Improved efficiency of CdSe photoanodes by photoelectrochemical etching

By illuminating a CdSe photoanode in an electrolyte in which it is photoelectrochemically unstable, a selective etching of the CdSe to a matte black surface occurs with formation of small pits (≈1000 Å diameter). This photoelectrochemical etch was found to improve the output characteristics of the CdSe-polysulfide photoelectrochemical cell through an increase in short-circuit current (SCC) for single-crystal CdSe, and an increase in fill factor and SCC for polycrystalline CdSe, where the improvement is more marked. This increase could be explained only partly through decreased reflectivity of the surface, and is probably connected with removal of (near) surface recombination centers.