Recently, a cobalt complex based electrolyte such as [Co(bpy)(3)](2+/3+) was suggested to replace the conventional I-3(-)/I- system because of its potential to provide high open circuit potential and power conversion efficiency in dye-sensitized solar cells (DSSCs). Here, a cobalt sulfide thin film was synthesized by electrochemical deposition and used for a counter electrode. A DSSC with the cobalt sulfide counter electrode exhibits J(sc) = 7.228 mA/cm(2), which is 13% higher than that with Pt (J(sc) = 6.443 mA/cm(2)), thereby achieving an enhanced power conversion efficiency. Electrochemical impedance spectroscopy measurements indicate that the reduced Warburg diffusion impedance and faster adsorption of [Co(bpy)(3)](3+) facilitate the reduction of the cobalt complex. (C) 2013 Elsevier Ltd. All rights reserved.