Controlled Growth of TiO2 Nanotubes on Conducting Glass

We report on nanotubular TiO2 on top of a compact TiO2 layer on conducting glass substrates. Highly regular structures were obtained from anodization of DC sputtered Ti films of thicknesses between 0.2 and 2 mu m in ammonium fluoride containing ethylene glycol solutions. The influence of different anodization parameters was systematically analyzed revealing that full control over tube length, diameter, spacing, and tube wall thickness is possible. Inner tube diameters and spacing between tubes can be controlled via the anodization field. Tube wall thickness can be tuned using different anodization bath temperatures. Tube length can be adjusted by sputtering appropriate layers of Ti. The resulting TiO2 structures can be readily used in poly(3-hexylthiophene)-TiO2 hybrid solar cells and solid state dye sensitized solar cells. In contrast to anodized Ti foils the presented geometry allows the fabrication of photovoltaic devices which can be frontside-illuminated (through the glass substrate).