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

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 alpha-MoO3-Carbon composite (alpha-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 alpha-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 alpha-MoO3-C composite used as counter electrode gives stable and reproducible performance. The improvement in efficiency with alpha-MoO3-Ccomposite 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. alpha-MoO3-C composite has shown more electrocatalytic response for the reduction of redox species of the polysulfide than platinum and Cu2S.