Tandem Solar Cell (tandem + solar_cell)

Distribution by Scientific Domains


Selected Abstracts


Solution-Processed Organic Tandem Solar Cells,

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2006
A. Hadipour
Abstract A solution-processed polymer tandem cell fabricated by stacking two single cells in series is demonstrated. The two bulk-heterojunction subcells have complementary absorption maxima at ,max,,,850,nm and ,max,,,550,nm, respectively. A composite middle electrode is applied that serves both as a charge-recombination center and as a protecting layer for the first cell during spin-coating of the second cell. The subcells are electronically coupled in series, which leads to a high open-circuit voltage of 1.4,V, equal to the sum of each subcell. The layer thickness of the first (bottom) cell is tuned to maximize the optical absorption of the second (top) cell. The performance of the tandem cell is presently limited by the relatively low photocurrent generation in the small-bandgap polymer of the top cell. The combination of our tandem architecture with more efficient small-bandgap materials will enable the realization of highly efficient organic solar cells in the near future. [source]


High-Efficiency Polymer Tandem Solar Cells with Three-Terminal Structure

ADVANCED MATERIALS, Issue 8 2010
Srinivas Sista
Tandem solar cells have the advantage of enhancing the absorption range of polymer solar cells. A three-terminal tandem cell based on two polymer bulk heterojunctions that have complementary absorption profile is demonstrated. In this device configuration the two subcells are connected in parallel through a common semitransparent metal interlayer and an efficiency of 4.8% with short circuit current of 15.1,mA cm,2 is achieved. [source]


RF sputtered HgCdTe films for tandem cell applications

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004
S. L. Wang
Abstract Polycrystalline Hg1,xCdxTe films were investigated for their potential as bottom cells of a CdTe-based tandem solar cell. The films were deposited by RF sputtering from a cold pressed target containing 30% HgTe + 70% CdTe. The as-deposited films were highly resistive with (111) preferred orientation and a bandgap of ,1.0 eV. Various thermal treatment schemes were investigated under different conditions of ambient and temperature to reduce the resistivity. The film properties were analyzed using infrared transmission spectra, energy dispersive X-ray spectra and X-ray diffraction. N doped p-HgCdTe films were also prepared by reactive sputtering in a N2/Ar ambient. P-n junction solar cells were fabricated with CdS films as the heterojunction partner. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


A monolithic three-terminal GaInAsP/GaInAs tandem solar cell

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2009
M. A. Steiner
Abstract We describe the design and performance of a three-terminal tandem solar cell for low-concentration terrestrial applications. Designed for operation under a GaAs filter, the tandem demonstrates cumulative conversion efficiencies of 10.2 and 11.9% at 1 sun and 45 suns, respectively, under the concentrated direct spectrum. The middle terminal is shared between the two subcells and allows them to be operated independently at their respective maximum power points. Copyright 2009 John Wiley & Sons, Ltd. [source]


Fill factor as a probe of current-matching for GaInP2/GaAs tandem cells in a concentrator system during outdoor operation

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2008
W. E. McMahon
Abstract Designing a tandem solar cell for use in a concentrator system is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct system design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple-junction cells. Copyright 2007 John Wiley & Sons, Ltd. [source]


The current,voltage characteristic of the ideal two-terminal tandem solar cell

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2003
Alexis De VosArticle first published online: 14 FEB 200
Abstract An ideal tandem solar cell, with an infinite number of diodes, has the same limit efficiency whether or not the diodes are connected electrically in series. In case of a series connection, the device has a single current,voltage characteristic. The latter can easily be deduced, and its efficiency therefore can easily be calculated. Copyright 2003 John Wiley & Sons, Ltd. [source]


A stacked chalcopyrite thin-film tandem solar cell with 1.2,V open-circuit voltage

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2003
S. Nishiwaki
Abstract CuGaSe2 (CGS) thin films were prepared on tin-doped indium oxide (ITO) coated soda-lime glass substrates by thermal co-evaporation to fabricate transparent solar cells. The films consisted of columnar grains with a diameter of approximately 1,,m. Some deterioration of the transparency of the ITO was observed after deposition of the CGS film. The CGS solar cells were electrically connected in series with Cu(In,Ga)Se2 (CIGS) solar cells and mechanically stacked on the CIGS cells to construct tandem cells. The tandem solar cell with the CGS cell as the top cell showed an efficiency of 7.4% and an open-circuit voltage of 1.18,V (AM,1.5, total area). Copyright 2003 John Wiley & Sons, Ltd. [source]


Limiting efficiency for current-constrained two-terminal tandem cell stacks

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2002
Andrew S. Brown
Tandem stacks of solar cells have clearly shown their ability to increase the efficiency of solar energy conversion. In the past, the challenge in making these devices often has been in the materials science area, working around the constraints imposed by different materials to meet requirements imposed by lattice constant and bandgap. However, developments in the field of low-dimensional structures; particularly superlattices, may allow generic approaches to developing tandem stacks of large numbers of cells. The current flowing through such devices will have to be constrained so that it is the same through all the cells within the stack since separately contacting such large numbers of cells is impractical. The series-constrained two-terminal tandem solar cell is compared with the unconstrained tandem solar cell for stacks containing both small and large numbers of cells. As expected, we find that the detailed balance limiting efficiencies for the two-terminal cell are less than those for the unconstrained device involving the same number of cells, due to the constraint imposed by current matching. However the difference is always less than 1.5% relative under the design spectrum. However, the two-terminal case shows much greater variation in efficiency if the spectrum varies from that for which the design was optimised. A relationship is derived between the performance of a two-terminal stack of a finite number of cells and the performance of an unconstrained stack of an infinite number of cells. This shows that the performance of the two-terminal device approaches that of the unconstrained device as the number of cells in the stack approaches infinity. Copyright 2002 John Wiley & Sons, Ltd. [source]


