A cobalt sulfide (CoS) thin film is deposited on fluorine doped SnO2 (FTO) glass by repetitive electrophoretic deposition (EPD) and ion exchange deposition (IED), then the thin film is treated with sodium borohydride or/and sulfuric acid solution. The film is used as the counter electrode of dye-sensitized solar cells (DSSCs), and is characterized by field emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and Tafel measurements. The results show that the CoS counter electrode has a honeycomb-like morphology with large specific surface area, good catalytic activity for reduction of I-3, lower charge-transfer and series resistances, which result in the better electrochemical property of CoS counter electrodes. Under a simulated solar light irradiation of 100 mWcm (2), the DSSC based on the CoS counter electrode achieves a power conversion efficiency of 7.72%, thus, synthesized CoS can serve as an efficient Pt-free counter electrode material for DSSCs. (C) 2015 Elsevier Ltd. All rights reserved.