Enhanced electrochemical performance of WO3 thin films prepared from polyvinyl alcohol-modified nanoparticle ink

Tungsten oxide (WO3) is a potential material in catalysis, sensors, electrochromic devices, etc. In this research work, porous WO3 thin films are prepared on FTO-glass employing spin coating of WO3 nanoparticle's ink modified with polyvinyl alcohol (PVA) in the concentration range of 0 to 25.0 wt%. This study explored the change in structure and morphology of WO3 thin films with varying PVA concentration in ink composition and their effect on the ability to intercalate and de-intercalate Li+ ions as a function of applied bias. The wettability of ink on FTO-glass improved by raising its PVA content. All WO3 thin films exhibited a monoclinic structure. Scanning electron microscopy images indicated that the porosity of WO3 thin films gradually increased with increasing PVA concentration up to 25 wt% but the thin film became highly nonuniform at a very high concentration of additive. WO3 thin film prepared with ink having 10 wt% of PVA had optimum porosity and uniformity, therefore, yielded better electrochemical performance compared with all other samples. The addition of an optimum amount of PVA to ink is found to be an effective approach to modulating ink's characteristics and inducing porosity in thin films which eventually improves their redox reaction characteristics.