, Achilleas; Burgués-Ceballos, Ignasi; Papazoglou, Giannis; Choulis, Stelios A

    2015-11-11

    A detailed investigation of the functionality of inverted organic photovoltaics (OPVs) using bare Ag contacts as the top electrode is presented. The inverted OPVs without a hole-transporting layer (HTL) exhibit a significant gain in hole-carrier selectivity and power-conversion efficiency (PCE) after exposure in ambient conditions. Inverted OPVs comprised of ITO-ZnO-poly(3-hexylthiophene-2,5-diyl)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)-Ag demonstrate over 3.5% power conversion efficiency only if the devices are exposed in air for over 4 days. As concluded through a series of measurements, the oxygen presence is essential to obtaining fully operational solar cell devices without HTL. Moreover, accelerated stability tests under damp heat conditions (RH = 85% and T = 65 °C) performed to nonencapsulated OPVs demonstrate that HTL-free inverted OPVs exhibit comparable stability to the reference inverted OPVs. Importantly, it is shown that bare Ag top electrodes can be efficiently used in inverted OPVs using various high-performance polymer-fullerene bulk heterojunction material systems demonstrating 6.5% power-conversion efficiencies.

  12. How disorder controls the kinetics of triplet charge recombination in semiconducting organic polymer photovoltaics.

    PubMed

    Bittner, Eric R; Lankevich, Vladimir; Gélinas, Simon; Rao, Akshay; Ginger, David A; Friend, Richard H

    2014-10-14

    Recent experiments by Rao et al. (Nature, 2013, 500, 435-439) indicate that recombination of triplet charge-separated states is suppressed in organic polymer-fullerene based bulk-heterojunction (BHJ) photovoltaic cells exhibiting a high degree of crystallinity in the fullerene phase relative to systems with more disorder. In this paper, we use a series of Frenkel-exciton lattice models to rationalize these results in terms of wave-function localization, interface geometry, and density of states. In one-dimensional co-linear and co-facial models of the interface, increasing local energetic disorder in one phase localizes the interfacial triplet charge-transfer ((3)CT) states and increases the rate at which these states relax to form lower-energy triplet excitons. In two dimensional BHJ models, energetic disorder within the fullerene phase plays little role in further localizing states pinned to the interface. However, inhomogeneous broadening introduces strong coupling between the interfacial (3)CT and nearby fullerene triplet excitons and can enhance the decay of these states in systems with higher degrees of energetic disorder.

  13. An Effective Two-Orbital Quantum Chemical Model for Organic Photovoltaic Materials.

    PubMed

    Raos, Guido; Casalegno, Mosè; Idé, Julien

    2014-01-14

    We present a coarse-grained quantum chemical model of organic photovoltaic materials, which is based on the classic idea that the main physical processes involve the electrons occupying the frontier orbitals (HOMO and LUMO) of each molecule or "site". This translates into an effective electronic Hamiltonian with two electrons and two orbitals per site. The on-site parameters (one- and two-electron integrals) can be rigorously related to the ionization energy, electron affinity, and singlet and triplet first excitation energies of that site. The intersite Hamiltonian parameters are introduced in a way that is consistent with classical electrostatics, and for the one-electron part, we use a simple approximation that could be refined using information from atomistic quantum chemical calculations. The model has been implemented within the GAMESS-US package. This allows the exploration of the physics of these materials using state-of-the art quantum chemical methods on relatively large systems (hundreds of electron-donor and electron-acceptor sites). To illustrate this point, we present ground- and excited-state calculations on dimers and two-dimensional arrays of sites using the Hartree-Fock, configuration interaction, and coupled-cluster methods. The calculations provide evidence for the possibility of low-energy, long-range electron transfer in donor-acceptor heterojunctions characterized by a moderate degree of disorder.

  14. Charge-Transfer State Dynamics Following Hole and Electron Transfer in Organic Photovoltaic Devices.

    PubMed

    Bakulin, Artem A; Dimitrov, Stoichko D; Rao, Akshay; Chow, Philip C Y; Nielsen, Christian B; Schroeder, Bob C; McCulloch, Iain; Bakker, Huib J; Durrant, James R; Friend, Richard H

    2013-01-01

    The formation of bound electron-hole pairs, also called charge-transfer (CT) states, in organic-based photovoltaic devices is one of the dominant loss mechanisms hindering performance. Whereas CT state dynamics following electron transfer from donor to acceptor have been widely studied, there is not much known about the dynamics of bound CT states produced by hole transfer from the acceptor to the donor. In this letter, we compare the dynamics of CT states formed in the different charge-transfer pathways in a range of model systems. We show that the nature and dynamics of the generated CT states are similar in the case of electron and hole transfer. However the yield of bound and free charges is observed to be strongly dependent on the HOMOD-HOMOA and LUMOD-LUMOA energy differences of the material system. We propose a qualitative model in which the effects of static disorder and sampling of states during the relaxation determine the probability of accessing CT states favorable for charge separation.

  15. Dual use of tantalum disulfides as hole and electron extraction layers in organic photovoltaic cells.

    PubMed

    Le, Quyet Van; Nguyen, Thang Phan; Choi, Kyoung Soon; Cho, Yoon-Ho; Hong, Young Joon; Kim, Soo Young

    2014-12-14

    UV/ozone treated (UVO-treated) TaS2 and non-treated TaS2 nanosheets are introduced into organic photovoltaic cells (OPVs) as hole extraction layers (HEL) and electron extraction layers (EEL). TaS2 nanosheets are obtained via ultrasonic vibration and size-controlled by centrifugation. Atomic force microscopy (AFM) images reveal that the thickness and lateral size of TaS2 nanosheets are approximately 1 and 70 nm, indicating that uniform and ultrathin TaS2 nanosheets are obtained. The work function of TaS2 increases from 4.4 eV to 4.9-5.1 eV after applying UVO treatment by forming Ta2O5. In addition, the power conversion efficiencies of normal OPV with UVO-treated TaS2 and inverted OPV with TaS2 are 3.06 and 2.73%, which are higher than those of OPV without TaS2 (1.56% for normal OPV and 0.22% for inverted OPV). These results indicate that TaS2 is a promising material for HEL and EEL layers in OPVs. PMID:25341448

  16. Analysis of degradation mechanisms in donor-acceptor copolymer based organic photovoltaic devices using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Srivastava, S. B.; Sonar, P.; Singh, S. P.

    2016-09-01

    The stability of organic photovoltaic (OPV) devices in ambient conditions has been a serious issue which needs to be addressed and resolved timely. In order to probe the degradation mechanism in a donor-acceptor polymer PDPP-TNT: PC71BM bulk heterojunction based OPV devices, we have studied current density-voltage (J-V) behavior and impedance spectroscopy of fresh and aged devices. The current-voltage characteristic of optimized fresh devices exhibit a short circuit current density (J sc) of 8.9 mA cm-2, open circuit voltage (V oc) of 0.79 V, fill factor (FF) of 54.6%, and power conversion efficiency (PCE) of 3.8%. For aged devices, J sc, V oc, FF, and PCE were reduced to 57.3%, 89.8%, 44.3% and 23.7% of its initial value, respectively. The impedance spectra measured under illumination for these devices were successfully fitted using a CPE-based circuit model. For aged devices, the low-frequency response in impedance spectra suggests an accumulation of the photo-generated charge carriers at the interfaces which leads to a significant lowering in fill factor. Such degradation in device performance is attributed to the incorporation of oxygen and water molecules in devices. An increase in the recombination resistance indicates a deterioration of free charge carrier generation and conduction in devices.

  17. Inkjet printed silver nanowire network as top electrode for semi-transparent organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Lu, Hui; Lin, Jian; Wu, Na; Nie, Shuhong; Luo, Qun; Ma, Chang-Qi; Cui, Zheng

    2015-03-01

    A method for direct inkjet printing of silver nanowire (Ag NW) to form transparent conductive network as the top electrode for inverted semi-transparent organic photovoltaic devices (OPV) was developed. The highest power conversion efficiency of the poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) based OPV was achieved to be 2.71% when the top electrode was formed by 7 times of printing. In general, devices with printed Ag NW top electrode had similar open-circuit voltage (VOC, around 0.60 V) but lower fill factor (FF, 0.33-0.54) than that of device with thermally deposited Ag opaque electrode (reference device). Both FF and short-circuit current density (JSC), however, were found to be increasing with the increase of printing times (3, 5, and 7), which could be partially attributed to the improved conductivity of Ag NW network electrodes. The solvent effect on device performances was studied carefully by comparing the current density-voltage (J-V) curves of different devices. The results revealed that solvent treatment on the anode buffer layer during printing led to a decrease of charge injection selectivity and an increase of charge recombination at the anode interface, which was considered to be the reason for the degrading of device performance.

  18. An optimization algorithm for designing robust and simple antireflection films for organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Kubota, S.; Kanomata, K.; Momiyama, K.; Suzuki, T.; Hirose, F.

    2013-10-01

    We propose an optimization algorithm to design multilayer antireflection (AR) structure, which has robustness against variations in layer thicknesses, for organic photovoltaic cells. When a set of available materials are given, the proposed method searches for the material and thickness of each AR layer to maximize the short-circuit current density (Jsc). This algorithm allows for obtaining a set of solutions, including optimal and quasi-optimal solutions, at the same time, so that we can clearly make comparison between them. In addition, the effects of deviations in the thicknesses of the AR layers are examined for the (quasi-)optimal solutions obtained. The expectation of the decrease in the AR performance is estimated by calculating the changes in Jsc when the thicknesses of all AR layers are varied independently. We show that some of quasi-optimal solutions may have simpler layer configuration and can be more robust against the deviations in film thicknesses, than the optimal solution. This method indicates the importance of actively searching valuable, nonoptimal solutions for practical design of AR films. We also discuss the optical conditions that lead to light absorption in the back metal contact and the effects of changing active layer thicknesses.

  19. Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

    SciTech Connect

    Dyck, Ondrej; Hu, Sheng; Das, Sanjib; Keum, Jong; Xiao, Kai; Khomami, Bamin; Duscher, Gerd

    2015-11-24

    Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. Our paper outlines the application of two electron energy-loss spectroscopic (EELS) imaging techniques that can complement and enhance current phase detection techniques. Specifically, the bulk plasmon peak position, often used to produce contrast between phases in energy filtered transmission electron microscopy (EFTEM), is quantitatively mapped across a sample cross section. One complementary spectrum image capturing the carbon and sulfur core loss edges is compared with the plasmon peak map and found to agree quite well, indicating that carbon and sulfur density differences between the two phases also allows phase discrimination. Additionally, an analytical technique for determining absolute atomic areal density is used to produce an absolute carbon and sulfur areal density map. We also show how these maps may be re-interpreted as a phase ratio map, giving quantitative information about the purity of the phases within the junction.

  20. Interpreting impedance spectra of organic photovoltaic cells—Extracting charge transit and recombination rates

    SciTech Connect

    Mullenbach, Tyler K.; Zou, Yunlong; Holmes, Russell J.; Holst, James

    2014-09-28

    Impedance spectroscopy has been widely used to extract the electron-hole recombination rate constant in organic photovoltaic cells (OPVs). This technique is typically performed on OPVs held at open-circuit. Under these conditions, the analysis is simplified with recombination as the only pathway for the decay of excess charge carriers; transit provides no net change in the charge density. In this work, we generalize the application and interpretation of impedance spectroscopy for bulk heterojunction OPVs at any operating voltage. This, in conjunction with reverse bias external quantum efficiency measurements, permits the extraction of both recombination and transit rate constants. Using this approach, the transit and recombination rate constants are determined for OPVs with a variety of electron donor-acceptor pairings and compositions. It is found that neither rate constant individually is sufficient to characterize the efficiency of charge collection in an OPV. It is demonstrated that a large recombination rate constant can be accompanied by a large transit rate constant, thus fast recombination is not necessarily detrimental to OPV performance. Extracting the transit and recombination rate constants permits a detailed understanding of how OPV architecture and processing conditions impact the transient behavior of charge carriers, elucidating the origin of optimum device configurations.

  1. Snow cleaning of substrates increases yield of large-area organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wang, Nana; Zimmerman, Jeramy D.; Tong, Xiaoran; Xiao, Xin; Yu, Junsheng; Forrest, Stephen R.

    2012-09-01

    We demonstrate large-area organic photovoltaic cells (OPVs) based on boron-subphthalocyanine chloride (SubPc)/C60 and 2,4-bis[4-(N,N-diphenylamino)-2,6 dihydroxyphenyl]squaraine/C60 heterojunctions on substrates "snow-cleaned" with a jet of mixed-phase CO2. Snow cleaning reduces particulates on the indium-tin-oxide (ITO)-coated glass substrates, thereby reducing device shorts and shunt paths. Snow cleaning improves yield of 1.44 cm2 SubPc/C60 OPV cells from zero for conventionally solvent-cleaned substrates to ˜70%. The standard deviation of power conversion efficiency for a population of 19 snow-cleaned devices is ≤4.0%. By using a sub-electrode structure, we obtain a power conversion efficiency of 2.21% ± 0.05% for 6.25 cm2 SubPc/C60 devices, compared to 2.69% ± 0.03%, for 0.008 cm2 devices, with the efficiency decrease due to series resistance of the ITO.

  2. Tandem organic photovoltaics using both solution and vacuum deposited small molecules

    NASA Astrophysics Data System (ADS)

    Lassiter, Brian E.; Zimmerman, Jeramy D.; Panda, Anurag; Xiao, Xin; Forrest, Stephen R.

    2012-08-01

    We demonstrate a tandem organic photovoltaic cell incorporating solution- and vacuum-deposited small molecules as the active layers. A blue and green-absorbing boron subphthalocyanine chloride:C70 graded heterojunction (HJ) sub-cell is combined with a green and red-absorbing functionalized squaraine/C70 bilayer HJ sub-cell, resulting in a tandem cell with a wavelength response from 350 nm to 800 nm. The efficiency of the cells depends on process conditions such as solvent annealing, resulting in nanocrystalline morphology that leads to improved charge and exciton transport compared with un-annealed cells. The incorporation of C70 in both sub-cells leads to an increase of short-circuit current by at least 30% compared to analogous cells using C60. The optimized power conversion efficiency of the tandem cell is 6.6% ± 0.1%, with an open-circuit voltage of 1.97 ± 0.1 V under simulated 1 sun, AM 1.5G illumination. The tandem cell voltage is equal to the sum of the constituent sub-cells, indicating that the transparent, Ag nanoparticle/MoO3 compound charge recombination layer interposed between the cells is nearly lossless.

  3. Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and -Stacking

    DOE PAGES

    Shewmon, Nathan; Watkins, Davita; Galindo, Johan; Zerdan, Raghida; Chen, Jihua; Keum, Jong Kahk; Roitberg, Adrian; Xue, Jiangeng; Castellano, Ronald

    2015-07-20

    For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom-up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H-bonding) interactions between π-conjugated electron donor molecules encourage formation of vertically aligned donor π-stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groupsmore » that are either capable or incapable of self-complementary H-bonding. When applied to OPVs, the H-bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H-bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X-ray scattering reveals a synergistic interplay of lateral H-bonding interactions and vertical π-stacking for directing the favorable morphology of the BHJ.« less

  4. Efficient organic photovoltaics utilizing nanoscale heterojunctions in sequentially deposited polymer/fullerene bilayer.

    PubMed

    Seok, Jeesoo; Shin, Tae Joo; Park, Sungmin; Cho, Changsoon; Lee, Jung-Yong; Yeol Ryu, Du; Kim, Myung Hwa; Kim, Kyungkon

    2015-01-01

    A highly efficient sequentially deposited bilayer (SD-bilayer) of polymer/fullerene organic photovoltaic (OPV) device is developed via the solution process. Herein, we resolve two essential problems regarding the construction of an efficient SD-bilayer OPV. First, the solution process fabrication of the SD-bilayer is resolved by incorporating an ordering agent (OA) to the polymer solution, which improves the ordering of the polymer chain and prevents the bottom-layer from dissolving into the top-layer solution. Second, a non-planar heterojunction with a large surface area is formed by the incorporation of a heterojunction agent (HA) to the top-layer solution. Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) is used for the bottom-layer and phenyl-C71-butyric-acid-methyl ester (PC70BM) is used for the top-layer. The SD-bilayer OPV produced utilizing both an OA and HA exhibits a power conversion efficiency (PCE) of 7.12% with a high internal quantum efficiency (IQE). We believe our bilayer system affords a new way of forming OPVs distinct from bulk heterojunction (BHJ) systems and offers a chance to reconsider the polymers that have thus far shown unsatisfactory performance in BHJ systems. PMID:25670623

  5. Electrosprayed Molybdenum Trioxide Aqueous Solution and Its Application in Organic Photovoltaic Cells

    PubMed Central

    Suzuki, Katsumi; Fukuda, Takeshi; Liao, Yingjie

    2014-01-01

    A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer. PMID:25148047

  6. Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and -Stacking

    SciTech Connect

    Shewmon, Nathan; Watkins, Davita; Galindo, Johan; Zerdan, Raghida; Chen, Jihua; Keum, Jong Kahk; Roitberg, Adrian; Xue, Jiangeng; Castellano, Ronald

    2015-07-20

    For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom-up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H-bonding) interactions between π-conjugated electron donor molecules encourage formation of vertically aligned donor π-stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groups that are either capable or incapable of self-complementary H-bonding. When applied to OPVs, the H-bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H-bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X-ray scattering reveals a synergistic interplay of lateral H-bonding interactions and vertical π-stacking for directing the favorable morphology of the BHJ.

  7. New N-Type Polymers for Organic Photovoltaics: Cooperative Research and Development Final Report, CRADA Number CRD-06-177

    SciTech Connect

    Olson, D.

    2014-08-01

    This CRADA will develop improved thin film organic solar cells using a new n-type semiconducting polymer. High efficiency photovoltaics (PVs) based on inorganic semiconductors have good efficiencies (up to 30%) but are extremely expensive to manufacture. Organic PV technology has the potential to overcome this problem through the use of high-throughput production methods like reel-to-reel printing on flexible substrates. Unfortunately, today's best organic PVs have only a few percent efficiency, a number that is insufficient for virtually all commercial applications. The limited choice of stable n-type (acceptor) organic semiconductor materials is one of the key factors that prevent the further improvement of organic PVs. TDA Research, Inc. (TDA) previously developed a new class of electron-deficient (n-type) conjugated polymers for use in organic light emitting diodes (OLEDs). During this project TDA in collaboration with the National Renewable Energy Laboratory (NREL) will incorporate these electron-deficient polymers into organic photovoltaics and investigate their performance. TDA Research, Inc. (TDA) is developing new materials and polymers to improve the performance of organic solar cells. Materials being developed at TDA include spin coated transparent conductors, charge injection layers, fullerene derivatives, electron-deficient polymers, and three-phase (fullerene/polythiophene/dye) active layer inks.

  8. INTERACTIONS OF SOLAR ULTRAVIOLET RADIATION AND DISSOLVED ORGANIC MATTER IN FRESHWATER AND MARINE ENVIRONMENTS

    EPA Science Inventory

    Solar radiation provides the primary driving force for the biogeochemical cycles upon which life and climate depend. Recent studies have demonstrated that the absorption of solar radiation, especially 'm the ultraviolet spectral region, results in photochemical reactions that can...

  9. Simulation and optimization of the performance of organic photovoltaic cells based on capped copolymers for bulk heterojunctions

    NASA Astrophysics Data System (ADS)

    Mhamdi, A.; Boukhili, W.; Raissi, M.; Mahdouani, M.; Vignau, L.; Bourguiga, R.

    2016-08-01

    Recently many investigations have been done to improve the performance of solar cells photovoltaic. One of this devices developed is the Bulk Heterojunction (BHJ) solar cells based on poly (3-hexylthiophene) (P3HT)/[6, 6]-phenyl C61-butyric acid methyl ester (PCBM) blend which have been fabricated by spin-coating. It is known that the nanostructure of the active layer of this device has an important impact on the photovoltaic performances. In this work, we analyze the results obtained on solar cells using a copolymer P3HT-b-PS based on poly (3-hexylthiophene) (P3HT) as a donor block and polystyrene (PS) as a soft block, their compatibility with the blend of P3HT/PCBM at various weight percentages (0%-5%). The addition of this weight percentage is in order to improve the performance of polymer solar cells. It has been demonstrated that the addition of a small amount of P3HT-b-PS (from 0.5%-1.5%) led to an increase in photovoltaic efficiency compared to devices made from P3HT/PCBM only. To study the impact of the added amount of the P3HT-b-PS on the performances of the fabricated organic cells, we used an equivalent circuit model based on single diode model with five photovoltaic parameters. Then, we extracted these physical parameters of the organic photovoltaic cells such as the saturation current density, the series and shunt resistances, the ideality factor and the photogenerated current density from the experimental characteristics (J-V) in the dark and under illumination. We proposed and developed the used procedure based on this model and we resolved the analytic equations of the density-current using the Lambert W-function. A good agreement between the theoretical model and the experimental data of electrical characteristics is obtained illustrating the enhancement of the addition of a small amount of P3HT-b-PS (≤1.5%) in the P3HT/PCBM blend on the characteristics of BHJ organic photovoltaic cells.

  10. Understanding device-structure-induced variations in open-circuit voltage for organic photovoltaics.

    PubMed

    Wang, Zhiping; Uemura, Yu; Zhou, Ying; Miyadera, Tetsuhiko; Azumi, Reiko; Yoshida, Yuji; Chikamatsu, Masayuki

    2015-05-27

    We investigate the structural influences on the device performance, especially on open-circuit voltage (V(OC)) in squaraine (SQ)/fullerene (C60) bilayer cells. Simply changing the SQ thickness could lead to 40% variation in V(OC) from 0.62 to 0.86 V. The ionization potential (IP) of SQ films and recombination at the anode surface as well as donor/acceptor (D/A) interface sensitively vary with film thicknesses, which account for the shifts in V(OC). The anode recombination can be effectively suppressed by preventing direct contact between C60 and the anode with a buffer layer, delivering an elevated V(OC). Through polarized infrared-multiple-angle incidence resolution spectroscopy measurement, the molecular structure of SQ films is found to gradually evolve from lying-down on indium-tin oxide substrates with noncentrosymmetric orientation at low thicknesses to random structure at high thicknesses. The different molecular orientation may yield different strengths of electronic coupling, which affects the charge-carrier recombination and thus V(OC). Moreover, the oriented SQ films would spontaneously compose aligned dipole moments at the D/A interface because of the strong dipolar effects in SQ molecules identified by density functional theory calculations, whereas no aligned interfacial dipole moment exists in the random structure. The resulting interfacial dipole moments would form an electric field at the D/A interface, leading to variations in the IP and thus impacting V(OC). Our findings demonstrate that V(OC) in organic photovoltaic cells is critically associated with the molecular orientation that affects the charge-carrier recombination and interfacial dipole alignment, which should be seriously taken into consideration for the design of organic molecules and optimization of the cell efficiency.

  11. Organic Photovoltaics and Bioelectrodes Providing Electrical Stimulation for PC12 Cell Differentiation and Neurite Outgrowth.

    PubMed

    Hsiao, Yu-Sheng; Liao, Yan-Hao; Chen, Huan-Lin; Chen, Peilin; Chen, Fang-Chung

    2016-04-13

    Current bioelectronic medicines for neurological therapies generally involve treatment with a bioelectronic system comprising a power supply unit and a bioelectrode device. Further integration of wireless and self-powered units is of practical importance for implantable bioelectronics. In this study, we developed biocompatible organic photovoltaics (OPVs) for serving as wireless electrical power supply units that can be operated under illumination with near-infrared (NIR) light, and organic bioelectronic interface (OBEI) electrode devices as neural stimulation electrodes. The OPV/OBEI integrated system is capable to provide electrical stimulation (ES) as a means of enhancing neuron-like PC12 cell differentiation and neurite outgrowth. For the OPV design, we prepared devices incorporating two photoactive material systems--β-carotene/N,N'-dioctyl-3,4,9,10-perylenedicarboximide (β-carotene/PTCDI-C8) and poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)--that exhibited open circuit voltages of 0.11 and 0.49 V, respectively, under NIR light LED (NLED) illumination. Then, we connected OBEI devices with different electrode gaps, incorporating biocompatible poly(hydroxymethylated-3,4-ethylenedioxythiophene), to OPVs to precisely tailor the direct current electric field conditions during the culturing of PC12 cells. This NIR light-driven OPV/OBEI system could be engineered to provide tunable control over the electric field (from 220 to 980 mV mm(-1)) to promote 64% enhancement in the neurite length, direct the neurite orientation on chips, or both. The OPV/OBEI integrated systems under NIR illumination appear to function as effective power delivery platforms that should meet the requirements for wirelessly offering medical ES to a portion of the nervous system; they might also be a key technology for the development of next-generation implantable bioelectronics. PMID:26999636

  12. Laser processing of organic photovoltaic cells with a roll-to-roll manufacturing process

    NASA Astrophysics Data System (ADS)

    Petsch, Tino; Haenel, Jens; Clair, Maurice; Keiper, Bernd; Scholz, Christian

    2011-03-01

    Flexible large area organic photovoltaic (OPV) is currently one of the fastest developing areas of organic electronics. New light absorbing polymer blends combined with new transparent conductive materials provide higher power conversion efficiencies while new and improved production methods are developed to achieve higher throughput at reduced cost. A typical OPV is formed by TCO layers as the transparent front contact and polymers as active layer as well as interface layer between active layer and front contact. The several materials have to be patterned in order to allow for a row connection of the solar cell. 3D-Micromac used ultra-short pulsed lasers to evaluate the applicability of various wavelengths for the selective ablation of the indium tin oxide (ITO) layer and the selective ablation of the bulk hetero junction (BHJ) consisting of poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) on top of a Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) without damaging the ITO. These lasers in combination with high performance galvanometer scanning systems achieve superior scribing quality without damaging the substrate. With scribing speeds of 10 m/s and up it is possible to integrate this technology into a roll-to-roll manufacturing tool. The functionality of an OPV usually also requires an annealing step, especially when using a BHJ for the active layer consisting of P3HT:PCBM, to optimize the layers structure and therewith the efficiency of the solar cell (typically by thermal treatment, e.g. oven). The process of laser annealing was investigated using a short-pulsed laser with a wavelength close to the absorption maximum of the BHJ.

  13. Organic Photovoltaics and Bioelectrodes Providing Electrical Stimulation for PC12 Cell Differentiation and Neurite Outgrowth.

