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Cell Efficiency (cell + efficiency)
Selected AbstractsMOCVD as a dry deposition method of ZnSe buffers for Cu(In,Ga)(S,Se)2 solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2004Susanne Siebentritt Abstract ZnSe prepared by metal organic chemical vapor deposition is used as a buffer layer in Cu(In,Ga)(S,Se)2 solar cells without any utilization of wet chemistry. Cell efficiencies are as good as cells with the conventional CdS buffer. Stability of unencapsulated cells under damp heat conditions is somewhat lower for the alternative buffer. The first stages of photoassisted growth are studied. X-ray photoemission spectroscopy shows that a continuous layer is formed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Efficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series ResistanceADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Jonathan D. Servaites Abstract Here, means to enhance power conversion efficiency (PCE or ,) in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells by optimizing the series resistance (Rs),also known as the cell internal resistance,are studied. It is shown that current state-of-the-art BHJ OPVs are approaching the limit for which efficiency can be improved via Rs reduction alone. This evaluation addresses OPVs based on a poly(3-hexylthiophene):6,6-phenyl C61 -butyric acid methyl ester (P3HT:PCBM) active layer, as well as future high-efficiency OPVs (,,>,10%). A diode-based modeling approach is used to assess changes in Rs. Given that typical published P3HT:PCBM test cells have relatively small areas (,0.1,cm2), the analysis is extended to consider efficiency losses for larger area cells and shows that the transparent anode conductivity is then the dominant materials parameter affecting Rs efficiency losses. A model is developed that uses cell sizes and anode conductivities to predict current,voltage response as a function of resistive losses. The results show that the losses due to Rs remain minimal until relatively large cell areas (>0.1,cm2) are employed. Finally, Rs effects on a projected high-efficiency OPV scenario are assessed, based on the goal of cell efficiencies >10%. Here, Rs optimization effects remain modest; however, there are now more pronounced losses due to cell size, and it is shown how these losses can be mitigated by using higher conductivity anodes. [source] The monolithic multicell: a tool for testing material components in dye-sensitized solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2007Henrik Pettersson Abstract A multicell is presented as a tool for testing material components in encapsulated dye-sensitized solar cells. The multicell is based on a four-layer monolithic cell structure and an industrial process technology. Each multicell plate includes 24 individual well-encapsulated cells. A sulfur lamp corrected to the solar spectrum has been used to characterize the cells. Efficiencies up to 6·8% at a light-intensity of 1000,W/msu2 (up to 7·5% at 250,W/m2) have been obtained with an electrolyte solution based on ,-butyrolactone. Additionally, a promising long-term stability at cell efficiencies close to 5% at 1000,W/m2 has been obtained with an electrolyte based on glutaronitrile. The reproducibility of the cell performance before and after exposure to accelerated testing has been high. This means that the multicell can be used as an efficient tool for comparative performance and stability tests. Copyright © 2006 John Wiley & Sons, Ltd. [source] Surface Design in Solid-State Dye Sensitized Solar Cells: Effects of Zwitterionic Co-adsorbents on Photovoltaic PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Mingkui Wang Abstract In solid-state dye sensitized solar cells (SSDSCs) charge recombination at the dye-hole transporting material interface plays a critical role in the cell efficiency. For the first time we report on the influence of dipolar co-adsorbents on the photovoltaic performance of sensitized hetero-junction solar cells. In the present study, we investigated the effect of two zwitterionic butyric acid derivatives differing only in the polar moiety attached to their common 4 carbon-chain acid, i.e., 4-guanidinobutyric acid (GBA) and 4-aminobutyric acid (ABA). These two molecules were implemented as co-adsorbents in conjunction with Z907Na dye on the SSDSC. It was found that a Z907Na/GBA dye/co-adsorbent combination increases both the open circuit voltage (Voc) and short-circuit current density (Jsc) as compared to using Z907Na dye alone. The Z907Na/ABA dye/co-adsorbent combination increases the Jsc. Impedance and transient photovoltage investigations elucidate the cause of these remarkable observations. [source] Numerical simulation of thermal,hydraulic characteristics in a proton exchange membrane fuel cellINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2003Y.M. Ferng Abstract The thermal,hydraulic characteristics of a proton exchange membrane fuel cell (PEMFC) are numerically simulated by a simplified two-phase, multi-component flow model. This model consists of continuity, momentum, energy and concentration equations, and appropriate equations to consider the varying flow properties of the gas,liquid two-phase region in a PEMFC. This gas,liquid two-phase characteristic is not considered in most of the previous simulation works. The calculated thermal,hydraulic phenomena of a PEMFC are reasonably presented in this paper, which include the distributions of flow vector, temperature, oxygen concentration, liquid water saturation, and current density, etc. Coupled with the electrochemical reaction equations, current flow model can predict the cell voltage vs current density curves (i.e. performance curves), which are validated by the single-cell tests. The predicted performance curves for a PEMFC agree well with the experimental data. In addition, the positive effect of temperature on the cell performance is also precisely captured by this model. The model presented herein is essentially developed from the thermal,hydraulic