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ABSTRACT: Concentrating photovoltaic (CPV) modules occupy the middle ground between conventional, flat-plate photovoltaics and concentrating solar power (CSP) technologies. CPV promises to deliver the best of both worlds: the highest efficiency of any photovoltaic system combined with the higher capacity factor and scale-up potential of dual-axis tracking systems characteristic of CSP power towers. Having demonstrated cell efficiencies over 40%, the CPV industry has now embarked on an aggressive program to demonstrate cost-effective, highly-reliable CPV modules in the field.
Photovoltaic Specialists Conference, 2008. PVSC '08. 33rd IEEE; 06/2008
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ABSTRACT: An efficiency of 40.7% was measured and independently confirmed for a metamorphic three-junction GaInP / GaInAs / Ge cell under the standard spectrum for terrestrial concentrator solar cells at 240 suns ( 24.0 W / cm <sup>2</sup> , AM1.5D, low aerosol optical depth, 25 ° C ). This is the initial demonstration of a solar cell with over 40% efficiency, and is the highest solar conversion efficiency yet achieved for any type of photovoltaic device. Lattice-matched concentrator cells have now reached 40.1% efficiency. Electron-hole recombination mechanisms are analyzed in metamorphic Ga <sub>x</sub> In <sub>1-x</sub> As and Ga <sub>x</sub> In <sub>1-x</sub> P materials, and fundamental power losses are quantified to identify paths to still higher efficiencies.
Applied Physics Letters 05/2007; · 3.84 Impact Factor
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ABSTRACT: Metamorphic III-V semiconductor materials offer access to bandgaps that span key portions of the solar spectrum, enabling new bandgap combinations in multijunction solar cells, and increasing both theoretical and practical efficiency limits for terrestrial concentrator cells. Experimental results are given for the quantum efficiency of metamorphic GaInAs solar cells with bandgap from 1.1 to 1.4 eV, and for metamorphic GaInP with both ordered and disordered group-III sublattices. Variable intensity J<sub>sc</sub> vs. V<sub>oc</sub> measurements are used to compare recombination components due to n=1 and n=2 mechanisms in metamorphic and lattice-matched GaInAs, GaInP, and 3-junction solar cells. A record efficiency metamorphic GaInP/GaInAs/Ge 3-junction solar cell has been produced with 38.8% efficiency independently confirmed (241 suns, AM1.5D, low-AOD, 25degC), essentially equaling the performance of a lattice-matched 3-junction cell with 39.0% efficiency, the highest efficiency yet demonstrated and verified for a solar photovoltaic conversion device. With the combination of high-quality metamorphic materials that are increasingly less controlled by recombination at dislocations, and the higher efficiency limits afforded by freedom of lattice constant selection, practical terrestrial concentrator cell efficiencies well over 40% are expected in the near future
Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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R.R. King,
C.M. Fetzer,
D.C. Law,
K.M. Edmondson,
Hojun Yoon, G.S. Kinsey,
D.D. Krut,
J.H. Ermer,
P. Hebert,
B.T. Cavicchi,
N.H. Karam
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ABSTRACT: III-V solar cells have become the dominant power generation technology in space, due to their unparalleled high efficiency, reliability in the space environment, and ability to be integrated into very lightweight panels. As remarkable as these attributes are, new types of space III-V solar cells are continually reaching new heights in performance. Commercially-available multijunction solar cells with 30% conversion efficiency under the AM0 space spectrum are just around the corner. Understanding of radiation resistance and thermal cycling reliability has reached levels never before attained, and is resulting in new standards of reliability. A flurry of research activity has resulted in very-thin, flexible, and extremely lightweight space solar cells and panels in several groups around the world, capable of being folded or rolled into a smaller stowage volume for launch than has been possible to date. This approach combines the very high efficiency and reliability of III-V multijunction cells with the thin, flexible PV blanket functionality normally associated only with thin-film polycrystalline or amorphous PV technology. This paper discusses the latest developments in III-V space solar cell technology, and explores opportunities for still higher performance in the future
Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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ABSTRACT: We report on the measurement of minority carrier lifetime and on the radiation damage resistance of bulk Ge. Lifetime measurements are performed using the resonance-coupled photoconductive decay (RCPCD) method. Specifically, we examine the dependence of the lifetime as a function of the Ge resistivity and various 1 MeV electron radiation fluences. We measure hole lifetimes ranging from ∼0.9-34 μs for n-type Ge samples, corresponding to diffusion lengths of ∼30-400 μm. Electron lifetimes in p-type Ge range from ∼0.6-19 μs, corresponding to diffusion lengths of ∼30-420 μm. Lifetime measurements are also made after exposure to 1 MeV electron fluences ranging from 10<sup>13</sup> to 10<sup>15</sup> cm<sup>-2</sup> and these results are used to estimate the minority carrier lifetime and diffusion length damage coefficients K<sub>τ</sub> and K<sub>L</sub>.
Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE; 02/2005
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G.S. Kinsey,
R.R. King,
K.M. Edmondson,
A.P. Stavrides,
H. Yoon,
C.M. Fetzer,
P.C. Colter,
J.H. Ermer,
M.S. Gillanders,
P. Hebert,
J.E. Granata,
N.H. Karam
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ABSTRACT: Solar cells suitable for the space environment must combine high efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed by Spectrolab builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design that is expected to deliver 28% beginning-of-life efficiency in production.
Energy Conversion Engineering Conference, 2002. IECEC '02. 2002 37th Intersociety; 08/2004
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J.E. Granata,
C. Fetzer,
J.H. Ermer,
R.R. King,
K. Edmondson,
A. Stavrides,
P. Hebert,
P. Colter, G.S. Kinsey,
Hojun Yoon,
M.S. Gillanders,
N. Beze,
K. Bui,
J. Hanley,
N.H. Karam,
B.T. Cavicchi
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ABSTRACT: Spectrolab introduces its latest multi-junction solar cell with efficiency at maximum power at beginning of life of 28.0% (AM0, 28/spl deg/C, 135.3 mW/cm/sup 2/) and 22.6% at 60/spl deg/C after 15 years in GEO orbit. The space-qualification program employed for the Ultra Triple Junction (UTJ) solar cell is the most comprehensive to date, leading the way to improving on-orbit performance predictions. The UTJ cell is currently in qualification and is expected to be in production 2Q 2003.
Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on; 06/2003
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ABSTRACT: Direct measurements of radiative coupling effects in GaInP/GaAs/Ge multijunction solar cells are presented. Radiative coupling between the GaInP and GaAs cells is observed by using isotype cells as well as specially fabricated 3-terminal device structures. Spectral response measurements of the GaAs cell in both isotype and 3-terminal approaches are shown to exhibit enhanced quantum efficiency in the short wavelength region under favorable radiative coupling conditions. Additionally, electroluminescence of the GaInP cell is shown to enhance the current output from the GaAs cell using a 3-terminal device structure. One consequence of this effect is the possible influence on the measured J-ratio of a multijunction cell. Consideration of radiative coupling may become increasingly important as multijunction III-V based solar cells - including 4- and 5- junction cells - continue to develop and improve in performance.
Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on; 06/2003
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R.R. King,
C.M. Fetzer,
P.C. Colter,
K.M. Edmondson,
D.C. Law,
A.P. Stavrides,
H. Yoon, G.S. Kinsey,
H.L. Cotal,
J.H. Ermer,
R.A. Sherif,
K. Emery,
W. Metzger,
R.K. Ahrenkiel,
N.H. Karam
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ABSTRACT: Recent developments in epitaxial III-V multijunction solar cell technology have allowed concentrator and 1-sun cells to reach new heights in efficiency under the terrestrial solar spectrum. The bandgaps of the GaInP and GaInAs subcells are controlled by varying indium content, up to 12% indium in the GaInAs middle cell, or 0.8% lattice mismatch. Shockley-Read-Hall recombination at dislocations in such metamorphic cells has been restricted to lower levels than previously achieved, and is compared to the lattice-matched case. Terrestrial GaInP/GaInAs/Ge 3-junction cells have been produced at Spectrolab with record efficiencies independently verified at NREL, of 31.3% for metamorphic 1-sun cells and 32.0% for lattice-matched 1-sun cells (25/spl deg/C, AM1.5G, 4.00 cm/sup 2/), and 35.2% for lattice-matched concentrator cells under the AM1.5 Direct, low-AOD spectrum (25/spl deg/C, 66 suns, 0.26 cm/sup 2/).
Photovoltaic Energy Conversion, 2003. Proceedings of 3rd World Conference on; 06/2003
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G.S. Kinsey,
R.R. King,
K.M. Edmondson,
A.P. Stavrides,
Hojun Yoon,
C.M. Fetzer,
P.C. Colter,
J.H. Ermer,
M.S. Gillanders,
P. Hebert,
J.E. Granata,
N.H. Karam
[show abstract]
[hide abstract]
ABSTRACT: Solar cells suitable for the space environment must combine high-efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design expected to deliver 28% beginning-of-life efficiency in production.
IEEE Aerospace and Electronic Systems Magazine 04/2003; · 0.30 Impact Factor