    PubMed

    Hsiao, Yu-Sheng; Liao, Yan-Hao; Chen, Huan-Lin; Chen, Peilin; Chen, Fang-Chung

    2016-04-13

    Current bioelectronic medicines for neurological therapies generally involve treatment with a bioelectronic system comprising a power supply unit and a bioelectrode device. Further integration of wireless and self-powered units is of practical importance for implantable bioelectronics. In this study, we developed biocompatible organic photovoltaics (OPVs) for serving as wireless electrical power supply units that can be operated under illumination with near-infrared (NIR) light, and organic bioelectronic interface (OBEI) electrode devices as neural stimulation electrodes. The OPV/OBEI integrated system is capable to provide electrical stimulation (ES) as a means of enhancing neuron-like PC12 cell differentiation and neurite outgrowth. For the OPV design, we prepared devices incorporating two photoactive material systems--β-carotene/N,N'-dioctyl-3,4,9,10-perylenedicarboximide (β-carotene/PTCDI-C8) and poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)--that exhibited open circuit voltages of 0.11 and 0.49 V, respectively, under NIR light LED (NLED) illumination. Then, we connected OBEI devices with different electrode gaps, incorporating biocompatible poly(hydroxymethylated-3,4-ethylenedioxythiophene), to OPVs to precisely tailor the direct current electric field conditions during the culturing of PC12 cells. This NIR light-driven OPV/OBEI system could be engineered to provide tunable control over the electric field (from 220 to 980 mV mm(-1)) to promote 64% enhancement in the neurite length, direct the neurite orientation on chips, or both. The OPV/OBEI integrated systems under NIR illumination appear to function as effective power delivery platforms that should meet the requirements for wirelessly offering medical ES to a portion of the nervous system; they might also be a key technology for the development of next-generation implantable bioelectronics.

  14. Use of silane-functionalized graphene oxide in organic photovoltaic cells and organic light-emitting diodes.

    PubMed

    Lee, Chang Yeong; Le, Quyet Van; Kim, Cheolmin; Kim, Soo Young

    2015-04-14

    Graphene oxide (GO) and silane-functionalized GO (sGO) sheets obtained through a simple sonication exfoliation method are employed as hole transport layers to improve the efficiency of organic photovoltaic (OPV) cells and organic light-emitting diodes (OLED). GO was functionalized using (3-glycidyl oxypropyl)trimethoxysilane (GPTMS) and triethoxymethylsilane (MTES). The appearance of new peaks in the Fourier-transform infrared spectra of the sGOs indicates the formation of Si-O-C, Si-O-Si, Si-H, and Si-O-C moieties, which provide evidence of the addition of silane to the GO surface. Furthermore, the appearance of Si-O-Si bonds in the synchrotron radiation photoelectron spectra (SRPES) of the MTES-sGO and GPTMS-sGO samples suggests that silane groups were effectively functionalized onto the GO sheets. An OPV cell with GO layers showed a lower performance with a power conversion efficiency (PCE) of 2.06%; in contrast, OPV cells based on GPTMS-sGO and MTES-sGO have PCE values of 3.00 and 3.08%, respectively. The OLED devices based on GPTMS-sGO and MTES-sGO showed a higher maximum luminance efficiency of 13.91 and 12.77 cd A(-1), respectively, than PEDOT:PSS-based devices (12.34 cd A(-1)). The SRPES results revealed that the work functions of GO, GPTMS-sGO, and MTES-sGO were 4.8, 4.9, and 5.0 eV, respectively. Therefore, the increase in the PCE value is attributed to improved band-gap alignment. It is thought that sGO could be used as an interfacial layer in OPV and OLED devices.

  15. The Harvard Clean Energy Project: High-throughput screening of organic photovoltaic materials using cheminformatics, machine learning, and pattern recognition

    NASA Astrophysics Data System (ADS)

    Olivares-Amaya, Roberto; Hachmann, Johannes; Amador-Bedolla, Carlos; Daly, Aidan; Jinich, Adrian; Atahan-Evrenk, Sule; Boixo, Sergio; Aspuru-Guzik, Alán

    2012-02-01

    Organic photovoltaic devices have emerged as competitors to silicon-based solar cells, currently reaching efficiencies of over 9% and offering desirable properties for manufacturing and installation. We study conjugated donor polymers for high-efficiency bulk-heterojunction photovoltaic devices with a molecular library motivated by experimental feasibility. We use quantum mechanics and a distributed computing approach to explore this vast molecular space. We will detail the screening approach starting from the generation of the molecular library, which can be easily extended to other kinds of molecular systems. We will describe the screening method for these materials which ranges from descriptor models, ubiquitous in the drug discovery community, to eventually reaching first principles quantum chemistry methods. We will present results on the statistical analysis, based principally on machine learning, specifically partial least squares and Gaussian processes. Alongside, clustering methods and the use of the hypergeometric distribution reveal moieties important for the donor materials and allow us to quantify structure-property relationships. These efforts enable us to accelerate materials discovery in organic photovoltaics through our collaboration with experimental groups.

  16. Enhanced photovoltaic performance of Cu-based metal-organic frameworks sensitized solar cell by addition of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lee, Deok Yeon; Shin, Chan Yong; Yoon, Seog Joon; Lee, Haw Young; Lee, Wonjoo; Shrestha, Nabeen K.; Lee, Joong Kee; Han, Sung-Hwan

    2014-02-01

    In the present work, TiO2 nanoparticle and multi-walled carbon nanotubes composite powder is prepared hydrothermally. After doctor blading the paste from composite powder, the resulted composite film is sensitized with Cu-based metal-organic frameworks using a layer-by-layer deposition technique and the film is characterized using FE-SEM, EDX, XRD, UV/Visible spectrophotometry and photoluminescence spectroscopy. The influence of the carbon nanotubes in photovoltaic performance is studied by constructing a Grätzel cell with I3-/I- redox couple containing electrolyte. The results demonstrate that the introduction of carbon nanotubes accelerates the electron transfer, and thereby enhances the photovoltaic performance of the cell with a nearly 60% increment in power conversion efficiency.

  17. Basic aspects for improving the energy conversion efficiency of hetero-junction organic photovoltaic cells

    PubMed Central

    Ryuzaki, Sou; Onoe, Jun

    2013-01-01

    Hetero-junction organic photovoltaic (OPV) cells consisting of donor (D) and acceptor (A) layers have been regarded as next-generation PV cells, because of their fascinating advantages, such as lightweight, low fabrication cost, resource free, and flexibility, when compared to those of conventional PV cells based on silicon and semiconductor compounds. However, the power conversion efficiency (η) of the OPV cells has been still around 8%, though more than 10% efficiency has been required for their practical use. To fully optimize these OPV cells, it is necessary that the low mobility of carriers/excitons in the OPV cells and the open circuit voltage (V OC), of which origin has not been understood well, should be improved. In this review, we address an improvement of the mobility of carriers/excitons by controlling the crystal structure of a donor layer and address how to increase the V OC for zinc octaethylporphyrin [Zn(OEP)]/C60 hetero-junction OPV cells [ITO/Zn(OEP)/C60/Al]. It was found that crystallization of Zn(OEP) films increases the number of inter-molecular charge transfer (IMCT) excitons and enlarges the mobility of carriers and IMCT excitons, thus significantly improving the external quantum efficiency (EQE) under illumination of the photoabsorption band due to the IMCT excitons. Conversely, charge accumulation of photo-generated carriers in the vicinity of the donor/acceptor (D/A) interface was found to play a key role in determining the V OC for the OPV cells. PMID:23853702

  18. Strong photocurrent enhancements in plasmonic organic photovoltaics by biomimetic nanoarchitectures with efficient light harvesting.

    PubMed

    Leem, Jung Woo; Kim, Sehwan; Park, Chihyun; Kim, Eunkyoung; Yu, Jae Su

    2015-04-01

    We propose the biomimetic moth-eye nanoarchitectures as a novel plasmonic light-harvesting structure for further enhancing the solar-generated photocurrents in organic photovoltaics (OPVs). The full moth-eye nanoarchitectures are composed of two-dimensional hexagonal periodic grating arrays on surfaces of both the front zinc oxide (ZnO) and rear active layers, which are prepared by a simple and cost-effective soft imprint nanopatterning technique. For the 380 nm period ZnO and 650 nm period active gratings (i.e., ZnO(P380)/Active(P650)), the poly(3-hexylthiophene-2,5-diyl):indene-C60 bis-adduct (P3HT:ICBA)-based plasmonic OPVs exhibit an improvement of the absorption spectrum compared to the pristine OPVs over a broad wavelength range of 350-750 nm, showing absorption enhancement peaks at wavelengths of ∼370, 450, and 670 nm, respectively. This leads to a considerable increase of short-circuit current density (Jsc) from 10.9 to 13.32 mA/cm(2), showing a large Jsc enhancement percentage of ∼22.2%. As a result, the strongly improved power conversion efficiency (PCE) of 6.28% is obtained compared to that (i.e., PCE = 5.12%) of the pristine OPVs. For the angle-dependent light-absorption characteristics, the plasmonic OPVs with ZnO(P380)/Active(P650) have a better absorption performance than that of the pristine OPVs at incident angles of 20-70°. For optical absorption characteristics and near-field intensity distributions of plasmonic OPVs, theoretical analyses are also performed by a rigorous coupled-wave analysis method, which gives a similar tendency with the experimentally measured data.

  19. What Controls the Rate of Ultrafast Charge Transfer and Charge Separation Efficiency in Organic Photovoltaic Blends.

    PubMed

    Jakowetz, Andreas C; Böhm, Marcus L; Zhang, Jiangbin; Sadhanala, Aditya; Huettner, Sven; Bakulin, Artem A; Rao, Akshay; Friend, Richard H

    2016-09-14

    In solar energy harvesting devices based on molecular semiconductors, such as organic photovoltaics (OPVs) and artificial photosynthetic systems, Frenkel excitons must be dissociated via charge transfer at heterojunctions to yield free charges. What controls the rate and efficiency of charge transfer and charge separation is an important question, as it determines the overall power conversion efficiency (PCE) of these systems. In bulk heterojunctions between polymer donor and fullerene acceptors, which provide a model system to understand the fundamental dynamics of electron transfer in molecular systems, it has been established that the first step of photoinduced electron transfer can be fast, of order 100 fs. But here we report the first study which correlates differences in the electron transfer rate with electronic structure and morphology, achieved with sub-20 fs time resolution pump-probe spectroscopy. We vary both the fullerene substitution and donor/fullerene ratio which allow us to control both aggregate size and the energetic driving force for charge transfer. We observe a range of electron transfer times from polymer to fullerene, from 240 fs to as short as 37 fs. Using ultrafast electro-optical pump-push-photocurrent spectroscopy, we find the yield of free versus bound charges to be weakly dependent on the energetic driving force, but to be very strongly dependent on fullerene aggregate size and packing. Our results point toward the importance of state accessibility and charge delocalization and suggest that energetic offsets between donor and acceptor levels are not an important criterion for efficient charge generation. This provides design rules for next-generation materials to minimize losses related to driving energy and boost PCE. PMID:27538341

  20. New acceptor-donor-acceptor (A-D-A) type copolymers for efficient organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ghomrasni, S.; Ayachi, S.; Alimi, K.

    2015-01-01

    Three new conjugated systems alternating acceptor-donor-acceptor (A-D-A) type copolymers have been investigated by means of Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) at the 6-31g (d) level of theory. 4,4‧-Dimethoxy-chalcone, also called the 1,3-bis(4-methoxyphenyl)prop-2-en-1-one (BMP), has been used as a common acceptor moiety. It forced intra-molecular S⋯O interactions through alternating oligo-thiophene derivatives: 4-AlkylThiophenes (4-ATP), 4-AlkylBithiophenes (4-ABTP) and 4-Thienylene Vinylene (4-TEV) as donor moieties. The band gap, HOMO and LUMO electron distributions as well as optical properties were analyzed for each molecule. The fully optimized resulting copolymers showed low band gaps (2.2-2.8 eV) and deep HOMO energy levels ranging from -4.66 to -4.86 eV. A broad absorption [300-900 nm] covering the solar spectrum and absorption maxima ranges from 486 to 604 nm. In addition, organic photovoltaic cells (OPCs) based on alternating copolymers in bulk heterojunction (BHJ) composites with the 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]-C61 (PCBM), as an acceptor, have been optimized. Thus, the band gap decreased to 1.62 eV, the power conversion efficiencies (PCEs) were about 3-5% and the open circuit voltage Voc of the resulting molecules decreased from 1.50 to 1.27 eV.

  1. Quantitative comparison of organic photovoltaic bulk heterojunction photostability under laser illumination

    SciTech Connect

    Lesoine, Michael D.; Bobbitt, Jonathan M.; Carr, John A.; Elshobaki, Moneim; Chaudhary, Sumit; Smith, Emily A.

    2014-11-20

    The photostability of bulk heterojunction organic photovoltaic films containing a polymer donor and a fullerene-derivative acceptor was examined using resonance Raman spectroscopy and controlled laser power densities. The polymer donors were poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). Four sample preparation methods were studied: (i) thin or (ii) thick films with fast solvent evaporation under nitrogen, (iii) thick films with slow solvent evaporation under nitrogen, and (iv) thin films dried under nitrogen followed by thermal annealing. Polymer order was assessed by monitoring a Raman peak’s full width at half-maximum and location as a function of illumination time and laser power densities from 2.5 × 103 to 2.5 × 105 W cm–2. Resonance Raman spectroscopy measurements show that before prolonged illumination, PCDTBT and PTB7 have the same initial order for all preparation conditions, while P3HT order improves with slow solvent drying or thermal annealing. All films exhibited changes to bulk heterojunction structure with 2.5 × 105 Wcm–2 laser illumination as measured by resonance Raman spectroscopy, and atomic force microscopy images show evidence of sample heating that affects the polymer over an area greater than the illumination profile. Furthermore, photostability data are important for proper characterization by techniques involving illumination and the development of devices suitable for real-world applications.

  2. Quantitative comparison of organic photovoltaic bulk heterojunction photostability under laser illumination

    DOE PAGES

    Lesoine, Michael D.; Bobbitt, Jonathan M.; Carr, John A.; Elshobaki, Moneim; Chaudhary, Sumit; Smith, Emily A.

    2014-11-20

    The photostability of bulk heterojunction organic photovoltaic films containing a polymer donor and a fullerene-derivative acceptor was examined using resonance Raman spectroscopy and controlled laser power densities. The polymer donors were poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). Four sample preparation methods were studied: (i) thin or (ii) thick films with fast solvent evaporation under nitrogen, (iii) thick films with slow solvent evaporation under nitrogen, and (iv) thin films dried under nitrogen followed by thermal annealing. Polymer order was assessed by monitoring a Raman peak’s full width at half-maximum and location as a function of illumination time and laser powermore » densities from 2.5 × 103 to 2.5 × 105 W cm–2. Resonance Raman spectroscopy measurements show that before prolonged illumination, PCDTBT and PTB7 have the same initial order for all preparation conditions, while P3HT order improves with slow solvent drying or thermal annealing. All films exhibited changes to bulk heterojunction structure with 2.5 × 105 Wcm–2 laser illumination as measured by resonance Raman spectroscopy, and atomic force microscopy images show evidence of sample heating that affects the polymer over an area greater than the illumination profile. Furthermore, photostability data are important for proper characterization by techniques involving illumination and the development of devices suitable for real-world applications.« less

  3. Bimolecular crystals with an intercalated structure improve poly(p-phenylenevinylene)-based organic photovoltaic cells.

    PubMed

    Lim, Kyung-Geun; Park, Jun-Mo; Mangold, Hannah; Laquai, Frédéric; Choi, Tae-Lim; Lee, Tae-Woo

    2015-01-01

    The exciton dissociation, recombination, and charge transport of bulk heterojunction organic photovoltaic cells (OPVs) is influenced strongly by the nanomorphology of the blend, such as the grain size and the molecular packing. Although it is well known that polymers based on amorphous poly(p-phenylenevinylene) (PPV) have a fundamental limit to their efficiency because of low carrier mobility, which leads to increased recombination and unbalanced charge extraction, herein, we demonstrate that the issue can be overcome by forming bimolecular crystals of an amorphous PPV-based polymer:phenyl-C61 -butyric acid methyl ester (PCBM) intercalated structure. We used amorphous poly(2,5-dioctyloxy-p-phenylene vinylene-alt-2',5'-thienylene vinylene) (PPVTV), which has a simple chemical structure. A reasonably high power conversion efficiency (∼3.5 %) was obtained, although the material has an intrinsically amorphous structure and a relatively large band gap (2.0 eV). We demonstrate a correlation between a well-ordered bimolecular crystal of PPVTV:PCBM and an improved hole mobility of a PPVTV:PCBM film compared to a pristine PPVTV film by using 2 D grazing incidence XRD and space-charge-limited current measurements. Furthermore, we show that the bimolecular crystal structure in high-performance OPVs is related to an optimum molecular packing, which is influenced by the PPVTV:PCBM blending ratio, side-chain length, and molecular weight of the PPVTV polymer. Improved charge transport in PPVTV:PCBM bimolecular crystals leads to a fast sweep out of charges and thus suppression of nongeminate recombination under the operating conditions.

  4. Importance of the donor:fullerene intermolecular arrangement for high-efficiency organic photovoltaics.

    PubMed

    Graham, Kenneth R; Cabanetos, Clement; Jahnke, Justin P; Idso, Matthew N; El Labban, Abdulrahman; Ngongang Ndjawa, Guy O; Heumueller, Thomas; Vandewal, Koen; Salleo, Alberto; Chmelka, Bradley F; Amassian, Aram; Beaujuge, Pierre M; McGehee, Michael D

    2014-07-01

    The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) (13)C{(1)H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material

  5. What Controls the Rate of Ultrafast Charge Transfer and Charge Separation Efficiency in Organic Photovoltaic Blends.

    PubMed

    Jakowetz, Andreas C; Böhm, Marcus L; Zhang, Jiangbin; Sadhanala, Aditya; Huettner, Sven; Bakulin, Artem A; Rao, Akshay; Friend, Richard H

    2016-09-14

    In solar energy harvesting devices based on molecular semiconductors, such as organic photovoltaics (OPVs) and artificial photosynthetic systems, Frenkel excitons must be dissociated via charge transfer at heterojunctions to yield free charges. What controls the rate and efficiency of charge transfer and charge separation is an important question, as it determines the overall power conversion efficiency (PCE) of these systems. In bulk heterojunctions between polymer donor and fullerene acceptors, which provide a model system to understand the fundamental dynamics of electron transfer in molecular systems, it has been established that the first step of photoinduced electron transfer can be fast, of order 100 fs. But here we report the first study which correlates differences in the electron transfer rate with electronic structure and morphology, achieved with sub-20 fs time resolution pump-probe spectroscopy. We vary both the fullerene substitution and donor/fullerene ratio which allow us to control both aggregate size and the energetic driving force for charge transfer. We observe a range of electron transfer times from polymer to fullerene, from 240 fs to as short as 37 fs. Using ultrafast electro-optical pump-push-photocurrent spectroscopy, we find the yield of free versus bound charges to be weakly dependent on the energetic driving force, but to be very strongly dependent on fullerene aggregate size and packing. Our results point toward the importance of state accessibility and charge delocalization and suggest that energetic offsets between donor and acceptor levels are not an important criterion for efficient charge generation. This provides design rules for next-generation materials to minimize losses related to driving energy and boost PCE.

  6. Strong photocurrent enhancements in plasmonic organic photovoltaics by biomimetic nanoarchitectures with efficient light harvesting.

    PubMed

    Leem, Jung Woo; Kim, Sehwan; Park, Chihyun; Kim, Eunkyoung; Yu, Jae Su

    2015-04-01

    We propose the biomimetic moth-eye nanoarchitectures as a novel plasmonic light-harvesting structure for further enhancing the solar-generated photocurrents in organic photovoltaics (OPVs). The full moth-eye nanoarchitectures are composed of two-dimensional hexagonal periodic grating arrays on surfaces of both the front zinc oxide (ZnO) and rear active layers, which are prepared by a simple and cost-effective soft imprint nanopatterning technique. For the 380 nm period ZnO and 650 nm period active gratings (i.e., ZnO(P380)/Active(P650)), the poly(3-hexylthiophene-2,5-diyl):indene-C60 bis-adduct (P3HT:ICBA)-based plasmonic OPVs exhibit an improvement of the absorption spectrum compared to the pristine OPVs over a broad wavelength range of 350-750 nm, showing absorption enhancement peaks at wavelengths of ∼370, 450, and 670 nm, respectively. This leads to a considerable increase of short-circuit current density (Jsc) from 10.9 to 13.32 mA/cm(2), showing a large Jsc enhancement percentage of ∼22.2%. As a result, the strongly improved power conversion efficiency (PCE) of 6.28% is obtained compared to that (i.e., PCE = 5.12%) of the pristine OPVs. For the angle-dependent light-absorption characteristics, the plasmonic OPVs with ZnO(P380)/Active(P650) have a better absorption performance than that of the pristine OPVs at incident angles of 20-70°. For optical absorption characteristics and near-field intensity distributions of plasmonic OPVs, theoretical analyses are also performed by a rigorous coupled-wave analysis method, which gives a similar tendency with the experimentally measured data. PMID:25785480

  7. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction

    NASA Astrophysics Data System (ADS)

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A.; Casanova, Fèlix; van der Zant, Herre S. J.; Castellanos-Gomez, Andres; Hueso, Luis E.

    2015-09-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ~11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials

  8. Linear pi-conjugated systems derivatized with C60-fullerene as molecular heterojunctions for organic photovoltaics.

    PubMed

    Roncali, Jean

    2005-06-01

    This tutorial review covers recent contributions in the area of linear pi-conjugated systems bound to fullerenes in view of their application as active materials in photovoltaic devices. The first part discusses the concepts of double-cable polymer and molecular hetero-junction and presents several examples of chemically or electrochemically synthesized C60-derivatized conjugated polymers. The second and main part of the article concerns the various classes of C60-derivatized pi-conjugated oligomers designed in view of their utilization in single-component photovoltaic devices. Thus, C60-containing pi-conjugated systems such as oligoarylenevinylenes, oligoaryleneethynylenes and oligothiophenes are discussed on the basis of the relationships between molecular structure, photophysical properties and performances of the derived photovoltaic devices. A brief last section presents some recent examples of surface-attached molecular hetero-junctions based on self-assembled monolayers and discusses possible routes for future research.

  9. Symmetry-breaking charge transfer in a zinc chlorodipyrrin acceptor for high open circuit voltage organic photovoltaics.

    PubMed

    Bartynski, Andrew N; Gruber, Mark; Das, Saptaparna; Rangan, Sylvie; Mollinger, Sonya; Trinh, Cong; Bradforth, Stephen E; Vandewal, Koen; Salleo, Alberto; Bartynski, Robert A; Bruetting, Wolfgang; Thompson, Mark E

    2015-04-29

    Low open-circuit voltages significantly limit the power conversion efficiency of organic photovoltaic devices. Typical strategies to enhance the open-circuit voltage involve tuning the HOMO and LUMO positions of the donor (D) and acceptor (A), respectively, to increase the interfacial energy gap or to tailor the donor or acceptor structure at the D/A interface. Here, we present an alternative approach to improve the open-circuit voltage through the use of a zinc chlorodipyrrin, ZCl [bis(dodecachloro-5-mesityldipyrrinato)zinc], as an acceptor, which undergoes symmetry-breaking charge transfer (CT) at the donor/acceptor interface. DBP/ZCl cells exhibit open-circuit voltages of 1.33 V compared to 0.88 V for analogous tetraphenyldibenzoperyflanthrene (DBP)/C60-based devices. Charge transfer state energies measured by Fourier-transform photocurrent spectroscopy and electroluminescence show that C60 forms a CT state of 1.45 ± 0.05 eV in a DBP/C60-based organic photovoltaic device, while ZCl as acceptor gives a CT state energy of 1.70 ± 0.05 eV in the corresponding device structure. In the ZCl device this results in an energetic loss between E(CT) and qV(OC) of 0.37 eV, substantially less than the 0.6 eV typically observed for organic systems and equal to the recombination losses seen in high-efficiency Si and GaAs devices. The substantial increase in open-circuit voltage and reduction in recombination losses for devices utilizing ZCl demonstrate the great promise of symmetry-breaking charge transfer in organic photovoltaic devices.

  10. Role of ultrathin metal fluoride layer in organic photovoltaic cells: mechanism of efficiency and lifetime enhancement.

    PubMed

    Lim, Kyung-Geun; Choi, Mi-Ri; Kim, Ji-Hoon; Kim, Dong Hun; Jung, Gwan Ho; Park, Yongsup; Lee, Jong-Lam; Lee, Tae-Woo

    2014-04-01

    Although rapid progress has been made recently in bulk heterojunction organic solar cells, systematic studies on an ultrathin interfacial layer at the electron extraction contact have not been conducted in detail, which is important to improve both the device efficiency and the lifetime. We find that an ultrathin BaF2 layer at the electron extraction contact strongly influences the open-circuit voltage (Voc ) as the nanomorphology evolves with increasing BaF2 thickness. A vacuum-deposited ultrathin BaF2 layer grows by island growth, so BaF2 layers with a nominal thickness less than that of single-coverage layer (≈3 nm) partially cover the polymeric photoactive layer. As the nominal thickness of the BaF2 layer increased to that of a single-coverage layer, the Voc and power conversion efficiency (PCE) of the organic photovoltaic cells (OPVs) increased but the short-circuit current remained almost constant. The fill factor and the PCE decreased abruptly as the thickness of the BaF2 layer exceeded that of a single-coverage layer, which was ascribed to the insulating nature of BaF2 . We find the major cause of the increased Voc observed in these devices is the lowered work function of the cathode caused by the reaction and release of Ba from thin BaF2 films upon deposition of Al. The OPV device with the BaF2 layer showed a slightly improved maximum PCE (4.0 %) and a greatly (approximately nine times) increased device half-life under continuous simulated solar irradiation at 100 mW cm(-2) as compared with the OPV without an interfacial layer (PCE=2.1 %). We found that the photodegradation of the photoactive layer was not a major cause of the OPV degradation. The hugely improved lifetime with cathode interface modification suggests a significant role of the cathode interfacial layer that can help to prolong device lifetimes.

