The photoelectric properties of ZnO microspheres, ZnO/Ag2S heterogeneous microspheres and Ag2S hollow microspheres were investigated systematically by surface photovoltage, transient photovoltage and surface photocurrent techniques. The ZnO/Ag2S heterostructure shows superior photoelectric properties in visible-light region compared with pure Ag2S. Transient photovoltage results reveal the separation processes of photo-generated charge carriers in the samples. The photoelectric ethanol sensing property induced by visible light for the ZnO/Ag2S heterostructure has been found, which should be valuable for the practical application of semiconductor gas sensors at room temperature. (C) 2012 Elsevier B.V. All rights reserved.