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Effect of Cu Deficiency on CuIn1-xGaxSe2 and High-efficiency Photovoltaic Solar Cells

Published online by Cambridge University Press:  01 February 2011

Sung-Ho Han ,
Falah S. Hasoon ,
Joel W. Pankow ,
Allen M. Hermann  and
Dean H. Levi
Sung-Ho Han
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393, U.S.A. Department of Physics, University of Colorado, 2000 Colorado Avenue, Boulder, CO 80303-0390, U.S.A.
Falah S. Hasoon
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393, U.S.A.
Joel W. Pankow
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393, U.S.A.
Allen M. Hermann
Affiliation:
Department of Physics, University of Colorado, 2000 Colorado Avenue, Boulder, CO 80303-0390, U.S.A.
Dean H. Levi
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393, U.S.A.
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Abstract

We report the results of our studies on the optical and electronic structure of a wide range of polycrystalline thin-film CuIn1-xGaxSe2 (CIGS) alloys. The composition range includes CIS and nearly stoichiometric (slightly Cu-poor) (24.3±0.3 at.% Cu) CIGS with x values located around the value that has the best efficiency (x ∼ 0.28). Relative to nearly stoichiometric CIS and CIGS, we find a reduction in the absorption strength in the spectral range 1-3 eV. This reduction can be explained in terms of the predominance of Cu 3d and Se 4p states at the valence band maximum (VBM). In addition, Cu-poor CIS and CIGS materials show an increase in bandgap because the p-d repulsive interaction in Cu-poor CIGS is less than that in nearly stoichiometric CIGS. High efficiency is discussed in terms of optical properties.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 865: Symposium F – Thin-Film Compound Semiconductor Photovoltaics , 2005 , F1.3
Copyright
Copyright © Materials Research Society 2005

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