  11. Photovoltaics industry profile

    NASA Astrophysics Data System (ADS)

    1980-10-01

    A description of the status of the U.S. photovoltaics industry is given. Principal end user industries are identified, domestic and foreign market trends are discussed, and industry organized and U.S. government organized trade promotion events are listed. Trade associations and trade journals are listed, and a photovoltaic product manufacturers list is included.

  12. A metallocene molecular complex as visible-light absorber for high-voltage organic-inorganic hybrid photovoltaic cells.

    PubMed

    Ishii, Ayumi; Miyasaka, Tsutomu

    2014-04-14

    A thin solid-state dye-sensitized photovoltaic cell is fabricated by composing organic and inorganic heterojunctions in which the visible-light sensitizers are cyclopentadiene derivatives (Cp*) coordinated to a metal oxide, typically TiO2. The coordination bonds of the metallocene molecular complex (Ti-Cp*) create a new LMCT (ligand-to-metal charge transfer) absorption band and induce a rectified charge transfer from the organic ligands to TiO2, leading to photocurrent generation. Photovoltaic junctions are completed by coating crystalline organic molecules (perylene) as a hole-transport layer on the Cp*-coordinated TiO2 surface by using the vapor deposition method. The molecular plane of Cp* on the TiO2 surfaces seems to help the hole-transport layer to form ordered structures, which effectively improve carrier conductivities and minimize interfacial resistance. The organic-inorganic hybrid thin-film photocell with metallocene molecular complexes is capable of generating high open-circuit voltages exceeding 1.2 V.

  13. Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions.

    PubMed

    Nguyen, Bichlien H; Perkins, Robert J; Smith, Jake A; Moeller, Kevin D

    2015-01-01

    The combination of visible light, photovoltaics, and electrochemistry provides a convenient, inexpensive platform for conducting a wide variety of sustainable oxidation reactions. The approach presented in this article is compatible with both direct and indirect oxidation reactions, avoids the need for a stoichiometric oxidant, and leads to hydrogen gas as the only byproduct from the corresponding reduction reaction.

  14. The effect of branching in a semiconducting polymer on the efficiency of organic photovoltaic cells.

    PubMed

    Heintges, Gaël H L; van Franeker, Jacobus J; Wienk, Martijn M; Janssen, René A J

    2016-01-01

    The impact of branching in a diketopyrrolopyrrole polymer on the performance of polymer-fullerene photovoltaic cells is investigated. Compared to the linear polymer, the branched polymer affords a more finely dispersed fibrillar network in the photoactive layer and as a result a large enhancement of the photocurrent and power conversion efficiency.

  15. An Azulene-Containing Low Bandgap Small Molecule for Organic Photovoltaics with High Open-Circuit Voltage.

    PubMed

    Chen, Yao; Zhu, Youqin; Yang, Daobin; Zhao, Suling; Zhang, Lei; Yang, Lin; Wu, Jianglin; Huang, Yan; Xu, Zheng; Lu, Zhiyun

    2016-10-01

    A simple azulene-containing squaraine dye (AzUSQ) showing bandgap of 1.38 eV and hole mobility up to 1.25×10(-4)  cm(2)  V(-1)  s(-1) was synthesized. With its low bandgap, an organic photovoltaic (OPV) device based on it has been made that exhibits an impressive open-circuit voltages (Voc ) of 0.80 V. Hence, azulene might be a promising structural unit to construct OPV materials with simultaneous low bandgap, high hole mobility and high Voc . PMID:27490139

  16. An Azulene-Containing Low Bandgap Small Molecule for Organic Photovoltaics with High Open-Circuit Voltage.

    PubMed

    Chen, Yao; Zhu, Youqin; Yang, Daobin; Zhao, Suling; Zhang, Lei; Yang, Lin; Wu, Jianglin; Huang, Yan; Xu, Zheng; Lu, Zhiyun

    2016-10-01

    A simple azulene-containing squaraine dye (AzUSQ) showing bandgap of 1.38 eV and hole mobility up to 1.25×10(-4)  cm(2)  V(-1)  s(-1) was synthesized. With its low bandgap, an organic photovoltaic (OPV) device based on it has been made that exhibits an impressive open-circuit voltages (Voc ) of 0.80 V. Hence, azulene might be a promising structural unit to construct OPV materials with simultaneous low bandgap, high hole mobility and high Voc .

  17. Trimetallic nitride endohedral C80 fullerenes and their application in Organic Photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel Brett

    Trimetallic nitride endohedral C80 fullerenes (TNEF) materials offer a reduced lowest unoccupied molecular orbital energy (LUMO) offset when compared with many of the polymer donor systems currently being employed in Organic Photovoltaic (OPV) research. This lower LUMO offset allows for higher open circuit voltages, and therefore, higher efficiencies in OPV devices. Presented here is a comprehensive study of the room temperature absorption and emission of a series of trimetallic nitride endohedral metallofullerenes, M3N C80, (M = Er, Gd, Ho, Lu, Sc, Y), as well the investigation and demonstration of TNEFs use as an acceptor material in OPV devices. Morphology and electrode contacts are shown to have large influence on TNEF-based OPV performance, in poly(3-hexyl)thiophene (P3HT) and 1-(3-hexoxycarbonyl)propyl-1-phenyl-[6,6]-Lu3N C81 (Lu3N C80-PCBH) based OPV devices. Decreasing the LUMO offset between P3HT and the acceptor material, reduced energy losses in the charge transfer process, which yield an increased open circuit voltage to 280mV above reference devices made with P3HT & [6,6]-phenyl-C61-butyric methyl ester (C60-PCBM). OPV energy conversion efficiencies of > 4% are observed with P3HT/Lu3N C80-PCBH active layer with a predicted upper limit on power conversion efficiency of > 6% for this donor/acceptor system. The data displayed within this work constitutes proof of concept that the varying reduction potential (160--290 meV vs. C 60-PCBM) of the TNEF acceptor molecules provides a pathway to enhancing OPV device performance by closing down the molecular orbital offset of the donor/acceptor heterojunction. TNEF acceptor materials in single bulk heterojunction devices offer a viable path to 11% conversion efficiency with already-reported-on low-band-gap donors, such as poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)- alt-4,7-(2,1,3-benzothiadiazole), PCPDTBT.

  18. Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application

    NASA Astrophysics Data System (ADS)

    Widjonarko, Nicodemus Edwin

    Organic photovoltaics (OPV) offers a potential for solar-electric power generation to be affordable. Crucial to OPV device performance is the incorporation of interlayers, ultra-thin films deposited between the photoactive material and the electrical contacts. These interlayers have various, targeted functionalities: optical window, encapsulation, or electronic bridge. The last category is known as "transport layers'', and is the focus of this thesis. In this thesis, we explore and investigate the physics that leads to improvements in OPV device performance when a transport layer is employed. We focus on the use of non-stoichiometric nickel oxide (NiOx) as a hole transport layer (HTL) in poly(3-hexylthiophene):phenyl-C 61-butryric acid methyl ester (P3HT:PCBM) solar cells. NiOx deposited by physical vapor deposition is chosen for this study because of its successful use as HTL, the ease to engineer its electronic properties by varying deposition parameters, and it leading to improved device lifetime. Our initial studies indicate that the well-known "high work-function'' rule is not adequate to explain the trends observed in the devices. More in-depth studies is required to fully understand the impact of HTL electronic properties on device performance. These series of investigations reveal that band-offsets at the NiOx / P3HT:PCBM interface need to be taken into account in order to explain the observed trends. Non-optimal band-offsets lead to either sigmoidal current-voltage characteristics or reduced photocurrent. The optimal energy level alignment depends on the energy levels of the photo-active material, which are measurable. This means that an HTL material must be optimized for different photoactive material. A simple and practical set of rules are proposed to achieve this optimal energy level alignment for a given photoactive material. The rules not only include the pervasively-used "high work-function'' rule, but also the impacts of band-offsets investigated

  19. Quantum Chemistry in Nanoscale Environments: Insights on Surface-Enhanced Raman Scattering and Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Olivares-Amaya, Roberto

    The understanding of molecular effects in nanoscale environments is becoming increasingly relevant for various emerging fields. These include spectroscopy for molecular identification as well as in finding molecules for energy harvesting. Theoretical quantum chemistry has been increasingly useful to address these phenomena to yield an understanding of these effects. In the first part of this dissertation, we study the chemical effect of surface-enhanced Raman scattering (SERS). We use quantum chemistry simulations to study the metal-molecule interactions present in these systems. We find that the excitations that provide a chemical enhancement contain a mixed contribution from the metal and the molecule. Moreover, using atomistic studies we propose an additional source of enhancement, where a transition metal dopant surface could provide an additional enhancement. We also develop methods to study the electrostatic effects of molecules in metallic environments. We study the importance of image-charge effects, as well as field-bias to molecules interacting with perfect conductors. The atomistic modeling and the electrostatic approximation enable us to study the effects of the metal interacting with the molecule in a complementary fashion, which provides a better understanding of the complex effects present in SERS. In the second part of this dissertation, we present the Harvard Clean Energy Project, a high-throughput approach for a large-scale computational screening and design of organic photovoltaic materials. We create molecular libraries to search for candidates structures and use quantum chemistry, machine learning and cheminformatics methods to characterize these systems and find structure-property relations. The scale of this study requires an equally large computational resource. We rely on distributed volunteer computing to obtain these properties. In the third part of this dissertation we present our work related to the acceleration of electronic structure

  20. Exploiting single photon vacuum ultraviolet photoionization to unravel the synthesis of complex organic molecules in interstellar ices

    NASA Astrophysics Data System (ADS)

    Abplanalp, Matthew J.; Förstel, Marko; Kaiser, Ralf I.

    2016-01-01

    Complex organic molecules (COM) such as aldehydes, ketones, carboxylic acids, esters, and amides are ubiquitous in the interstellar medium, but traditional gas phase astrochemical models cannot explain their formation routes. By systematically exploiting on line and in situ vacuum ultraviolet photoionization coupled with reflectron time of flight mass spectrometry (PI-ReTOF-MS) and combining these data with infrared spectroscopy (FTIR), we reveal that complex organic molecules can be synthesized within interstellar ices that are condensed on interstellar grains via non-equilibrium reactions involving suprathermal hydrogen atoms at temperatures as low as 5 K. By probing for the first time specific structural isomers without their degradation (fragment-free), the incorporation of tunable vacuum ultraviolet photoionization allows for a much greater understanding of reaction mechanisms that exist in interstellar ices compared to traditional methods, thus eliminating the significant gap between observational and laboratory data that existed for the last decades. With the commission of the Atacama Large Millimeter/Submillimeter Array (ALMA), the number of detections of more complex organic molecules in space will continue to grow - including biorelevant molecules connected to the Origins of Life theme - and an understanding of these data will rely on future advances in sophisticated physical chemistry laboratory experiments.

  1. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications.

  2. Gate-tunable diode and photovoltaic effect in an organic-2D layered material p-n junction.

    PubMed

    Vélez, Saül; Ciudad, David; Island, Joshua; Buscema, Michele; Txoperena, Oihana; Parui, Subir; Steele, Gary A; Casanova, Fèlix; van der Zant, Herre S J; Castellanos-Gomez, Andres; Hueso, Luis E

    2015-10-01

    The semiconducting p-n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p-n junctions. In that context, we present here an organic (Cu-phthalocyanine)-2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 10(4), while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic-2D p-n junctions promising candidates for future technological applications. PMID:26335856

  3. 25th anniversary article: organic photovoltaic modules and biopolymer supercapacitors for supply of renewable electricity: a perspective from Africa.

    PubMed

    Inganäs, Olle; Admassie, Shimelis

    2014-02-12

    The role of materials in civilization is well demonstrated over the centuries and millennia, as materials have come to serve as the classifier of stages of civilization. With the advent of materials science, this relation has become even more pronounced. The pivotal role of advanced materials in industrial economies has not yet been matched by the influence of advanced materials during the transition from agricultural to modern societies. The role of advanced materials in poverty eradication can be very large, in particular if new trajectories of social and economic development become possible. This is the topic of this essay, different in format from the traditional scientific review, as we try to encompass not only two infant technologies of solar energy conversion and storage by means of organic materials, but also the social conditions for introduction of the technologies. The development of organic-based photovoltaic energy conversion has been rapid, and promises to deliver new alternatives to well-established silicon photovoltaics. Our recent development of organic biopolymer composite electrodes opens avenues towards the use of renewable materials in the construction of wooden batteries or supercapacitors for charge storage. Combining these new elements may give different conditions for introduction of energy technology in areas now lacking electrical grids, but having sufficient solar energy inputs. These areas are found close to the equator, and include some of the poorest regions on earth.

  4. Ultraviolet-photoproduced organic solids synthesized under simulated Jovian conditions - Molecular analysis

    NASA Technical Reports Server (NTRS)

    Khare, B. N.; Sagan, C.; Bandurski, E. L.; Nagy, B.

    1978-01-01

    In an earlier paper, Khare and Sagan reported the production of a brownish polymeric material from the near-ultraviolet irradiation of simulated jovian atmospheres with a low hydrogen abundance. Examination of this product indicates that hydrogen sulfide is the initial photon acceptor; the powder resulting after extraction with benzene is 84 percent sulfur, largely S8. In results reported here, the remaining 16 percent was pyrolyzed and then examined by gas chromatography-mass spectrometry. Pyrolysis at 450 C yielded a series of alkanes, alkenes, C3-alkylbenzenes, aromatics, thiophenes, alkylthiophenes, alkylmercaptans, alkyldisulfides, together with the nitrogenous compounds hydrogen cyanide, methyl cyanide, alkylisothiocyanates, acrylonitrile, and allylisothiocyanates. Some of these compounds might be sought on Jupiter and Saturn and their satellites by remote infrared and ultraviolet spectroscopy and directly by entry probes.

  5. Photo-enhanced toxicity of fluoranthene to Gulf of Mexico marine organisms at different larval ages and ultraviolet light intensities.

    PubMed

    Finch, Bryson E; Stubblefield, William A

    2016-05-01

    Significant increases in toxicity have been observed as a result of polycyclic aromatic hydrocarbon (PAH) absorption of ultraviolet (UV) radiation in aquatic organisms. Early life stage aquatic organisms are predicted to be more susceptible to PAH photo-enhanced toxicity as a result of their translucence and tendency to inhabit shallow littoral or surface waters. The objective of the present study was to evaluate the sensitivity of varying ages of larval mysid shrimp (Americamysis bahia), inland silverside (Menidia beryllina), sheepshead minnow (Cyprinodon variegatus), and Gulf killifish (Fundulus grandis) to photo-enhanced toxicity and to examine the correlation between photo-enhanced toxicity and organism pigmentation. Organisms were exposed to fluoranthene and artificial UV light at different larval ages and results were compared using median lethal concentrations (LC50s) and the lethal time-to-death (LT50s). In addition, a high UV light intensity, short-duration (4-h) experiment was conducted at approximately 24 W/m(2) of ultraviolet radiation A (UV-A) and compared with a low-intensity, long-duration (12-h) experiment at approximately 8 W/m(2) of UV-A. The results indicated decreased toxicity with increasing age for all larval organisms. The amount of organism pigmentation was correlated with observed LC50 and LT50 values. High-intensity short-duration exposure resulted in greater toxicity than low-intensity long-duration UV treatments for mysid shrimp, inland silverside, and sheepshead minnow. Data from these experiments suggest that toxicity is dependent on age, pigmentation, UV light intensity, and fluoranthene concentration. PMID:26590351

  6. Photo-enhanced toxicity of fluoranthene to Gulf of Mexico marine organisms at different larval ages and ultraviolet light intensities.

    PubMed

    Finch, Bryson E; Stubblefield, William A

    2016-05-01

    Significant increases in toxicity have been observed as a result of polycyclic aromatic hydrocarbon (PAH) absorption of ultraviolet (UV) radiation in aquatic organisms. Early life stage aquatic organisms are predicted to be more susceptible to PAH photo-enhanced toxicity as a result of their translucence and tendency to inhabit shallow littoral or surface waters. The objective of the present study was to evaluate the sensitivity of varying ages of larval mysid shrimp (Americamysis bahia), inland silverside (Menidia beryllina), sheepshead minnow (Cyprinodon variegatus), and Gulf killifish (Fundulus grandis) to photo-enhanced toxicity and to examine the correlation between photo-enhanced toxicity and organism pigmentation. Organisms were exposed to fluoranthene and artificial UV light at different larval ages and results were compared using median lethal concentrations (LC50s) and the lethal time-to-death (LT50s). In addition, a high UV light intensity, short-duration (4-h) experiment was conducted at approximately 24 W/m(2) of ultraviolet radiation A (UV-A) and compared with a low-intensity, long-duration (12-h) experiment at approximately 8 W/m(2) of UV-A. The results indicated decreased toxicity with increasing age for all larval organisms. The amount of organism pigmentation was correlated with observed LC50 and LT50 values. High-intensity short-duration exposure resulted in greater toxicity than low-intensity long-duration UV treatments for mysid shrimp, inland silverside, and sheepshead minnow. Data from these experiments suggest that toxicity is dependent on age, pigmentation, UV light intensity, and fluoranthene concentration.

  7. Studies on the Properties of Organic Photovoltaic Cells Using TiOx and DMDCNQI as Double Buffer Layers.

    PubMed

    Kim, Gyu Min; Han, Seong Hun; Oh, Se Young

    2015-02-01

    Various types of n-type buffer layers have been used in organic electronic devices. These buffer layers turned out to expedite carrier injection and reduce series resistance, leading to good performance of organic electronic devices. In our current work, we have fabricated organic photovoltaic (OPV) cells consisting of ITO/PEDOT:PSS/P3HT:PCBM/TiOx/DMDCNQI/AI which were fabricated in the presence of air. To incorporate the individual advantages of each n-type buffer layer, a DMDCNQI and TiOx layers were inserted to act as n-type double buffer layers. This leads to an increase of short-circuit current (JSC) and fill factor (FF) with good stability, in comparison to P3HT:PCBM based conventional cells. The results imply that the structures of double buffer layers can provide possible alternative to achieving high performance and air durability.

  8. Polyethylenimine Interfacial Layers in Inverted Organic Photovoltaic Devices: Effects of Ethoxylation and Molecular Weight on Efficiency and Temporal Stability.

    PubMed

    Courtright, Brett A E; Jenekhe, Samson A

    2015-12-01

    We report a comparative study of polyethylenimine (PEI) and ethoxylated-polyethylenimine (PEIE) cathode buffer layers in high performance inverted organic photovoltaic devices. The work function of the indium-tin oxide (ITO)/zinc oxide (ZnO) cathode was reduced substantially (Δφ = 0.73-1.09 eV) as the molecular weight of PEI was varied from 800 g mol(-1) to 750 000 g mol(-1) compared with the observed much smaller reduction when using a PEIE thin film (Δφ = 0.56 eV). The reference inverted polymer solar cells based on the small band gap polymer PBDTT-FTTE (ITO/ZnO/PBDTT-FTTE:PC70BM/MoO3/Ag), without a cathode buffer layer, had an average power conversion efficiency (PCE) of 6.06 ± 0.22%. Incorporation of a PEIE cathode buffer layer in the same PBDTT-FTTE:PC70BM blend devices gave an enhanced performance with a PCE of 7.37 ± 0.53%. In contrast, an even greater photovoltaic efficiency with a PCE of 8.22 ± 0.10% was obtained in similar PBDTT-FTTE:PC70BM blend solar cells containing a PEI cathode buffer layer. The temporal stability of the inverted polymer solar cells was found to increase with increasing molecular weight of the cathode buffer layer. The results show that PEI is superior to PEIE as a cathode buffer layer in high performance organic photovoltaic devices and that the highest molecular weight PEI interlayer provides the highest temporal stability. PMID:26550983

  9. Polyethylenimine Interfacial Layers in Inverted Organic Photovoltaic Devices: Effects of Ethoxylation and Molecular Weight on Efficiency and Temporal Stability.

    PubMed

    Courtright, Brett A E; Jenekhe, Samson A

    2015-12-01

    We report a comparative study of polyethylenimine (PEI) and ethoxylated-polyethylenimine (PEIE) cathode buffer layers in high performance inverted organic photovoltaic devices. The work function of the indium-tin oxide (ITO)/zinc oxide (ZnO) cathode was reduced substantially (Δφ = 0.73-1.09 eV) as the molecular weight of PEI was varied from 800 g mol(-1) to 750 000 g mol(-1) compared with the observed much smaller reduction when using a PEIE thin film (Δφ = 0.56 eV). The reference inverted polymer solar cells based on the small band gap polymer PBDTT-FTTE (ITO/ZnO/PBDTT-FTTE:PC70BM/MoO3/Ag), without a cathode buffer layer, had an average power conversion efficiency (PCE) of 6.06 ± 0.22%. Incorporation of a PEIE cathode buffer layer in the same PBDTT-FTTE:PC70BM blend devices gave an enhanced performance with a PCE of 7.37 ± 0.53%. In contrast, an even greater photovoltaic efficiency with a PCE of 8.22 ± 0.10% was obtained in similar PBDTT-FTTE:PC70BM blend solar cells containing a PEI cathode buffer layer. The temporal stability of the inverted polymer solar cells was found to increase with increasing molecular weight of the cathode buffer layer. The results show that PEI is superior to PEIE as a cathode buffer layer in high performance organic photovoltaic devices and that the highest molecular weight PEI interlayer provides the highest temporal stability.

  10. Impact of the organic halide salt on final perovskite composition for photovoltaic applications

    SciTech Connect

    Moore, David T.; Sai, Hiroaki; Wee Tan, Kwan; Estroff, Lara A.; Wiesner, Ulrich

    2014-08-01

    The methylammonium lead halide perovskites have shown significant promise as a low-cost, second generation, photovoltaic material. Despite recent advances, however, there are still a number of fundamental aspects of their formation as well as their physical and electronic behavior that are not well understood. In this letter we explore the mechanism by which these materials crystallize by testing the outcome of each of the reagent halide salts. We find that components of both salts, lead halide and methylammonium halide, are relatively mobile and can be readily exchanged during the crystallization process when the reaction is carried out in solution or in the solid state. We exploit this fact by showing that the perovskite structure is formed even when the lead salt's anion is a non-halide, leading to lower annealing temperature and time requirements for film formation. Studies into these behaviors may ultimately lead to improved processing conditions for photovoltaic films.

  11. Syntheses of D-A-A Type Small Molecular Donor Materials Having Various Electron Accepting Moiety for Organic Photovoltaic Application.

    PubMed

    Kim, Nahyeon; Park, Sangman; Lee, Myong-Hoon; Lee, Jaemin; Lee, Changjin; Yoon, Sung Cheol

    2016-03-01

    Small molecular donor, DTDCTB achieved a high power conversion efficiency (PCE) value of 6.6 ± 0.2% in vacuum-deposited planar mixed heterojunction (PMHJ) structure. However, the same material just recorded PCE of 0.34% in solution processed small molecule based bulk heterjunction (BHJ) organic photovoltaic cells. For the improvement of organic photovoltaic cells (OPVs), In this study, we designed and synthesized several D-A-A (donor-acceptor-acceptor) type molecular electron donating materials. Ditolylaminothienyl moiety as an electron donating group connected to 1,2,5-benzothiadiazole as a conjugated electron accepting unit, simultaneously with an electron accepting terminal group such as cyano alkyl acetate and N-alkyl rhodanine. The thermal, photophysical, and electrochemical properties of prepared small molecules were investigated by DSC, UV/Vis spectroscopy and Cyclic Voltametry, respectively. As a result, 0.89% of PCE can be obtained from OPV using a mixture of DTATBTER and PCBM as an active layer with a Voc of 0.87 V, a Jsc of 3.20 mA/cm2, and a fill factor of 31.9%. PMID:27455734

  12. Syntheses of D-A-A Type Small Molecular Donor Materials Having Various Electron Accepting Moiety for Organic Photovoltaic Application.

    PubMed

    Kim, Nahyeon; Park, Sangman; Lee, Myong-Hoon; Lee, Jaemin; Lee, Changjin; Yoon, Sung Cheol

    2016-03-01

    Small molecular donor, DTDCTB achieved a high power conversion efficiency (PCE) value of 6.6 ± 0.2% in vacuum-deposited planar mixed heterojunction (PMHJ) structure. However, the same material just recorded PCE of 0.34% in solution processed small molecule based bulk heterjunction (BHJ) organic photovoltaic cells. For the improvement of organic photovoltaic cells (OPVs), In this study, we designed and synthesized several D-A-A (donor-acceptor-acceptor) type molecular electron donating materials. Ditolylaminothienyl moiety as an electron donating group connected to 1,2,5-benzothiadiazole as a conjugated electron accepting unit, simultaneously with an electron accepting terminal group such as cyano alkyl acetate and N-alkyl rhodanine. The thermal, photophysical, and electrochemical properties of prepared small molecules were investigated by DSC, UV/Vis spectroscopy and Cyclic Voltametry, respectively. As a result, 0.89% of PCE can be obtained from OPV using a mixture of DTATBTER and PCBM as an active layer with a Voc of 0.87 V, a Jsc of 3.20 mA/cm2, and a fill factor of 31.9%.

  13. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-09-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates 1-3. Various approaches including optimizing morphology of the active layers 1, 2, introducing new materials as the donor and acceptor 3,4, new device structures such as tandem structure 5, 6 have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer 5, 7.

  14. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-03-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates [1-3]. Various approaches including optimizing morphology of the active layers [1,2], introducing new materials as the donor and acceptor [3,4], new device structures such as tandem structure [5,6] have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer [5,7].

  15. The Effect of Interfacial Geometry on Charge-Transfer States in the Phthalocyanine/Fullerene Organic Photovoltaic System.

    PubMed

    Lee, Myeong H; Geva, Eitan; Dunietz, Barry D

    2016-05-19

    The dependence of charge-transfer states on interfacial geometry at the phthalocyanine/fullerene organic photovoltaic system is investigated. The effect of deviations from the equilibrium geometry of the donor-donor-acceptor trimer on the energies of and electronic coupling between different types of interfacial electronic excited states is calculated from first-principles. Deviations from the equilibrium geometry are found to destabilize the donor-to-donor charge transfer states and to weaken their coupling to the photoexcited donor-localized states, thereby reducing their ability to serve as charge traps. At the same time, we find that the energies of donor-to-acceptor charge transfer states and their coupling to the donor-localized photoexcited states are either less sensitive to the interfacial geometry or become more favorable due to modifications relative to the equilibrium geometry, thereby enhancing their ability to serve as gateway states for charge separation. Through these findings, we eludicate how interfacial geometry modifications can play a key role in achieving charge separation in this widely studied organic photovoltaic system.

