X-ray photoelectron and auger electron spectroscopic analyses of surface treatments and electrochemical decomposition of CuInSe2 photoelectrodes.

CuInSe2 photoanodes can be optimized for use in electrochemical photovoltaic cells, containing aqueous polyiodide as the electrolyte, by wet chemical etching in Br2/MeOH and subsequent thermal treatment (air oxidation). Surface analyses show formation of a rather clean, Cu-depleted surface with some adsorbed oxygen after Br2/MeOH etch, and the formation of indium-oxygen bonds after thermal treatment, in accordance with previous studies that show indium oxides to be the native ones on this semiconductor. Samples that underwent photoanodic decomposition in the iodide electrolyte and those that were purposely decomposed in acetonitrile showed severe to near-total Cu-depletion near their surface and the presence of lower valent Se.