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Heterojunction Solar Cells (heterojunction + solar_cell)
Kinds of Heterojunction Solar Cells Selected AbstractsNanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Xuan-Dung Dang Abstract Photoconductive atomic force microscopy is employed to study the nanoscale morphology and optoelectronic properties of bulk heterojunction solar cells based on small molecules containing a benzofuran substituted diketopyrrolopyrrole (DPP) core (3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione, DPP(TBFu)2, and [6,6],phenyl-C71 -butyric acid methyl ester (PC71BM), which were recently reported to have power conversion efficiencies of 4.4%. Electron and hole collection networks are visualized for blends with different donor:acceptor ratios. Formation of nanostructures in the blends leads to a higher interfacial area for charge dissociation, while maintaining bicontinuous collection networks; conditions that lead to the high efficiency observed in the devices. An excellent agreement between nanoscale and bulk open-circuit voltage measurements is achieved by surface modification of the indium tin oxide (ITO) substrate by using aminopropyltrimethoxysilane. The local open-circuit voltage is linearly dependent on the cathode work function. These results demonstrate that photoconductive atomic force microscopy coupled with surface modification of ITO substrate can be used to study nanoscale optoelectronic phenomena of organic solar cells. [source] Nanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Xuan-Dung Dang Abstract Photoconductive atomic force microscopy is employed to study the nanoscale morphology and optoelectronic properties of bulk heterojunction solar cells based on small molecules containing a benzofuran substituted diketopyrrolopyrrole (DPP) core (3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione, DPP(TBFu)2, and [6,6],phenyl-C71 -butyric acid methyl ester (PC71BM), which were recently reported to have power conversion efficiencies of 4.4%. Electron and hole collection networks are visualized for blends with different donor:acceptor ratios. Formation of nanostructures in the blends leads to a higher interfacial area for charge dissociation, while maintaining bicontinuous collection networks; conditions that lead to the high efficiency observed in the devices. An excellent agreement between nanoscale and bulk open-circuit voltage measurements is achieved by surface modification of the indium tin oxide (ITO) substrate by using aminopropyltrimethoxysilane. The local open-circuit voltage is linearly dependent on the cathode work function. These results demonstrate that photoconductive atomic force microscopy coupled with surface modification of ITO substrate can be used to study nanoscale optoelectronic phenomena of organic solar cells. [source] The Effect of Nanoparticle Shape on the Photocarrier Dynamics and Photovoltaic Device Performance of Poly(3-hexylthiophene):CdSe Nanoparticle Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Smita Dayal Abstract The charge separation and transport dynamics in CdSe nanoparticle:poly(3-hexylthiophene) (P3HT) blends are reported as a function of the shape of the CdSe-nanoparticle electron acceptor (dot, rod, and tetrapod). For optimization of organic photovoltaic device performance it is crucial to understand the role of various nanostructures in the generation and transport of charge carriers. The sample processing conditions are carefully controlled to eliminate any processing-related effects on the carrier generation and on device performance with the aim of keeping the conjugated polymer phase constant and only varying the shape of the inorganic nanoparticle acceptor phase. The electrodeless, flash photolysis time-resolved microwave conductivity (FP-TRMC) technique is used and the results are compared to the efficiency of photovoltaic devices that incorporate the same active layer. It is observed that in nanorods and tetrapods blended with P3HT, the high aspect ratios provide a pathway for the electrons to move away from the dissociation site even in the absence of an applied electric field, resulting in enhanced carrier lifetimes that correlate to increased efficiencies in devices. The processing conditions that yield optimum performance in high aspect ratio CdSe nanoparticles blended with P3HT result in poorly performing quantum dot CdSe:P3HT devices, indicating that the latter devices are inherently limited by the absence of the dimensionality that allows for efficient, prolonged charge separation at the polymer:CdSe interface. [source] P3HT/PCBM Bulk Heterojunction Solar Cells: Impact of Blend Composition and 3D Morphology on Device PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Svetlana S. van Bavel Abstract The performance of polymer solar cells (PSC) strongly depends on the 3D morphological organization of the donor and acceptor compounds within the bulk heterojunction active layer. The technique of electron tomography is a powerful tool for studying 3D morphology of the layers composed of poly(3-hexylthiophene) (P3HT) and a fullerene derivative ([6,6]-phenyl-C61-butyric acid methyl ester; PCBM), especially to quantify the amount and distribution of fibrillar P3HT nanocrystals throughout the volume of the active layer. In this study, electron tomography is used to characterize P3HT/PCBM layers with different blend compositions, both