  16. Improvement of quantum efficiency of P3HT:PCBM-based organic photovoltaic cells using DMDCNQI as an N-type dopant and buffer layer.

    PubMed

    Lee, Joo Hyung; Yang, Eui Yeol; Oh, Se Young

    2013-03-01

    In previous work, we have reported that a P3HT:PCBM-based organic photovoltaic cell using a thermally evaporated DMDCNQI buffer layer shows a high power conversion efficiency. In the present work, we have fabricated organic photovoltaic cells consisting of ITO/PEDOT:PSS/P3HT:PCBM:DMDCNQI/DMDCNQI/Al using an all-solution process. A thin, uniform DMDCNQI film was obtained in a methanol solution with high solubility and low viscosity. The prepared device shows a high power conversion efficiency of 2.9%. In particular, a maximum external quantum efficiency of 81% was obtained.

  17. Microstructured porous ZnO thin film for increased light scattering and improved efficiency in inverted organic photovoltaics.

    PubMed

    Nirmal, Amoolya; Kyaw, Aung Ko Ko; Sun, Xiao Wei; Demir, Hilmi Volkan

    2014-10-20

    Microstructured porous zinc oxide (ZnO) thin film was developed and demonstrated as an electron selective layer for enhancing light scattering and efficiency in inverted organic photovoltaics. High degree of porosity was induced and controlled in the ZnO layer by incorporation of polyethylene glycol (PEG) organic template. Scanning electron microscopy, contact angle and absorption measurements prove that the ZnO:PEG ratio of 4:1 is optimal for the best performance of porous ZnO. Ensuring sufficient pore-filling, the use of porous ZnO leads to a marked improvement in device performance compared to non-porous ZnO, with 35% increase in current density and 30% increase in efficiency. Haze factor studies indicate that the performance improvement can be primarily attributed to the improved light scattering enabled by such a highly porous structure.

  18. Novel High Efficient Organic Photovoltaic Materials: Appendix for Summary of Research. Appendix

    NASA Technical Reports Server (NTRS)

    Sun, Sam

    2002-01-01

    There are many different kinds of conjugated polymers that may be useful in photovoltaic devices. So far, the most popular and successful conjugated polymers used in photovoltaic devices include poly(1,4-)phenylenevinylenes (PPV), C60 and their derivatives. The discovery of electro-luminescence in PPV has stimulated a great deal of interest in developing "plastic" solid-state semiconductor devices. The overall synthetic methodology for the preparation of PPV can be divided into three main categories: (1) side chain derivatization, (2) precursor approach, and (3) in-situ polymerization. In this project, the first method was adopted. As discussed in project proposal and literatures, the overall efficiency of photovoltaic devices containing conjugated polymers is determined by the materials ability to generate excitons from incoming radiation, and then to separate the charges at donor/acceptor interfaces, and then to transport charges to respective electrodes. Given that effective exciton diffusion range are typical less then 30 nm, unique morphological structures are needed. This need led to several research groups to the idea that interpenetrating or bi-continuous networks of donor (electron donating) and acceptor (electron withdrawing) polymers should give better results. One approach involved the use of functionalized PPV. The attachment of electron withdrawing cyano groups to a PPV forms the CN-PPV, making it a strong electron acceptor. Underivatized PPV is a generally considered a hole-transporting material. Using blends of MEH-PPV, a soluble donor PPV derivative, as a hole transporter and CN-PPV as an electron transporter, a quantum efficiencies of up to 6% was achieved.

  19. Urea, Glycolic Acid, and Glycerol in an Organic Residue Produced by Ultraviolet Irradiation of Interstellar/Pre-Cometary Ice Analogs

    NASA Astrophysics Data System (ADS)

    Nuevo, Michel; Bredehöft, Jan Hendrik; Meierhenrich, Uwe J.; d'Hendecourt, Louis; Thiemann, Wolfram H.-P.

    2010-03-01

    More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH3OH:NH3â = 1:1 ice mixture was UV irradiated at ˜80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar/pre-cometary conditions are proposed.

  20. Urea, glycolic acid, and glycerol in an organic residue produced by ultraviolet irradiation of interstellar/pre-cometary ice analogs.

    PubMed

    Nuevo, Michel; Bredehöft, Jan Hendrik; Meierhenrich, Uwe J; d'Hendecourt, Louis; Thiemann, Wolfram H-P

    2010-03-01

    More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH(3)OH:NH(3) = 1:1 ice mixture was UV irradiated at approximately 80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar/pre-cometary conditions are proposed.

  1. Urea, glycolic acid, and glycerol in an organic residue produced by ultraviolet irradiation of interstellar/pre-cometary ice analogs.

    PubMed

    Nuevo, Michel; Bredehöft, Jan Hendrik; Meierhenrich, Uwe J; d'Hendecourt, Louis; Thiemann, Wolfram H-P

    2010-03-01

    More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH(3)OH:NH(3) = 1:1 ice mixture was UV irradiated at approximately 80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar/pre-cometary conditions are proposed. PMID:20402585

  2. Towards an organic photobattery - Photovoltaic properties of some thermal copolyamino acids

    NASA Technical Reports Server (NTRS)

    Przybylski, A. T.; Syren, R. M.; Fox, S. W.

    1983-01-01

    Thermal copolymers of amino acids have been examined as a novel material for photovoltaic devices. Due to the steric effects of amino acids during polymerization, these polymers are highly ordered, and pigments such as flavins and pterins are formed as part of the polymer. The controllably varied composition of the amino acids in the polymer makes it possible to get either electron-donor or electron-acceptor, or both kinds of groups in varying degrees. The constituent photosensitive element has been made either of photosensitive polymer film or spherule.

  3. High fill factor and thermal stability of bilayer organic photovoltaic cells with an inverted structure

    NASA Astrophysics Data System (ADS)

    Wang, Zhongqiang; Hong, Ziruo; Zhuang, Taojun; Chen, Guo; Sasabe, Hisahiro; Yokoyama, Daisuke; Kido, Junji

    2015-02-01

    In this study, we fabricated planar heterojunction photovoltaic cells with inverted device structures based on tetraphenyldibenzoperiflanthene and fullerene-70 (C70). With proper designs of device architecture and selection of electrode buffers, a high fill factor and power conversion efficiency were obtained due to large shunt resistance (Rsh) and efficient carrier collection. Optical simulation reveals that field-dependent recombination is depressed in the inverted structure cells because of less light absorption in short wavelength range, resulting in high fill factor. More importantly, high thermal stability of inverted structure cells was demonstrated via utilizing stable electrode buffers.

  4. High performance organic integrated device with ultraviolet photodetective and electroluminescent properties consisting of a charge-transfer-featured naphthalimide derivative

    SciTech Connect

    Wang, Hanyu; Wang, Xu; Yu, Junsheng E-mail: jsyu@uestc.edu.cn; Zhou, Jie; Lu, Zhiyun E-mail: jsyu@uestc.edu.cn

    2014-08-11

    A high performance organic integrated device (OID) with ultraviolet photodetective and electroluminescent (EL) properties was fabricated by using a charge-transfer-featured naphthalimide derivative of 6-(3,5-bis-[9-(4-t-butylphenyl)-9H-carbazol-3-yl]-phenoxy)-2- (4-t-butylphenyl)-benzo[de]isoquinoline-1,3-dione (CzPhONI) as the active layer. The results showed that the OID had a high detectivity of 1.5 × 10{sup 11} Jones at −3 V under the UV-350 nm illumination with an intensity of 0.6 mW/cm{sup 2}, and yielded an exciplex EL light emission with a maximum brightness of 1437 cd/m{sup 2}. Based on the energy band diagram, both the charge transfer feature of CzPhONI and matched energy level alignment were responsible for the dual ultraviolet photodetective and EL functions of OID.

  5. Solution-processed tBu4-ZnPc:C61 bulk heterojunction organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Bekalé, Laurent; Barazzouk, Saïd; Sakai, Nobuya; Murakami, Takurou; Miyoshi, Kozo; Miyasaka, Tsutomu; Hotchandani, Surat

    2016-03-01

    A bulk heterojunction (BHJ) organic photovoltaic cell employing tetra-tert-butyl zinc phthalocyanine as electron donor and [6,6]-phenyl C61-buturic acid methyl ester as electron acceptor has been fabricated. The effect of TiOx cathode interlayer, the weight ratio of donor:acceptor in the photoactive layer, and the thermal annealing of photoactive layer on the performance of the cells were investigated. The results show that the insertion of TiOx layer leads to an increase in the photocurrent density of the cells by 11 times compared to those without cathode interlayer. Atomic force microscopy images reveal the formation of well-connected percolated pathways for each phase separated component (donor and acceptor) upon annealing of the film at 150 °C. An important aspect of the present BHJ photovoltaic cell is that it has been obtained by simple wet processes, and most of the fabrication steps have been carried out in ambient air without the use of a glove box.

  6. General method for simultaneous optimization of light trapping and carrier collection in an ultra-thin film organic photovoltaic cell

    SciTech Connect

    Tsai, Cheng-Chia Grote, Richard R.; Beck, Jonathan H.; Kymissis, Ioannis; Osgood, Richard M.; Englund, Dirk

    2014-07-14

    We describe a general method for maximizing the short-circuit current in thin planar organic photovoltaic (OPV) heterojunction cells by simultaneous optimization of light absorption and carrier collection. Based on the experimentally obtained complex refractive indices of the OPV materials and the thickness-dependence of the internal quantum efficiency of the OPV active layer, we analyze the potential benefits of light trapping strategies for maximizing the overall power conversion efficiency of the cell. This approach provides a general strategy for optimizing the power conversion efficiency of a wide range of OPV structures. In particular, as an experimental trial system, the approach is applied here to a ultra-thin film solar cell with a SubPc/C{sub 60} photovoltaic structure. Using a patterned indium tin oxide (ITO) top contact, the numerically optimized designs achieve short-circuit currents of 0.790 and 0.980 mA/cm{sup 2} for 30 nm and 45 nm SubPc/C{sub 60} heterojunction layer thicknesses, respectively. These values correspond to a power conversion efficiency enhancement of 78% for the 30 nm thick cell, but only of 32% for a 45 nm thick cell, for which the overall photocurrent is actually higher. Applied to other material systems, the general optimization method can elucidate if light trapping strategies can improve a given cell architecture.

  7. An approach for an advanced anode interfacial layer with electron-blocking ability to achieve high-efficiency organic photovoltaics.

    PubMed

    Yeo, Jun-Seok; Yun, Jin-Mun; Kang, Minji; Khim, Dongyoon; Lee, Seung-Hoon; Kim, Seok-Soon; Na, Seok-In; Kim, Dong-Yu

    2014-11-26

    The interfacial properties of PEDOT:PSS, pristine r-GO, and r-GO with sulfonic acid (SR-GO) in organic photovoltaic are investigated to elucidate electron-blocking property of PEDOT:PSS anode interfacial layer (AIL), and to explore the possibility of r-GO as electron-blocking layers. The SR-GO results in an optimized power conversion efficiency of 7.54% for PTB7-th:PC71BM and 5.64% for P3HT:IC61BA systems. By combining analyses of capacitance-voltage and photovoltaic-parameters dependence on light intensity, it is found that recombination process at SR-GO/active film is minimized. In contrast, the devices using r-GO without sulfonic acid show trap-assisted recombination. The enhanced electron-blocking properties in PEDOT:PSS and SR-GO AILs can be attributed to surface dipoles at AIL/acceptor. Thus, for electron-blocking, the AIL/acceptor interface should be importantly considered in OPVs. Also, by simply introducing sulfonic acid unit on r-GO, excellent contact selectivity can be realized in OPVs.

  8. General method for simultaneous optimization of light trapping and carrier collection in an ultra-thin film organic photovoltaic cell

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Chia; Grote, Richard R.; Beck, Jonathan H.; Kymissis, Ioannis; Osgood, Richard M.; Englund, Dirk

    2014-07-01

    We describe a general method for maximizing the short-circuit current in thin planar organic photovoltaic (OPV) heterojunction cells by simultaneous optimization of light absorption and carrier collection. Based on the experimentally obtained complex refractive indices of the OPV materials and the thickness-dependence of the internal quantum efficiency of the OPV active layer, we analyze the potential benefits of light trapping strategies for maximizing the overall power conversion efficiency of the cell. This approach provides a general strategy for optimizing the power conversion efficiency of a wide range of OPV structures. In particular, as an experimental trial system, the approach is applied here to a ultra-thin film solar cell with a SubPc/C60 photovoltaic structure. Using a patterned indium tin oxide (ITO) top contact, the numerically optimized designs achieve short-circuit currents of 0.790 and 0.980 mA/cm2 for 30 nm and 45 nm SubPc/C60 heterojunction layer thicknesses, respectively. These values correspond to a power conversion efficiency enhancement of 78% for the 30 nm thick cell, but only of 32% for a 45 nm thick cell, for which the overall photocurrent is actually higher. Applied to other material systems, the general optimization method can elucidate if light trapping strategies can improve a given cell architecture.

  9. High-performance ultraviolet photodetector based on organic-inorganic hybrid structure.

    PubMed

    Shao, Dali; Yu, Mingpeng; Sun, Hongtao; Xin, Guoqing; Lian, Jie; Sawyer, Shayla

    2014-08-27

    An ultraviolet (UV) photodetector is fabricated by sandwiching a nanocomposite active layer between charge-selective semiconducting polymers. The nanocomposite active layer composed of TiO2 nanoparticles (NPs) blended with 1,3-bis(N-carbazolyl)benzene (mCP), which acts as a "valve" controller that enables hole injection into the device upon UV illumination. The UV photodetector demonstrated a high photocurrent to dark current ratio (∼10(4)), a large linear dynamic range of 60 dB, and a remarkable external quantum efficiency (∼8.5 × 10(4)%) for the UV light at 351 nm. In addition to discussing the performance of the UV photodetector, a general strategy for design and fabrication of high-performance UV photodetectors with hole injection operation mode is suggested.

  10. Ultraviolet and visible spectra of the 1,3,5-trinitrobenzolates of polycyclic aromatic hydrocarbons and other organic compounds: A method for their identification (Part II)

    SciTech Connect

    Tombesi, O.L.; Frontera, M.A.; Tomas, M.A.; Badajoz, M.A. )

    1993-01-01

    In a previous paper, a study of ultraviolet and visible spectra of the picrates of polycyclic aromatic hydrocarbons and other representative organic compounds was reported. In the present paper, a similar study of 1,3,5-trinitrobenzolates derivatives is described. In the following discussion, the ultraviolet and visible spectra of the 1,3,5-trinitrobenzolates of polycyclic aromatic hydrocarbons [naphthalene (I), [beta]-methylnaphthalene (II), anthracene (III), phenanthrene (IV), chrysene (V), pyrene (VI), fluorene (VII), and acenaphthene (VIII)] and other representative organic compounds [dibenzofuran (IX), [beta]-naphthol (X), and [alpha]-naphthylamine (XI)] are given. 9 refs.

  11. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size

    NASA Astrophysics Data System (ADS)

    Roehling, John D.; Baran, Derya; Sit, Joseph; Kassar, Thaer; Ameri, Tayebeh; Unruh, Tobias; Brabec, Christoph J.; Moulé, Adam J.

    2016-08-01

    High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100’s of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu3N@PC80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu3N@PC80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu3N@PC80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu3N@PC80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.

  12. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size.

    PubMed

    Roehling, John D; Baran, Derya; Sit, Joseph; Kassar, Thaer; Ameri, Tayebeh; Unruh, Tobias; Brabec, Christoph J; Moulé, Adam J

    2016-01-01

    High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100's of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu3N@PC80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu3N@PC80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu3N@PC80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu3N@PC80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all. PMID:27498880

  13. Effect of annealing on photovoltaic performance of fabricated planar organic-inorganic perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Baltakesmez, Ali; Biber, Mehmet; Tüzemen, Sebahattin

    2016-04-01

    We fabricated planar perovskite solar cells used CH3NH3PbI3-xClx for light harvesting to investigate effect of annealing on photovoltaic performance of fabricated device. The devices have an architecture of Glass/ITO/Pedot:PSS/Perovskite/PC61BM/Al. Layers of hole transport (Pedot:PSS), active and electron transport (PC61BM) were prepared from solution based one step deposition method by a spin coater and standard annealing procedure. The current‑voltage curves of devices were measured inside the glovebox using a Keithley 2400 sourcemeter. The cells were illuminated by a solar simulator have optical intensity value of 300 mW/cm2. For the best cells, while PCE value of 5.78% before the annealing, photovoltaic efficiency was improved average 13% delivered a short-circuit current density of 3.20 mA/cm2, open-circuit voltage of 0.82 V and fill factor of 0.74, leading to an efficiency of 6.54% with respect to prior to annealing.

  14. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size

    PubMed Central

    Roehling, John D.; Baran, Derya; Sit, Joseph; Kassar, Thaer; Ameri, Tayebeh; Unruh, Tobias; Brabec, Christoph J.; Moulé, Adam J.

    2016-01-01

    High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100’s of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu3N@PC80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu3N@PC80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu3N@PC80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu3N@PC80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all. PMID:27498880

  15. High efficiency polarization-sensitive photovoltaic devices using oriented organic thin film

    NASA Astrophysics Data System (ADS)

    Tanaka, Hideyuki; Yasuda, Takeshi; Fujita, Katsuhiko; Tsutsui, Tetsuo

    2005-10-01

    We report the fabrication of polarization-sensitive photovoltaic devices made of hetero-junction type vacuum-sublimed multilayer films composed of aligned 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (aligned-PTCBI) and titanyl phthalocyanine (TiOPc). The PTCBI layer was successfully made to be well aligned without losing high photovoltaic power-conversion efficiency. High polarization sensitivity was achieved at around 540 nm. The device configuration was ITO/In/aligned-PTCBI/TiOPc/PEDOT:PSS/Au and the thickness of each layer was optimized for polarization-sensitive photo-detection. The power-conversion efficiencies under the polarized white light parallel and perpendicular to the molecular-orientation axis, through the ITO electrode were 0.78% and 0.45%, respectively. The ratio of short-circuit current, parallel to perpendicular, was 1.66. This device can be used as transparent photo-detectors, because the transmittance of the Au electrode was about 40% at 500-600nm. The short-circuit current ratio was increased to 3.0, when 510nm monochromatic polarized light through the Au electrode was used.

  16. Effect of annealing on photovoltaic performance of fabricated planar organic-inorganic perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Baltakesmez, Ali; Biber, Mehmet; Tüzemen, Sebahattin

    2016-04-01

    We fabricated planar perovskite solar cells used CH3NH3PbI3-xClx for light harvesting to investigate effect of annealing on photovoltaic performance of fabricated device. The devices have an architecture of Glass/ITO/Pedot:PSS/Perovskite/PC61BM/Al. Layers of hole transport (Pedot:PSS), active and electron transport (PC61BM) were prepared from solution based one step deposition method by a spin coater and standard annealing procedure. The current-voltage curves of devices were measured inside the glovebox using a Keithley 2400 sourcemeter. The cells were illuminated by a solar simulator have optical intensity value of 300 mW/cm2. For the best cells, while PCE value of 5.78% before the annealing, photovoltaic efficiency was improved average 13% delivered a short-circuit current density of 3.20 mA/cm2, open-circuit voltage of 0.82 V and fill factor of 0.74, leading to an efficiency of 6.54% with respect to prior to annealing.

  17. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size.

    PubMed

    Roehling, John D; Baran, Derya; Sit, Joseph; Kassar, Thaer; Ameri, Tayebeh; Unruh, Tobias; Brabec, Christoph J; Moulé, Adam J

    2016-08-08

    High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100's of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu3N@PC80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu3N@PC80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu3N@PC80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu3N@PC80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.

  18. Remarkable improvement in electroluminescence benefited from appropriate electron injection and transporting in ultraviolet organic light-emitting diode

    NASA Astrophysics Data System (ADS)

    You, Fengjiao; Mo, Bingjie; Liu, Liming; Wang, Honghang; Bin Wei; Xu, Jiwen; Zhang, Xiaowen

    2016-08-01

    Suitable thickness of LiF and 4,7-diphenyl-1, 10-phenanthroline with slightly weakened electron injection and transporting is proposed to match the intractable hole injection capacity in ultraviolet organic light-emitting diode (UV OLED). By using this strategy, the device performance is remarkably improved. With 4,4‧-bis(carbazol-9-yl)biphenyl (CBP) and 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ) as emitters, the UV OLED shows maximum radiance of 5.8 mW/cm2 and external quantum efficiency of 2.1% with emission peak of ~380 nm predominantly from TAZ and noticeable shoulder emission of ~410 nm from CBP. The retarded electron injection and transporting contribute to optimizing hole-electron recombination zone and balance within the emitting layers, which accounts for the improved electroluminescent intensity. The detailed mechanism is further clarified with impedance spectroscopy.

  19. Degradation of organic ultraviolet filter diethylamino hydroxybenzoyl hexyl benzoate in aqueous solution by UV/H2O2.

    PubMed

    Gong, Ping; Yuan, Haixia; Zhai, Pingping; Dong, Wenbo; Li, Hongjing

    2015-07-01

    Steady-state and transient-state photolysis experiments were conducted to investigate the degradation of organic ultraviolet filter diethylamino hydroxybenzoyl hexyl benzoate (DHHB) in the aqueous solution by UV/H2O2. Results showed that the obvious degradation of DHHB was not observed under UV irradiation (λ = 254 nm), and the DHHB degradation was conducted due to the oxidation by hydroxyl radical (HO·). While the H2O2 concentration was between 0.05 and 0.10 mol L(-1), the highest DHHB degradation efficiency was obtained. The lower solution pH favored the transformation of DHHB, and the coexisting Cl(-) and NO3(-) ions slightly enhanced the conversion. The degradation of DHHB by HO· followed a pseudo-first-order kinetic model with different initial DHHB concentrations. By intermediate products during DHHB oxidation and laser flash photolysis spectra analysis, a primary degradation pathway was proposed.

  20. Controlling the Morphology of BDTT-DPP-Based Small Molecules via End-Group Functionalization for Highly Efficient Single and Tandem Organic Photovoltaic Cells.

    PubMed

    Kim, Ji-Hoon; Park, Jong Baek; Yang, Hoichang; Jung, In Hwan; Yoon, Sung Cheol; Kim, Dongwook; Hwang, Do-Hoon

    2015-11-01

    A series of narrow-band gap, π-conjugated small molecules based on diketopyrrolopyrrole (DPP) electron acceptor units coupled with alkylthienyl-substituted-benzodithiophene (BDTT) electron donors were designed and synthesized for use as donor materials in solution-processed organic photovoltaic cells. In particular, by end-group functionalization of the small molecules with fluorine derivatives, the nanoscale morphologies of the photoactive layers of the photovoltaic cells were successfully controlled. The influences of different fluorine-based end-groups on the optoelectronic and morphological properties, carrier mobilities, and the photovoltaic performances of these materials were investigated. A high power conversion efficiency (PCE) of 6.00% under simulated solar light (AM 1.5G) illumination has been achieved for organic photovoltaic cells based on a small-molecule bulk heterojunction system consisting of a trifluoromethylbenzene (CF3) end-group-containing oligomer (BDTT-(DPP)2-CF3) as the donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor. As a result, the introduction of CF3 end-groups has been found to enhance both the short circuit current density (JSC) and fill factor (FF). A tandem photovoltaic device comprising an inverted BDTT-(DPP)2-CF3:PC71BM cell and a poly(3-hexylthiophene) (P3HT):indene-C60-bisadduct (IC60BA)-based cell as the top and bottom cell components, respectively, showed a maximum PCE of 8.30%. These results provide valuable guidelines for the rational design of conjugated small molecules for applications in high-performance organic photovoltaic cells. Furthermore, to the best of our knowledge, this is the first report on the design of fluorine-functionalized BDTT-DPP-based small molecules, which have been shown to be a viable candidate for use in inverted tandem cells. PMID:26457421

  1. Controlling the Morphology of BDTT-DPP-Based Small Molecules via End-Group Functionalization for Highly Efficient Single and Tandem Organic Photovoltaic Cells.

    PubMed

    Kim, Ji-Hoon; Park, Jong Baek; Yang, Hoichang; Jung, In Hwan; Yoon, Sung Cheol; Kim, Dongwook; Hwang, Do-Hoon

    2015-11-01

    A series of narrow-band gap, π-conjugated small molecules based on diketopyrrolopyrrole (DPP) electron acceptor units coupled with alkylthienyl-substituted-benzodithiophene (BDTT) electron donors were designed and synthesized for use as donor materials in solution-processed organic photovoltaic cells. In particular, by end-group functionalization of the small molecules with fluorine derivatives, the nanoscale morphologies of the photoactive layers of the photovoltaic cells were successfully controlled. The influences of different fluorine-based end-groups on the optoelectronic and morphological properties, carrier mobilities, and the photovoltaic performances of these materials were investigated. A high power conversion efficiency (PCE) of 6.00% under simulated solar light (AM 1.5G) illumination has been achieved for organic photovoltaic cells based on a small-molecule bulk heterojunction system consisting of a trifluoromethylbenzene (CF3) end-group-containing oligomer (BDTT-(DPP)2-CF3) as the donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor. As a result, the introduction of CF3 end-groups has been found to enhance both the short circuit current density (JSC) and fill factor (FF). A tandem photovoltaic device comprising an inverted BDTT-(DPP)2-CF3:PC71BM cell and a poly(3-hexylthiophene) (P3HT):indene-C60-bisadduct (IC60BA)-based cell as the top and bottom cell components, respectively, showed a maximum PCE of 8.30%. These results provide valuable guidelines for the rational design of conjugated small molecules for applications in high-performance organic photovoltaic cells. Furthermore, to the best of our knowledge, this is the first report on the design of fluorine-functionalized BDTT-DPP-based small molecules, which have been shown to be a viable candidate for use in inverted tandem cells.

  2. Patterning ITO by Template-Assisted Colloidal-Lithography for Enhancing Power Conversion Efficiency in Organic Photovoltaic.

