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Photovoltaic Applications (photovoltaic + application)
Selected AbstractsPerylene,Oligothiophene,Perylene Triads for Photovoltaic ApplicationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2005Jens Cremer Abstract A series of novel acceptor,donor,acceptor triad systems, consisting of head-to-tail-coupled oligo(3-hexylthiophene)s integrated between two terminal perylenemonoimides are described. These hybrid molecules, which differ by the length of the oligothiophene units from a quaterthiophene up to a dodecithiophene were synthesized by an effective palladium-catalyzed Ullmann-type homo-coupling reaction in good yields. The optical and electrochemical properties of these compounds were determined, and on the basis of this series structure-property relationships have been established which provide vital information for the fabrication of the corresponding photovoltaic devices. Because the synthesized perylenyl-oligothiophenes distinguish themselves by a high absorption between 300 and 550 nm and an almost complete fluorescence quenching of the perylene acceptor, they meet the requirements for organic solar cells. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Copolymers of Cyclopentadithiophene and Electron-Deficient Aromatic Units Designed for Photovoltaic ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Johan C. Bijleveld Abstract Alternating copolymers based on cyclopentadithiophene (CPDT) and five different electron-deficient aromatic units with reduced optical band gaps are synthesized via Suzuki coupling. All polymers show a significant photovoltaic response when mixed with a fullerene acceptor. The frontier orbital levels of the new polymers are designed to minimize energy losses by increasing the open-circuit voltage with respect to the optical band gap, while maintaining a high coverage of the absorption with the solar spectrum. The best cells are obtained for a copolymer of CPDT and benzooxadiazole (BO) with a band gap of 1.47,eV. This cell gives a short-circuit current of 5.4,mA cm,2, an open-circuit voltage of 0.78,V, and a fill factor of 0.6, resulting in a power conversion efficiency of about 2.5%. [source] Infiltrating Semiconducting Polymers into Self-Assembled Mesoporous Titania Films for Photovoltaic Applications,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2003K.M. Coakley Abstract Interpenetrating networks of organic and inorganic semiconductors are attractive for photovoltaic cells because electron transfer between the two semiconductors splits excitons. In this paper we show that films of titania with a uniform distribution of pore sizes can be made using a block copolymer as a structure-directing agent, and that 33,% of the total volume of the film can be filled with a semiconducting polymer. [source] A New Supramolecular Route for Using Rod-Coil Block Copolymers in Photovoltaic ApplicationsADVANCED MATERIALS, Issue 6 2010Nicolas Sary A new polymer blend formed by poly(3-hexylthiophene)-poly(4-vinylpyridine) (P3HT- P4VP) block copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is reported. The P4VP and PCBM are mixed together by weak supramolecular interactions, and the resulting materials exhibit microphase separated morphologies of electron-donor and electron-acceptor rich domains. The properties of the blend, used in photovoltaic devices as active layers, are also discussed. [source] CuInS2 Films for Photovoltaic Applications Deposited by a Low-Cost Method.CHEMINFORM, Issue 37 2006T. Todorov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Highly Emissive and Electrochemically Stable Thienylene Vinylene Oligomers and Copolymers: An Unusual Effect of Alkylsulfanyl SubstituentsADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Shehzad Jeeva Abstract The synthesis, unexpected efficient photoluminescence, and reversible electrochemical p- and n-doping of new conjugated thienylene vinylene materials functionalized with alkylsulfanyl substituents poly(trithienylene vinylene) (PTTV) and poly(dithienylvinyl- co -benzothiadiazole) (PDTVB) along with dithienylvinylene-based oligomers is reported. The materials are studied by thermal and X-ray diffraction analysis, optical spectroscopy, cyclic voltammetry, and spectroelectrochemistry. Organic field-effect transistors (OFETs) are fabricated with PTTV and PDTVB. The polymers, prepared by Stille polycondensation, exhibit good thermal stability and a photoluminescent quantum yield in the range 34%,68%. Low bandgaps (1.5,1.8,eV), estimated by optical and electrochemical measurements along with high stability of both redox states, suggest that these structures are promising materials for photovoltaic applications. OFETs fabricated with PDTVB reveal a hole mobility of 7,×,10,3,cm2 V,1 s,1 with on/off ratio 105, which are