Use of Rayleigh-Rice Theory for Analysis of Ellipsometry Data on Rough CIGS Films

Abstract

Ellipsometry is a useful tool for studying the optical properties of thin films such as photovoltaic devices. We employ Muller matrix ellipsometry to study the thin film photovoltaic material copper indium gallium selenide Cu(In,Ga) Se2 (CIGS), a commercially relevant material with high energy conversion efficiency. Confocal microscopy reveals an rms roughness of 68 nm, which greatly affects the ellipsometry data. Rayleigh-Rice theory is employed to account for the optical properties of the surface roughness in the ellipsometry experiment, and a library search method is used to compare Muller parameters calculated for various CIGS compositions, to the measured data. The Muller parameters calculated with the Rayleigh-Rice model are found to correspond well with the measured data, and a surface roughness of 37nm and a correlation length of 125nm are extracted.