Copper sulfide/Lead sulfide as a Highly Catalytic Counter Electrode for Zinc Oxide Nanorod Based Quantum Dot Solar Cells

•Voc is increased from 0.63 V to 0.72 V with CuS/(4cycle)PbS counter electrode.•The maximum η 2.2%, is achieved in QDSSCs when cycle of PbS is 4.•The Rct is reduced with increasing cycle of PbS up to 4 and raised thereafter.•CuS/PbS counter electrode has higher redox current densities than the bare CuS.

This work investigates the improvement in efficiency of quantum dot sensitized solar cells (QDSSCs) using CuS/PbS as counter electrode, which results in formation of highly efficient counter electrode for liquid-junction QDSSCs. The QDSSC on based CuS/PbS counter electrode exhibits power conversion efficiency (η) of 2.2%, which is higher than that of CuS counter electrode, 1.17%. The improvement in η is probably attributed to the reduction of electron back into CuS/PbS counter electrode. Electrochemical impedance spectroscopy and cyclic voltammetry results confirm that higher value of η in CuS/PbS counter electrode is because of this novel counter electrode which shows superior photo-electrochemical performance and electro-catalytic properties. Another reason for this higher η might be the reduction in the charge transfer resistance at the counter electrode/electrolyte interfaces.