A comparative study of the density of surface states in solid and hollow TiO₂ microspheres

As a crucial photoelectric material, TiO₂ microspheres have been widely applied as photoanodes in photovoltaic devices owing to their large surface area, suitable pore size and prominent scattering effect. However, surface states in the TiO₂ films playing a significant role in the charge transport process are an important factor influencing the photovoltaic performance. Herein, solid and hollow TiO₂ microspheres were compared to investigate the influence of the density and distribution of surface states. The density and distribution of surface states, charge recombination process and band edge shifts were investigated. The results showed that the density of surface states of the TiO₂ microspheres decreased after recrystallization, leading to a suppressed charge recombination rate. Moreover, owing to the hollow architecture, recrystallized hollow microspheres (rHM) have higher photon utilization. As a result, a photoelectric conversion efficiency of dye-sensitized solar cells based on the rHM up to 10.57% was obtained.