Solar cells

Topics: Solar cell, Photovoltaics, Photovoltaic module Pages: 15 (9259 words) Published: October 28, 2014
Prog. Photovolt: Res. Appl. (2012)
Published online in Wiley Online Library ( DOI: 10.1002/pip.1255


Solar cell generations over 40% efficiency
R. R. King*, D. Bhusari, D. Larrabee, X.-Q. Liu, E. Rehder, K. Edmondson, H. Cotal, R. K. Jones, J. H. Ermer, C. M. Fetzer, D. C. Law and N. H. Karam
Spectrolab, Inc., 12500 Gladstone Ave, Sylmar, CA 91342, USA

Multijunction III-V concentrator cells of several different types have demonstrated solar conversion efficiency over 40% since 2006, and represent the only third-generation photovoltaic technology to enter commercial power generation markets so far. The next stage of solar cell efficiency improvement, from 40% to 50%-efficient production cells, is perhaps the most important yet, since it is in this range that concentrator photovoltaic (CPV) systems can become the lowest cost option for solar electricity, competing with conventional power generation without government subsidies. The impact of 40% and 50% cell efficiency on cost-effective geographic regions for CPV systems is calculated in the continental US, Europe, and North Africa. We take a systematic look at a progression of multijunction cell architectures that will take us up to 50% efficiency, using modeling grounded in well-characterized solar cell materials systems of today’s 40% cells, discussing the theoretical, materials science, and manufacturing considerations for the most promising approaches. The effects of varying solar spectrum and current balance on energy production in 4-junction, 5-junction, and 6-junction terrestrial concentrator cells are shown to be noticeable, but are far outweighed by the increased efficiency of these advanced cell designs. Production efficiency distributions of the last five generations of terrestrial concentrator solar cells are discussed. Experimental results are shown for a highly manufacturable, upright metamorphic 3-junction GaInP/GaInAs/Ge solar cell with 41.6% efficiency independently confirmed at 484 suns (48.4 W/cm2) (AM1.5D, ASTM G173-03, 25  C), the highest demonstrated for a cell of this type requiring a single metalorganic vapor-phase epitaxy growth run. Copyright © 2012 John Wiley & Sons, Ltd. KEYWORDS

multijunction; high efficiency; concentrator; III-V; metamorphic; 4-junction, 5-junction, 6-junction; energy production; cost modeling *Correspondence
Richard King, Spectrolab, Inc., 12500 Gladstone Ave, Sylmar, CA 91342, USA. E-mail:
Received 2 September 2011; Revised 2 November 2011; Accepted 22 November 2011

Multijunction III-V concentrator cells have the highest
energy conversion efficiency of any solar cell technology,
with several different types of cell architecture reaching
over 40% efficiency since 2006 [1–7]. Such cells represent the only third-generation photovoltaic technology to enter commercial power generation markets so far,
and continue to demonstrate what is possible for other
emerging solar cell technologies that divide the sun’s
spectrum into discrete slices for higher efficiency, such
as flat-plate multijunction polycrystalline semiconductor
cells, tandem organic solar cells, and spectral splitting
optical systems.
III-V multijunction concentrator cells using these highefficiency innovations are now by far the dominant type of solar cells used in concentrator photovoltaic (CPV) solar
electric systems, due to their dramatic efficiency advantages. Copyright © 2012 John Wiley & Sons, Ltd.

Photovoltaics have grown at a phenomenal rate of over 40%
per year for the last decade, but much of this growth has been sustained by hefty government subsidies. To become a
technology that truly changes the way the global community
generates most of its electricity, photovoltaics will become too large to be helped substantially by funding from any
government, and will need...

References: Prog. Photovolt: Res. Appl. (2012) © 2012 John Wiley & Sons, Ltd.
Solar Junction press release, April 14, 2011, Diandra
Cell Efficiency, June 1, 2011, https://eere-exchange.
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