The effects of hydrothermal temperature on the preparation of TiO2 colloids, and their film thickness on fluorine-doped tin oxide (FTO) glass, toward the performance of a dye-sensitized solar cell (DSSC) were investigated. Pore diameter and surface area of the TiO2 are of paramount importance in determining the cell efficiency. With the increase of hydrothermal temperature, the pore diameter increases linearly; however, the surface area shows the reverse effect. It is found that the DSSC assembled with the TiO2 films prepared under the hydrothermal temperature of 240 degrees C, and the film thickness larger than 10 mu m gives optimal performance. The effect of film thickness of TiO2 on the performance of the DSSC can be explained by the relative size of reactive species diffusing into the thin film and the lifetime of injected electrons. Electrochemical impedance spectroscopy (EIS) was also used to analyze the resistance of the cell, developed as a result of the change in the thickness of the TiO2 thin film. The at-rest stability for over 200 days was monitored and the results show that the solar energy conversion efficiency was found to decrease from 5.0% of initial value to 3.0% at the end. (c) 2006 Elsevier B.V. All rights reserved.