Rapid thermal annealing treatment on WO3 thin films for energy efficient smart windows

Electrochromic devices (ECDs) based on tungsten trioxide (WO3) have garnered significant attention in the areas of smart windows, dynamic display, low-power displays, and in other advanced sectors. The electrochromic property of WO3 is primarily influenced by both electron conduction and ion diffusion processes. This research investigates on the influence of rapid thermal annealing (RTA) on the electrochromic performance of RF sputtered tungsten oxide thin films, which relies on ion diffusion process. RTA treated film showed a mixture of amorphous and crystalline (monoclinic), heterostructure phase. Structural, compositional, electrical, optical, morphological, and electrochromic studies were carried out using various techniques. Based on the electrochromic analysis, WO3 thin films, RTA treated at 300oC showed higher diffusion coefficient with larger optical modulation (ΔT) of 80 % due the formation of heterostructure with more oxygen vacancies. We hope that this research could propose the possibility for developing high-performance electrochromic smart windows.