R&D activities of silicon-based thin-film solar cells in China

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2006
Yuwen Zhao
Abstract The status and progress of R&D activities of silicon-based thin-film solar cells in China are described briefly in this paper, including amorphous Si solar cells and microcrystalline Si film solar cells based on PECVD technology and polycrystalline film solar cells based on RTCVD technology. Especially, the microcrystalline thin-film solar cells and the tandem solar cells of amorphous Si with microcrystalline Si have made great progress. The polycrystalline film solar cells have made remarkable achievements as well. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


High potential of thin (<1,m) a-Si: H/c-Si:H tandem solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2010
S. Schicho
Abstract Silicon based thin tandem solar cells were fabricated by plasma enhanced chemical vapor deposition (PECVD) in a 30,,30,cm2 reactor. The layer thicknesses of the amorphous top cells and the microcrystalline bottom cells were significantly reduced compared to standard tandem cells that are optimized for high efficiency (typically with a total absorber layer thickness from 1.5 to 3,m). The individual absorber layer thicknesses of the top and bottom cells were chosen so that the generated current densities are similar to each other. With such thin cells, having a total absorber layer thickness varying from 0.5 to 1.5,m, initial efficiencies of 8.6,10.7% were achieved. The effects of thickness variations of both absorber layers on the device properties have been separately investigated. With the help of quantum efficiency (QE) measurements, we could demonstrate that by reducing the bottom cell thickness the top cell current density increased which is addressed to back-reflected light. Due to a very thin a-Si:H top cell, the thin tandem cells show a much lower degradation rate under continuous illumination at open circuit conditions compared to standard tandem and a-Si:H single junction cells. We demonstrate that thin tandem cells of around 550,nm show better stabilized efficiencies than a-Si:H and c-Si:H single junction cells of comparable thickness. The results show the high potential of thin a-Si/c-Si tandem cells for cost-effective photovoltaics. Copyright 2010 John Wiley & Sons, Ltd. [source]


Thin film solar cells incorporating microcrystalline Si1,xGex as efficient infrared absorber: an application to double junction tandem solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2010
Takuya Matsui
Abstract We have fabricated efficient (,7,8%) hydrogenated microcrystalline Si1,xGex (c-Si1,xGex:H, x,,,0.1,0.17) single junction p-i-n solar cells with markedly higher short-circuit current densities than for c-Si:H (x,=,0) solar cells due to enhanced infrared absorption. By replacing the conventional c-Si:H with the c-Si1,xGex:H as infrared absorber in double junction tandem solar cells, the bottom cell thickness can be reduced by more than half while preserving the current matching with hydrogenated amorphous silicon (a-Si:H) top cell. An initial efficiency of 11.2% is obtained for a-Si:H/c-Si0.9Ge0.1:H solar cell with bottom cell thickness less than 1,m. Copyright 2009 John Wiley & Sons, Ltd. [source]


Effects of ultra-high flux and intensity distribution in multi-junction solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2006
Eugene 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]


CdTe solar cell in a novel configuration

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2004
A. N. Tiwari
Abstract Polycrystalline thin-film CdTe/CdS solar cells have been developed in a configuration in which a transparent conducting layer of indium tin oxide (ITO) has been used for the first time as a back electrical contact on p-CdTe. Solar cells of 79% efficiency were developed on SnOx:F-coated glass substrates with a low-temperature (<450C) high-vacuum evaporation method. After the CdCl2 annealing treatment of the CdTe/CdS stack, a bromine methanol solution was used for etching the CdTe surface prior to the ITO deposition. The unique features of this solar cell with both front and back contacts being transparent and conducting are that the cell can be illuminated from either or both sides simultaneously like a ,bi-facial' cell, and it can be used in tandem solar cells. The solar cells with transparent conducting oxide back contact show long-term stable performance under accelerated test conditions. Copyright 2004 John Wiley & Sons, Ltd. [source]


Modeled performance of polycrystalline thin-film tandem solar cells,

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2002
Timothy J. Coutts
The optimum bandgaps for two-terminal monolithic multijunction devices have typically been studied under a fixed set of environmental conditions, using ideal device models. This study examines the effects of a realistic dark-current for typical state-of-the-art thin-film polycrystalline cells on the optimum energy gap for a series-connected two-junction cell. The optimum energy gaps are compared for a series-connected tandem cell under standard reference conditions and the energy produced for five different reference days where the temperature, spectral irradiance and total irradiance varied. The optimum bandgaps were found to be 1.72,,0.02,eV for the top cell and 1.14,,0.02,eV for the bottom cell. Published in 2002 by John Wiley & Sons, Ltd. [source]