Sulfurization of some wide-band gap metal oxides forms photoactive sulfides on metal oxide electrodes. Very high-incident photon-to-current conversion efficiencies are achieved on In2S3/In2O3, Bi2S3/Bi2O3, and MgIn2S4/MgIn2O4 electrodes in a polysulfide electrolyte. Semiconductor sensitization is responsible for the generation of the photocurrent on those electrodes. A semiconductor sensitization process was not observed on ZnS/ZnO electrodes. Different kinetics at the semiconductor/semiconductor interface are the reasons for the observed difference of the incident photon-to-current conversion efficiency, for the electrodes. (C) 2003 Elsevier B.V. All rights reserved.