TiO2 nanoparticle/ZnO nanowire hybrid photoanode for enhanced quantum dot-sensitized solar cell performance

Abstract

A hybrid structured TiO₂/ZnO photoanode was composed of highly ordered ZnO nanowires (NWs) and small TiO₂ nanoparticles (NPs) filling the gaps among ZnO NWs. In this way, ZnO NWs provide a direct pathway to facilitate electron collection and transport and increase light scattering and trapping. TiO₂ NPs provide a large specific surface to effectively adsorb quantum dots (QDs). In experiments, the density of ZnO NW arrays was first controlled by regulating the ratio of TiO₂ NPs to ZnO NPs and the concentration of ZnO NPs in the hybrid NP seed precursor, and then the TiO₂ paste was successfully use to fill the gaps among NWs by a large centrifugal force. Using TiO₂ NP/ZnO NW films as photoanodes, we fabricated CdSe QD-sensitized solar cells and tested their photovoltaic (PV) performances. The results demonstrated a remarkably enhanced short-circuit current density (J_sc) of 7.9 mA cm⁻² and power conversion efficiency (η) of 1.55%, and this η is enhanced by 19.2% and 30.3%, respectively, compared to those of a TiO₂ NP device with an η of 1.3% and a ZnO NW device with an η of 1.19%.