Photoelectrochemical Stability of Electrodeposited Cu2O Films

We report on the photoelectrochemical stability of electrodeposited films of cuprous oxide (Cu2O) in aqueous solutions. p-type Cu2O was electrodeposited from an alkaline lactate solution onto Au substrates with a (111) preferred orientation. The as-deposited films exhibit a strong (111) orientation and a columnar morphology, terminating at the surface with pyramidal features. Stability of the photoelectrochemical response was studied via repeated cycling polarization and by monitoring the photocurrent within a voltage window where only the CuO/Cu2O transformation would occur. The Cu2O film morphology changes from a dense structure to a more stable network of elongated leaf-like crystals. We attributed this behavior to the energy differences among the various crystallographic facets of Cu2O, with the {111} facets being the most stable. Photocurrent evolution over time was explained in terms of an initial increase in surface area at the start of the process, followed by a decrease due to increased recombination losses resulting from having only the {111} surface exposed to the electrolyte.