Preparing ZnO nanowires in mesoporous TiO₂ photoanode by an in-situ hydrothermal growth for enhanced light-trapping in quantum dots-sensitized solar cells

Highlights: • To prepare the mesoporous TiO₂/ZnO NPs hybrid films. • Growing ZnO NWs in mesoporous TiO₂ by an in-situ hydrothermal growth. • To improve the light-trapping by the strong light scatting effect of ZnO NWs. - Abstract: This paper describes a solution-processed method for preparing TiO₂ nanoparticles (NPs) and ZnO nanowires (NWs) hybrid photoanodes, which includes two steps: the preparation of mesoporous (m) TiO₂/ZnO NPs hybrid films and the growth of ZnO NWs in the m-NPs hybrid films by an in-situ hydrothermal growth. This novel hybrid structure not only retains high surface areas of conventional TiO₂ NPs photoanodes in favor of photosensitizers adsorption, but also improves the light-trapping due to the strong light scatting effect of ZnO NWs with large size and facilitates the electron collection and transfer in hybrid photoanodes by a continuous NWs pathway. Herein, we used hybrid structured films as photoanodes in CdSe-sensitized solar cells. Due to the repeating reflections of injected light in hybrid films, the transmission of visible light was greatly reduced and the injected light was effectively confined in photoanodes. Thus, the incident photon-to-electron conversion efficiency (IPCE) and short-circuit current density (Jsc) were greatly improved. The results exhibited a remarkably enhanced Jsc of 18.2 mA cm⁻² and the power conversion efficiency (η) of 2.8% (i.e., 134% enhancement in Jsc and a 47.4% enhancement in η as compared to the pure TiO₂ NPs-based cell with Jsc of 7.79 mA cm⁻² and η of 1.9%).