Investigating the structural and optoelectronic properties of co-sputtered Fe-doped WO3 thin films and their suitability for photocatalytic applications

Tungsten oxide (WO3) thin films are widely used as functional coatings in electrochromic smart windows, gas sensing, and photocatalysis. Tailoring their properties is needed for their optimum use as coatings to meet the intended applications, with extrinsic doping as one of the best ways to achieve this objective. Fe has emerged as one of the most effective doping agents in WO3 owing to the similar ionic radii of W and Fe. Previous results highlighted an improvement in the structural, optoelectronic, and functional properties of Fe-doped WO3. In this work, Fe-doped WO3 thin films were deposited by co-sputtering. Contrary to previous reports, the films showed reduced crystallinity, enhanced electrical resistivity, and widened band gap, leading to inferior performance of functional coatings, as demonstrated by their lower photocatalytic water oxidation efficiency.