before and after thermal annealing. The power conversion efficiency of the corresponding PSCs is strongly dependent on the overall crystallinity of P3HT and the way P3HT crystals are distributed throughout the thickness of the active layer. [source] Near IR Sensitization of Organic Bulk Heterojunction Solar Cells: Towards Optimization of the Spectral Response of Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Markus Koppe Abstract The spectroscopic response of a poly(3-hexylthiophene)/[6,6]-phenyl-C61 -butyric acid methyl ester (P3HT/PCBM)-based bulk heterojunction solar cell is extended into the near infrared region (NIR) of the spectrum by adding the low bandgap polymer 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] to the blend. The dominant mechanism behind the enhanced photosensitivity of the ternary blend is found to be a two-step process: first, an ultrafast and efficient photoinduced charge transfer generates positive charges on P3HT and PCPDTBT and a negative charge on PCBM. In a second step, the positive charge on PCPDTBT is transferred to P3HT. Thus, P3HT serves two purposes. On the one hand it is involved in the generation of charge carriers by the photoinduced electron transfer to PCBM, and, on the other hand, it forms the charge transport matrix for the positive carriers transferred from PCPDTBT. Other mechanisms, such as energy transfer or photoinduced charge transfer directly between the two polymers, are found to be absent or negligible. [source] High-Performance Air-Processed Polymer,Fullerene Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Chang-Yong Nam Abstract High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen charge trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an ,4,nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface. [source] Flexible Organic Solar Cells: Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Mater. The inside cover of this issue illustrates the fabrication of lightweight and flexible organic solar cells, developed by B. Walker et al. on page 3063, from a solution of fullerene and diketopyrrolopyrrole-based materials. The texture of the organic film on the substrate was taken from an atomic force microscope phase image of the high performance device (4.4% power conversion efficiency), showing the phase separation behavior of the two molecular semiconducting materials. [source] Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Bright Walker Abstract Research relating to organic solar cells based on solution-processed, bulk heterojunction (BHJ) films has been dominated by polymeric donor materials, as they typically have better film-forming characteristics and film morphology than their small-molecule counterparts. Despite these morphological advantages, semiconducting polymers suffer from synthetic reproducibility and difficult purification procedures, which hinder their commercial viability. Here, a non-polymeric, diketopyrrolopyrrole-based donor material that can be solution processed with a fullerene acceptor to produce good quality films is reported. Thermal annealing leads to suitable phase separation and material distribution so that highly effective BHJ morphologies are obtained. The frontier orbitals of the material are well aligned with those of the fullerene acceptor, allowing efficient electron transfer and suitable open-circuit voltages, leading to power conversion efficiencies of 4.4,±,0.4% under AM1.5G illumination (100,mW cm,2). Small molecules can therefore be solution processed to form high-quality BHJ films, which may be used for low-cost, flexible organic solar cells. [source] Material Solubility-Photovoltaic Performance Relationship in the Design of Novel Fullerene Derivatives for Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Pavel A. Troshin Abstract The preparation of 27 different derivatives of C60 and C70 fullerenes possessing various aryl (heteroaryl) and/or alkyl groups that are appended to the fullerene cage via a cyclopropane moiety and their use in bulk heterojunction polymer solar cells is reported. It is shown that even slight variations in the molecular structure of a compound can cause a significant change in its physical properties, in particular its solubility in organic solvents. Furthermore, the solubility of a fullerene derivative strongly affects the morphology of its composite with poly(3-hexylthiophene), which is commonly used as active material in bulk heterojunction organic solar cells. As a consequence, the solar cell parameters strongly depend on the structure and the properties of the fullerene-based material. The power conversion efficiencies for solar cells comprising these fullerene derivatives range from negligibly low (0.02%) to considerably high (4.1%) values. The analysis of extensive sets of experimental data reveals a general dependence of all solar cell parameters on the solubility of the fullerene derivative used as acceptor component in the photoactive layer of an organic solar cell. It is concluded that the best material combinations are those where donor and acceptor components are of similar and sufficiently high solubility in the solvent used for the deposition of the active layer. [source] Organic Electronics: Improved Performance of Polymer Bulk Heterojunction Solar Cells Through the Reduction of Phase Separation via Solvent Additives (Adv. Mater.ADVANCED MATERIALS, Issue 8 20108/2010) The fabrication of bulk heterojunction organic solar cells from solution-casting techniques using low-cost materials makes them a promising new technology for converting sunlight into electricity. T.