Porous W-doped VO sub(2) films with simultaneously enhanced visible transparency and thermochromic properties

• Published in: Journal of sol-gel science and technology Vol. 77; no. 1; pp. 85 - 93
• Main Authors: Hu, Lingting, Tao, Haizheng, Chen, Guohua, Pan, Ruikun, Wan, Meinan, Xiong, Dehua, Zhao, Xiujian
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Annealing; Metal-insulator transition; Modulation; Sol gel process; Transmittance; Tungsten; Vanadium oxides
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-015-3832-z

Porous thermochromic pure and tungsten (W)-doped vanadium dioxide (VO sub(2)) films have been prepared on silica substrates by spin coating via a sol-gel process and annealing in ammonia (NH sub(3)) atmosphere. NH sub(3) with weak reducing capacity can prevent V super(4+) from further oxidization and contribute to the formation of porous structure. These films exhibit enhanced visible transparency and switching property at near-infrared wavelengths across the metal-insulator transition (MIT). The transmittance change in the VO sub(2) film annealed at 2.0 10 super(3)Pa is as high as 52.9 % at lambda = 2000 nm, and its solar modulation efficiency reaches up to 9.4 %. W-doping shifts the MIT temperature of the VO sub(2) films from 55 to 28 degree C, while the films remain the excellent modulating ability in near-infrared region, and the decreasing efficiency of V sub(0.99)W sub(0.01)O sub(2) film can achieve to 20 K/at.%, which will greatly favor the practical application of VO sub(2)-based smart windows. Graphical Abstract Transmittance spectra for pure VO sub(2) film in the range of 250-2500 nm and the recorded transmittance-temperature hysteresis loop in the range of 20-90 degree C of the W-doping VO sub(2) films after annealing at 500 degree C for 30 min (middle inset). https://static-content.springer.com/image/art%3A10.1007%2Fs10971-0 1 5-3832-z/MediaObjects/10971_2015_3832_Figa_HTML.gif