Nanosheet-based hierarchical ZnO structure decorated with TiO2 particles for enhanced performance in dye-sensitized solar cell

Abstract

A hierarchical ZnO structure assembled by nanosheets was prepared through a low temperature chemical bath deposition and a growing-melting mechanism was proposed to elucidate the shape evolution. Afterwards, a poly (vinylpyrrolidone) (PVP) assisted hydrothermal method was adopted to decorate TiO₂ particles onto the ZnO structure. When used in dye-sensitized solar cells, the device employing the hybrid ZnO/TiO₂ photoanode exhibited improved short-circuit current density (J_sc), open-circuit voltage (V_oc) and filling factor (FF), which resulted in a higher power conversion efficiency (PCE) of 3.60% in comparison to 1.96% from the pure ZnO cell. Based on the investigation of UV-vis absorption and diffuse-reflection spectra, Mott-Schottky analysis, electronic impedance spectra (EIS) and incident monochromatic photo-to-electron conversion efficiency (IPCE), the effect of TiO₂ modification on the photovoltage performances of the ZnO sheet-based hierarchical structures was studied in detail.