Cobalt sulfide (CoS) agglomerated nanoparticle thin films obtained by a facile chemical bath method at different deposition times. The CoS counter electrode (CE) deposited at 3 h deposition time (CC-3h) based quantum dot sensitized solar cells (QDSSCs) achieves higher power conversion efficiency (eta) of 3.67% than those of CC-2h (1.83%), CC-4h (2.52%), and Pt (1.48%) CEs, under one sun illumination (100 mW cm(-2), AM 1.5 G). The electrochemical analysis revealed that CC-3h CE shows a smaller charge transfer resistance (9.22 Omega) at the CE/electrolyte interface than the CC-2h (23.34 Omega), CC-4h (19.73 Omega) and Pt (139.92 Omega) CEs, respectively. (C) 2017 Elsevier B.V. All rights reserved.