Enhanced electrocatalytic activity and electrochemical stability of Cu2S/PbS counter electrode for quantum-dot-sensitized solar cells

•PbS nanoparticles were grown by SILAR technique on electrochemically synthesized Cu2S nanosheets.•FTO/Cu2S/PbS CE has the stepwise energy level configuration which enhances the fast charge transportation.•FTO/Cu2S/PbS CE has enhanced electrocatalytic activity as compared to the FTO/Cu2S CE.•FTO/Cu2S/PbS exhibited excellent electrochemical stability in polysulfide electrolyte.•QDSSC with the FTO/Cu2S/PbS (3 SILAR cycles) CE showed the highest efficiency.