Branched hierarchical photoanode of anatase TiO2 nanotubes on rutile TiO2 nanorod arrays for efficient quantum dot-sensitized solar cells

Abstract

We report novel hierarchical three-dimensional (3D) TiO₂ nanotube-branched rutile TiO₂ nanorod arrays (H-TiO₂ NRAs) on FTO substrates that serve as model architecture for efficient quantum dot-sensitized solar cells (QDSCs). The newly designed H-TiO₂ NRA photoanode offers a large surface area for high QD loading with high light scattering properties. In the meantime, the presence of anatase–rutile heterojunction at the interface helps the rutile nanorods to efficiently collect photo-injected electrons from the anatase nanotubes, reducing electron recombination with the electrolyte and QDs. As a result, the H-TiO₂ NRA photoanode with a thickness of only 1 μm, exhibits a solar energy conversion efficiency of 1.04%, which is 2.7 times higher than that found in the pristine nanorod array-based QDSCs, demonstrating the synergistic effect of rutile nanorods and anatase nanotubes for photoelectrochemical solar energy conversion.