Constructing hierarchical porous titania microspheres from titania nanosheets with exposed (001) facets for dye-sensitized solar cells

In this paper, a facile approach for constructing hierarchical porous TiO2 microspheres from TiO2 nanosheets with exposed (001) facets has been demonstrated, which are synthesized using HF generated in situ by reaction of (NH4)2TiF6 and H3BO3 as a capping and stabilizing agent without introducing any additional HF or HCl under hydrothermal condition. The photoanode constructed with hierarchical porous TiO2 microspheres as top layer exhibits an improved photoelectric conversion efficiency (7.44%), which is about 1.2 times larger as than that of the commercial TiO2 nanoparticles as a benchmark photoanode (6.29%). This result is attributed to the superior light-scattering effect of microspheres, excellent light-reflecting ability of the mirror-like plane (001) facets and effective suppression of the back reaction. Therefore, TiO2 microspheres with exposed (001) facets have the potential applications in the construction of dye-sensitized solar cells.