Hierarchical TiO2 Structures Derived from F− Mediated Oriented Assembly as Triple-functional Photoanode Material for Improved Performances in CdS/CdSe Sensitized Solar Cells

Abstract

A facile solvothermal method was adopted to prepare unique hierarchical TiO2 structures which are assembled from single-crystal tubes and inflated with oriented aligned nanoparticles. A F− mediated anisotropic assembling mechanism was proposed based on time dependent experiments and density function theory calculation. Hydrofluoric acid was found to play crucial roles on the nucleation, growth and assembling stages and hierarchical TiO2 structures consisted of solid and hollow branches could be selectively prepared via simply altering the hydrofluoric acid dosages. The as-prepared hierarchical TiO2 structures were employed as triple-functional photoanode material to boost the performances of CdS/CdSe sensitized solar cells. The hexagonal tubes with well-defined crystal facets exhibited high light-reflection rate for the incident light. Meanwhile, the inflated nanoparticles offered high accessible surface area of ∼71m2g−1, and the oriented aligned structures minimized the inter-particles defects to suppress the undesired charge recombination. Due to these structural qualities, the light harvesting efficiency and electron life time were substantially enhanced, which leads to a power conversion efficiency of 4.9%, representing a ∼40% improvement compared with nanoparticle based device (3.5%).