TiO₂ nanotube as additive to TiO₂ film for improving performance of dye-sensitized solar cells

The titanium dioxide nanotubes (TiNTs) were directly prepared from commercial P25 TiO₂ powder via alkali hydrothermal transformation. The fabricated nanotubes had an average outer diameter of 8-10 nm and the inner diameter of 46 nm with several hundred nanometers in length. The prepared nanotubes were added into TiO₂ nanoporous electrodes for the fabrication of dye-sensitized solar cells (DSCs). The photoelectrochemical characteristics and dye-adsorption properties were investigated by varying the proportion of the nanotubes incorporated into TiO₂ working electrodes. The electron transport resistance, electron life time, and dye adsorption properties were evaluated in terms of electrochemical impedance spectra and photovoltaic characteristics of the solar cells. Compared to DSCs based on TiO₂ nanoparticles, the fill factor, open-voltage, and photocurrent based on TiNT/P25 hybrid increased significantly. High conversion efficiency of light-to-electricity of 7.41% under illumination of simulated AM 1.5 sunlight (100 mW/cm²) was achieved for DSCs using optimized proportions of TiO₂ nanotubes incorporated into TiO₂ electrodes. The studies provided a promising method for the development of high efficiency and low cost DSCs.