point of view and can be considered as a stepping-stone towards a full complete PEMFC simulation model that can help the optima design for the PEMFC and the enhancement of cell efficiency. Copyright © 2003 John Wiley & Sons, Ltd. [source] Increasing the Photovoltaic EfficiencyLASER TECHNIK JOURNAL, Issue 1 2010Laser Doping of Crystalline Solar Cells Driven by falling prices and competitive pressure manufacturers of photovoltaic cells are seeking for new methods and cell concepts to reduce production costs and increase cell efficiency. Developments which have been of more academic interest over the past years are close to find their way into volume production. While laser applications are already standard for structuring of thin film PV glass panels, they are not yet widely established in the silicon-wafer-based cell manufacturing, which still represents more than 80% of the photovoltaic market. However, without adding too much complexity to the process flow most of the new cell concepts are only feasible by introduction of laser processes. [source] Polycrystalline sputtered Cd(Zn, Mn)Te films for top cells in PV tandem structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004Sung Hyun Lee Abstract The CdTe-ZnTe or CdTe,MnTe alloy system is evaluated for application in high efficiency polycrystalline thin film multijunction solar cells. CdZnTe alloy films with 1.6 and 1.7 eV band gap and CdMnTe with 1.6 and 1.8 eV were deposited by RF magnetron sputtering from targets made of mixed powders of CdTe and ZnTe (25% and 40%) or MnTe (13% and 25%), respectively. Without postdeposition treatment, however, both of these alloy films exhibit quite low photovoltaic performance when used to make cells with CdS as the heterojunction partner. Therefore, we have searched for an appropriate postdeposition treatment to improve the efficiency of these alloy films. As-grown films have been postdeposition treated with vapors of chlorine-containing materials such as HCl gas, CdCl2, ZnCl2 or MnCl2 in dry air or H2+Ar atmosphere. When the CdCl2 + ZnCl2 or MnCl2 vapor was used, the ratio of CdCl2 to ZnCl2 or MnCl2 was adjusted to match the stoichiometry of alloy films. The temperature of the treatment was chosen to represent conditions employed for those alloy films/CdS structures. As a result, the postdeposition treated CdZnTe and CdMnTe cell efficiency can be improved by a factor of over 100. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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] Encapsulating Eu3+ complex doped layers to improve Si-based solar cell efficiencyPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2009Alessia Le Donne Abstract This paper reports the electrical characterization of commercially available crystalline silicon solar cells encapsulated with poly-vinylacetate doped with different Eu3+ organic complexes. The inclusion of these complexes in the encapsulating matrix allows down-shifting of the solar spectrum components below 420,nm toward the maximum quantum efficiency of the solar cells. This effect has been proven under Air Mass 1·5 conditions (simulating terrestrial applications) where an increase of the total power delivered by the encapsulated cells has been observed. Moreover, this enhancement has been obtained using very low percentage by weight of organolanthanide dopants, allowing a reduction in the Watt peak price. At higher concentrations a strong quenching of the energy transfer from the organic antenna to the lanthanide ion has been observed. Copyright © 2009 John Wiley & Sons, Ltd. [source] A masked process for the industrial production of buried contact solar cells on multi-crystalline siliconPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2008Michelle McCann Abstract This paper reports on the development of a masked process for the production of buried contact solar cells on multi-crystalline silicon. The process results in high efficiencies, and only includes steps that would be feasible in an industrial environment. We report here on different mask candidates and on the importance of hydrogenation with the new process. Using the developed process, we produced 111 large area (12,×,12,cm2) cells and achieved an average cell efficiency of 16·2%. The best cell had an efficiency of 16·9%, a Voc of 616,mV, a Jsc of 35·0,mA/cm2 and a fill factor of 78·3%. Copyright © 2008 John Wiley & Sons, Ltd. [source] 8% Efficient thin-film polycrystalline-silicon solar cells based on aluminum- induced crystallization and thermal CVDPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2007I. Gordon Abstract A considerable cost reduction could be achieved in photovoltaics if efficient solar cells could be made from polycrystalline-silicon (pc-Si) thin films on inexpensive substrates. We recently showed promising solar cell results using pc-Si layers obtained by aluminum-induced crystallization (AIC) of amorphous silicon in combination with thermal chemical vapor deposition (CVD). To obtain highly efficient pc-Si solar cells, however, the material quality has to be optimized and cell processes different from those applied for standard bulk-Si solar cells have to be developed. In this work, we present the different process steps that we recently developed to enhance the efficiency of pc-Si solar cells on alumina substrates made by AIC in combination with thermal CVD. Our present pc-Si solar cell process yields cells in substrate configuration with efficiencies so far of up to 8·0%. Spin-on oxides are used to smoothen the alumina substrate surface to enhance the electronic quality of the absorber layers. The cells have heterojunction emitters consisting of thin a-Si layers that yield much higher Voc values than classical diffused emitters. Base and emitter contacts are on top of the cell in interdigitated finger patterns, leading to fill factors above 70%. The front surface of the cells is plasma textured to increase the current density. Our present pc-Si solar cell efficiency of 8% together with the fast progression that we have made over the last few years indicate the large potential of pc-Si solar cells based on the AIC seed layer approach. