α-MoO3-C composite as counter electrode for quantum dot sensitized solar cells

Abstract

Counter electrodes plays a vital role in electron transport in operation of QDSSCs. The lower charge transfer resistance at counter electrode - electrolyte interface fecilitates improvement in photoconversion efficiency. The present study describes a novel and facile Spray Pyrolysis method for fabrication of low cost α-MoO3-Carbon composite (α-MoO3–C) material which is used as counter electrode (CE) in QDSSCs. The QDSSC with TiO2 photoanode sensitized by cadmium sulphide (CdS) QDs and polysulfide as electrolyte and α-MoO3-C composite as counter electrode exhibited solar energy-to-electricity conversion efficiency of 1.29%, which is better than those of the cells that used platinum and Cu2S as counter electrodes. QDSSCs with α-MoO3-C composite used as counter electrode gives stable and reproducible performance. The improvement in efficiency with α-MoO3-C composite Counter electrode was mainly driven by the improvement in photocurrent density and decrease in charge transfer resistance at counter electrode – electrolyte interface. Electrochemical impedence spectroscopy studies are carried out to understand electron transport in the device at various interfaces. α-MoO3-C composite has shown more electrocatalytic response for the reduction of redox species of the polysulfide than platinum and Cu2S.