    PubMed

    Lee, Jin-Su; Yu, Jung-Hun; Hwang, Ki-Hwan; Nam, Sang-Hun; Boo, Jin-Hyo; Yun, Sang H

    2016-05-01

    Highly structured interfaces are very desirable in organic photovoltaic solar cells (OPVs), in order to enhance power conversion efficiency (PCE) by decreasing of the transport path for excited charge carriers in the absorber and increasing the optical path length for photon absorption. Many complicated, high-cost lithographic methods have been attempted to modify the surface of the absorber or substrate. However, solution-based colloidal-lithography processes are scalable and cost-effective, but generally result in non-uniform structured surfaces. In this report, we demonstrated an optimized silica-templated colloidal lithographical approach to create a well-defined and controlled transparent ITO layer for enhancing power conversion efficiency (PCE). Additionally, morphological effects of the patterned ITO on optical properties and PCE were analyzed in detail. PMID:27483864

  3. A series connection architecture for large-area organic photovoltaic modules with a 7.5% module efficiency

    NASA Astrophysics Data System (ADS)

    Hong, Soonil; Kang, Hongkyu; Kim, Geunjin; Lee, Seongyu; Kim, Seok; Lee, Jong-Hoon; Lee, Jinho; Yi, Minjin; Kim, Junghwan; Back, Hyungcheol; Kim, Jae-Ryoung; Lee, Kwanghee

    2016-01-01

    The fabrication of organic photovoltaic modules via printing techniques has been the greatest challenge for their commercial manufacture. Current module architecture, which is based on a monolithic geometry consisting of serially interconnecting stripe-patterned subcells with finite widths, requires highly sophisticated patterning processes that significantly increase the complexity of printing production lines and cause serious reductions in module efficiency due to so-called aperture loss in series connection regions. Herein we demonstrate an innovative module structure that can simultaneously reduce both patterning processes and aperture loss. By using a charge recombination feature that occurs at contacts between electron- and hole-transport layers, we devise a series connection method that facilitates module fabrication without patterning the charge transport layers. With the successive deposition of component layers using slot-die and doctor-blade printing techniques, we achieve a high module efficiency reaching 7.5% with area of 4.15 cm2.

  4. Characterization of plasmonic hole arrays as transparent electrical contacts for organic photovoltaics using high-brightness Fourier transform methods

    DOE PAGES

    Camino, Fernando E.; Nam, Chang-Yong; Pang, Yutong T.; Hoy, Jessica; Eisaman, Matthew D.; Black, Charles T.; Sfeir, Matthew Y.

    2014-05-15

    Here we present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm2). Lastly, this allows for rapid fabrication of variable-pitch sub-wavelength hole arrays in metal films for use asmore » transparent electrical contacts, and evaluation of the evanescent and propagating mode coupling to resonances in the active layer.« less

  5. Comparative studies on rigid π linker-based organic dyes: structure-property relationships and photovoltaic performance.

    PubMed

    Li, Hairong; Koh, Teck Ming; Hao, Yan; Zhou, Feng; Abe, Yuichiro; Su, Haibin; Hagfeldt, Anders; Grimsdale, Andrew C

    2014-12-01

    A series of six structurally correlated donor-π bridge-acceptor organic dyes were designed, synthesized, and applied as sensitizers in dye-sensitized solar cells. Using the most widely studied donor (triarylamine) and cyclopenta[1,2-b:5,4-b']dithiophene or cyclopenta[1,2-b:5,4-b']dithiophene[2',1':4,5]thieno[2,3-d]thiophene as π spacers, their structure-property relationships were investigated in depth by photophysical techniques and theoretical calculations. It was found that the photovoltaic performance of these dyes largely depends on their electronic structures, which requires synergistic interaction between donors and acceptors. Increasing the electron richness of the donor or the elongation of π-conjugated bridges does not necessarily lead to higher performance. Rather, it is essential to rationally design the dyes by balancing their light-harvesting capability with achieving suitable energy levels to guarantee unimpeded charge separation and transport.

  6. Simultaneous Engineering of the Substrate Temperature and Mixing Ratio to Improve the Performance of Organic Photovoltaic Cells.

    PubMed

    Song, Hyung-Jun; Roh, Jeongkyun; Lee, Changhee

    2016-05-01

    In this study, we investigated the effect of the donor/acceptor mixing ratio and the substrate temperature (T(SUB)) during the co-deposition process on the performance of bulk heterojunction organic photovoltaic cells. We found that the ratio of dispersed donor islands (less than 10 nm), which hinders charge carrier transport, increased as the donor concentration (C(D)) increased in the film processed at room temperature. By contrast, the donor cluster (larger than 10 nm), providing percolation paths for the carriers, was enlarged in the film containing a high C(D) fabricated at high T(SUB) (70 degrees C). This enhanced phase separation in the mixed layer led to an improved fill factor and a decreased activation energy of the short-circuit current (J(SC)). Therefore, we demonstrated a 23% improvement in the device performance by employing an elevated T(SUB) and optimized mixing ratio in comparison with the device fabricated at room temperature.

  7. The appearance of Ti3+ states in solution-processed TiOx buffer layers in inverted organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhidkov, Ivan S.; McLeod, John A.; Kurmaev, Ernst Z.; Korotin, Michael A.; Kukharenko, Andrey I.; Savva, Achilleas; Choulis, Stelios A.; Korotin, Danila M.; Cholakh, Seif O.

    2016-07-01

    We study the low-temperature solution processed TiOx films and device structures using core level and valence X-ray photoelectron spectroscopy (XPS) and electronic structure calculations. We are able to correlate the fraction of Ti3+ present as obtained from Ti 2p core level XPS with the intensity of the defect states that appear within the band gap as observed with our valence XPS. Constructing an operating inverted organic photovoltaic (OPV) using the TiOx film as an electron selective contact may increase the fraction of Ti3+ present. We provide evidence that the number of charge carriers in TiOx can be significantly varied and this might influence the performance of inverted OPVs.

  8. A series connection architecture for large-area organic photovoltaic modules with a 7.5% module efficiency.

    PubMed

    Hong, Soonil; Kang, Hongkyu; Kim, Geunjin; Lee, Seongyu; Kim, Seok; Lee, Jong-Hoon; Lee, Jinho; Yi, Minjin; Kim, Junghwan; Back, Hyungcheol; Kim, Jae-Ryoung; Lee, Kwanghee

    2016-01-01

    The fabrication of organic photovoltaic modules via printing techniques has been the greatest challenge for their commercial manufacture. Current module architecture, which is based on a monolithic geometry consisting of serially interconnecting stripe-patterned subcells with finite widths, requires highly sophisticated patterning processes that significantly increase the complexity of printing production lines and cause serious reductions in module efficiency due to so-called aperture loss in series connection regions. Herein we demonstrate an innovative module structure that can simultaneously reduce both patterning processes and aperture loss. By using a charge recombination feature that occurs at contacts between electron- and hole-transport layers, we devise a series connection method that facilitates module fabrication without patterning the charge transport layers. With the successive deposition of component layers using slot-die and doctor-blade printing techniques, we achieve a high module efficiency reaching 7.5% with area of 4.15 cm(2).

  9. Characterization of plasmonic hole arrays as transparent electrical contacts for organic photovoltaics using high-brightness Fourier transform methods

    SciTech Connect

    Camino, Fernando E.; Nam, Chang-Yong; Pang, Yutong T.; Hoy, Jessica; Eisaman, Matthew D.; Black, Charles T.; Sfeir, Matthew Y.

    2014-05-15

    Here we present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm2). Lastly, this allows for rapid fabrication of variable-pitch sub-wavelength hole arrays in metal films for use as transparent electrical contacts, and evaluation of the evanescent and propagating mode coupling to resonances in the active layer.

  10. Stability and degradation of organic photovoltaics fabricated, aged, and characterized by the ISOS 3 inter-laboratory collaboration

    NASA Astrophysics Data System (ADS)

    Tanenbaum, David M.; Hermenau, Martin; Voroshazi, Eszter; Lloyd, Matthew T.; Galagan, Yulia; Zimmermann, Birger; Hösel, Markus; Dam, Henrik F.; Jørgensen, Mikkel; Gevorgyan, Suren; Kudret, Suleyman; Maes, Wouter; Lutsen, Laurence; Vanderzande, Dirk; Würfel, Uli; Andriessen, Ronn; Rösch, Roland; Hoppe, Harald; Lira-Cantu, Monica; Teran-Escobar, Gerardo; Dupuis, Aurélie; Bussière, Pierre-Olivier; Rivaton, Agnès.; Uzunoglu, Gülsah Y.; Germack, David; Andreasen, Birgitta; Madsen, Morten V.; Norrman, Kion; Bundgaard, Eva; Krebs, Frederik C.

    2012-09-01

    Seven distinct sets (n >= 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Characterization includes current-voltage curves, light beam induced current (LBIC) imaging, dark lock-in thermography (DLIT), photoluminescence (PL), electroluminescence (EL), in situ incident photon-to-electron conversion efficiency (IPCE), time of flight secondary ion mass spectrometry (TOF-SIMS), cross sectional electron microscopy (SEM), UV visible spectroscopy, fluorescence microscopy, and atomic force microscopy (AFM). Over 100 devices with more than 300 cells were used in the study. We present here design of the device sets, results both on individual devices and uniformity of device sets from the wide range of characterization methods applied at different stages of aging under the three illumination conditions. We will discuss how these data can help elucidate the degradation mechanisms as well as the benefits and challenges associated with the unprecedented size of the collaboration.

  11. Surface-Engineered Graphene Quantum Dots Incorporated into Polymer Layers for High Performance Organic Photovoltaics

    PubMed Central

    Kim, Jung Kyu; Kim, Sang Jin; Park, Myung Jin; Bae, Sukang; Cho, Sung-Pyo; Du, Qing Guo; Wang, Dong Hwan; Park, Jong Hyeok; Hong, Byung Hee

    2015-01-01

    Graphene quantum dots (GQDs), a newly emerging 0-dimensional graphene based material, have been widely exploited in optoelectronic devices due to their tunable optical and electronic properties depending on their functional groups. Moreover, the dispersibility of GQDs in common solvents depending on hydrophobicity or hydrophilicity can be controlled by chemical functionalization, which is particularly important for homogeneous incorporation into various polymer layers. Here we report that a surface-engineered GQD-incorporated polymer photovoltaic device shows enhanced power conversion efficiency (PCE), where the oxygen-related functionalization of GQDs enabled good dispersity in a PEDOT:PSS hole extraction layer, leading to significantly improved short circuit current density (Jsc) value. To maximize the PCE of the device, hydrophobic GQDs that are hydrothermally reduced (rGQD) were additionally incorporated in a bulk-heterojunction layer, which is found to promote a synergistic effect with the GQD-incorporated hole extraction layer. PMID:26392211

  12. Photovoltaic enhancement of organic solar cells by a bridged donor-acceptor block copolymer approach

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Zhang, Cheng; Ledbetter, Abram; Choi, Soobum; Seo, Kang; Bonner, Carl E.; Drees, Martin; Sariciftci, Niyazi Serdar

    2007-01-01

    The authors show that a photovoltaic device composed of a -donor-bridge-acceptor-bridge- type block copolymer thin film exhibits a significant performance improvement over its corresponding donor/acceptor blend (Voc increased from 0.14to1.10V and Jsc increased from 0.017 to 0.058mA/cm2) under identical conditions, where donor is an alkyl derivatized poly-p-phenylenevinylene (PPV) conjugated block, acceptor is a sulfone-alkyl derivatized PPV conjugated block, and bridge is a nonconjugated and flexible unit. The authors attribute such improvement to the block copolymer intrinsic nanophase separation and molecular self-assembly that results in the reduction of the exciton and carrier losses.

  13. Inverted photovoltaic device based on ZnO and organic small molecule heterojunction

    NASA Astrophysics Data System (ADS)

    Liu, J. P.; Wang, S. S.; Bian, Z. Q.; Shan, M. N.; Huang, C. H.

    2009-02-01

    The solar cells with an inverted structure of indium tin oxide (ITO)/ZnO/copper-phthalocyanine (CuPc):fullerene (C 60)/CuPc/poly(3,4-oxyethyleneoxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/Ag were fabricated. The current density-voltage curve indicates that ZnO was a highly effective electron-selective contact and plays important roles on the rectification behavior and the photovoltaic performance improvement. The incident photo to current conversion efficiency combined with the absorption spectrum indicates that most of the photocurrent generation was attributed to the excitation of CuPc. The shelf lifetime of unencapsulated devices was over 900 h in air due to the inverted structure which gives a promising way for fabrication of solar cells with improved stability.

  14. High efficiency organic photovoltaic cells employing hybridized mixed-planar heterojunctions

    DOEpatents

    Xue, Jiangeng; Uchida, Soichi; Rand, Barry P.; Forrest, Stephen

    2015-08-18

    A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first photoactive organic layer that is a mixture of an organic acceptor material and an organic donor material, wherein the first photoactive organic layer has a thickness not greater than 0.8 characteristic charge transport lengths; a second photoactive organic layer in direct contact with the first organic layer, wherein the second photoactive organic layer is an unmixed layer of the organic acceptor material of the first photoactive organic layer, and the second photoactive organic layer has a thickness not less than about 0.1 optical absorption lengths; and a third photoactive organic layer disposed between the first electrode and the second electrode and in direct contact with the first photoactive organic layer. The third photoactive organic layer is an unmixed layer of the organic donor layer of the first photoactive organic layer and has a thickness not less than about 0.1 optical absorption lengths.

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

    DOEpatents

    Marks, Iobin J.; Hains, Alexander W.

    2011-02-15

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

  16. Efficient ternary organic photovoltaics incorporating a graphene-based porphyrin molecule as a universal electron cascade material

    NASA Astrophysics Data System (ADS)

    Stylianakis, M. M.; Konios, D.; Kakavelakis, G.; Charalambidis, G.; Stratakis, E.; Coutsolelos, A. G.; Kymakis, E.; Anastasiadis, S. H.

    2015-10-01

    A graphene-based porphyrin molecule (GO-TPP) was synthesized by covalent linkage of graphene oxide (GO) with 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (TPP-NH2). The yielded graphene-based material is a donor-acceptor (D-A) molecule, exhibiting strong intermolecular interactions between the GO core (A) and the covalently anchored porphyrin molecule (D). To demonstrate the universal role of GO-TPP as an electron cascade material, ternary blend organic photovoltaics based on [6,6]-phenyl-C71-butyric-acid-methyl-ester (PC71BM) as an electron acceptor material and two different polymer donor materials, poly[N-9'-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) and the highly efficient poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7), were fabricated. The addition of GO-TPP into the active layer implies continuous percolation paths between the D-A interfaces, enhancing charge transport, reducing exciton recombination and thus improving the photovoltaic performance of the device. A simultaneous increase of short circuit current density (Jsc), open-circuit voltage (Voc) and fill factor (FF), compared to the PTB7:PC71BM reference cell, led to an improved power conversion efficiency (PCE) of 8.81% for the PTB7:GO-TPP:PC71BM-based device, owing mainly to the more efficient energy level offset between the active layer components.A graphene-based porphyrin molecule (GO-TPP) was synthesized by covalent linkage of graphene oxide (GO) with 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (TPP-NH2). The yielded graphene-based material is a donor-acceptor (D-A) molecule, exhibiting strong intermolecular interactions between the GO core (A) and the covalently anchored porphyrin molecule (D). To demonstrate the universal role of GO-TPP as an electron cascade material, ternary blend organic photovoltaics based on [6,6]-phenyl-C71-butyric

  17. High efficiency organic photovoltaic cells employing hybridized mixed-planar heterojunctions

    DOEpatents

    Xue, Jiangeng; Uchida, Soichi; Rand, Barry P; Forrest, Stephen

    2013-11-19

    A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first organic layer comprising a mixture of an organic acceptor material and an organic donor material, wherein the first organic layer has a thickness not greater than 0.8 characteristic charge transport lengths, and a second organic layer in direct contact with the first organic layer, wherein: the second organic layer comprises an unmixed layer of the organic acceptor material or the organic donor material of the first organic layer, and the second organic layer has a thickness not less than about 0.1 optical absorption lengths. Preferably, the first organic layer has a thickness not greater than 0.3 characteristic charge transport lengths. Preferably, the second organic layer has a thickness of not less than about 0.2 optical absorption lengths. Embodiments of the invention can be capable of power efficiencies of 2% or greater, and preferably 5% or greater.

  18. Efficient ternary organic photovoltaics incorporating a graphene-based porphyrin molecule as a universal electron cascade material.

    PubMed

    Stylianakis, M M; Konios, D; Kakavelakis, G; Charalambidis, G; Stratakis, E; Coutsolelos, A G; Kymakis, E; Anastasiadis, S H

    2015-11-14

    A graphene-based porphyrin molecule (GO-TPP) was synthesized by covalent linkage of graphene oxide (GO) with 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (TPP-NH2). The yielded graphene-based material is a donor-acceptor (D-A) molecule, exhibiting strong intermolecular interactions between the GO core (A) and the covalently anchored porphyrin molecule (D). To demonstrate the universal role of GO-TPP as an electron cascade material, ternary blend organic photovoltaics based on [6,6]-phenyl-C71-butyric-acid-methyl-ester (PC71BM) as an electron acceptor material and two different polymer donor materials, poly[N-9'-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) and the highly efficient poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7), were fabricated. The addition of GO-TPP into the active layer implies continuous percolation paths between the D-A interfaces, enhancing charge transport, reducing exciton recombination and thus improving the photovoltaic performance of the device. A simultaneous increase of short circuit current density (Jsc), open-circuit voltage (Voc) and fill factor (FF), compared to the PTB7:PC71BM reference cell, led to an improved power conversion efficiency (PCE) of 8.81% for the PTB7:GO-TPP:PC71BM-based device, owing mainly to the more efficient energy level offset between the active layer components.

  19. Comparing Vacuum and Extreme Ultraviolet Radiation for Postionization of Laser Desorbed Neutrals from Bacterial Biofilms and Organic Fullerene

    SciTech Connect

    Gaspera, Gerald L.; Takahashi, Lynelle K.; Zhou, Jia; Ahmed, Musahid; Moored, Jerry F.; Hanley, Luke

    2010-12-08

    Vacuum and extreme ultraviolet radiation from 8 - 24 eV generated at a synchrotron was used to postionize laser desorbed neutrals of antibiotic-treated biofilms and a modified fullerene using laser desorption postionization mass spectrometry (LDPI-MS). Results show detection of the parent ion, various fragments, and extracellular material from biofilms using LDPI-MS with both vacuum and extreme ultraviolet photons. Parent ions were observed for both cases, but extreme ultraviolet photons (16-24 eV) induced more fragmentation than vacuum ultraviolet (8-14 eV) photons.

  20. Single Component Lanthanide Hybrids Based on Metal-Organic Framework for Near-Ultraviolet White Light LED.

    PubMed

    Zhao, Yan-Wu; Zhang, Fu-Qiang; Zhang, Xian-Ming

    2016-09-14

    Near-UV single-phase white-light phosphor (Eu0.045Tb0.955CPOMBA/La0.6Eu0.1Tb0.3CPOMBA) based on metal-organic framework was prepared by in situ doping isostructural lanthanide MOF with Eu(3+) and Tb(3+), and it is found that the energy can effectively transfer from organic ligand to lanthanides, which can overcome weak absorption under direct excitation of lanthanide ions due to the forbidden f-f transitions. The photoluminescence and thermostability of the new MOF phosphor are investigated, and effective white-light emission is achieved under 365 and 380 nm excitations. By employing Eu0.045Tb0.955CPOMBA as phosphor, we fabricated a near-ultraviolet white-light-emitting diode (n-UV WLED) (365 nm) with low CCT (5733 K), high CRI (Ra = 73.4), and CIE chromaticity coordinate (0.3264, 0.3427). This approach may open new perspectives for developing single-phase UV phosphors. PMID:27560457

  1. Single Component Lanthanide Hybrids Based on Metal-Organic Framework for Near-Ultraviolet White Light LED.

    PubMed

    Zhao, Yan-Wu; Zhang, Fu-Qiang; Zhang, Xian-Ming

    2016-09-14

    Near-UV single-phase white-light phosphor (Eu0.045Tb0.955CPOMBA/La0.6Eu0.1Tb0.3CPOMBA) based on metal-organic framework was prepared by in situ doping isostructural lanthanide MOF with Eu(3+) and Tb(3+), and it is found that the energy can effectively transfer from organic ligand to lanthanides, which can overcome weak absorption under direct excitation of lanthanide ions due to the forbidden f-f transitions. The photoluminescence and thermostability of the new MOF phosphor are investigated, and effective white-light emission is achieved under 365 and 380 nm excitations. By employing Eu0.045Tb0.955CPOMBA as phosphor, we fabricated a near-ultraviolet white-light-emitting diode (n-UV WLED) (365 nm) with low CCT (5733 K), high CRI (Ra = 73.4), and CIE chromaticity coordinate (0.3264, 0.3427). This approach may open new perspectives for developing single-phase UV phosphors.

  2. Desorption Dynamics, Internal Energies and Imaging of Organic Molecules from Surfaces with Laser Desorption and Vacuum Ultraviolet (VUV) Photoionization

    SciTech Connect

    Kostko, Oleg; Takahashi, Lynelle K.; Ahmed, Musahid

    2011-04-05

    There is enormous interest in visualizing the chemical composition of organic material that comprises our world. A convenient method to obtain molecular information with high spatial resolution is imaging mass spectrometry. However, the internal energy deposited within molecules upon transfer to the gas phase from a surface can lead to increased fragmentation and to complications in analysis of mass spectra. Here it is shown that in laser desorption with postionization by tunable vacuum ultraviolet (VUV) radiation, the internal energy gained during laser desorption leads to minimal fragmentation of DNA bases. The internal temperature of laser-desorbed triacontane molecules approaches 670 K, whereas the internal temperature of thymine is 800 K. A synchrotron-based VUV postionization technique for determining translational temperatures reveals that biomolecules have translational temperatures in the range of 216-346 K. The observed low translational temperatures, as well as their decrease with increased desorption laser power is explained by collisional cooling. An example of imaging mass spectrometry on an organic polymer, using laser desorption VUV postionization shows 5 mu m feature details while using a 30 mu m laser spot size and 7 ns duration. Applications of laser desorption postionization to the analysis of cellulose, lignin and humic acids are briefly discussed.

  3. The effects of ultraviolet light on the degradation of organic compounds - A possible explanation for the absence of organic matter on Mars

    NASA Technical Reports Server (NTRS)

    Oro, J.; Holzer, G.

    1979-01-01

    The analysis of the top layer of the Martian regolith at the two Viking landing sites did not reveal any indigenous organic compounds. However, the existence of such compounds at deeper layers cannot be ruled out. Cosmochemical considerations indicate various potential sources for organic matter on Mars, such as comets and meteorites. The study tested the stability of a sample of the Murchison meteorite and various organic substances which have been detected in carbonaceous chondrites, such as glycine, adenine and naphthalene, to the action of ultraviolet light. The compounds were adsorbed on powdered quartz and on California desert soil and were irradiated in the presence or absence of oxygen. The organic content, before and after irradiation, was measured by carbon elementary analysis, UV-absorption, amino acid analysis or pyrolysis-gas chromatography-mass spectrometry. In the absence of oxygen, adenine and glycine appear to be stable over the given part of irradiation. A definite degradation was noticed in the case of naphtalene and the Murchison meteorite. In the presence of oxygen in amounts comparable to those on Mars all compounds were degraded. The degree of degradation was influenced by the irradiation time, temperature and oxygen content.

  4. Facile Preparation of Molybdenum Bronzes as an Efficient Hole Extraction Layer in Organic Photovoltaics.

    PubMed

    Wang, Jiantai; Zhang, Jun; Meng, Bin; Zhang, Baohua; Xie, Zhiyuan; Wang, Lixiang

    2015-06-24

    We proposed a facile and green one-pot strategy to synthesize Mo bronzes nanoparticles to serve as an efficient hole extraction layer in polymer solar cells. Mo bronzes were obtained through reducing the fractional self-aggregated ammonium heptamolybdate with appropriate reducing agent ascorbic acid, and its optoelectronic properties were fully characterized. The synthesized Mo bronzes displayed strong n-type semiconductor characteristics with a work function of 5.2-5.4 eV, matched well with the energy levels of current donor polymers. The presented gap states of the Mo bronzes near the Fermi level were beneficial for facilitating charge extraction. The as-synthesized Mo bronzes were used as hole extraction layer in polymer solar cells and significantly enhanced the photovoltaic performance and stability. The power conversion efficiency was increased by more than 18% compared with the polyethylene dioxythiophene:polystyrenesulfonate-based reference cell. The excellent performance and facile preparation render the as-synthesized solution-processed Mo bronzes nanoparticles a promising candidate for hole extraction layer in low-cost and efficient polymer solar cells.

  5. Structural influences on charge carrier dynamics for small-molecule organic photovoltaics

    SciTech Connect

    Wang, Zhiping Shibata, Yosei; Yamanari, Toshihiro; Matsubara, Koji; Yoshida, Yuji; Miyadera, Tetsuhiko; Saeki, Akinori; Seki, Shu; Zhou, Ying

    2014-07-07

    We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C{sub 60}) photovoltaic cells by introducing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and 2,5-bis(4-biphenylyl)-bithiophene (BP2T) between indium tin oxide and ZnPc layers. ZnPc films can be tuned to be round, long fiber-like, and short fiber-like structure, respectively. Time-resolved microwave conductivity measurements reveal that charge carrier lifetime in ZnPc/C{sub 60} bilayer films is considerably affected by the intra-grain properties. Transient photocurrent of ZnPc single films indicated that the charge carriers can transport for a longer distance in the long fiber-like grains than that in the round grains, due to the greatly lessened grain boundaries. By carefully controlling the structure of ZnPc films, the short-circuit current and fill factor of a ZnPc/C{sub 60} heterojunction solar cell with BP2T are significantly improved and the power conversion efficiency is increased to 2.6%, which is 120% larger than the conventional cell without BP2T.

