Electrochromic properties of TiO2 anatase thin films prepared by a dipping sol-gel method

Electrochromic TiO2 anatase thin films on ITO were prepared by the sol-gel dipping method using a solution of titanium tetraisopropoxide, diethanolamine and ethanol. The films were transparent in the visible range and can be colored in a solution of LiClO4 in propylene carbonate. The transmittances of the colored films were found to be strongly dependent on the Li+ inserted charge. Combining the experimental data obtained from in situ Raman and in situ transmittance spectra with the data from chronoamperometic measurements, it was demonstrated that the fully colorated state of the TiO2 anatase films is Li0.5TiO2 with a crystalline structure of Imma space group symmetry. In the Raman spectra this coloration state exhibits five characteristic bands at 176, 224, 316, 531 and 629 cm(-1). (C) 2002 Elsevier Science B.V. All rights reserved.