Effect of growth conditions on microstructure of sputtered precursor for CuIn1-xGaxSe2 (CIGS) absorber layer deposited on stainless steel substrates

In this paper, we report the effect of growth conditions on the properties of sputtered precursor thin films for CuIn1-xGaxSe2 (CIGS) absorber layers. Specifically, precursor films containing Cu, In, Ga, and Se were deposited via co-sputtering on flexible Mo-coated stainless steel substrates over a wide range of compositions and deposition conditions. The impact on precursor film phase, morphology, and elemental distribution was investigated as a function of precursor Se content, substrate temperature, target type (CIG/CIG vs. In/Cu3Ga), and Na content. Precursor films selenized at high temperature (>500 °C) to form stoichiometric CIGS and completed using a CdS n-type buffer layer and transparent conducting oxide window layers exhibited full-cell efficiencies as high as 11.5%.