Hybrid electrochromic device with Tungsten oxide (WO3-x) and nafion   membrane: performance with varying tungsten oxide thickness
  Electrochromic devices, which dynamically change color under the applied potential, are widely studied because of its wide range of applications such as energy-efficient smart windows, rear view mirrors and display devices etc. In this study we are reporting four layer electrochromic device based on tungsten oxide as a electrochromic layer and nafion membrane as a ionic conducting layer. Nafion membranes are generally used in fuel cell applications because of its high ionic conductivity and high optical transparency which is suitable for electrochromic device to attain higher efficiencies. We have prepared an electrochromic device by sandwiching ITO coated glass and WO3 coated ITO thin film between nafion membrane. The overall structure of the device is Glass/ITO/WO3/Nafion/ITO/Glass. We deposited tungsten oxide thin films with different thickness on ITO coated glass substrate at room temperature by using reactive DC Magnetron sputtering and we studied the performance of the electrochromic device with the function of thickness. We have observed that electrochromic efficiency is increasing with increase in the tungsten oxide layer thickness. The efficiency of the device increased from 24.8 cm2/C to 184.3 cm2/C. 
K Uday Kumar, S D Bhat, V V Giridhar and A Subrahmanyam
cond-mat.mtrl-sci