Material Properties And Re Application For Cu

1724 Words7 Pages
Christopher Wheatley
Fall 2015 Term Paper
Dr. Stefan Stefanoski

Overview of the Material Properties and RE Application for Cu(In,Ga)Se2

Introduction and Historical Notes

I have chosen to review the material properties and applications for the compound semiconductor copper indium gallium selenide as it is used in photovoltaic cells. A chalcopyrite-based material, the chemical formula is often written as CuIn1-xGaxSe2 (CIGS) to represent the alloy system where the stoichiometric ratio of the compound can vary from pure CuInSe2 (CIS) to CuGaSe2 (CGS). For the purposes of this document, however, the entire range of combinations will simply be referred to as CIGS. I selected this material for a few reasons. I am fascinated with
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This document, however, will provide a much more general and top-level view of the material properties.

The first chalcopyrite solar cells were reported by Wagner et al. in 1974 when a 12% efficient cell was created based on single crystal CuInSe2 absorber. [1] Later, Kazmerski et al. demonstrated that a thin film solar cell could be created by an evaporation process. [2] Commercial CIGS modules were not produced, however, for another 20 years. Since that time the material has been continuously studied and improved. Ga was added to stabilize the p-type conductivity and increase the band gap. It was also discovered that the addition of Na, either through the use of soda-lime glass substrate or added during the growth process, helps to boost the conductivity of the material and control the film growth and free carrier concentration. [2] As of 2014, the record for CIGS efficiency demonstrated in a laboratory setting was held by researchers at Stuttgart’s Centre for Solar Energy and Hydrogen Research (ZSW), for their achievement of a 21.7% efficient cell. [3] As of May 2015, the Taiwanese company TSMC Solar has reported the highest efficiency module that is commercially available with a rating of 16.5%. [4]

Synthesis and Crystal Structure

There are a variety of methods for synthesizing the CIGS absorber layer. However, for
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