Symmetrical SnO2/W-doped VO2/SnO2 sandwich structures with high luminous transmittance, excellent solar modulation ability and low phase transition temperature

Abstract

Until now, it is still a challenging task to obtain VO2-based smart windows with high luminous transmittance (Tlum), satisfactory solar modulation ability (ΔTsol) and low phase transition temperature (Tc) close to room temperature. In this work, symmetrical SnO2(d nm)/W doped VO2 (W-VO2, 60 nm)/SnO2(d nm) (d = 0, 90, 150, 230, 260, 330) multilayer films were proposed and deposited on quartz glass substrates by pulsed laser deposition. The bottom SnO2 layer acted as buffer to improve the crystallinity of VO2, while the top SnO2 layer served as antireflection layer to enhance the optical properties. When SnO2 layer reached a certain thickness, the crystallinity of W-VO2 interlayer was significantly improved, and therefore the optical properties of the obtained tri-layer films were greatly increased. In comparison with the W-VO2 monolayer film, Tlum and ΔTsol of the tri-layer film with d = 260 nm increased from 45.0% to 54.4% and from 2.6% to 10.7%, respectively, while maintaining a low Tc of 39.0 °C. Interestingly, the prepared SnO2/W-VO2/SnO2 tri-layer films showed lively golden yellow or iridescent colors. The results provide a possibility for the design of VO2-based smart windows with low phase transition temperature and excellent thermochromic properties.