Electrochromic properties of tungsten trioxide (WO3) layers grown on ITO/glass substrates by magnetron sputtering

WO3 layers were grown on glass substrates by pulsed DC magnetron sputtering. A series of WO3 layers were deposited at different growth powers changing from 0.7 kW to 1.5 kW. The effects of the growth power on the electrochromic properties of WO3 thin films were investigated. By using X-ray diffractometry, it was obtained that WO3 thin films had amorphous crystal structure. Electrochromic measurements were studied by cyclic voltmeter, chronoamperometry and lifetime cycle measurements. An increase in the coloration efficiency from 55 cm(2)/C to 87 cm(2)/C was found with decreasing growth power. Moreover, the decrease in the growth power leads to a decrease in the coloration and bleaching times from 11.75 s to 5.93 s and from 17.35 s to 9.69 s, respectively. All the changes in the coloration efficiency and coloration and bleaching times with a decrease in growth power could be explained by the kinetics of electrochromic reactions. This is associated with the density of the WO3 thin films which is increasing from 7.06 g/cm(3) to 7.59 g/cm(3) by increasing the growth power from 0.7 kW to 1.5 kW. (C) 2015 Elsevier Ltd. All rights reserved.