Abstract

Quantum dot sensitized solar cells based on cascade structure of TiO₂/ZnO/CdS electrode and polysulfide electrolyte were fabricated. The ZnO layer was deposited on screen-printed TiO₂ layer by ultrasonic spray pyrolysis method. The structure, morphology and impedance of TiO₂/ZnO film photoanode and the photovoltaic performance of TiO₂/ZnO/CdS cell were investigated. It is found that the short circuit current density and conversion efficiency are significantly improved by the introduction of ZnO layer into TiO₂/CdS film. A power conversion efficiency of about 1.56% has been obtained for TiO₂/ZnO/CdS cell, which is about 57% higher than that for TiO₂/CdS cell (0.99%). The formation of an inherent energy barrier between TiO₂ and CdS films and the passivation of surface traps on the TiO₂ film caused by the introduction of ZnO layer, which reduces the charge recombination and favors the electron transport, should be mainly responsible for the performance enhancement of TiO₂/ZnO/CdS cell