-Q. Nguyen, G. C. Bazan, et al. report on p. E63 that undesirable large-scale aggregation and phase separation that may arise during deposition can be reduced by incorporating a small amount of a well-chosen solvent additive. [source] Bulk Heterojunction Solar Cells: The Role of Processing in the Fabrication and Optimization of Plastic Solar Cells (Adv. Mater.ADVANCED MATERIALS, Issue 14-15 200915/2009) Alan Heeger and co-workers report on page 1521 on the role of processing methodology in the fabrication and optimization of bulk heterojunction (BHJ) ,plastic' solar cells. Several techniques that have recently been used to optimize the BHJ nanomorphology are discussed and compared and some insights are given into the mechanisms behind these various techniques. The cover image depicts a multilayer solar cell ribbon along with the polymer, fullerene, and solvent additive, which were used to fabricate a low bandgap polymer solar cell with greater than 5% power conversion efficiency. [source] Planarized Star-Shaped Oligothiophenes as a New Class of Organic Semiconductors for Heterojunction Solar Cells,ADVANCED MATERIALS, Issue 22 2003R. de Bettignies Although compounds 1 and 2 (see Figure) have comparable conjugation lengths, the characterization of vacuum evaporated thin solid films shows that the star-shaped geometry of compound 1 favors a preferential horizontal orientation of the molecules onto the surface of the substrate, which results in a increase of the efficiency of the corresponding heterojunction solar cells under white-light illumination by a factor of 20. [source] Near IR Sensitization of Organic Bulk Heterojunction Solar Cells: Towards Optimization of the Spectral Response of Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Markus Koppe Abstract The spectroscopic response of a poly(3-hexylthiophene)/[6,6]-phenyl-C61 -butyric acid methyl ester (P3HT/PCBM)-based bulk heterojunction solar cell is extended into the near infrared region (NIR) of the spectrum by adding the low bandgap polymer 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] to the blend. The dominant mechanism behind the enhanced photosensitivity of the ternary blend is found to be a two-step process: first, an ultrafast and efficient photoinduced charge transfer generates positive charges on P3HT and PCPDTBT and a negative charge on PCBM. In a second step, the positive charge on PCPDTBT is transferred to P3HT. Thus, P3HT serves two purposes. On the one hand it is involved in the generation of charge carriers by the photoinduced electron transfer to PCBM, and, on the other hand, it forms the charge transport matrix for the positive carriers transferred from PCPDTBT. Other mechanisms, such as energy transfer or photoinduced charge transfer directly between the two polymers, are found to be absent or negligible. [source] Nanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Xuan-Dung Dang Abstract Photoconductive atomic force microscopy is employed to study the nanoscale morphology and optoelectronic properties of bulk heterojunction solar cells based on small molecules containing a benzofuran substituted diketopyrrolopyrrole (DPP) core (3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione, DPP(TBFu)2, and [6,6],phenyl-C71 -butyric acid methyl ester (PC71BM), which were recently reported to have power conversion efficiencies of 4.4%. Electron and hole collection networks are visualized for blends with different donor:acceptor ratios. Formation of nanostructures in the blends leads to a higher interfacial area for charge dissociation, while maintaining bicontinuous collection networks; conditions that lead to the high efficiency observed in the devices. An excellent agreement between nanoscale and bulk open-circuit voltage measurements is achieved by surface modification of the indium tin oxide (ITO) substrate by using aminopropyltrimethoxysilane. The local open-circuit voltage is linearly dependent on the cathode work function. These results demonstrate that photoconductive atomic force microscopy coupled with surface modification of ITO substrate can be used to study nanoscale optoelectronic phenomena of organic solar cells. [source] Nanostructure and Optoelectronic Characterization of Small Molecule Bulk Heterojunction Solar Cells by Photoconductive Atomic Force MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Xuan-Dung Dang Abstract Photoconductive atomic force microscopy is employed to study the nanoscale morphology and optoelectronic properties of bulk heterojunction solar cells based on small molecules containing a benzofuran substituted diketopyrrolopyrrole (DPP) core (3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione, DPP(TBFu)2, and [6,6],phenyl-C71 -butyric acid methyl ester (PC71BM), which were recently reported to have power conversion efficiencies of 4.4%. Electron and hole collection networks are visualized for blends with different donor:acceptor ratios. Formation of nanostructures in the blends leads to a higher interfacial area for charge dissociation, while maintaining bicontinuous collection networks; conditions that lead to the high efficiency observed in the devices. An excellent agreement between nanoscale and bulk open-circuit voltage