Hierarchical TiO2 microspheres comprised of anatase nanospindles for improved electron transport in dye-sensitized solar cells

Abstract

Hierarchical TiO₂ microspheres assembled by nanospindles were prepared via a two-step hydrothermal method. The as-prepared products have uniform diameters of ∼450 nm and surface area of ∼88 m² g⁻¹. The optical investigation evidenced that the photoanode film has a prominent light scattering effect at a wavelength range of 600–800 nm and possesses enhanced dye loading capacity. In addition, the electron recombination and transport dynamic measurements indicated that these hierarchical products could suppress the recombination and improve the diffusion coefficient of the photoelectrons, which can be attributed to the improvement of the connectivity by bridging the neighbouring microspheres through the embedded nanospindles. As a result, a high power conversion efficiency of 8.5% was demonstrated, indicating a ∼30% improvement compared with the cell derived from the well-defined nanocrystalline microspheres (6.5%).