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

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.