Electrochromic properties of TiO2 thin films prepared by chemical solution deposition method

Electrochromic titanium dioxide (TiO2) films were deposited on TiO2 (sputtered)/indium-tin-oxide (ITO)-glass substrates by the chemical solution deposition method (CSD) using a solution mixture of titanium diisopropoxide bis(acetylacetonate) and 2-methoxyethanol. The sputtered TiO2 thin film was used as a buffer layer to increase the adhesion between TiO2 film and ITO-glass substrate. TiO2 films were dried in air at 150 degrees C for 10 min, and coating/drying operations were repeated until the desired thickness was obtained. By changing the heating temperature (150-400 degrees C), the effects of various processing parameters on the films' characteristics are studied. Electrochromic properties of TiO2 films were investigated using cyclic voltammograms (CVs) and in situ transmittance measurements, which were carried out on TiO2 films immersed in an electrolyte of 1 M LiClO4 in propylene carbonate (PC). TiO2 films were found to show reversible blue coloration upon Li+ ion intercalation in this study. Experimental results reveal that the processing parameters will influence the electrochromic properties of TiO2 films such as transmittance, CVs, inserted charge, optical density change, coloration efficiency and insertion coefficient. (C) 2007 Elsevier Ltd. All rights reserved.