ZnO nanowire/TiO2 nanoparticle photoanodes prepared by the ultrasonic irradiation assisted dip-coating method

Hybrid ZnO/TiO2 photoanodes for dye-sensitized solar cells were prepared by combining ZnO nanowire (NW) arrays and TiO2 nanoparticles (NPs) with the assistance of the ultrasonic irradiation assisted dip-coating method. Results show that the ultrasonic irradiation was an efficient way to promote the gap filling of TiO2 NPs in the interstices of ZnO NWs. Hybrid ZnO NW/TiO2 NP electrodes prepared with ultrasonic treatment exhibited better gap filling efficiency and higher visible absorptance. The overall conversion efficiency of the hybrid electrode was 0.79%, representing 35% improvement compared with that of the traditional one (0.58%). The enlarged surface area and improved attachments of TiO2 NPs onto the walls of ZnO NWs induced by the application of ultrasonic irradiation may be the underlying reason. Electrochemical impedance spectroscopy measurements indicated that hybrid electrodes combined the advantages of improved electron transport along the ZnO NWs and increased surface area provided by infiltrated TiO2 NPs, both of which are responsible for the improved cell efficiency.