TiO2 film for use as dye-sensitized solar cell was prepared using the TiO2 colloidal sols (unpeptized sol and peptized sol). The optical properties and photocurrent-voltage characteristics of the resultant films were investigated. The optical transmittance of TiO2 thin film prepared front the peptized colloidal so] was over 90%, while that of TiO2 film from the unpeptized so] was under 80%. The TiO2 photoelectrode prepared from the peptized colloidal sol showed low photoelectric conversion efficiency (eta), 1.30%, whereas the efficiency of photoelectrode from the unpeptized sol was 2.21%. The high optical transmittance and low conversion efficiency of TiO2 film from the peptized so] are discussed in terms of dense microstructure due to the drying nature of well-dispersed colloidal sol. (C) 2004 Elsevier Inc. All rights reserved.