Characteristics of Low-Temperature Annealed TiO₂ Films Deposited by Precipitation from Hydrolyzed TiCl₄ Solutions

The effect of annealing temperature on the properties of TiO 2 films prepared from hydrolyzed TiCl 4 solutions was characterized by X-ray diffraction (XRD) and photoelectrochemical measurements. It is found that the amount of rutile in the TiO 2 films increases from room temperature to 250 °C. Above 250 °C, the amount of crystalline rutile material did not change. Analysis of XRD data suggests that a noncrystalline phase is converted to the rutile phase of TiO 2 by heat treatment of the films. Furthermore, the analysis indicates that the size of the rutile crystallites increases with temperature from about 100 to 400 °C. The photocurrent and conversion efficiency of the cells improved substantially with annealing temperature. The higher photocurrent appears to correlate with the increased crystallinity of the film. The TiO 2 material displayed a photochromic effect.