  6. Structural influences on charge carrier dynamics for small-molecule organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Wang, Zhiping; Miyadera, Tetsuhiko; Saeki, Akinori; Zhou, Ying; Seki, Shu; Shibata, Yosei; Yamanari, Toshihiro; Matsubara, Koji; Yoshida, Yuji

    2014-07-01

    We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C60) photovoltaic cells by introducing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and 2,5-bis(4-biphenylyl)-bithiophene (BP2T) between indium tin oxide and ZnPc layers. ZnPc films can be tuned to be round, long fiber-like, and short fiber-like structure, respectively. Time-resolved microwave conductivity measurements reveal that charge carrier lifetime in ZnPc/C60 bilayer films is considerably affected by the intra-grain properties. Transient photocurrent of ZnPc single films indicated that the charge carriers can transport for a longer distance in the long fiber-like grains than that in the round grains, due to the greatly lessened grain boundaries. By carefully controlling the structure of ZnPc films, the short-circuit current and fill factor of a ZnPc/C60 heterojunction solar cell with BP2T are significantly improved and the power conversion efficiency is increased to 2.6%, which is 120% larger than the conventional cell without BP2T.

  7. Computational Analysis of Energy Pooling to Harvest Low-Energy Solar Energy in Organic Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Lacount, Michael; Shaheen, Sean; Rumbles, Garry; van de Lagemaat, Jao; Hu, Nan; Ostrowski, Dave; Lusk, Mark

    2014-03-01

    Current photovoltaic energy conversions do not typically utilize low energy sunlight absorption, leaving large sections of the solar spectrum untapped. It is possible, though, to absorb such radiation, generating low-energy excitons, and then pool them to create higher energy excitons, which can result in an increase in efficiency. Calculation of the rates at which such upconversion processes occur requires an accounting of all possible molecular quantum electrodynamics (QED) pathways. There are two paths associated with the upconversion. The cooperative mechanism involves a three-body interaction in which low energy excitons are transferred sequentially onto an acceptor molecule. The accretive pathway, requires that an exciton transfer its energy to a second exciton that subsequently transfers its energy to the acceptor molecule. We have computationally modeled both types of molecular QED obtaining rates using a combination of DFT and many-body Green function theory. The simulation platform is exercised by considering upconversion events associated with material composed of a high energy absorbing core of hexabenzocoronene (HBC) and low energy absorbing arms of oligothiophene. In addition, we make estimates for all competing processes in order to judge the relative efficiencies of these two processes.

  8. Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated martian surface ultraviolet radiation conditions.

    PubMed

    Poch, Olivier; Jaber, Maguy; Stalport, Fabien; Nowak, Sophie; Georgelin, Thomas; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

    2015-03-01

    Most of the phyllosilicates detected at the surface of Mars today are probably remnants of ancient environments that sustained long-term bodies of liquid water at the surface or subsurface and were possibly favorable for the emergence of life. Consequently, phyllosilicates have become the main mineral target in the search for organics on Mars. But are phyllosilicates efficient at preserving organic molecules under current environmental conditions at the surface of Mars? We monitored the qualitative and quantitative evolutions of glycine, urea, and adenine in interaction with the Fe(3+)-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K), and pressure (6 ± 1 mbar) in a laboratory simulation setup. We tested organic-rich samples that were representative of the evaporation of a small, warm pond of liquid water containing a high concentration of organics. For each molecule, we observed how the nontronite influences its quantum efficiency of photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine; their efficiencies of photodecomposition were reduced by a factor of 5 when mixed at a concentration of 2.6 × 10(-2) mol of molecules per gram of nontronite. Moreover, when the amount of nontronite in the sample of glycine was increased by a factor of 2, the gain of photoprotection was multiplied by a factor of 5. This indicates that the photoprotection provided by the nontronite is not a purely mechanical shielding effect but is also due to stabilizing interactions. No new evolution product was firmly identified, but the results obtained with urea suggest a particular reactivity in the presence of nontronite, leading to an increase of its dissociation rate.

  9. Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated martian surface ultraviolet radiation conditions.

    PubMed

    Poch, Olivier; Jaber, Maguy; Stalport, Fabien; Nowak, Sophie; Georgelin, Thomas; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

    2015-03-01

    Most of the phyllosilicates detected at the surface of Mars today are probably remnants of ancient environments that sustained long-term bodies of liquid water at the surface or subsurface and were possibly favorable for the emergence of life. Consequently, phyllosilicates have become the main mineral target in the search for organics on Mars. But are phyllosilicates efficient at preserving organic molecules under current environmental conditions at the surface of Mars? We monitored the qualitative and quantitative evolutions of glycine, urea, and adenine in interaction with the Fe(3+)-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K), and pressure (6 ± 1 mbar) in a laboratory simulation setup. We tested organic-rich samples that were representative of the evaporation of a small, warm pond of liquid water containing a high concentration of organics. For each molecule, we observed how the nontronite influences its quantum efficiency of photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine; their efficiencies of photodecomposition were reduced by a factor of 5 when mixed at a concentration of 2.6 × 10(-2) mol of molecules per gram of nontronite. Moreover, when the amount of nontronite in the sample of glycine was increased by a factor of 2, the gain of photoprotection was multiplied by a factor of 5. This indicates that the photoprotection provided by the nontronite is not a purely mechanical shielding effect but is also due to stabilizing interactions. No new evolution product was firmly identified, but the results obtained with urea suggest a particular reactivity in the presence of nontronite, leading to an increase of its dissociation rate. PMID:25734356

  10. Ultraviolet Waves

    ERIC Educational Resources Information Center

    Molde, Trevor

    1973-01-01

    Outlines the discovery and nature of ultraviolet light, discusses some applications for these wavelengths, and describes a number of experiments with ultraviolet radiation suitable for secondary school science classes. (JR)

  11. The Harvard Clean Energy Project: High-throughput screening of organic photovoltaic materials using first-principles electronic structure theory

    NASA Astrophysics Data System (ADS)

    Hachmann, Johannes; Olivares-Amaya, Roberto; Atahan-Evrenk, Sule; Amador-Bedolla, Carlos; Aspuru-Guzik, Alan

    2012-02-01

    We present the Harvard Clean Energy Project (CEP) which is concerned with the computational screening and design of new organic photovoltaic materials. CEP has established an automated, high-throughput, in silico framework to study millions of potential candidate structures. This presentation discusses the CEP branch which employs first-principles computational quantum chemistry for the characterization of molecular motifs and the assessment of their quality with respect to applications as electronic materials. In addition to finding specific structures with certain properties, it is the goal of CEP to illuminate and understand the structure-property relations in the domain of organic electronics. Such insights can open the door to a rational, systematic, and accelerated development of future high-performance materials. CEP is a large-scale investigation which utilizes the massive computational resource of IBM's World Community Grid. In this context, it is deployed as a screensaver application harvesting idle computing time on donor machines. This cyberinfrastructure paradigm has already allowed us to characterize 3.5 million molecules of interest in about 50 million DFT calculations.

  12. Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

    2011-03-01

    We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

  13. PEDOT:PSS with embedded TiO2 nanoparticles as light trapping electrode for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Park, Yoonseok; Müller-Meskamp, Lars; Vandewal, Koen; Leo, Karl

    2016-06-01

    The performance of organic optoelectronic devices can be improved by employing a suitable optical cavity design beyond the standard plane layer approach, e.g., by the inclusion of periodically or randomly textured structures which increase light incoupling or extraction. One of the simplest approaches is to add an additional layer containing light scattering particles into the device stack. Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films are promising for replacing the brittle and expensive indium tin oxide transparent electrode. We use a blend of 100 nm TiO2 scattering particles in PEDOT:PSS solution to fabricate transparent electrode films which also functions as a scattering layer. When utilized in an organic photovoltaic device, a power conversion efficiency of 7.92% is achieved, which is an 8.6% relative improvement compared to a device with a neat PEDOT:PSS electrode without the nanoparticles. This improvement is caused by an increase in short-circuit current due to an improved photon harvesting in the 320 nm-700 nm spectral wavelength range.

  14. Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics.

    PubMed

    Jailaubekov, Askat E; Willard, Adam P; Tritsch, John R; Chan, Wai-Lun; Sai, Na; Gearba, Raluca; Kaake, Loren G; Williams, Kenrick J; Leung, Kevin; Rossky, Peter J; Zhu, X-Y

    2013-01-01

    Photocurrent generation in organic photovoltaics (OPVs) relies on the dissociation of excitons into free electrons and holes at donor/acceptor heterointerfaces. The low dielectric constant of organic semiconductors leads to strong Coulomb interactions between electron-hole pairs that should in principle oppose the generation of free charges. The exact mechanism by which electrons and holes overcome this Coulomb trapping is still unsolved, but increasing evidence points to the critical role of hot charge-transfer (CT) excitons in assisting this process. Here we provide a real-time view of hot CT exciton formation and relaxation using femtosecond nonlinear optical spectroscopies and non-adiabatic mixed quantum mechanics/molecular mechanics simulations in the phthalocyanine-fullerene model OPV system. For initial excitation on phthalocyanine, hot CT excitons are formed in 10(-13) s, followed by relaxation to lower energies and shorter electron-hole distances on a 10(-12) s timescale. This hot CT exciton cooling process and collapse of charge separation sets the fundamental time limit for competitive charge separation channels that lead to efficient photocurrent generation.

  15. Drift-Diffusion Modeling of the Effects of Structural Disorder and Carrier Mobility on the Performance of Organic Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Finck, Benjamin Y.; Schwartz, Benjamin J.

    2015-09-01

    We probe the effects of structural disorder on the performance of organic photovoltaic (OPV) devices via drift-diffusion modeling. We utilize ensembles of spatially disordered one-dimensional mobility profiles to approximate the three-dimensional structural disorder present in actual devices. Each replica in our ensemble approximates one high-conductivity pathway through the three-dimensional network(s) present in a polymer-based bulk heterojunction solar cell, so that the ensemble-averaged behavior provides a good approximation to a full three-dimensional structurally disordered device. Our calculations show that the short-circuit current, fill factor, and power conversion efficiency of simulated devices are all negatively impacted by the inclusion of structural disorder, but that the open-circuit voltage is nearly impervious to structural defects. This is in contrast to energetic disorder, where previous studies found that spatial variation in the energy in OPV active layers causes a decrease in the open-circuit voltage. We also show that structural disorder causes the greatest detriment to device performance for feature sizes between 2 and 10 nm. Since this is on the same length scale as the fullerene crystallites in experimental devices, it suggests both that controlling structural disorder is critical to the performance of OPV devices and that the effects of structural disorder should be included in future drift-diffusion modeling studies of organic solar cells.

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

    SciTech Connect

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

    2006-05-01

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

  17. Synergetic Solvent Engineering of Film Nanomorphology to Enhance Planar Perylene Diimide-Based Organic Photovoltaics.

    PubMed

    Wang, Jialin; Liang, Ziqi

    2016-08-31

    Solvent additive has proven as a useful protocol for improving the film nanomorphology of polymer donor (D): fullerene acceptor (A) blends in bulk heterojunction (BHJ) photovoltaic cells. By contrast, the effect of such solvent additive on nonfullerene BHJ cells based on perylene diimide acceptor, for instance, is less effective because of their highly planar structure and strong π-aggregation in solid state. Here we choose N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) and thieno[3,4-b]thiophene-alt-benzodithiophene (PTB7) as a model D:A blend system to investigate how solvent engineering strategy synergistically impacts the blend film nanomorphology. Based on the differences of solvent volatility and solubility, various host solvents-chloroform (CF) and chlorobenzene (CB) and solvent additives-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) are selected for comparative studies. It is found that the π-aggregation of PDIs can be largely suppressed by using low-boiling point (Tb) CF solvent, yet enlarged by using high-Tb CB. Moreover, CN additive provides good solubility of PDI molecules and hence reduces large PDI aggregates in CB system, while DIO exhibiting poor solubility works oppositely. By contrast, DIO that presents larger Tb difference with CF prolongs the film-forming, which assists in optimizing the PDI aggregation and increases the intermixed PTB7:PDI phases more significantly than CN in CF system, yielding the finest phase-separation morphology and balanced charge mobility. Consequently, the inverted BHJ cells based on CF-processed PTB7:PDI blend film with 0.4 vol % DIO exhibit the highest PCE of 3.55% with a fill factor of 56%, both of which are among the best performance for such a paradigm PTB7:PDI blend-based BHJ cells. PMID:27513281

  18. Synergetic Solvent Engineering of Film Nanomorphology to Enhance Planar Perylene Diimide-Based Organic Photovoltaics.

    PubMed

    Wang, Jialin; Liang, Ziqi

    2016-08-31

    Solvent additive has proven as a useful protocol for improving the film nanomorphology of polymer donor (D): fullerene acceptor (A) blends in bulk heterojunction (BHJ) photovoltaic cells. By contrast, the effect of such solvent additive on nonfullerene BHJ cells based on perylene diimide acceptor, for instance, is less effective because of their highly planar structure and strong π-aggregation in solid state. Here we choose N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) and thieno[3,4-b]thiophene-alt-benzodithiophene (PTB7) as a model D:A blend system to investigate how solvent engineering strategy synergistically impacts the blend film nanomorphology. Based on the differences of solvent volatility and solubility, various host solvents-chloroform (CF) and chlorobenzene (CB) and solvent additives-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) are selected for comparative studies. It is found that the π-aggregation of PDIs can be largely suppressed by using low-boiling point (Tb) CF solvent, yet enlarged by using high-Tb CB. Moreover, CN additive provides good solubility of PDI molecules and hence reduces large PDI aggregates in CB system, while DIO exhibiting poor solubility works oppositely. By contrast, DIO that presents larger Tb difference with CF prolongs the film-forming, which assists in optimizing the PDI aggregation and increases the intermixed PTB7:PDI phases more significantly than CN in CF system, yielding the finest phase-separation morphology and balanced charge mobility. Consequently, the inverted BHJ cells based on CF-processed PTB7:PDI blend film with 0.4 vol % DIO exhibit the highest PCE of 3.55% with a fill factor of 56%, both of which are among the best performance for such a paradigm PTB7:PDI blend-based BHJ cells.

  19. Heterogeneity in polymer solar cells: local morphology and performance in organic photovoltaics studied with scanning probe microscopy.

    PubMed

    Groves, Chris; Reid, Obadiah G; Ginger, David S

    2010-05-18

    The use of organic photovoltaics (OPVs) could reduce production costs for solar cells because these materials are solution processable and can be manufactured by roll-to-roll printing. The nanoscale texture, or film morphology, of the donor/acceptor blends used in most OPVs is a critical variable that can dominate both the performance of new materials being optimized in the lab and efforts to move from laboratory-scale to factory-scale production. Although efficiencies of organic solar cells have improved significantly in recent years, progress in morphology optimization still occurs largely by trial and error, in part because much of our basic understanding of how nanoscale morphology affects the optoelectronic properties of these heterogeneous organic semiconductor films has to be inferred indirectly from macroscopic measurements. In this Account, we review the importance of nanoscale morphology in organic semiconductors and the use of electrical scanning probe microscopy techniques to directly probe the local optoelectronic properties of OPV devices. We have observed local heterogeneity of electronic properties and performance in a wide range of systems, including model polymer-fullerene blends such as poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM), newer polyfluorene copolymer-PCBM blends, and even all polymer donor-acceptor blends. The observed heterogeneity in local photocurrent poses important questions, chiefly what information is contained and what is lost when using average values obtained from conventional measurements on macroscopic devices and bulk samples? We show that in many cases OPVs are best thought of as a collection of nanoscopic photodiodes connected in parallel, each with their own morphological and therefore electronic and optical properties. This local heterogeneity forces us to carefully consider the adequacy of describing OPVs solely by "average" properties such as the bulk carrier mobility

  20. Solar ultraviolet radiation, vitamin D and skin cancer surveillance in organ transplant recipients (OTRs): an update.

    PubMed

    Reichrath, Jörg

    2014-01-01

    During the last decades, the annual numbers of performed solid organ transplants have continuously increased world-wide. Solid organ transplant recipients (OTR) have a greater risk to develop malignancies, with skin cancer representing the most common neoplasia. Additionally, OTRs in general develop a more aggressive form of malignancies. In consequence, dermatologic surveillance is of high importance for OTRs and these patients represent an increasing and significant challenge to clinicians including dermatologists. In OTRs, patient and organ survival have increased considerably and continuously over the past two decades as a result of better immunosuppressive regimens and better posttransplant care. Great progress has been made in our understanding that individual immunosuppressive regiments differ in their effect on skin cancer risk in OTRs, and that effects of individual immunosuppressive regiments on skin cancer risk depend on various other factors including viral infections. Since sunlight is the major source of vitamin D for most humans, OTRs, who have to protect themselves consequently against solar or artificial UV radiation, are at high risk of developing vitamin D deficiency. Vitamin D deficiency is not only associated with increased risk for metabolic bone disease, but with other severe health problems including various types of malignancies. As a consequence, screening for and treatment of vitamin D deficiency is warranted in OTRs. In this review, we give an update on our present understanding of skin cancer surveillance in OTRs.

  1. Free Carrier Generation in Organic Photovoltaic Bulk Heterojunctions of Conjugated Polymers with Molecular Acceptors: Planar versus Spherical Acceptors

    SciTech Connect

    Nardes, Alexandre M.; Ferguson, Andrew J.; Wolfer, Pascal; Gui, Kurt; Burn, Paul L.; Meredith, Paul; Kopidakis, Nikos

    2014-03-05

    We present a comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85 % of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. Here, we propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  2. Technical Note: Nanometric organic photovoltaic thin film detectors for dose monitoring in diagnostic x-ray imaging

    SciTech Connect

    Elshahat, Bassem; Gill, Hardeep Singh; Kumar, Jayant; Filipyev, Ilya; Zygmanski, Piotr; Shrestha, Suman; Karellas, Andrew; Hesser, Jürgen; Sajo, Erno

    2015-07-15

    Purpose: To fabricate organic photovoltaic (OPV) cells with nanometric active layers sensitive to ionizing radiation and measure their dosimetric characteristics in clinical x-ray beams in the diagnostic tube potential range of 60–150 kVp. Methods: Experiments were designed to optimize the detector’s x-ray response and find the best parameter combination by changing the active layer thickness and the area of the electrode. The OPV cell consisted of poly (3-hexylthiophene-2,5-diyl): [6,6]-phenyl C{sub 61} butyric acid methyl ester photoactive donor and acceptor semiconducting organic materials sandwiched between an aluminum electrode as an anode and an indium tin oxide electrode as a cathode. The authors measured the radiation-induced electric current at zero bias voltage in all fabricated OPV cells. Results: The net OPV current as a function of beam potential (kVp) was proportional to kVp{sup −0.5} when normalized to x-ray tube output, which varies with kVp. Of the tested configurations, the best combination of parameters was 270 nm active layer thicknesses with 0.7 cm{sup 2} electrode area, which provided the highest signal per electrode area. For this cell, the measured current ranged from approximately 0.7 to 2.4 nA/cm{sup 2} for 60–150 kVp, corresponding to about 0.09 nA–0.06 nA/mGy air kerma, respectively. When compared to commercial amorphous silicon thin film photovoltaic cells irradiated under the same conditions, this represents 2.5 times greater sensitivity. An additional 40% signal enhancement was observed when a 1 mm layer of plastic scintillator was attached to the cells’ beam-facing side. Conclusions: Since both OPVs can be produced as flexible devices and they do not require external bias voltage, they open the possibility for use as thin film in vivo detectors for dose monitoring in diagnostic x-ray imaging.

  3. SU-E-CAMPUS-I-01: Nanometric Organic Photovoltaic Thin Film X-Ray Detectors for Clinical KVp Beams

    SciTech Connect

    Elshahat, Bassem; Gill, Hardeep; Kumar, Jayant; Sajo, Erno; Filipyev, Ilya; Zygmanski, Piotr; Shrestha, Suman; Hesser, Jurgen; Karellas, Andrew

    2014-06-15

    Purpose: To fabricate and test nanometric organic photovoltaic (OPV) cells made of various active-layer/electrode thicknesses and sizes; to determine the optimal material combinations and geometries suitable for dose measurements in clinical kilovoltage x-ray beams. Methods: The OPV consisted of P3HT:PCBM photoactive materials sandwiched between aluminum and Indium Tin Oxide (ITO) electrodes. Direct conversion of xrays in the active layer composed of donor and acceptor semiconducting organic materials generated signal in photovoltaic mode (without external voltage bias). OPV cells were fabricated with different active layer thicknesses (150, 270, 370 nm) and electrode areas (0.4, 0.7, 0.9, 1.4, 2.6 cm{sup 2}). A series of experiments were preformed in the energy range of 60–150 kVp. The net current per unit area (nA/cm{sup 2}) was measured using 200 mAs time-integrated beam current. Results: The net OPV current as function of beam energy (kVp) was proportional to ∼E{sup 0,4} {sup 5} when adjusted for beam output. The best combination of parameters for these cells was 270 nm active layer thicknesses for 0.7 cm{sup 2} electrode area. The measured current ranged from 0.69 to 2.43 nA/cm{sup 2} as a function of x-ray energy between 60 and 150 kVp, corresponding to 0.09 – 0.06 nA/cm{sup 2}/mGy, respectively, when adjusted for the beam output. Conclusion: The experiments indicate that OPV detectors possessing 270 nm active layer and 0.7 cm{sup 2} Al electrode areas have sensitivity by a factor of 2.5 greater than commercial aSi thin film PV. Because OPV can be made flexible and they do not require highvoltage bias supply, they open the possibility for using as in-vivo detectors in radiation safety in x-ray imaging beams.

  4. Free carrier generation in organic photovoltaic bulk heterojunctions of conjugated polymers with molecular acceptors: planar versus spherical acceptors.

    PubMed

    Nardes, Alexandre M; Ferguson, Andrew J; Wolfer, Pascal; Gui, Kurt; Burn, Paul L; Meredith, Paul; Kopidakis, Nikos

    2014-06-01

    A comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device is presented. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85% of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. We propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  5. Free carrier generation in organic photovoltaic bulk heterojunctions of conjugated polymers with molecular acceptors: planar versus spherical acceptors.

    PubMed

    Nardes, Alexandre M; Ferguson, Andrew J; Wolfer, Pascal; Gui, Kurt; Burn, Paul L; Meredith, Paul; Kopidakis, Nikos

    2014-06-01

    A comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device is presented. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85% of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. We propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  6. Photovoltaic device

    DOEpatents

    Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.

    2015-06-02

    The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device with a multilayered photovoltaic cell assembly and a body portion joined at an interface region and including an intermediate layer, at least one interconnecting structural member, relieving feature, unique component geometry, or any combination thereof.

  7. Photovoltaic device

    DOEpatents

    Reese, Jason A.; Keenihan, James R.; Gaston, Ryan S.; Kauffmann, Keith L.; Langmaid, Joseph A.; Lopez, Leonardo C.; Maak, Kevin D.; Mills, Michael E.; Ramesh, Narayan; Teli, Samar R.

    2015-09-01

    The present invention is premised upon an improved photovoltaic device ("PV device"), more particularly to an improved photovoltaic device (10) with a multilayered photovoltaic cell assembly (100) and a body portion (200) joined at an interface region (410) and including an intermediate layer (500), at least one interconnecting structural member (1500), relieving feature (2500), unique component geometry, or any combination thereof.

  8. Nanostructured photovoltaics

    NASA Astrophysics Data System (ADS)

    Fu, Lan; Tan, H. Hoe; Jagadish, Chennupati

    2013-01-01

    Energy and the environment are two of the most important global issues that we currently face. The development of clean and sustainable energy resources is essential to reduce greenhouse gas emission and meet our ever-increasing demand for energy. Over the last decade photovoltaics, as one of the leading technologies to meet these challenges, has seen a continuous increase in research, development and investment. Meanwhile, nanotechnology, which is considered to be the technology of the future, is gradually revolutionizing our everyday life through adaptation and incorporation into many traditional technologies, particularly energy-related technologies, such as photovoltaics. While the record for the highest efficiency is firmly held by multijunction III-V solar cells, there has never been a shortage of new research effort put into improving the efficiencies of all types of solar cells and making them more cost effective. In particular, there have been extensive and exciting developments in employing nanostructures; features with different low dimensionalities, such as quantum wells, nanowires, nanotubes, nanoparticles and quantum dots, have been incorporated into existing photovoltaic technologies to enhance their performance and/or reduce their cost. Investigations into light trapping using plasmonic nanostructures to effectively increase light absorption in various solar cells are also being rigorously pursued. In addition, nanotechnology provides researchers with great opportunities to explore the new ideas and physics offered by nanostructures to implement advanced solar cell concepts such as hot carrier, multi-exciton and intermediate band solar cells. This special issue of Journal of Physics D: Applied Physics contains selected papers on nanostructured photovoltaics written by researchers in their respective fields of expertise. These papers capture the current excitement, as well as addressing some open questions in the field, covering topics including the

  9. [Research on rapid determination of organic matter concentration in aquaculture water based on ultraviolet/visible spectroscopy].

    PubMed

    Cao, Hong; Qu, Wen-Tai; Yang, Xiang-Long; Jia, Sheng-Yao; Wang, Chun-Long; Lu, Chen

    2014-11-01

    Ultraviolet/visible (UV/Vis) spectroscopy was investigated for the rapid determination of chemical oxygen demand (COD) which was an indicator to measure the concentration of organic matter in aquaculture water. A total number of 135 collected turtle breeding water samples were scanned for UV/Vis spectrum, uninformative variable elimination (UVE) and successive projections algorithm (SPA) were combined as a mixed variable selection method to perform characteristic wavelength selection from the full wavelength spectrum, 7 characteristic wavelengths were selected from full 201 UV/Vis spectral variables, which were just 3.48% number of the full range spectrum, and the calibration time and complexity of the modeling were greatly reduced. The predicted results which were obtained by using least squares-support vector machine (LS-SVM) calibration showed that the characteristic wavelengths achieved better results (0.89 for correlation coefficient (r), 15.46 mg x L(-1) for root mean square error of prediction (RMSEP)) than full wavelengths did (0.88 for r and 15.71 mg x L(-1) for RMSEP). The comprehensive results revealed that the UV/Vis characteristic wavelengths which were obtained by UVE-SPA variable selection method, combined with LS-SVM calibration could apply to the rapid and accurate determination of COD in aquaculture water. Moreover, this study laid the foundation for further implementation of online analysis of aquaculture water and rapid determination of other water quality parameters.

  10. UV Crosslinkable Polythiophene for Nano-imprinting and Photolithography toward Ordered Bulk Heterojunction in Organic Photovoltaics

    SciTech Connect

    Yang, Q.; Hlaing, H.; Ocko, B.; Black, C.; Grubbs, R.B.

