The use of cells based on cobalt sulfide (CoS2) and nickel sulfide (NiS) has found a steep upsurge in solar cell applications and as a substitute for conventional Pt-based cells owing to their low cost, low-temperature processing ability, and promising electro-catalytic activity. In this study, CoS2, NiS and Ni-doped CoS2 nanoparticles were incorporated on a fluorine-doped tin oxide (FTO) substrate by simple chemical bath deposition (CBD). The surface morphology of the obtained films was analyzed by scanning electron microscope. Tafel polarization, electrochemical impedance spectroscopy and cyclic voltammograms of the Ni-doped CoS2 (Ni 15%) films indicated enhanced electro-catalytic activity for I-3(-) reduction in dye sensitized solar cells (DSSCs) compared to a Pt CE. The Ni-doped CoS2 CE also showed an impressive photovoltaic conversion efficiency of 5.50% under full sunlight illumination (100 mW cm(-2), AM 1.5 G), exceeding that of DSSCs using a Pt CE (5.21%). We show that the highest conversion efficiency mainly depends on the charge transfer resistance and adequate Ni ion doping with CoS2 nanoparticles (C) 2015 Elsevier B.V. All rights reserved.