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Optical Functions of Thin-Film Polycrystalline Chalcopyrite CuIn1-xGaxSe2

Published online by Cambridge University Press:  01 February 2011

Sung-Ho Han ,
Dean H. Levi ,
Hamda A. Althani ,
Falah S. Hasoon ,
Raghu N. Bhattacharya  and
Allen M. Hermann
Sung-Ho Han
Affiliation:
Department of Physics, University of Colorado, Boulder, CO 80309, USA
Dean H. Levi
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401, USA
Hamda A. Althani
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401, USA
Falah S. Hasoon
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401, USA
Raghu N. Bhattacharya
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401, USA
Allen M. Hermann
Affiliation:
Department of Physics, University of Colorado, Boulder, CO 80309, USA
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Abstract

The highest efficiency CuIn1-xGaxSe2 (CIGS) solar cells use thin-film polycrystalline CIGS absorber layers. We have applied variable angle spectroscopic ellipsometry (VASE) to characterize the dielectric functions of polycrystalline thin films of CIGS with Ga: (In + Ga) ratios ranging from 0.18 to 1.0. The Cu: (In + Ga) ratios in these films are approximately 0.90, which is the ratio that yields the highest efficiency CIGS devices. Spectra were measured over the energy range 0.7 to 5.0 eV at room temperatures. Models used to analyze the ellipsometry data include the full multi-layer structure of the sample, which enables us to report the actual dielectric function rather than the pseudo-dielectric function. We present data on how the critical points change with composition, and compare and contrast our results with measurements of single-crystal and bulk polycrystalline samples reported in the literature. Auger electron spectroscopy, atomic force microscopy, and X-ray diffraction have been used to verify the homogeneity, surface roughness, and phase purity, respectively.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 763: Symposium B – Compound Semiconductor Photovoltaics , 2003 , B1.8
Copyright
Copyright © Materials Research Society 2003

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