Tungsten Oxide Thin Films for Electrochromic Applications: Pulse Width-Controlled Deposition by High-Power Impulse Magnetron Sputtering

Tungsten oxide (WO3) thin films have been of prime interest among electrochromic materials because of their chemical stability, strong adherence to various substrates, and high coloration efficiency. High-power impulse magnetron sputtering (HiPIMS) holds great potential in fabricating durable WO3-based electrochromic layers. However, the tungsten target-plasma interactions in reactive-HiPIMS deposition of WO3 and their role in modulating the electrochromic function of the resulting WO3 coatings are yet to be understood. Herein, by controlling the HiPIMS pulse length, the stoichiometry of tungsten oxide structures can be tuned to optimize the transparency and electrochromic function of the coatings. X-ray photoelectron spectroscopy data shows that at pulse lengths shorter than 85 mu s, the concentration of suboxide compounds is less than that of tungsten trioxide, while for pulse lengths longer than 100 mu s, this balance is reversed. The average optical transparency of the coatings in the range of visible light is higher than 80%. The optical transmittance modulation (Delta T) of 38.1, 36.2, and 34.3% and coloration efficiency of 41.3, 38.4, and 35.9 cm2 C-1 are measured for the WOx samples deposited at pulse lengths of 70, 85, and 100 mu s, respectively. Tuning the HiPIMS pulse characteristics is a simple strategy to deposit tungsten oxide films with tuned electrochromic properties for an array of applications, from smart windows to wearable displays. This article reports the fabrication of tungsten oxide electrochromic coatings using reactive high-power impulse magnetron sputtering (HiPIMS). Results demonstrate the tunability of tungsten oxide structures via HiPIMS pulse length, optimizing coating transparency and electrochromic properties. Tuning HiPIMS pulse characteristics offers a straightforward approach to deposit tailored tungsten oxide films for diverse engineering applications, including smart windows and wearable displays.image (c) 2024 WILEY-VCH GmbH