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effects of ultra-high flux and intensity distribution in multi-junction solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2006Eugene A. Katz Abstract We report results of high-flux experiments on tandem solar cells, with a real-sun probe predicated on mini-dish fiber-optic concentrators. Experimental results and their interpretation focus on: (a) a striking insensitivity of cell efficiency to flux map; (b) the predictability of the flux values at which cell efficiency peaks; and (c) performance of the same cell architecture at markedly smaller cell area. Copyright © 2006 John Wiley & Sons, Ltd. [source] Limiting efficiency of crystalline silicon solar cells due to Coulomb-enhanced Auger recombinationPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2003Mark J. Kerr Excitonic effects are known to enhance the rate of intrinsic recombination processes in crystalline silicon. New calculations for the limiting efficiency of silicon solar cells are presented here, based on a recent parameterization for the Coulomb-enhanced Auger recombination rate, which accounts for its dopant type and dopant density dependence at an arbitrary injection level. Radiative recombination has been included along with photon recycling effects modeled by three-dimensional ray tracing. A maximum cell efficiency of 29.05% has been calculated for a 90-,m-thick cell made from high resistivity silicon at 25°C. For 1,,,cm p -type silicon, the maximum efficiency reduces from 28.6% for a 55-,m-thick cell in the absence of surface recombination, down to 27.0% for a thickness in the range 300,500,,m when surface recombination limits the open-circuit voltage to 720,mV. Copyright © 2002 John Wiley & Sons, Ltd. [source] Space and terrestrial photovoltaics: synergy and diversity,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2002Sheila G. Bailey A historical view of the research and development in photovoltaics from the perspective of both the terrestrial and the space communities is presented from the early days through the 1970s and 1980s, 1990s and beyond. The synergy of both communities, both at the beginning and in the present, and hopefully in the future, are highlighted, with examples of the important features in each program. The space community which was impressed by the light weight and reliability of photovoltaics drove much of the early development. Even today, nearly every satellite and other scientific space probe that has been launched has included some solar power. However, since the cost of these power systems was only a small fraction of the satellite and launch cost, the use of much of this technology in the terrestrial marketplace was not feasible. It was clear that the focus of the terrestrial community would be best served by reducing costs. This would include addressing a variety of manufacturing issues and raising the rate of production. Success in these programs and a resulting globalization of effort resulted in major strides in the reduction of PV module costs and increased production. Although, the space community derived benefit from some of these advances, its focus was on pushing the envelope with regard to cell efficiency. The gap between theoretical efficiencies and experimental efficiencies for silicon, gallium arsenide and indium phosphide became almost nonexistent. Recent work by both communities have focused on the development thin-film cells of amorphous silicon, CuInSe2 and CdTe. These cells hold the promise of lower costs for the terrestrial community as well as possible flexible substrates, better radiation resistance, and higher specific power for the space community. It is predicted that future trends in both communities will be directed toward advances through the application of nanotechnology. A picture is emerging in which the space and terrestrial solar cell communities shall once again share many common goals and, in fact, companies may manufacture both space and terrestrial solar cells in III,V materials and thin-film materials. Basic photovoltaics research, including these current trends in nanotechnology, provides a valuable service for both worlds in that fundamental understanding of cell processes is still vitally important, particularly with new materials or new cell structures. It is entirely possible that one day we might have one solar array design that will meet the criteria for success in both space and on the Earth or perhaps the Moon or Mars. Published in 2002 by John Wiley & Sons, Ltd. [source] Design optimization for higher stabilized efficiency and reduced light-induced degradation in boron-doped Czochralski silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2002B. Damiani Traditional boron-doped Czochralski-grown Si solar cells are known to suffer from light-induced degradation (LID). By replacing B with Ga as the dopant in the Cz melt or by reducing the oxygen content by implementing the magnetic-Cz (MCz) growth technique, not only can LID be eliminated, but also higher efficiency manufacturable screen-printed cells can be achieved. The use of thinner wafers for cell fabrication can significantly reduce the impact of LID on conventional boron-doped Cz cells. Knowledge of the degraded cell parameters can be used to determine the optimal thickness for the highest stabilized efficiency. A methodology is developed to maximize the stabilized efficiency after LID by using thinner wafers. A combination of device modeling and experimental data is used to demonstrate that, for traditional B-doped Cz Si, which degraded from 75 to 20,,s, the optimum cell thickness is in the range of 150,190,,m for a back-surface recombination velocity of ,104 cm/s. This cell design reduces the material cost and the absolute efficiency degradation from 0.75% (375,,m device) to 0.24% (157,,m device) and gives the highest stabilized Cz cell efficiency. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||