comparatively high values for completely amorphous polymer semiconductors. [source] Polymer Photovoltaic Cells Based on Solution-Processable Graphene and P3HTADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Qian Liu Abstract A soluble graphene, which has a one-atom thickness and a two-dimensional structure, is blended with poly(3-hexylthiophene) (P3HT) and used as the active layer in bulk heterojunction (BHJ) polymer photovoltaic cells. Adding graphene to the P3HT induces a great quenching of the photoluminescence of the P3HT, indicating a strong electron/energy transfer from the P3HT to the graphene. In the photovoltaic devices with an ITO/PEDOT:PSS/P3HT:graphene/LiF/Al structure, the device efficiency increases first and then decreases with the increase in the graphene content. The device containing only 10,wt % of graphene shows the best performance with a power conversion efficiency of 1.1%, an open-circuit voltage of 0.72,V, a short-circuit current density of 4.0,mA cm,2, and a fill factor of 0.38 under simulated AM1.5G conditions at 100,mW cm,2 after an annealing treatment at 160,°C for 10,min. The annealing treatment at the appropriate temperature (160,°C, for example) greatly improves the device performance; however, an annealing at overgenerous conditions such as at 210,°C results in a decrease in the device efficiency (0.57%). The morphology investigation shows that better performance can be obtained with a moderate content of graphene, which keeps good dispersion and interconnection. The functionalized graphene, which is cheap, easily prepared, stable, and inert against the ambient conditions, is expected to be a competitive candidate for the acceptor material in organic photovoltaic applications. [source] Synthesis and characterization of cyclopentadithiophene-based low bandgap copolymers containing electron-deficient benzoselenadiazole derivatives for photovoltaic devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010In Hwan Jung Abstract We have synthesized two cyclopentadithiophene (CDT)-based low bandgap copolymers, poly[(4,4-bis(2-ethyl-hexyl)-4H -cyclopenta[2,1- b:3,4- b,]dithiophene-2,6-diyl)- alt -(benzo[c][1,2,5]selenadiazole-4,7-diyl)] (PCBSe) and poly[(4,4-bis(2-ethyl-hexyl)-4H -cyclopenta[2,1- b:3,4- b,]dithiophene-2,6-diyl)- alt -(4,7-dithiophen-2-yl-benzo[c][1,2,5]selenadiazole-5,5,-diyl)] (PCT2BSe), for use in photovoltaic applications. Through the internal charge transfer interaction between the electron-donating CDT unit and the electron-accepting benzoselenadiazole, we realized exceedingly low bandgap polymers with bandgaps of 1.37,1.46 eV. The UV,vis absorption maxima of PCT2BSe were subjected to larger hypsochromic shifts than those of PCBSe, because of the distorted electron donor,acceptor (D,A) structures of the PCT2BSe backbone. These results were supported by the calculations of the D,A complex using the ab initio Hartree-Fock method with a split-valence 6-31G* basis set. However, PCT2BSe exhibited a better molar absorption coefficient in the visible region, which can lead to more efficient absorption of sunlight. As a result, PCT2BSe blended with [6,6]-phenyl-C61 -butyric acid methyl ester (PC61BM) exhibited a better photovoltaic performance than PCBSe because of the larger spectral overlap integral with respect to the solar spectrum. Furthermore, when the polymers were blended with PC71BM, PCT2BSe showed the best performance, with an open circuit voltage of 0.55 V, a short-circuit current of 6.63 mA/cm2, and a power conversion efficiency of 1.34% under air mass 1.5 global illumination conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1423,1432, 2010 [source] Preparation and characterization of pulse electrodeposited GaAs filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006K. R. Murali Abstract GaAs is a III,V compound possessing high mobility and a direct band gap of 1.43 eV, making it a very suitable candidate for photovoltaic applications. Thin GaAs films were prepared by plating an aqueous solution containing GaCl3 and As2O3 at a pH of 2 and at room temperature. The current density was kept at 50 mA cm,2 and the duty cycle was varied in the range 10,50%. The films were deposited on titanium, nickel and tin oxide coated glass substrates. Films exhibited polycrystalline nature with peaks corresponding to single-phase GaAs. Optical absorption measurements indicated a direct band gap of 1.40 eV. Atomic force microscope measurements indicated uniform coverage with large crystallites for the films deposited at higher duty cycles. Photoelectrochemical cells were made using the films as photoelectrodes and graphite as counter electrode in 1 M polysulphide electrolyte. At 60 mW cm,2 illumination, an open-circuit voltage of 0.5 V and a short-circuit current density of 5.0 mA cm,2 were observed for the films deposited at a duty cycle of 50%. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Donor,acceptor nanocomposite structures for organic photovoltaic applicationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009Konstantinos Fostiropoulos Abstract We investigated the effect of substrate temperature TS on the growth of 80,nm donor,acceptor nanocomposite (DAN) layers consisting of co-evaporated Zn-phthalocyanine (ZnPc) and C60 as absorber materials in organic solar cells. High temperature devices show lower series resistances RS but also reduced VOC. Both effects are diminished when the upper 20,nm of the blend are deposited at room temperature (RT). Moreover, the temperature profile improves the photocurrent density JSC. Best efficiencies (up to 2.1%) were achieved applying a 90,°C/RT profile. Transmission electron microscopy studies on the corresponding DAN revealed the temperature-dependent formation of crystalline C60 phases (already at low TS) and crystalline ZnPc phases (at highest TS). The strong phase separation at 90,°C results in less compact and mechanical unstable films. Such devices exhibit low parallel resistance RP. When the cold cover layer is applied RP doubles. [source] Aligned microcrystalline silicon nanorods prepared by glancing angle hotwire chemical vapor deposition for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Yanhong Ma Abstract Aligned Si nanorods (SiNRs) were prepared by hot wire chemical vapor deposition (HWCVD) with the glancing angle incident flux. The morphologies of SiNRs are pressure dependent. Crystallized SiNRs were achieved under a substrate temperature of 140 °C with H dilution. The optical and electrical properties of SiNRs were investigated. In a first step, a radial p-n junction solar cell with core-shell structure was prepared by depositing a-Si layer on the SiNRs. The hybrid solar cells were fabricated by spin coating 3-hexylthiophene (P3HT) into the SiNRs arrays. The P3HT shows well penetration into the SiNRs. The quenching of the PL intensity of P3HT/SiNRs indicates an effective electron transfer from P3HT to SiNRs. The hybrid solar cell with the structure of metal grids/ITO/P3HT/SiNRs/c-Si/Al shows a power conversion efficiency of 0.2% under AM 1.5 illumination. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical and structural properties of p -type nanocrystalline silicon grown by LEPECVD for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Gabriel Micard Abstract p-doped hydrogenated nanocrystalline silicon (p-nc-Si:H) is one of the most critical layers in thin film silicon solar cells. LEPECVD is a new technique for the growth of nc-Si at high growth rate without compromising the layer quality, using a dense but low energy plasma. Thin p-nc-Si:H layers are grown on glass and ZnO:Al coated glass and their structural and electrical properties are investigated as a function of the silane dilution (d) and of the doping ratio (DR). The influence of the substrate on the structural properties is investigated and discussed. The incubation layer is clearly observed on both substrate types and its thickness is estimated. LEPECVD distinguishes itself from other high growth rate methods by a very low impurity distribution coefficient to obtain a comparable conductivity and boron density. The conduction path is shown to be dependent on the density of boron in the layer while a significant decrease of conductivity at high DR is not observed in the studied range (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Amorphous silicon-based multilayers for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010M. Zeman Abstract Multilayer (ML) structures were fabricated by alternating deposition of hydrogenated amorphous silicon (a-Si:H) and amorphous silicon nitride (a-SiNx:H) using plasma enhanced chemical vapour deposition. The ML structures were grown with and without hydrogen dilution of the source gas mixture. A blue shift of the absorption spectra was observed upon reduction of the a-Si:H thickness below 5 nm. Hydrogen dilution was found to improve the abruptness of the interfaces between subsequent a-Si:H and a-SiNx:H layers to below 1 nm. In order to investigate the potential of a-Si:H based ML structures as absorbers in solar cells and to study transport perpendicular to the interfaces, we have incorporated ML absorbers in a single junction p-i-n solar cell. We have determined the J-V characteristics and the external quantum efficiency of solar cells with a 60 period ML absorber, composed of 5 nm thick a-Si:H and 1 nm thick a-SiNx:H layers. The solar cell with ML absorber operated at efficiency of 1.8% (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structure, chemistry and electrical properties of extended defects in crystalline silicon for photovoltaicsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2009M. Seibt