Facile Preparation of TiO₂ Nanobranch/Nanoparticle Hybrid Architecture with Enhanced Light Harvesting Properties for Dye-Sensitized Solar Cells

We report TiO₂ nanobranches/nanoparticles (NBN) hybrid architectures that can be synthesized by a facile solution phase method. The hybrid architecture simultaneously improves light harvesting and charge collection performances for a dye-sensitized solar cell. First, TiO₂ nanorods with a trunk length of 2 m were grown on a fluorine-doped tin oxide (FTO)/glass substrate, and then nanobranches and nanoparticles were deposited on the nanorods' trunks through a solution method using an aqueous TiCl₃ solution at 80°C. The relative amount of nanobranches and nanoparticles can be controlled by multiplying the number of TiCl₃ treatments to maximize the amount of surface area. We found that the resultant TiO₂ NBN hybrid architecture greatly improves the amount of dye adsorption (five times compared to bare nanorods) due to the enhanced surface area, while maintaining a fast charge collection, leading to a three times higher current density and thus tripling the maximum power conversion efficiency for a dye-sensitized solar cell.