Silver sulfide (Ag2S) nanocrystals as a co-sensitizer with complementary absorption spectra are deposited on the surface of titanium dioxide (TiO2) nanocrystalline/ITO photoelectrodes to improve the photocurrent densities of cadmium sulfide (CdS) sensitized TiO2/ITO photoelectrodes. Both Ag2S and CdS are directly synthesized using a newly developed molecular precursor decomposition method. The effect of deposited Ag2S on the photoelectrochemical properties of the CdS/Ag2S/TiO2/ITO photoelectrodes has been investigated. Compared to the CdS/TiO2/ITO electrode without Ag2S, the deposited Ag2S nanocrystals significantly increase the light absorption of the CdS/Ag2S/TiO2/ITO electrode. Moreover, the photocurrent density of the CdS/Ag2S/TiO2/ITO electrode can be improved due to the increased light absorption and reduced charge recombination. However, excessive deposition amount of Ag2S is not conducive to the further increase of photocurrent density of the CdS/TiO2/ITO electrode. (C) 2015 Elsevier B.V. All rights reserved.