Synthesis and Photovoltaic Devices Performance of Single Crystalline TiO2 Nanowire Bundle Arrays

Highly oriented single-crystalline TiO2 nanowire bundle arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates were prepared by hydrothermal method using the precursors of tetrabutyl titanate, deionized water and hydrochloric acid. The structure and morphology characteristics of all the samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Results show that highly uniform and dense vertical arrays of single crystalline nanowire bundles with flat tetragonal crystallographic planes are formed. The nanowire bundles have a width of 110-210 nm (approximately 20-40 nanowires in each bundle), the single nanowire's diameter is between 4-6 nm, and the length of the nanowire bundle is about 3 mu m. Dye-sensitized solar cells (DSSCs) made from oriented TiO2 nanowire arrays anode are studied. The open circuit voltage, short circuit current density and fill factor of the cells are about 0.72 V, 2.9 mA/cm(2) and 0.42, respectively. The power conversion efficiency is about 0.88%.