Hydrothermal synthesis of rutile-anatase TiO2 nanobranched arrays for efficient dye-sensitized solar cells

Abstract Rutile–anatase TiO 2 nanobranched arrays were prepared in two sequential hydrothermal-synthesis steps. The morphologies and crystalline nanostructures of the samples were investigated by controlling growth time and the concentration of the titanium precursor. All samples were characterized by field-emission scanning electron microscopy and X-ray diffraction analysis. It was found that treating the surfaces of rutile TiO 2 nanorods with aqueous TiCl 4 solutions allows the anatase TiO 2 nanobranches to grow perpendicular to the main rutile TiO 2 nanorods attached to the FTO glass. Irregularly shaped, dense TiO 2 structures formed in the absence of TiCl 4 treatment. A light-to-electricity conversion efficiency of 3.45% was achieved using 2.3 μm tall TiO 2 nanobranched arrays in a dye-sensitized solar cell. This value is significantly higher than that observed for pure rutile TiO 2 nanorods.