Abstract The electronic properties of present-day multicrystalline silicon (mc-Si) materials for photovoltaic applications are strongly influenced by point defects, their mutual interaction and their interaction with dislocations and grain boundaries. This paper presents results from fundamental investigations of metal impurity interaction with extended defects, namely a small-angle grain boundary and bulk microdefects. It is shown that the distribution of copper silicide precipitates closely follows the density of bulk microdefects indicating the underlying physics of ,good' and ,bad' grains frequently observed in mc-Si. Co-precipitation of copper and nickel in the same samples leads to virtually the same distribution of multimetal silicide precipitates which according to light-beam induced current measurements show the same recombination activity as single-metal silicide particles. Transmission electron microscopy is used to show that for copper-rich and nickel-rich conditions two types of silicides co-exist, i.e. Cu3Si precipitates containing a small amount of nickel and NiSi2 precipitates containing some copper. Finally, phosphorus-diffusion gettering (PDG) is discussed as the main gettering process used in presentday silicon photovoltaics. Special emphasis is put on the effect of extended defects and their interaction with metal impurities on PDG kinetics. It is shown that different limiting processes will be simultaneously operative in mc-Si as a result of inhomogeneous bulk defect distributions (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Proceedings of the Conference on Photo-responsive MaterialsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2004Andrew Leitch The Conference on Photo-responsive Materials took place 25,29 February 2004 at Kariega Game Reserve, South Africa. It was focused primarily on III-nitrides (GaN, AlGaN, InGaN), SiC, ZnO and other wide gap materials, chalcopyrites such as CuInSe2 for photovoltaic applications, and novel photoresponsive materials including polymers. Material-related issues within the scope of the conference were crystal growth and epitaxy, characterisation (photoluminescence, DLTS, IR spectroscopy), defect-related studies, processing, and opto-electronic devices (modelling and novel structures). [source] Preface: phys. stat. sol. (c) 1/9PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2004Andrew Leitch The Conference on Photo-responsive Materials took place at the Kariega Game Reserve in the Eastern Cape, South Africa from 25,29 February 2004. More than 60 delegates from 12 different countries participated in the four-day event. The purpose of the conference was to bring together scientists working on various aspects of photo-responsive materials, so as to stimulate this important field of solid state physics in Southern Africa. As may be seen from the list of papers appearing in these proceedings, there was much interest in copper indium diselenide as a thin film material for photovoltaic applications. Also worth mentioning were the valuable contributions on ZnO, GaN and other materials that are currently attracting attention worldwide. The conference program allowed sufficient time for interaction and exchanging of views. Being in a game reserve in the heart of the beautiful Eastern Cape, delegates were also taken on game drives and had the opportunity of taking a river cruise up the Kariega River to view the majestic fish eagle. The members of the academic program committee were: Vivian Alberts (Rand Afrikaans University), Danie Auret (University of Pretoria), Darrell Comins (University of the Witwatersrand), and Reinhardt Botha and Andrew Leitch (University of Port Elizabeth). All papers appearing in these proceedings underwent a strict reviewing process separate from the conference. We express our appreciation to the referees for their diligence in this important task. The conference was organized by the Department of Physics at the University of Port Elizabeth, under the auspices of the Condensed Matter Physics and Materials Science (CMPMS) subgroup of the South African Institute of Physics. It was sponsored by EMF Limited (UK), Sensors Unlimited Inc. (USA), and Carl Zeiss (Pty) Ltd. Special thanks must go to Dr Eunete van Wyk for her professional assistance in the preparation of these proceedings. [source] High Productive Deposited Mo Layers for Back Ohmic Contacts of Solar CellsPLASMA PROCESSES AND POLYMERS, Issue S1 2009Jens-Peter Heinß Abstract In the paper, thin molybdenum (Mo) layers produced by magnetron sputtering [state of the art in production for photovoltaic applications (PV)] are compared with those produced by high-rate electron beam (EB) deposition technology. Stainless steel and borofloat glass served as substrate materials. Mo layers deposited by DC-magnetron