Effect of Highly Ordered Single-Crystalline TiO2 Nanowire Length on the Photovoltaic Performance of Dye-Sensitized Solar Cells

One-dimensional semiconductor nanostructures grown directly onto transparent conducting oxide substrates with a high internal surface area are most desirable for high-efficiency dye-sensitized solar cells (DSSCs). Herein, we present a multicycle hydrothermal synthesis process to produce vertically aligned, single crystal rutile TiO2 nanowires with different lengths between 1 and 8 mu m for application as the working electrode in DSSCs. Optimum performance was obtained with a TiO2 nanowire length of 2.0 mu m, which may be ascribed to a smaller nanowire diameter with a high internal surface area and better optical transmittance with an increase in the incident light intensity on the N719 dye; as well as a firm connection at the FTO/TiO2 nanowire interface.