Forest-like TiO2 hierarchical structures for efficient dye-sensitized solar cells

Forest-like TiO2 hierarchical structures are prepared by the acid-assisted hydrothermal method without the use of any template or additive. The performances of dye sensitized solar cells (DSSCs) fabricated with the nanoforest structures are much higher than those assembled with nanorod array films. Crystalline nanorods and nanobranches act as preferential electron pathways for efficient charge collection. Nanobranches filling in the spaces among the nanorods increase the amount of dye-loading and enhance the light-harvesting property. Thus, our photoanode can take advantage of both fast electron transport and high surface area. DSSCs made of nanoforest films with a thin layer of nanocrystalline TiO2 as the adhesive show the maximum energy conversion efficiency. Without any mediator, we can also fix films on FTO glasses through physical effects, which suggests potential applications in flexible solar cells.