sputtering were produced as a reference and investigated by analysis of structure and specific electrical resistance. Alternative layers prepared by high-rate EB-deposition with a rate up to 240,nm·s,1 were characterised by inquests of mechanical properties, sheet resistance and cell efficiency. A strong dependency of specific electrical resistance on residual gas conditions was determined. The specific electrical resistance dropped from 18 to 11,µ,·cm. Compactness of Mo layers increased with implementation of plasma activation. The layer formation became denser and comparable to the magnetron sputtered Mo layers. [source] Reactive ion etching of dielectrics and silicon for photovoltaic applicationsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2006Prakash N. K. Deenapanray Abstract This paper investigates the reactive ion etching of SiO2, Si3N4, and Si using CHF3/O2 plasma. In particular, we have characterized the time and rf power dependence of the carrier lifetimes in n- and p-type FZ Si. The time dependence of reactive ion etching (RIE) at different rf powers provide insight into the two competing processes of damage accumulation and damage removal in the near-surface region of the Si during plasma etching. The carrier lifetime, measured using the quasi-steady-state photoconductance (QSSPC) technique, has a quadratic dependence on the rf power, which can be related to changes in the dc self-bias generated by the plasma at different rf powers. The change in carrier lifetime is similar in both n- and p-type Si of the same doping concentration. Using this fact, together with the electronic properties of defects obtained by deep level transient spectroscopy (DLTS), we have modeled the injection-dependence of the measured carrier lifetimes using the Shockley,Read,Hall model. The isochronal annealing behavior of plasma etched Si has also been studied. Copyright © 2006 John Wiley & Sons, Ltd. [source] Characterization of optical collectors for concentration photovoltaic applicationsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2003I. Antón Abstract The design and characterization of the collector of a photovoltaic concentrator system is commonly carried out for a given receiver, the optical parameters of the collector being linked to it. This paper, which has substantial tutorial content, deals with the characterization of collectors for concentrator photovoltaic systems, independently of any receiver, and providing the necessary parameters for the design of a system. This strategy allows the parameters related to the collector and the receiver, which are usually manufactured by different industries, to be totally separated. It also allows the optical collectors coming from non-photovoltaic industries to be evaluated. The information that the mirror and lens manufacturers should provide for a photovoltaic concentrator application can be summarized under three characteristics: overall optical efficiency; light distribution; and acceptance angle. Theory, equipment, and procedures to carry out the optical characterization of the collectors are explained. Copyright © 2003 John Wiley & Sons, Ltd. [source] Experimental testing of a random medium optical model of porous silicon for photovoltaic applicationsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2001A. A. Abouelsaood We have developed a model for light propagation in porous silicon (PS) based on the theory of wave propagation in random media. The low porosity case is considered, with silicon being the host material assuming randomly distributed spherical voids as scattering particles. The specular and the diffuse part of the light could be determined and treated separately. The model is applied to the case in which porous silicon would be used as a diffuse back reflector in a thin-film crystalline silicon solar cell realized in an ultrathin (1,3,,m) epitaxially grown Si layer on PS. Three,layer structures (epi/PS/Si) have been fabricated by atmospheric pressure chemical vapor deposition (APCVD) of 150,1000 nm epitaxial silicon layers on silicon wafers of which 150,450 nm of the surface has been electrochemically etched. An excellent agreement is found between the experimentally measured reflection data in the 400,1000 nm wavelength range and those calculated using the proposed model. The values of the layer thickness agree, within a reasonable experimental error, with those obtained independently by cross,sectional transmission electron microscopy (XTEM) analysis. This provides an experimental verification of the random,medium approach to porous silicon in the low porosity case. The analysis shows that the epitaxial growth process has led to appreciable porosity decrease of an initially high,porosity layer from about 60% to 20,30%. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||||||||