Thin film TiO₂ electrodes derived by sol-gel process for photovoltaic applications

Nanocrystalline anatase TiO₂ thin films are prepared by a single spin-coating process from the sols with different ethanol content. The influence of the ethanol content and the heat treatment temperature on the structural and optical properties of the thin films is characterized by X-ray diffraction, atomic electron microscopy, and UV-vis spectroscopy. The results indicate that an anatase phase structure TiO₂ thin film with nanocrystallite size of about 20 nm and high transmittance can be obtained at the heat treatment temperature of 400 °C or above, that is to say, at the heat treatment temperature below 300 °C, the thin films grow in amorphous phase with a smooth surface; while the heat treatment temperature is increased up to 400 °C or above, the thin film develops a crystalline phase corresponding to the titanium oxide anatase phase.