Zinc oxide/copper sulfide nanorods as a highly catalytic counter electrode material for quantum dot sensitized solar cells

Abstract

Copper sulfide deposited ZnO nanorods (ZnO NRs/CuS) have been applied as a new counter electrode material with high electrocatalytic activity towards polysulfide electrolyte, which results in the formation of a highly efficient counter electrode for QDSSCs. It was observed from the current density–voltage (J–V) characteristics that the short-circuit current density (J_sc), power conversion efficiency (PCE), and fill factor (FF) were enhanced from 7.63 mA cm⁻² to 14.48 mA cm⁻², 1.59% to 4.18%, and 0.29 to 0.38, respectively, when a bare CuS counter electrode was changed to a ZnO NRs/CuS counter electrode. Electrochemical impedance spectroscopy (EIS), Tafel polarization and cyclic voltammetry (CV) measurements demonstrate that the higher PCE value obtained using the ZnO NRs/CuS counter electrode is due to its superior photoelectrochemical performance and electrocatalytic activity. Another reason for this higher PCE might be the reduction in charge transfer resistance at the counter electrode/polysulfide interface.