Mercurochrome-sensitized composite TiO2/SnO2 and ZnO/SnO2 photoelectrochemical cells (DSC) have been fabricated from the mixture of the SnO2 particles and the semiconductor colloid (TiO2, ZnO). The influence of the mixed ratio on the performances of the composite semiconductor photoelectrochemical cells was studied. Comparing the composite TiO2/SnO2 and ZnO/SnO2 cells with the corresponding TiO2 and ZnO cells, the incident photon-to-current conversion efficiency of the composite cells was improved greatly. The photovoltage spectra (SPS) indicated that the dye molecule was adsorbed mainly by the TiO2 and ZnO particles respectively in the composite cells. The energy barriers between the different semiconductors contributed to the improvement of the short-circuit photocurrent. The possible transport mechanism of the photogenerated electrons in composite cells was percolation through the SnO2 particles. (C) 2004 Elsevier B.V. All rights reserved.