measurements is achieved by surface modification of the indium tin oxide (ITO) substrate by using aminopropyltrimethoxysilane. The local open-circuit voltage is linearly dependent on the cathode work function. These results demonstrate that photoconductive atomic force microscopy coupled with surface modification of ITO substrate can be used to study nanoscale optoelectronic phenomena of organic solar cells. [source] High-Performance Air-Processed Polymer,Fullerene Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Chang-Yong Nam Abstract High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen charge trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an ,4,nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface. [source] Scanning Kelvin Probe Microscopy on Bulk Heterojunction Polymer BlendsADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Klára Maturová Abstract Here, correlated AFM and scanning Kelvin probe microscopy measurements with sub-100,nm resolution on the phase-separated active layer of polymer-fullerene (MDMO-PPV:PCBM) bulk heterojunction solar cells in the dark and under illumination are described. Using numerical modeling a fully quantitative explanation for the contrast and shifts of the surface potential in dark and light is provided. Under illumination an excess of photogenerated electrons is present in both the donor and acceptor phases. From the time evolution of the surface potential after switching off the light the contributions of free and trapped electrons can be identified. Based on these measurements the relative 3D energy level shifts of the sample are calculated. Moreover, by comparing devices with fine and coarse phase separation, it is found that the inferior performance of the latter devices is, at least partially, due to poor electron transport. [source] Bimolecular Crystals of Fullerenes in Conjugated Polymers and the Implications of Molecular Mixing for Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009A. C. Mayer The performance of polymer:fullerene bulk heterojunction solar cells is heavily influenced by the interpenetrating nanostructure formed by the two semiconductors because the size of the phases, the nature of the interface, and molecular packing affect exciton dissociation, recombination, and charge transport. Here, X-ray diffraction is used to demonstrate the formation of stable, well-ordered bimolecular crystals of fullerene intercalated between the side-chains of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2- b]thiophene. It is shown that fullerene intercalation is general and is likely to occur in blends with both amorphous and semicrystalline polymers when there is enough free volume between the side-chains to accommodate the fullerene molecule. These findings offer explanations for why luminescence is completely quenched in crystals much larger than exciton diffusion lengths, how the hole mobility of poly(2-methoxy-5-(3,,7,-dimethyloxy)-p-phylene vinylene) increases by over 2 orders of magnitude when blended with fullerene derivatives, and why large-scale phase separation occurs in some polymer:fullerene blend ratios while thermodynamically stable mixing on the molecular scale occurs for others. Furthermore, it is shown that intercalation of fullerenes between side chains mostly determines the optimum polymer:fullerene blending ratios. These discoveries suggest a method of intentionally designing bimolecular crystals and tuning their properties to create novel materials for photovoltaic and other applications. [source] For the Bright Future,Bulk Heterojunction Polymer Solar Cells with Power Conversion Efficiency of 7.4%ADVANCED MATERIALS, Issue 20 2010Yongye Liang The photovoltaic performance of polymer bulk heterojunction solar cells is studied systematically. Using a new benzodithiophene polymer (PTB7) and PC71BM (see figure) a power conversion efficiency of 7.4% has been achieved in PTB7/PC71BM-blend film, indicating a great potential and bright future for polymer solar cells (FF,=,fill factor, PCE,;=,power-conversion efficiency). [source] A New Poly(thienylenevinylene) Derivative with High Mobility and Oxidative Stability for Organic Thin-Film Transistors and Solar CellsADVANCED MATERIALS, Issue 27 2009Bogyu Lim A novel thiophene-thienylenevinylene copolymer is synthesized and evaluated for use in organic field-effect transistors and organic solar cells. PETV12T shows good solution processability and high structural organization after annealing. Organic thin-film transistors based on the polymer exhibit high mobility and a high resistance to oxidation. In addition, PETV12T shows potential as an electron donor in bulk heterojunction solar cells. [source] Planarized Star-Shaped Oligothiophenes as a New Class of Organic Semiconductors for Heterojunction Solar Cells,ADVANCED MATERIALS, Issue 22 2003R. de Bettignies Although compounds 1 and 2 (see Figure) have comparable conjugation lengths, the characterization of vacuum evaporated thin solid films shows that the star-shaped geometry of compound 1 favors a preferential horizontal orientation of the molecules onto the surface of the substrate, which results in a increase of the efficiency of the corresponding heterojunction solar cells under white-light illumination by a factor of 20. [source] Role of the work function of transparent conductive oxide on the performance of amorphous/crystalline silicon heterojunction