CdS quantum dots sensitized mesoporous BiVO4 heterostructures for solar cells with enhanced photo-electrical conversion efficiency

Abstract

CdS quantum dots sensitized olive-shaped mesoporous BiVO4 for solar cells with enhanced photo-electrical conversion efficiency was prepared by solvothermal chemical reaction and successive ionic layer adsorption and chemical reaction (SILAR) techniques. An improved photo-electrical conversion efficiency of up to 1.29% is achieved for quantum dot sensitized solar cell (QDSCs) based on CdS/BiVO4 heterostructure photoanode, about two times larger than that of QDSCs based on pure BiVO4 photoanode (0.62%). Coupling CdS and BiVO4 with visible light response behavior can further improve the light absorbing range of the CdS/BiVO4 heterostructure photoanode and enhance the light absorbing ability, which can be confirmed by the UV–vis diffuse reflectance measurements. A uniquely matched energy band structure for CdS/BiVO4 heterostructure can be conducive to efficiently separate photogenerated charge carriers, and reduces the probability of recombination between light-induced electrons and holes, thus results in greatly enhanced photoelectric conversion efficiency. Electrochemical impedance spectroscopy measurements suggest that coupling m-BiVO4 with CdS QDs can effectively improve the charge transfer behavior. Furthermore, the formation of CdS/BiVO4 heterostructure can effectively prolong the charge carriers' lifetime. The large specific surface area and properly mesoporous structure of CdS/BiVO4 heterostructure can effectively adsorb more sensitizer and create more reaction center on the contact interface between the electrolyte and photoanode.