PASSIVATION OF PHOTOCARRIER RECOMBINATION ON CDS PHOTOANODE BY 2-COLOR EXCITATION

A CdS single-crystal photoelectrode in aqueous solution containing sodium sulfite was subjected to two-color excitation. The photocurrent caused by UV excitation was markedly enhanced by simultaneous sub-bandgap excitation; no photocurrent occurred for the sub-bandgap excitation alone. The enhancement is explained in terms of passivation of a recombination center by sub-bandgap excitation. The presence of such a recombination center is supported by photocapacitance measurement. Polarized two-color excitation and electrolyte electroreflectance spectroscopy revealed that the recombination center is not localized on the uppermost surface layer but penetrates inside. © 1990 American Chemical Society.