Electrochromic Properties of Reactive Magnetron Sputtered WO3 Thin Films Prepared by Neon as Sputter Gas

Abstract

Electrochromic phenomenon is an emerging technology for renewable energy applications. Several material oxides used for the electrochromic application, the tungsten oxide (WO3) has shown good coloration efficiency (CE). Present manuscript, we are reporting the results of the coloration efficiency of DC magnetron sputtered WO3 films for electrochromic applications (thicknesses 190 nm to 700 nm) with sputter gas neon at 300 K. Hydrogen and Lithium ions have been intercalated into WO3 lattice for coloration. The CE value is increasing with increase of thickness of WO3 thin films; CE for 700 nm thick films are: 87 cm2/C and 137 cm2/C for H+ and Li+ respectively. The coloration efficiency (CE) observed to be increasing with wavelength. The maximum efficiency of the hydrogen intercalated neon sputtered films achieved at 860 nm wavelength is about 129.9 cm2/C and for the lithium intercalatedWO3 films the maximum efficiency achieved at 780 nm with 238.5 cm2/C. These neon sputtered WO3 thin films show good stability of coloration efficiency even after 500 cycles of coloring and bleaching cycles. The work function of the colored and transparent states of WO3 thin films are 4.513 eV and 4.755 eV respectively. Finally we have fabricated the electrochromic device (ECD) prepared with nafion thin film as an ion conducting layer and the ECD has shown a maximum coloration efficiency (CE) of 112.1 cm2/C.