Electrochromic properties of ITO nanoparticles/viologen composite film electrodes

Nanostructured composite electrodes were prepared by dip-coating a mixed dispersion of ITO nanoparticles and 1,1'-didodecyl-4,4'-bipyridinium (DDV2+) dibromide on an ITO-coated glass plate, and their electrochromic properties were investigated in a 0.1 M Li2SO4 aqueous solution. The electrodes showed a color change from pale white to violet as they were oxidized and reduced, respectively, and good electrochromic performances; i.e., switching times of coloration (500 ms) and decoloration (380 ms), coloration efficiency of 140 cm(2) C-1, long-term stability (>500 test cycles), and a memory life time greater than at least 24 h.