solar cells studied by computer simulationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2008L. Zhao Abstract The role of the work function of transparent conductive oxide (WTCO) on the performance of amorphous/crystalline silicon heterojunction (SHJ) solar cells was investigated in detail with other various parameters by utilizing AFORS-HET software as a numerical computer simulation tool. The results for SHJ solar cells based on p-type and n-type substrates were demonstrated and analyzed comparatively with or without the insertion of the intrinsic amorphous silicon layer between the doped amorphous emitter and the crystalline base. It was indicated that there was an optimized threshold thickness of the emitter for the solar cells to obtain the best performance for any given WTCO and the doping concentration of the emitter. Thus, design criteria of TCO/emitter for the practical SHJ solar cells were provided. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] New routes to sustainable photovoltaics: evaluation of Cu2ZnSnS4 as an alternative absorber materialPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008Jonathan J. Scragg Abstract Thin film heterojunction solar cells based on chalcopyrites such as Cu(In,Ga)Se2 have achieved impressive efficiencies. However concern about the long term sustainability of photovoltaics based on scarce or expensive raw materials has prompted the search for alternative absorber materials. In this work, films of the p-type absorber Cu2ZnSnS4 (CZTS) were prepared by electroplating metallic precursors sequentially onto a molybdenum-coated glass substrate followed by an nealing in a sulfur atmosphere. The polycrystalline CZTS films were characterized by photoelectrochemical methods, which showed films were p-type with doping densities of the order of 1016 cm,3 and a band gap of 1.49 eV, close to the optimum value for terrestrial solar energy conversion. Preliminary results obtained for solar cells fabricated with this material are promising. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Plasmas for texturing, cleaning, and deposition: towards a one pump down process for heterojunction solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Mario Moreno Abstract Low temperature plasma deposition of a-Si:H thin films has emerged as a promising alternative for high efficiency hetero junction (HJ) solar cells. In this work we study plasma processes for texturing and cleaning c-Si wafers pursuing a low cost dry fabrication process of HJ solar cells. We have studied two independent plasma processes: i) Texturing of c-Si wafers using SF6 - O2 plasmas in a RIE system, in order to reduce the surface reflectance and therefore improve the light trapping. The effects of the RF power and gas ratio on the c-Si surface texture have been studied in detail. Highly textured surfaces, with very low reflectance values (around 6% in the range of 300 , 1000 nm) have been achieved. ii) Etching of the native oxide and passivation of the c-Si surface by plasma, in a standard RF PECVD system. We used SiF4 plasma with optimized conditions for an efficient native oxide removal, and without breaking the vacuum, 40 nm of a-Si:H were deposited in order to passivate the c-Si surface. High effective lifetime values were obtained (,eff , 1.5 ms), providing high implicit open circuit voltages (Voc , 0.713 V) and low surface recombination velocities (Seff < 9 cm s -1). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of thin-film Cu(In,Ga)Se2 and CdTe solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2-3 2004A. Romeo Abstract Cu(In,Ga)Se2 and CdTe heterojunction solar cells grown on rigid (glass) or flexible foil substrates require p -type absorber layers of optimum optoelectronic properties and n -type wide-bandgap partner layers to form the p,n junction. Transparent conducting oxide and specific metal layers are used for front and back electrical contacts. Efficiencies of solar cells depend on various deposition methods as they control the optoelectronic properties of the layers and interfaces. Certain treatments, such as addition of Na in Cu(In,Ga)Se2 and CdCl2 treatment of CdTe have a direct influence on the electronic properties of the absorber layers and efficiency of solar cells. Processes for the development of superstrate and substrate solar cells are reviewed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Role of the CdS buffer layer as an active optical element in Cu(In,Ga)Se2 thin-film solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2002Kay Orgassa ZnO/CdS/Cu(In,Ga)Se2 (CIGS) thin-film heterojunction solar cells with CdS buffer layers of thicknesses between 0 and 85,nm are characterized by current,voltage, quantum efficiency, and optical reflection measurements. We investigate the correlation between the short-circuit current density and the CdS layer thickness, focusing on the counteracting effects of light absorption and reduced optical reflection induced by the CdS layer. Both effects almost compensate each other for CdS layer thicknesses between 0 and 40,nm. Thus, an optimization of the short-circuit current density is not achieved by omitting the CdS layer, but rather by replacing the CdS buffer with an alternative buffer material with higher bandgap energy and optical constants similar to those of CdS. Copyright © 2002 John Wiley & Sons, Ltd. 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