Double-layer VO2 thin film patterned by SiO2 spheres with improved thermochromic properties for smart windows
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The double-layer vanadium dioxide (VO2) thin film patterned by SiO2 spheres has been fabricated to enhance luminous transmittance (Tlum) without severely expense of solar modulation ability (ΔTsol) for the thermochromic smart windows. The first layer of vanadium thin film was deposited on the substrate with self-assembly SiO2 spheres and then the SiO2 spheres was removed by ultrasonic oscillation. The orderly perforated vanadium thin film with regular pores formed. Afterwards, the second layer of vanadium thin film was deposited on the perforated vanadium thin film. The semi-perforated double layer of vanadium thin film formed and was rapid thermal annealed forming the semi-perforated double VO2 thin films. Compared with continuous VO2 thin film(Tlum, 8.8%, ΔTsol, 5.9%), the semi-perforated double VO2 layer possesses orderly-patterned crater, which facilitate Tlum (42.6%) and only slightly attenuate the ΔTsol (5.5%). The phase transition temperatures for continuous VO2 thin film and the optimized semi-perforated VO2 double layer thin film were 58 °C and 52 °C, respectively, far below 68 °C of bulky VO2. This structure should be very meaningful for the real application of VO2-based smart window in the future.
This work was supported by the National Natural Science Foundation of China (Grant No. 61471264, 61271070, 60771019, 61101055) and the Natural Science Foundation of Tianjin (Grant No. 15JCYBJC46800).