Thinning of CIGS solar cells: Part I: Chemical processing in acidic bromine solutions

CIGSe absorber was etched in HBr/Br₂/H₂O to prepare defined thicknesses of CIGSe between 2.7 and 0.5 μm. We established a reproducible method of reducing the absorber thickness via chemical etching. We determine the dissolution kinetics rate of CIGSe using trace analysis by graphite furnace atomic absorption spectrometry of Ga and Cu. The roughness of the etching surface decreases during the first 500 nm of the etching to a steady state value of the root-mean-square roughness near 50 nm. X-ray photoelectron spectroscopy analyses demonstrate an etching process occurring with a constant chemical composition of the treated surface acidic bromine solutions provide a controlled chemical thinning process resulting in an almost flat surface and a very low superficial Se⁰ enrichment.