ELECTRODISSOLUTION AND CORROSION OF CUINS2 PHOTOANODES WITH LAMELLAR MORPHOLOGY

Crystals of n-CuInS2 grown in a steep temperature gradient show lamellar morphology, prone to cleavage, and inclusions of copper-poor phases like CuIn5S8. Photoelectrooxidation of n-CuInS2 in 1 M HClO4, a non-protective electrolyte, results in massive dissolution of the metal ions and deposition of sulfur, with marked photocurrent quenching. Operation of n-CuInS2 (photo)anodes in acidic polyiodide medium causes significant corrosion and decay of photocurrent output. Micrographs of corroded areas show progressive and irregular etching of the CuInS2 layers, which appear strongly polycristalline. EDX microanalyses show very similar composition before and after corrosion, suggesting that the latter causes stoichiometric removal and dissolution of the components and does not form new phases of significant thickness.