    2010-07-25

    Exciton travel distance in organic material is on the order of 10-20 nm, thus the morphology of the organic active layer is critical to achieve high performance in OPVs. An ordered bulk heterojunction (BHJ) morphology with phase separation on the order of 10-20 nm will collect all excitons at the interface and give uninterrupted paths to all separated charges to reach the corresponding electrodes.

  11. Ultrashort-pulsed laser processing and solution based coating in roll-to-roll manufacturing of organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Hördemann, C.; Hirschfelder, K.; Schaefer, M.; Gillner, A.

    2015-09-01

    The breakthrough of flexible organic electronics and especially organic photovoltaics is highly dependent on cost-efficient production technologies. Roll-2-Roll processes show potential for a promising solution in terms of high throughput and low-cost production of thin film organic components. Solution based material deposition and integrated laser patterning processes offer new possibilities for versatile production lines. The use of flexible polymeric substrates brings along challenges in laser patterning which have to be overcome. One main challenge when patterning transparent conductive layers on polymeric substrates are material bulges at the edges of the ablated area. Bulges can lead to short circuits in the layer system leading to device failure. Therefore following layers have to have a sufficient thickness to cover and smooth the ridge. In order to minimize the bulging height, a study has been carried out on transparent conductive ITO layers on flexible PET substrates. Ablation results using different beam shapes, such as Gaussian beam, Top-Hat beam and Donut-shaped beam, as well as multi-pass scribing and double-pulsed ablation are compared. Furthermore, lab scale methods for cleaning the patterned layer and eliminating bulges are contrasted to the use of additional water based sacrificial layers in order to obtain an alternative procedure suitable for large scale Roll-2-Roll manufacturing. Besides progress in research, ongoing transfer of laser processes into a Roll-2-Roll demonstrator is illustrated. By using fixed optical elements in combination with a galvanometric scanner, scribing, variable patterning and edge deletion can be performed individually.

  12. Tunable ultraviolet laser-induced fluorescence detection of trace plastics and dissolved organic compounds in water

    NASA Astrophysics Data System (ADS)

    Sivaprakasam, Vasanthi; Killinger, Dennis K.

    2003-11-01

    We developed a tunable (220-285-nm) UV and fixed 266-nm laser-induced fluorescence (LIF) system using a spectrometer and a cooled CCD imaging detector to measure the excitation-emission matrix spectra of various compounds in water, including quinine sulfate and plastic compound bisphenol-A. The LIF instrument was used for the fast, nonspecific determination of trace amounts of dissolved organic compounds present in natural water supplies and various brand name bottled distilled water and bottled drinking water. Plastic-related compounds that leached out of plastic utensils and containers were also detected with this instrument. The sensitivity of the system was approximately 1-2 orders of magnitude better than that for a commercial system.

  13. Effect of molecular electrical doping on polyfuran based photovoltaic cells

    SciTech Connect

    Yu, Shuwen; Opitz, Andreas; Salzmann, Ingo; Frisch, Johannes; Cohen, Erez; Bendikov, Michael; Koch, Norbert

    2015-05-18

    The electronic, optical, and morphological properties of molecularly p-doped polyfuran (PF) films were investigated over a wide range of doping ratio in order to explore the impact of doping in photovoltaic applications. We find evidence for integer-charge transfer between PF and the prototypical molecular p-dopant tetrafluoro-tetracyanoquinodimethane (F4TCNQ) and employed the doped polymer in bilayer organic solar cells using fullerene as acceptor. The conductivity increase in the PF films at dopant loadings ≤2% significantly enhances the short-circuit current of photovoltaic devices. For higher doping ratios, however, F4TCNQ is found to precipitate at the heterojunction between the doped donor polymer and the fullerene acceptor. Ultraviolet photoelectron spectroscopy reveals that its presence acts beneficial to the energy-level alignment by doubling the open-circuit voltage of solar cells from 0.2 V to ca. 0.4 V, as compared to pristine PF.

  14. Effect of molecular electrical doping on polyfuran based photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Yu, Shuwen; Frisch, Johannes; Opitz, Andreas; Cohen, Erez; Bendikov, Michael; Koch, Norbert; Salzmann, Ingo

    2015-05-01

    The electronic, optical, and morphological properties of molecularly p-doped polyfuran (PF) films were investigated over a wide range of doping ratio in order to explore the impact of doping in photovoltaic applications. We find evidence for integer-charge transfer between PF and the prototypical molecular p-dopant tetrafluoro-tetracyanoquinodimethane (F4TCNQ) and employed the doped polymer in bilayer organic solar cells using fullerene as acceptor. The conductivity increase in the PF films at dopant loadings ≤2% significantly enhances the short-circuit current of photovoltaic devices. For higher doping ratios, however, F4TCNQ is found to precipitate at the heterojunction between the doped donor polymer and the fullerene acceptor. Ultraviolet photoelectron spectroscopy reveals that its presence acts beneficial to the energy-level alignment by doubling the open-circuit voltage of solar cells from 0.2 V to ca. 0.4 V, as compared to pristine PF.

  15. Development of New Absorber Materials to Achieve Organic Photovoltaic Commercial Modules with 15% Efficiency and 20 Years Lifetime: Cooperative Research and Development Final Report, CRADA Number CRD-12-498

    SciTech Connect

    Olson, D.

    2014-08-01

    Under this CRADA the parties will develop intermediates or materials that can be employed as the active layer in dye sensitized solar cells printed polymer systems, or small molecule organic photovoltaics.

  16. An ultrathin, smooth, and low-loss Al-doped Ag film and its application as a transparent electrode in organic photovoltaics.

    PubMed

    Zhang, Cheng; Zhao, Dewei; Gu, Deen; Kim, Hyunsoo; Ling, Tao; Wu, Yi-Kuei Ryan; Guo, L Jay

    2014-08-27

    An ultrathin, smooth, and low-loss Ag film without a wetting layer is achieved by co-depositing a small amount of Al into Ag. The film can be as thin as 6 nm, with a roughness below 1 nm and excellent mechanical flexibility. Organic photovoltaics that use these thin films as transparent electrode show superior efficiency to their indium tin oxide (ITO) counterparts because of improved photon management. PMID:24943876

  17. The Effect of Processing Additives on Energetic Disorder in Highly Efficient Organic Photovoltaics: A Case Study on PBDTTT-C-T:PC71 BM.

    PubMed

    Gao, Feng; Himmelberger, Scott; Andersson, Mattias; Hanifi, David; Xia, Yuxin; Zhang, Shaoqing; Wang, Jianpu; Hou, Jianhui; Salleo, Alberto; Inganäs, Olle

    2015-07-01

    Energetic disorder, an important parameter affecting the performance of organic photovoltaics, is significantly decreased upon the addition of processing additives in a highly efficient benzodithiophene-based copolymer blend (PBDTTT-C-T:PC71 BM). Wide-angle and small-angle X-ray scattering measurements suggest that the origin of this reduced energetic disorder is due to increased aggregation and a larger average fullerene domain size together with purer phases.

  18. Characterization of organic matter in beef feedyard manure by ultraviolet-visible and fourier transform infrared spectroscopies.

    PubMed

    Waldrip, Heidi M; He, Zhongqi; Todd, Richard W; Hunt, James F; Rhoades, Marty B; Cole, N Andy

    2014-03-01

    Manure from beef cattle feedyards is a valuable source of nutrients and assists with maintaining soil quality. However, humification and decomposition processes occurring during feedyard manure's on-farm life cycle influence the forms, concentrations, and availability of carbon (C) and nutrients such as nitrogen (N) and phosphorus (P). Improved understanding of manure organic matter (OM) chemistry will provide better estimates of potential fertilizer value of manure from different feedyard sources (e.g., manure accumulated in pens, stockpiled manure after pen scraping) and in settling basin and retention pond sediments. This will also assist with identifying factors related to nutrient loss and environmental degradation via volatilization of ammonia and nitrous oxide and nitrate leaching. We used Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopies to characterize structural and functional properties of OM and water-extractable OM (WEOM) from different sources (surface manure, manure pack, settling basin, retention pond) on a typical commercial beef feedyard in the Texas Panhandle. Results showed that as beef manure completes its on-farm life cycle, concentrations of dissolved organic C and N decrease up to 98 and 95%, respectively. The UV-vis analysis of WEOM indicated large differences in molecular weight, lignin content, and proportion of humified OM between manures from different sources. The FTIR spectra of OM and WEOM indicate preferential decomposition of fats, lipids, and proteins over aromatic polysaccharides such as lignin. Further work is warranted to evaluate how application of feedyard manure from different sources influences soil metabolic functioning and fertility. PMID:25602670

  19. The lowest-energy charge-transfer state and its role in charge separation in organic photovoltaics.

    PubMed

    Nan, Guangjun; Zhang, Xu; Lu, Gang

    2016-06-29

    Energy independent, yet higher than 90% internal quantum efficiency (IQE), has been observed in many organic photovoltaics (OPVs). However, its physical origin remains largely unknown and controversial. The hypothesis that the lowest charge-transfer (CT) state may be weakly bound at the interface has been proposed to rationalize the experimental observations. In this paper, we study the nature of the lowest-energy CT (CT1) state, and show conclusively that the CT1 state is localized in typical OPVs. The electronic couplings in the donor and acceptor are found to determine the localization of the CT1 state. We examine the geminate recombination of the CT1 state and estimate its lifetime from first principles. We identify the vibrational modes that contribute to the geminate recombination. Using material parameters determined from first principles and experiments, we carry out kinetic Monte Carlo simulations to examine the charge separation of the localized CT1 state. We find that the localized CT1 state can indeed yield efficient charge separation with IQE higher than 90%. Dynamic disorder and configuration entropy can provide the energetic and entropy driving force for charge separation. Charge separation efficiency depends more sensitively on the dimension and crystallinity of the acceptor parallel to the interface than that normal to the interface. Reorganization energy is found to be the most important material parameter for charge separation, and lowering the reorganization energy of the donor should be pursued in the materials design.

  20. Surfactant-free, low band gap conjugated polymer nanoparticles and polymer:fullerene nanohybrids with potential for organic photovoltaics.

    PubMed

    Wang, Suxiao; Singh, Amita; Walsh, Nichola; Redmond, Gareth

    2016-06-17

    Stable, aqueous dispersions of nanoparticles based on the low band gap polymers poly [2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) and poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) were prepared, using a flexible, surfactant-free reprecipitation method, and characterized by a variety of optical techniques. Light scattering measurements indicated average nanoparticle hydrodynamic diameters of approximately 40 nm. The particles presented wide-bandwidth absorption and photoluminescence excitation spectra with high absorption cross-sections on the order of 10(-12) cm(2). Nanoparticle emission spectra were significantly red-shifted, with decreased emission quantum yields and lifetimes, consistent with increased inter-polymer chain interactions in the condensed phase. Single particle photoluminescence studies highlighted the multi-chromophoric nature of the polymer nanoparticles and confirmed their favorable photostabilities. When the nanoparticles were doped with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), the correspondence of photoluminescence emission quenching, quantum yield decreases, emission lifetime shortening, and increased non-radiative rates with increasing PCBM concentration suggested efficient photo-induced donor-to-acceptor charge transfer between the conjugated polymers and the fullerene dopants co-localized in the nanoparticle cores. Taken together, the data suggest that these surfactant-free hybrid nanomaterials may be useful for integration with future nanostructured organic photovoltaics technologies.

  1. Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

    PubMed Central

    2014-01-01

    Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10−4 Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films. PMID:25352768

  2. Visibly transparent organic photovoltaic with improved transparency and absorption based on tandem photonic crystal for greenhouse application.

    PubMed

    Yang, Fan; Zhang, Ye; Hao, Yuying; Cui, Yanxia; Wang, Wenyan; Ji, Ting; Shi, Fang; Wei, Bin

    2015-12-01

    We demonstrate a visible transparent organic photovoltaic (OPV) with improved transmission and absorption based on tandem photonic crystals (TPCs) for greenhouse applications. The proposed device has an average transmittance of 40.3% in the visible range of 400-700 nm and a high quality transparency spectrum for plant growth with a crop growth factor of 41.9%, considering the weight of the AM 1.5G solar spectrum. Compared with the corresponding transparent OPV without photonic crystals, an enhancement of 20.7% in the average transmittance and of 24.5% in the crop growth factor are achieved. Detailed investigations reveal that the improved transmittance is attributed to the excitation of the optical Tamm state and the light interference effect in TPC. Concomitantly, the total absorption efficiency in the active layer of the designed TPC based transparent OPV reaches 51.5%, being 1.78% higher than that of the transparent OPV without PC and 76% of that of the opaque counterpart. The improved absorption originates from the Bragg forbidden reflectance of TPC. Overall, our proposal achieves the optimized utilization of sunlight by light manipulation of TPC. PMID:26836682

  3. Unraveling the Fundamental Mechanisms of Solvent-Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices.

    PubMed

    Herath, Nuradhika; Das, Sanjib; Zhu, Jiahua; Kumar, Rajeev; Chen, Jihua; Xiao, Kai; Gu, Gong; Browning, James F; Sumpter, Bobby G; Ivanov, Ilia N; Lauter, Valeria

    2016-08-10

    The realization of controllable morphologies of bulk heterojunctions (BHJ) in organic photovoltaics (OPVs) is one of the key factors enabling high-efficiency devices. We provide new insights into the fundamental mechanisms essential for the optimization of power conversion efficiencies (PCEs) with additive processing to PBDTTT-CF:PC71BM system. We have studied the underlying mechanisms by monitoring the 3D nanostructural modifications in BHJs and correlated the modifications with the optical analysis and theoretical modeling of charge transport. Our results demonstrate profound effects of diiodooctane (DIO) on morphology and charge transport in the active layers. For small amounts of DIO (<3 vol %), DIO promotes the formation of a well-mixed donor-acceptor compact film and augments charge transfer and PCE. In contrast, for large amounts of DIO (>3 vol %), DIO facilitates a loosely packed mixed morphology with large clusters of PC71BM, leading to deterioration in PCE. Theoretical modeling of charge transport reveals that DIO increases the mobility of electrons and holes (the charge carriers) by affecting the energetic disorder and electric field dependence of the mobility. Our findings show the implications of phase separation and carrier transport pathways to achieve optimal device performances. PMID:27403964

  4. Efficiency improvements in single-heterojunction organic photovoltaic cells by insertion of wide-bandgap electron-blocking layers

    NASA Astrophysics Data System (ADS)

    Ho, Chiu-Sheng; Lee, Ching-Sung; Hsu, Wei-Chou; Lin, Cheng-Yung; Lai, Ying-Nan; Wang, Ching-Wu

    2012-10-01

    This letter reports efficiency improvements in single-heterojunction organic photovoltaic (OPV) cells exploiting different wide-bandgap electron-blocking layer (EBL) materials of N,N,NO',N' tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), Tris(phenypyrazole)iridium (Ir(ppz)3), or 4,4,4"-tris-(3-methylphenylphenylamino)triphenylamine (m-MTDATA), respectively. The OPV structure consists of an indium-tin-oxide (ITO) anode, 4 nm m-MTDATA, 30 nm copper phthalocyanine (CuPc), 40 nm fullerene (C60), 10 nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and a 100 nm Al cathode. Optimum device performances by insertion the EBL of m-MTDATA have been achieved, including short-circuit current density (JSC) of 7.26 mA/cm2, open-circuit voltage (VOC) of 0.5 V, fill-factor (FF) of 43%, and power conversion efficiency (PCE) of 1.56% at an illumination intensity of 100 mW/cm2.

  5. 3D reconstruction modeling of bulk heterojunction organic photovoltaic cells: Effect of the complexity of the boundary on the morphology

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Jin; Jeong, Daun; Kim, SeongMin; Choi, Yeong Suk; Ihn, Soo-Ghang; Yun, Sungyoung; Lim, Younhee; Lee, Eunha; Park, Gyeong-Su

    2016-02-01

    Although the morphology of the active layer in bulk heterojunction organic photovoltaic (BHJ-OPV) cells is critical for determining the quantum efficiency (QE), predicting the real QE for a 3-dimensional (3D) morphology has long been difficult because structural information on the composition complexity of donor (D): acceptor (A) blends with small domain size is limited to 2D observations via various image-processing techniques. To overcome this, we reconstruct the 3D morphology by using an isotropic statistical approach based on 2D energy-filtered transmission electron microscopy (EF-TEM) images. This new reconstruction method is validated to obtain the internal QE by using a dynamic Monte Carlo simulation in the BHJ-OPV system with different additives such as 4 vol% 1-chloronaphthalene (CN) and 4 vol% 1,8-diiodooctane (DIO) (compared to the case of no additive); the resulting trend is compared with the experimental QE. Therefore, our developed method can be used to predict the real charge transport performance in the OPV system accurately.

  6. Integrated optical and electrical modeling of plasmon-enhanced thin film photovoltaics: A case-study on organic devices

    SciTech Connect

    Rourke, Devin; Ahn, Sungmo; Nardes, Alexandre M.; Lagemaat, Jao van de; Kopidakis, Nikos; Park, Wounjhang

    2014-09-21

    The nanoscale light control for absorption enhancement of organic photovoltaic (OPV) devices inevitably produces strongly non-uniform optical fields. These non-uniformities due to the localized optical modes are a primary route toward absorption enhancement in OPV devices. Therefore, a rigorous modeling tool taking into account the spatial distribution of optical field and carrier generation is necessary. Presented here is a comprehensive numerical model to describe the coupled optical and electrical behavior of plasmon-enhanced polymer:fullerene bulk heterojunction (BHJ) solar cells. In this model, a position-dependent electron-hole pair generation rate that could become highly non-uniform due to photonic nanostructures is directly calculated from the optical simulations. By considering the absorption and plasmonic properties of nanophotonic gratings included in two different popular device architectures, and applying the Poisson, current continuity, and drift/diffusion equations, the model predicts quantum efficiency, short-circuit current density, and desired carrier mobility ratios for bulk heterojunction devices incorporating nanostructures for light management. In particular, the model predicts a significant degradation of device performance when the carrier species with lower mobility are generated far from the collecting electrode. Consequently, an inverted device architecture is preferred for materials with low hole mobility. This is especially true for devices that include plasmonic nanostructures. Additionally, due to the incorporation of a plasmonic nanostructure, we use simulations to theoretically predict absorption band broadening of a BHJ into energies below the band gap, resulting in a 4.8% increase in generated photocurrent.

  7. The Miscibility and Depth Profile of PCBM in P3HT: Thermodynamic Information to Improve Organic Photovoltaics

    SciTech Connect

    Dadmun, Mark D

    2012-01-01

    Recent work has shown that poly(3-hexylthiophene) (P3HT) and the surface functionalized fullerene 1-(3-methyloxycarbonyl)propy(1-phenyl [6,6]) C61 (PCBM) are much more miscible than originally thought, and the evidence of this miscibility requires a return to understanding the optimal morphology and structure of organic photovoltaic active layers. This manuscript describes the results of experiments that were designed to provide quantitative thermodynamic information on the miscibility, interdiffusion, and depth profile of P3HT:PCBM thin films that are formed by thermally annealing initial bilayers. It is found that the resultant thin films consist of a bulk layer that is not influenced by the air or substrate surface. The composition of PCBM in this bulk layer increases with increased PCBM loading in the original bilayer until the bulk layer contains 22 vol% PCBM. The introduction of additional PCBM into the sample does not increase the amount of PCBM dispersed in this bulk layer. This observation is interpreted to indicate that the miscibility limit of PCBM in P3HT is 22 vol%, while the precise characterization of the depth profiles in these films shows that the PCBM selectively segregates to the silicon and near air surface. The selective segregation of the PCBM near the air surface is ascribed to an entropic driving force.

  8. Effects of ytterbium on electrical and optical properties of BCP/Ag/WO3 transparent electrode based organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Oh, Il Soo; Ji, Chan Hyuk; Oh, Se Young

    2016-01-01

    This study introduces dielectric/metal/dielectric multilayers based on a WO3/Ag/WO3 (WAW) anode and Yb/BCP/Ag/WO3 (Yb/BAW) cathode for use in organic photovoltaic cells (OPVs). Here, the Yb/BCP hybrid multilayer provides an effective electron transport layer (ETL), while the Yb doping ensures that voltage loss due to interfacial band bending is effectively suppressed. Transparent OPVs produced with a structure of WAW/P3HT:PCBM/Yb/BAW are shown to exhibit a power conversion efficiency (PCE) of up to 2.42%, achieving a 65.4% fill factor (FF) under one sun irradiation. These results indicate that the use of Yb in transparent OPVs is vastly superior to other ETLs, as it improves the majority of critical parameters such as short circuit current (Jsc), fill factor (FF) and PCE. This is attributed to a decrease in the series resistance and increase in the shunt resistance, while an increase in electron mobility also helps to ensure faster sweep out. [Figure not available: see fulltext.

  9. Effects of thermal treatment and depth profiling analysis of solution processed bulk-heterojunction organic photovoltaic cells.

    PubMed

    Mbule, Pontsho S; Swart, Hendrik C; Ntwaeaborwa, Odireleng M

    2014-12-15

    We report the use of solution processed zinc oxide (ZnO) nanoparticles as a buffer layer inserted between the top metal electrode and the photo-active layer in bulk-heterojunction (BHJ) organic solar cell (OSC) devices. The photovoltaic properties were compared for devices annealed before (Device A) or after (Device B) the deposition of the Al top electrode. The post-annealing treatment was shown to improve the power conversion efficiency up to 2.93% and the fill factor (FF) up to 63% under AM1.5 (100mW/cm(2)) illumination. We performed the depth profile/interface analysis and elemental mapping using the time-of-flight secondary ion mass spectrometry (TOF-SIMS). Signals arising from (27)Al, (16)O, (12)C, (32)S, (64)Zn, (28)Si, (120)Sn and (115)In give an indication of successive deposition of Al, ZnO, P3HT:PCBM and PEDOT:PSS layers on ITO coated glass substrates. Furthermore, we discuss the surface imaging and visualize the chemical information on the surface of the devices.

  10. Improvement of pentathiophene/fullerene planar heterojunction photovoltaic cells by improving the organic films morphology through the anode buffer bilayer

    NASA Astrophysics Data System (ADS)

    El Jouad, Zouhair; Cattin, Linda; Martinez, Francisco; Neculqueo, Gloria; Louarn, Guy; Addou, Mohammed; Predeep, Padmanabhan; Manuvel, Jayan; Bernède, Jean-Christian

    2016-05-01

    Organic photovoltaic cells (OPVCs) are based on a heterojunction electron donor (ED)/electron acceptor (EA). In the present work, the electron donor which is also the absorber of light is pentathiophene. The typical cells were ITO/HTL/pentathiophene/fullerene/Alq3/Al with HTL (hole transport layer) = MoO3, CuI, MoO3/CuI. After optimisation of the pentathiophene thickness, 70 nm, the highest efficiency, 0.81%, is obtained with the bilayer MoO3/CuI as HTL. In order to understand these results the pentathiophene films deposited onto the different HTLs were characterized by scanning electron microscopy, atomic force microscopy, X-rays diffraction, optical absorption and electrical characterization. It is shown that CuI improves the conductivity of the pentathiophene layer through the modification of the film structure, while MoO3 decreases the leakage current. Using the bilayer MoO3/CuI allows cumulating the advantages of each layer. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  11. Solution Synthesized p-Type Copper Gallium Oxide Nanoplates as Hole Transport Layer for Organic Photovoltaic Devices.

    PubMed

    Wang, Jian; Ibarra, Vanessa; Barrera, Diego; Xu, Liang; Lee, Yun-Ju; Hsu, Julia W P

    2015-03-19

    p-Type metal-oxide hole transport layer (HTL) suppresses recombination at the anode and hence improves the organic photovoltaic (OPV) device performance. While NiOx has been shown to exhibit good HTL performance, very thin films (<10 nm) are needed due to its poor conductivity and high absorption. To overcome these limitations, we utilize CuGaO2, a p-type transparent conducting oxide, as HTL for OPV devices. Pure delafossite phase CuGaO2 nanoplates are synthesized via microwave-assisted hydrothermal reaction in a significantly shorter reaction time compared to via conventional heating. A thick CuGaO2 HTL (∼280 nm) in poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) devices achieves 3.2% power conversion efficiency, on par with devices made with standard HTL materials. Such a thick CuGaO2 HTL is more compatible with large-area and high-volume printing process.

  12. Short-lived charge-transfer excitons in organic photovoltaic cells studied by high-field magneto-photocurrent.

    PubMed

    Devir-Wolfman, Ayeleth H; Khachatryan, Bagrat; Gautam, Bhoj R; Tzabary, Lior; Keren, Amit; Tessler, Nir; Vardeny, Z Valy; Ehrenfreund, Eitan

    2014-07-29

    The main route of charge photogeneration in efficient organic photovoltaic cells based on bulk hetero-junction donor-acceptor blends involves short-lived charge-transfer excitons at the donor-acceptor interfaces. The cell efficiency is critically affected by the charge-transfer exciton recombination and dissociation processes. By measuring the magneto-photocurrent under ambient conditions at room temperature, we show here that magnetic field-induced spin-mixing among the charge-transfer exciton spin sublevels occurs in fields up to at least 8.5 Tesla. The resulting magneto-photocurrent increases at high fields showing non-saturating behaviour up to the highest applied field. We attribute the observed high-field spin-mixing mechanism to the difference in the donor-acceptor g-factors. The non-saturating magneto-photocurrent response at high field indicates that there exist charge-transfer excitons with lifetime in the sub-nanosecond time domain. The non-Lorentzian high-field magneto-photocurrent response indicates a dispersive decay mechanism that originates due to a broad distribution of charge-transfer exciton lifetimes.

  13. Enhanced performance of inverted organic photovoltaic cells using CNTs-TiO(X) nanocomposites as electron injection layer.

    PubMed

    Zhang, Hong; Xu, Meifeng; Cui, Rongli; Guo, Xihong; Yang, Shangyuan; Liao, Liangsheng; Jia, Quanjie; Chen, Yu; Dong, Jinquan; Sun, Baoyun

    2013-09-01

    In this study, we fabricated inverted organic photovoltaic cells with the structure ITO/carbon nanotubes (CNTs)-TiO(X)/P3HT:PCBM/MoO₃/Al by spin casting CNTs-TiO(X) nanocomposite (CNTs-TiO(X)) as the electron injection layer onto ITO/glass substrates. The power conversion efficiency (PCE) of the 0.1 wt% single-walled nanotubes (SWNTs)-TiO(X) nanocomposite device was almost doubled compared with the TiO(X) device, but with increasing concentration of the incorporated SWNTs in the TiO(X) film, the performance of the devices appeared to decrease rapidly. Devices with multi-walled NTs in the TiO(X) film have a similar trend. This phenomenon mainly depends on the inherent physical and chemical characteristics of CNTs such as their high surface area, their electron-accepting properties and their excellent carrier mobility. However, with increasing concentration of CNTs, CNTs-TiO(X) current leakage pathways emerged and also a recombination of charges at the interfaces. In addition, there was a significant discovery. The incorporated CNTs were highly conducive to enhancing the degree of crystallinity and the ordered arrangement of the P3HT in the active layers, due to the intermolecular π-π stacking interactions between CNTs and P3HT.

