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

Abstract

A new strategy has been successfully developed for highly efficient copper sulfide/lead sulfide (Cu2S/PbS) counter electrodes (CEs) for quantum-dot-sensitized solar cells (QDSSCs). PbS nanoparticles were grown by successive ionic layer adsorption and reaction (SILAR) technique for various cycles (from 1 to 4) on electrochemically deposited Cu2S nanosheets. All the Cu2S and Cu2S/PbS CEs showed petal-like morphology and nanosized PbS nanoparticles were deposited over the Cu2S nanosheets. All FTO/Cu2S/PbS CEs exhibited superior electrocatalytic activity than FTO/Pt and FTO/Cu2S CEs. In particular, QDSSCs with FTO/Cu2S/PbS CE (3 SILAR cycles) exhibited extremely high short-circuit current density (18.08 mA cm−2) and fill factor (53.55%), resulting in a significantly enhanced power conversion efficiency as high as 5.28%. This is because the FTO/Cu2S/PbS CE not only exhibits the cascaded, stepwise energy level configuration, which enhances the fast charge transportation, but also serves as a blocking layer to prevent electrons from returning from the electrolyte to the Cu2S. Furthermore, FTO/Cu2S/PbS exhibited excellent electrochemical stability unlike FTO/Cu2S, owing to the passivation of PbS. © 2020 Elsevier B.V.