Electrochromic Co3O4 electrodes have been synthesized through soft solution chemistry on ITO-coated glass substrates followed by heat treatment. X-ray diffraction result reveals that the crystalline Co3O4 phase is formed over the treated temperatures from 100 to 500 degrees C and its crystallinity becomes stronger as the temperature increases. Among the tested electrodes, the best electrochromic performance is obtained for the electrode treated at 100 degrees C by showing ca. 15% of optical change, relatively fast response times and high coloration efficiency of ca. 32.5 cm(2) C-1. This low temperature synthesis process allows the electrochromic active Co3O4 film to be formed on flexible polymer substrates. (c) 2008 Elsevier B.V. All rights reserved.