Hydrothermal growth of branched hierarchical TiO2 nanorod arrays for application in dye-sensitized solar cells

In this study, rutile branched hierarchical TiO2 nanorod arrays were prepared on transparent conductive glass (FTO) through a facile two-step hydrothermal method. The microstructure and growth mechanism of branched TiO2 nanorod arrays were investigated respectively by means of X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The dye-sensitized solar cells based on the branched TiO2 nanorod arrays which were only about 1.5 mu m in length show a overall power conversion efficiency of 2.01%, which is nearly three times as high as that of pure nanorod arrays. The enhanced efficiency can be ascribed to the increased specific surface area from the nanobranches, which can improve the amount of dye adsorption, as well as the better light scattering effect. Furthermore, the electrochemical impedance spectra results show that the branched TiO2 nanorod arrays can also decrease the resistance of the electron transfer at the TiO2/dye/electrolyte interface, and leading to a rapid electron transport.