alpha-Ag2S, with a direct forbidden bandgap of about 1.0 eV, is a non-toxic low bandgap semiconductor which can readily be deposited in the form of a thin film by chemical bath deposition. In a solar cell configuration, it can potentially provide a high short-circuit current due to the infrared absorption, and is compatible with the polysulfide electrolyte. Its practical use in a solar cell depends, however, critically on band alignment between the Ag2S, the oxide anode and the electrolyte redox potential. Here we examine the conduction band (CB) offsets in the nanostructured alpha-Ag2S sensitized TiO2 and SnO2 electrodes by X-ray Photoelectron Spectroscopy, and show that they can significantly differ from the extrapolated bulk values. The much higher CB offset for SnO2/Ag2S interface (similar to 0.6 eV) compared with that of similar to 0.2 eV for TiO2/Ag2S, supplied a sufficient injection driving force and was favorable for the electron separation at the heterojunction. When fabricated into solar cells, a dramatically higher current density under AM 1.5 illumination for the SnO2/Ag2S heterojunction was obtained, which was contributed by the efficient electron injection. (C) 2013 Elsevier B.V. All rights reserved.