Green Fluorine-Free Synthesis of Hollow Rectangular Prism-like TiO2 Mesocrystals with Exposed {001} Facets for High-Performance Dye-Sensitized Solar Cells

In this work, the hollow rectangular prism-like TiO2 (HRP-TiO2) mesocrystals with exposed {001} facets were synthesized via an in-situ hydrothermal process without introducing any additional hydrofluoric acid or fluoride-containing compounds. A double-layer structured photoanode based on HRP-TiO2 mesocrystals (as the light scattering top layer) and TiO2 nanocrystalline (TiO2-NC, as the underlayer) was constructed. The dye-sensitized solar cell (DSSC) based on the double-layer photoanode showed a remarkable efficiency of 9.16%, which was superior to the pure TiO2-NC photoanode-based counterpart (8.19%). The efficiency improvement was attributed to the multiple advantages of HRP-TiO2 mesocrystals with high crystallinity and superior light scattering capability. More importantly, the anatase phase mesocrystals with exposed {001} facets could provide efficient pathway for electrolyte diffusion and electron transport.