Surface reinforced platinum counter electrode for quantum dots sensitized solar cells

•CuS nanoplatlet prepared by chemical bath deposition method.•Low charge transfer resistance measured from cyclic voltammetry.•High exchange current density from Tafel measurement.•Long term stability with high open circuit voltage and fill factor is added advantageous.

Surface modified platinum counter electrode with high catalytic activity and long term stability in polysulfide redox electrolyte is reported. The surface reinforcement was performed using a thin passivating layer of copper sulfide nanoplatlets over Pt surface by simple chemical bath deposition technique. This results in a very low charge transfer resistance of 8.21 Ω; which is several orders of magnitude lower than that of conventional Pt counter electrode against polysulfide electrolyte. Apart from this, modified Pt counter electrode shows an enhanced current density, high stability and overall improvement in photovoltaic and electrochemical performance of TiO2/CdS/ZnS quantum dot sensitized solar cells compared with bare Pt and CuS counter electrodes.