Bunchy TiO2hierarchical spheres with fast electron transport and large specific surface area for highly efficient dye-sensitized solar cells

The exploration of TiO2nanostructures with fast electron transport and large specific surface area is essential for their applications in solar cells. For this aim, bunchy TiO2hierarchical spheres (BS-TiO2), consisting of multiple TiO2microspheres constructed by nanosheets and the 1D TiO2nanobelt, were rationally designed and fabricated. BS-TiO2enables the much fast charge transport properties in the photoanode (with a long electron diffusion length of 36μm) and shows large specific surface area (higher than 200m2/g), leading to excellent electron collection and light harvesting, which enable the increased conversion efficiency of the dye-sensitized solar cell by 34% for BS-TiO2photoanode (7.5%) compared to nanoparticle (P25) photoanode. This work provides an important approach for the rational design of the TiO2nanostructures, which also implies the application of the bunchy TiO2hierarchical spheres in other type of solar cells, artificial photosynthesis, and other optoelectronic applications.