  14. High-Pressure Solvent Vapor Annealing with a Benign Solvent To Rapidly Enhance the Performance of Organic Photovoltaics.

    PubMed

    Jung, Buyoung; Kim, Kangmin; Eom, Yoomin; Kim, Woochul

    2015-06-24

    A high-pressure solvent vapor annealing (HPSVA) treatment is suggested as an annealing process to rapidly achieve high-performance organic photovoltaics (OPVs); this process can be compatible with roll-to-roll processing methods and uses a benign solvent: acetone. Solvent vapor annealing can produce an advantageous vertical distribution in the active layer; however, conventional solvent vapor annealing is also time-consuming. To shorten the annealing time, high-pressure solvent vapor is exposed on the active layer of OPVs. Acetone is a nonsolvent for poly(3-hexylthiophene-2,5-diyl) (P3HT), but it can dissolve small amounts of 1-(3-methoxycarbonyl)-propyl-1,1-phenyl-(6,6)C61 (PCBM). Acetone vapor molecules can penetrate into the active layer under high vapor pressure conditions to alter the morphology. HPSVA induces a PCBM-rich phase near the cathode and facilitates the transport of free charge carriers to the electrode. Although P3HT is not soluble in acetone, locally rearranged P3HT crystallites are generated. The performance of OPV films was enhanced after HPSVA; the film treated at 30 kPa for 10 s showed optimum performance. Additionally, this HPSVA method could be adapted for mass production because the temporary exposure of films to high-pressure acetone vapor in ambient conditions also improved performance.

  15. Unraveling the Fundamental Mechanisms of Solvent-Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices.

    PubMed

    Herath, Nuradhika; Das, Sanjib; Zhu, Jiahua; Kumar, Rajeev; Chen, Jihua; Xiao, Kai; Gu, Gong; Browning, James F; Sumpter, Bobby G; Ivanov, Ilia N; Lauter, Valeria

    2016-08-10

    The realization of controllable morphologies of bulk heterojunctions (BHJ) in organic photovoltaics (OPVs) is one of the key factors enabling high-efficiency devices. We provide new insights into the fundamental mechanisms essential for the optimization of power conversion efficiencies (PCEs) with additive processing to PBDTTT-CF:PC71BM system. We have studied the underlying mechanisms by monitoring the 3D nanostructural modifications in BHJs and correlated the modifications with the optical analysis and theoretical modeling of charge transport. Our results demonstrate profound effects of diiodooctane (DIO) on morphology and charge transport in the active layers. For small amounts of DIO (<3 vol %), DIO promotes the formation of a well-mixed donor-acceptor compact film and augments charge transfer and PCE. In contrast, for large amounts of DIO (>3 vol %), DIO facilitates a loosely packed mixed morphology with large clusters of PC71BM, leading to deterioration in PCE. Theoretical modeling of charge transport reveals that DIO increases the mobility of electrons and holes (the charge carriers) by affecting the energetic disorder and electric field dependence of the mobility. Our findings show the implications of phase separation and carrier transport pathways to achieve optimal device performances.

  16. Efficiency enhancement and angle-dependent color change in see-through organic photovoltaics using distributed Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Dong, Wan Jae; Lo, Nhat-Truong; Jung, Gwan Ho; Ham, Juyoung; Lee, Jong-Lam

    2016-03-01

    A distributed Bragg reflector (DBR) is conducted as a bottom reflector in see-through organic photovoltaics (OPVs) with an active layer of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The DBR consists of alternative layers of the high- and low-refractive index materials of Ta2O5 (n = 2.16) and SiO2 (n = 1.46). The DBR selectively reflects the light within a specific wavelength region (490 nm-630 nm) where the absorbance of P3HT:PCBM is maximum. The see-through OPVs fabricated on DBR exhibit efficiency enhancement by 31% compared to the device without DBR. Additionally, the angle-dependent transmittance of DBR is analysed using optical simulation and verified by experimental results. As the incident angle of light increases, peak of reflectance shifts to shorter wavelength and the bandwidth gets narrower. This unique angle-dependent optical properties of DBR allows the facile color change of see-through OPVs.

  17. Simultaneous Engineering of the Substrate Temperature and Mixing Ratio to Improve the Performance of Organic Photovoltaic Cells.

    PubMed

    Song, Hyung-Jun; Roh, Jeongkyun; Lee, Changhee

    2016-05-01

    In this study, we investigated the effect of the donor/acceptor mixing ratio and the substrate temperature (T(SUB)) during the co-deposition process on the performance of bulk heterojunction organic photovoltaic cells. We found that the ratio of dispersed donor islands (less than 10 nm), which hinders charge carrier transport, increased as the donor concentration (C(D)) increased in the film processed at room temperature. By contrast, the donor cluster (larger than 10 nm), providing percolation paths for the carriers, was enlarged in the film containing a high C(D) fabricated at high T(SUB) (70 degrees C). This enhanced phase separation in the mixed layer led to an improved fill factor and a decreased activation energy of the short-circuit current (J(SC)). Therefore, we demonstrated a 23% improvement in the device performance by employing an elevated T(SUB) and optimized mixing ratio in comparison with the device fabricated at room temperature. PMID:27483881

  18. Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes.

    PubMed

    Park, Hyesung; Brown, Patrick R; Bulović, Vladimir; Kong, Jing

    2012-01-11

    In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications. PMID:22107487

  19. Ultrafast Transient Absorption Spectroscopy Investigation of Photoinduced Dynamics in Novel Donor-Acceptor Core-Shell Nanostructures for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Strain, Jacob; Jamhawi, Abdelqader; Abeywickrama, Thulitha M.; Loomis, Wendy; Rathnayake, Hemali; Liu, Jinjun

    2016-06-01

    Novel donor-acceptor nanostructures were synthesized via covalent synthesis and/or UV cross-linking method. Their photoinduced dynamics were investigated with ultrafast transient absorption (TA) spectroscopy. These new nanostructures are made with the strategy in mind to reduce manufacturing steps in the process of fabricating an organic photovoltaic cell. By imitating the heterojunction interface within a fixed particle domain, several fabrication steps can be bypassed reducing cost and giving more applicability to other film deposition methods. Such applications include aerosol deposition and ink-jet printing. The systems that were studied by TA spectroscopy include PDIB core, PDIB-P3HT core-shell, and PDIB-PANT core-shell which range in size from 60 to 130 nm. Within the experimentally accessible spectra range there resides a region of ground state bleaching, stimulated emission, and excited-state absorption of both neutrals and anions. Control experiments have been carried out to assign these features. At high pump fluences the TA spectra of PDIB core alone also indicate an intramolecular charge separation. The TA spectroscopy results thus far suggest that the core-shells resemble the photoinduced dynamics of a standard film although the particles are dispersed in solution, which indicates the desired outcome of the work.

  20. Efficiently-designed hybrid tandem photovoltaic with organic and inorganic single cells

    NASA Astrophysics Data System (ADS)

    Vincent, Premkumar; Bae, Jin-Hyuk; Kim, Hyeok

    2016-05-01

    Conjugated polymers for solar-cell applications have been extensively studied and have proven highly beneficial in tandem solar-cell structures. This study focuses on achieving power conversion efficiencies of greater than 10% when in tandem with a highly efficient copper indium gallium diselenide (CIGS) solar cell. The optimal design is suggested based on the result of optical simulations on the organic-CIGS tandem structure. This is one of the first reports to show theoretically an organic-CIGS tandem solar cell to obtain an efficiency of greater than 10%. The best PCE was at a thickness of 200 nm for PTB7:PCBM, the active layer of the organic solar cell, and 400 nm for CIGS active layer. Our best datum showed an efficiency of 11.41% with a short-circuit current density of 11.56 mA/cm2 and a good spectral response at our optimized thicknesses.

  1. Improved photovoltaic performance of silicon nanowire/organic hybrid solar cells by incorporating silver nanoparticles.

    PubMed

    Liu, Kong; Qu, Shengchun; Zhang, Xinhui; Tan, Furui; Wang, Zhanguo

    2013-02-18

    Silicon nanowire (SiNW) arrays show an excellent light-trapping characteristic and high mobility for carriers. Surface plasmon resonance of silver nanoparticles (AgNPs) can be used to increase light scattering and absorption in solar cells. We fabricated a new kind of SiNW/organic hybrid solar cell by introducing AgNPs. Reflection spectra confirm the improved light scattering of AgNP-decorated SiNW arrays. A double-junction tandem structure was designed to manufacture our hybrid cells. Both short-circuit current and external quantum efficiency measurements show an enhancement in optical absorption of organic layer, especially at lower wavelengths.

  2. Improved photovoltaic performance of silicon nanowire/organic hybrid solar cells by incorporating silver nanoparticles

    PubMed Central

    2013-01-01

    Silicon nanowire (SiNW) arrays show an excellent light-trapping characteristic and high mobility for carriers. Surface plasmon resonance of silver nanoparticles (AgNPs) can be used to increase light scattering and absorption in solar cells. We fabricated a new kind of SiNW/organic hybrid solar cell by introducing AgNPs. Reflection spectra confirm the improved light scattering of AgNP-decorated SiNW arrays. A double-junction tandem structure was designed to manufacture our hybrid cells. Both short-circuit current and external quantum efficiency measurements show an enhancement in optical absorption of organic layer, especially at lower wavelengths. PMID:23418988

  3. Molecular depth profiling of organic photovoltaic heterojunction layers by ToF-SIMS: comparative evaluation of three sputtering beams.

    PubMed

    Mouhib, T; Poleunis, C; Wehbe, N; Michels, J J; Galagan, Y; Houssiau, L; Bertrand, P; Delcorte, A

    2013-11-21

    With the recent developments in secondary ion mass spectrometry (SIMS), it is now possible to obtain molecular depth profiles and 3D molecular images of organic thin films, i.e. SIMS depth profiles where the molecular information of the mass spectrum is retained through the sputtering of the sample. Several approaches have been proposed for "damageless" profiling, including the sputtering with SF5(+) and C60(+) clusters, low energy Cs(+) ions and, more recently, large noble gas clusters (Ar500-5000(+)). In this article, we evaluate the merits of these different approaches for the in depth analysis of organic photovoltaic heterojunctions involving poly(3-hexylthiophene) (P3HT) as the electron donor and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as the acceptor. It is demonstrated that the use of 30 keV C60(3+) and 500 eV Cs(+) (500 eV per atom) leads to strong artifacts for layers in which the fullerene derivative PCBM is involved, related to crosslinking and topography development. In comparison, the profiles obtained using 10 keV Ar1700(+) (∼6 eV per atom) do not indicate any sign of artifacts and reveal fine compositional details in the blends. However, increasing the energy of the Ar cluster beam beyond that value leads to irreversible damage and failure of the molecular depth profiling. The profile qualities, apparent interface widths and sputtering yields are analyzed in detail. On the grounds of these experiments and recent molecular dynamics simulations, the discussion addresses the issues of damage and crater formation induced by the sputtering and the analysis ions in such radiation-sensitive materials, and their effects on the profile quality and the depth resolution. Solutions are proposed to optimize the depth resolution using either large Ar clusters or low energy cesium projectiles for sputtering and/or analysis.

  4. The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics.

    PubMed

    Causa', Martina; De Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C; Buchaca-Domingo, Ester; Moser, Jacques-E; Stingelin, Natalie; Banerji, Natalie

    2016-01-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.

  5. Nanostructured organic/inorganic semicondutor photovoltaics: Investigation on morphology and optoelectronics performance

    NASA Astrophysics Data System (ADS)

    Wanninayake, Aruna Pushpa Kumara

    Organic solar cell is a promising technology because of the versatility of organic materials in terms of tunability of their electrical and optical properties. In addition, their relative insensitivity to film imperfections potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved in order to be competitive with grid parity. This work is focused on the design and characterization of a new organic/inorganic hybrid device to enhance the efficiency factors of bilayer organic solar cells such as: light absorption, exciton diffusion, exciton dissociation, charge transportation and charge collection at the electrodes. In a hybrid solar cell operation, external quantum efficiency is determined by these five factors. The external quantum efficiency has linear relationship to the power conversation efficiency via short circuit current density. Bulk heterojunction (BHJ) PSCs benefit from a homogeneous donor-acceptor (D-A) contact interface compared to their inorganic counterpart. A homogenous D-A interface offers a longer free path for charge carriers, resulting in a longer diffusional pathway and a larger coulomb interaction between electrons and holes. This is triggered by the low dielectric constant of organic semiconductors. Among various conventional donor-acceptor structures, poly(3-hexylthiophene)/[6,6]-phenyl-C70-butyric acid methyl ester (P3HT/PCBM) mixture is the most promising and ideal donor-acceptor pair due to their unique properties. In order to take benefits from both organic and inorganic materials, inorganic nanoparticles are incorporated in this donor-acceptor polymer structure. Light trapping enhances light absorption and increases efficiencies with thinner device structure. In this study, copper oxide nanoparticles are used in the P3HT/PC70BM active layer to optimize the optical absorption properties in the blend. In addition, zinc

  6. The fate of electron–hole pairs in polymer:fullerene blends for organic photovoltaics

    PubMed Central

    Causa', Martina; De Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C.; Buchaca-Domingo, Ester; Moser, Jacques-E.; Stingelin, Natalie; Banerji, Natalie

    2016-01-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron–hole pairs—whether they will dissociate to free charges or geminately recombine—is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%. PMID:27586309

  7. The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Causa', Martina; de Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C.; Buchaca-Domingo, Ester; Moser, Jacques-E.; Stingelin, Natalie; Banerji, Natalie

    2016-09-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs--whether they will dissociate to free charges or geminately recombine--is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.

  8. Field-enhanced recombination at low temperatures in an organic photovoltaic blend

    NASA Astrophysics Data System (ADS)

    Athanasopoulos, S.; Greenham, N. C.; Friend, R. H.; Chepelianskii, A. D.

    2015-09-01

    We report on the nontrivial field dependence of charge-carrier recombination in an organic blend at low temperatures. A new microwave resonance technique for monitoring charge recombination in organic semiconductors at low temperatures is applied in bulk heterojunction poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester blends with results showing that an external electric field can in fact increase recombination. Monte Carlo simulations suggest that this contradiction to conventional wisdom relates to electron-hole pairs that are separated at donor-acceptor interfaces where the electric field acts in synergy with their Coulomb attraction. For this behavior to occur a critical initial separation of ˜5 nm between the carriers is required.

  9. The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics.

    PubMed

    Causa', Martina; De Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C; Buchaca-Domingo, Ester; Moser, Jacques-E; Stingelin, Natalie; Banerji, Natalie

    2016-01-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%. PMID:27586309

  10. Very high efficiency photovoltaic cells based on fully organic multiple quantum wells. Quarterly technical progress report, 15 February 1995--15 May 1995

    SciTech Connect

    Forrest, S R

    1997-03-01

    The principal project objective is to demonstrate relatively high solar conversion efficiency using extremely low-cost, thin-film technology based on crystalline organic multiple quantum well (MQW) photovoltaic cells. The authors base their work on recent observations both in the laboratory and elsewhere that have indicated the quantum efficiency of organic photoconductors based on vacuum-deposited thin films can be increased by at least two orders of magnitude (to at least 10%) if the organic films are grown in a highly ordered manner, and if organic multiple quantum wells are used in the absorption region. The authors are investigating the physical origin of this phenomenon, and they are growing thin-film MQW cells that demonstrate relatively high quantum efficiencies to determine the practicality of crystalline organic thin-film cells for solar power applications. The investigations are based on a unique, ultrahigh-vacuum organic molecular beam deposition system in the laboratory.

  11. Spatial and temporal variability in the amount and source of dissolved organic carbon: Implications for ultraviolet exposure in amphibian habitats

    USGS Publications Warehouse

    Brooks, P.D.; O'Reilly, C. M.; Diamond, S.A.; Campbell, D.H.; Knapp, R.; Bradford, D.; Corn, P.S.; Hossack, B.; Tonnessen, K.

    2005-01-01

    The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1–2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R2 = 0.39, F = 25.71, P < 0.0001) and across all parks in 2000 (R2 = 0.44, F = 38.25, P < 0.0001). The relatively low R2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600–2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia–Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV-B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations.

  12. Photonic Flash Sintering of Ink-Jet-Printed Back Electrodes for Organic Photovoltaic Applications.

    PubMed

    Polino, Giuseppina; Shanmugam, Santhosh; Bex, Guy J P; Abbel, Robert; Brunetti, Francesca; Di Carlo, Aldo; Andriessen, Ronn; Galagan, Yulia

    2016-01-27

    A study of the photonic flash sintering of a silver nanoparticle ink printed as the back electrode for organic solar cells is presented. A number of sintering settings with different intensities and pulse durations have been tested on both full-area and grid-based silver electrodes, using the complete emission spectrum of the flash lamps from UV-A to NIR. However, none of these settings was able to produce functional devices with performances comparable to those of reference cells prepared using thermally sintered ink. Different degradation mechanisms were detected in the devices with a flash-sintered back electrode. The P3HT:PCBM photoactive layer appears to be highly heat-sensitive and turned out to be severely damaged by the high temperatures generated in the silver layer during the sintering. In addition, UV-induced photochemical degradation of the functional materials was identified as another possible source of performance deterioration in the devices with grid-based electrodes. Reducing the light intensity does not provide a proper solution because in this case the Ag electrode is not sintered sufficiently. For both types of devices, with full-area and grid-based electrodes, these problems could be solved by excluding the short wavelength contribution from the flash light spectrum using a filter. Optimized sintering parameters allowed manufacture of OPV devices with performance equal to those of the reference devices. Photonic flash sintering of the top electrode in organic solar cells was demonstrated for the first time. It reveals the great potential of this sintering method for the future roll-to-roll manufacturing of organic solar cells from solution. PMID:26704172

  13. Photonic Flash Sintering of Ink-Jet-Printed Back Electrodes for Organic Photovoltaic Applications.

    PubMed

    Polino, Giuseppina; Shanmugam, Santhosh; Bex, Guy J P; Abbel, Robert; Brunetti, Francesca; Di Carlo, Aldo; Andriessen, Ronn; Galagan, Yulia

    2016-01-27

    A study of the photonic flash sintering of a silver nanoparticle ink printed as the back electrode for organic solar cells is presented. A number of sintering settings with different intensities and pulse durations have been tested on both full-area and grid-based silver electrodes, using the complete emission spectrum of the flash lamps from UV-A to NIR. However, none of these settings was able to produce functional devices with performances comparable to those of reference cells prepared using thermally sintered ink. Different degradation mechanisms were detected in the devices with a flash-sintered back electrode. The P3HT:PCBM photoactive layer appears to be highly heat-sensitive and turned out to be severely damaged by the high temperatures generated in the silver layer during the sintering. In addition, UV-induced photochemical degradation of the functional materials was identified as another possible source of performance deterioration in the devices with grid-based electrodes. Reducing the light intensity does not provide a proper solution because in this case the Ag electrode is not sintered sufficiently. For both types of devices, with full-area and grid-based electrodes, these problems could be solved by excluding the short wavelength contribution from the flash light spectrum using a filter. Optimized sintering parameters allowed manufacture of OPV devices with performance equal to those of the reference devices. Photonic flash sintering of the top electrode in organic solar cells was demonstrated for the first time. It reveals the great potential of this sintering method for the future roll-to-roll manufacturing of organic solar cells from solution.

  14. Plasmon-enhanced charge carrier generation in organic photovoltaic films using silver nanoprisms.

    PubMed

    Kulkarni, Abhishek P; Noone, Kevin M; Munechika, Keiko; Guyer, Samuel R; Ginger, David S

    2010-04-14

    We use photoinduced absorption spectroscopy to measure long-lived photogenerated charge carriers in optically thin donor/acceptor conjugated polymer blend films near plasmon-resonant silver nanoprisms. We measure up to 3 times more charge generation, as judged by the magnitude of the polaron absorption signal, in 35 nm thin blend films of poly(3-hexylthiophene)/phenyl-C(61)-butyric acid methyl ester on top of films of silver nanoprisms (approximately 40-100 nm edge length). We find that the polaron yields increase linearly with the total sample extinction. These excitation enhancements could in principle be used to increase photocurrents in thin organic solar cells.

  15. The emerging multiple metal nanostructures for enhancing the light trapping of thin film organic photovoltaic cells.

    PubMed

    Choy, Wallace C H

    2014-10-18

    Recently, various metal nanostructures have been introduced into organic solar cells (OSCs) for performance enhancement. Here, we review the recent progress in OSCs incorporated with multiple metal nanostructures including various metal nanopatterns and metal nanomaterials. Multiple physical effects arise from these incorporated nanostructures, which require careful distinction. Changes induced by the metal nanostructures are examined in detail from the optical and electrical aspects. With the comprehensive understanding of the physical mechanisms for various metal nanostructures, further improvement in device performance and emerging applications can be expected for the new class of nanostructure-incorporated OSCs.

  16. Synthesis and functionalization of gold nanorods for probing plasmonic enhancement mechanisms in organic photovoltaic active layers

    NASA Astrophysics Data System (ADS)

    Wadams, Robert Christopher

    DNA nanotechnology is one of the most flourishing interdisciplinary research fields. Through the features of programmability and predictability, DNA nanostructures can be designed to self-assemble into a variety of periodic or aperiodic patterns of different shapes and length scales, and more importantly, they can be used as scaffolds for organizing other nanoparticles, proteins and chemical groups. By leveraging these molecules, DNA nanostructures can be used to direct the organization of complex bio-inspired materials that may serve as smart drug delivery systems and in vitro or in vivo bio-molecular computing and diagnostic devices. In this dissertation I describe a systematic study of the thermodynamic properties of complex DNA nanostructures, including 2D and 3D DNA origami, in order to understand their assembly, stability and functionality and inform future design endeavors. It is conceivable that a more thorough understanding of DNA self-assembly can be used to guide the structural design process and optimize the conditions for assembly, manipulation, and functionalization, thus benefiting both upstream design and downstream applications. As a biocompatible nanoscale motif, the successful integration, stabilization and separation of DNA nanostructures from cells/cell lysate suggests its potential to serve as a diagnostic platform at the cellular level. Here, DNA origami was used to capture and identify multiple T cell receptor mRNA species from single cells within a mixed cell population. This demonstrates the potential of DNA nanostructure as an ideal nano scale tool for biological applications.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  18. Ferroelectric Thin-Film Capacitors As Ultraviolet Detectors

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1995-01-01

    Advantages include rapid response, solar blindness, and relative invulnerability to ionizing radiation. Ferroelectric capacitor made to function as photovoltaic detector of ultraviolet photons by making one of its electrodes semitransparent. Photovoltaic effect exploited more fully by making Schottky barrier at illuminated semitransparent-electrode/ferroelectric interface taller than Schottky barrier at other electrode/ferroelectric interface.

  19. External quantum efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell.

    PubMed

    Congreve, Daniel N; Lee, Jiye; Thompson, Nicholas J; Hontz, Eric; Yost, Shane R; Reusswig, Philip D; Bahlke, Matthias E; Reineke, Sebastian; Van Voorhis, Troy; Baldo, Marc A

    2013-04-19

    Singlet exciton fission transforms a molecular singlet excited state into two triplet states, each with half the energy of the original singlet. In solar cells, it could potentially double the photocurrent from high-energy photons. We demonstrate organic solar cells that exploit singlet exciton fission in pentacene to generate more than one electron per incident photon in a portion of the visible spectrum. Using a fullerene acceptor, a poly(3-hexylthiophene) exciton confinement layer, and a conventional optical trapping scheme, we show a peak external quantum efficiency of (109 ± 1)% at wavelength λ = 670 nanometers for a 15-nanometer-thick pentacene film. The corresponding internal quantum efficiency is (160 ± 10)%. Analysis of the magnetic field effect on photocurrent suggests that the triplet yield approaches 200% for pentacene films thicker than 5 nanometers. PMID:23599489

  20. π-conjugated donor-acceptor porphyrin copolymers for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Peng, Xiaobin; Huang, Yuying; Li, Lisheng; Cao, Yong

    2015-01-01

    Conjugated donor-acceptor (D-A) molecular structures play a very important role in the significant progress of organic photovotaics. However, the reports on conjugated D-A porphyrin polymers for organic solar cells are very limited. In this work, five conjugated D-A porphyrin copolymers PEZPEBTA(C12), PEZPEBT, PEZPEBTff, PEZPETPD(O), and PEZPETDPPT(O) were synthesized by Sonagashira coupling of a porphyrin donor unit with five typical acceptor units 2-dodecyl-2H-benzotriazole, benzo[1,2,5]thiadiazole, 5,6-difluoro-benzo[1,2,5]thiadiazole, 5-octyl-thieno[3,4-c]pyrrole-4,6-dione, and 3,6-bis-(thiophen-2-yl)-2,5-dioctyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione linked by ethynylene linkages, respectively. They possess excellent thermal stability with a decomposition temperature of around 400°C. All absorption spectra of the copolymers were significantly red shifted with enhanced Q bands at the near-infrared region both in solutions and in films due to the simultaneous introduction of ethynylene linkages and acceptor units, which make the polymer main chains coplanar and π-conjugated and enhance the intramolecular charge transfer. PEZPEBT and PEZPEBTff are electrochemically active in both the oxidation and reduction regions, while PEZPEBTA(C12), PEZPETPD(O), and PEZPETDPPT(O) show only oxidation peaks. Power conversion efficiencies of 0.12%, 0.41%, 0.26%, 0.19%, and 0.41% were achieved for the polymer solar cells based on PEZPEBTA(C12), PEZPEBT, PEZPEBTff, PEZPETPD(O), and PEZPETDPPT(O), respectively, under AM 1.5, 100 mW/cm2 with methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) (1:2, w/w) as the active layer in the presence of 3% pyridine.