Preparation of WO3 Films with Controllable Crystallinity for Improved Near-Infrared Electrochromic Performances

In this study, a WO3 film with controllable crystallinity has been prepared by radio frequency magnetron sputtering. The WO3 film with about 400 nm thickness and controllable crystallinity not only has the advantages of amorphous WO3 with large transmittance modulation and short switching response time but also has the outstanding cyclic stability of crystalline WO3. Therefore, this WO3 film exhibits superior electrochromic performances including large transmittance modulation in the near infrared regime (72.5% at lambda = 1000 nm), short coloration/bleaching switching response time (5.3 s for coloration and 3.0 s for bleaching), high coloration efficiency at lambda = 1000 nm (80.5 cm(2) C-1), and excellent cycle stability. The strategy of preparing a WO3 film with controllable crystallinity by a simple magnetron sputtering method presents an innovative direction to obtain high-performance WO3 electrochromic materials applied in the fields of smart windows, spacecraft thermal control, and infrared camouflage.