TERNARY CHALCOGENIDE-BASED PHOTOELECTROCHEMICAL CELLS - PART V: SURFACE ANALYSES OF THE CuInX₂/AQUEOUS POLYSULFIDE INTERFACE (X equals S, Se) BY X-RAY PHOTOELECTRON SPECTROSCOPY; ABSENCE OF Se/S EXCHANGE IN THE CuInSe₂/S_SYSTEM.

n-CuInS//2 and n-CuInSe//2 were subjected to surface analyses by x-ray photoelectron and Auger electron spectroscopy, after their use as photoanodes in polysulfide solutions. For CuInS//2 samples that had a poor conversion efficiency, a rather heterogeneous surface was found, with patches rich in In, which is probably present mainly as oxide. Some CuO was found as well, although the top layer was depleted in Cu, compared to a reference sample. More efficient samples showed a more homogeneous surface and even strong Cu depletion. These changes are ascribed to additional surface treatments, viz. , dipping in hot KCN solution and thermal oxidation of the resultant etched surface. It is suggested that the occurrence of an indium oxide top layer, aided by thermal oxidation of the electrode in the case of CuInSe//2, has a beneficial effect on electrode performance.