Thickness-dependent electrochromic properties of solution thermolyzed tungsten oxide thin films

Tungsten oxide (WO3) thin films are prepared by using a simple and inexpens ive solution thermolysis technique. Thin film samples of different thicknes s are obtained by varying quantity of ammonium tungstate solution sprayed o nto the preheated conducting glass substrate. A simple three-electrode cell has been formed to study the electrochemical and electrochromic properties . The electrochemical parameters of the cell such as anodic peak current, a nodic peak potential, threshold voltage, amount of H+ ions intercalated int o and deintercalated out of the WO3 samples are calculated. The effect of f ilm thickness on these parameters are studied. The extent of electrochromis m and reversibility of the colouration/bleaching processes of various WO3 s amples are described. The colouration efficiencies at 633 nm are calculated . The maximum colouration efficiency obtained for thicker film, is 56 cm(2) /C. The samples were found to be stable in 0.05N H2SO4 electrolyte up to 1 x 10(3) colour/bleach cycles. (C) 2000 Elsevier Science B.V. All rights res erved.