S/Se Substitution in Polycrystalline CdSe Photoelectrodes: Photoelectrochemical Energy Conversion

On the basis of x‐ray photoelectron spectroscopy (XPS) studies of polycrystalline electrodes, the occurrence of S/Se substitution in these electrodes, when immersed in polysulfide solution, is verified. The substitution process is enhanced considerably when the electrode is illuminated as part of a photoelectrochemical cell. The mechanism of the S/Se exchange is discussed, as well as the consequences of such an exchange for electrode stability. The resulting presence of a thin (several tens of angstroms) layer of on top of the is taken into account in constructing a rough band scheme for the system. The layer is shown to influence the photovoltage and, to a lesser extent, the photocurrent obtainable from this kind of photoelectrochemical cell. Its relation to the slow deactivation of highly crystalline photoelectrodes is discussed.