Abstract
Porous thermochromic pure and tungsten (W)-doped vanadium dioxide (VO2) films have been prepared on silica substrates by spin coating via a sol–gel process and annealing in ammonia (NH3) atmosphere. NH3 with weak reducing capacity can prevent V4+ 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 VO2 film annealed at 2.0 × 103Pa is as high as 52.9 % at λ = 2000 nm, and its solar modulation efficiency reaches up to 9.4 %. W-doping shifts the MIT temperature of the VO2 films from 55 to 28 °C, while the films remain the excellent modulating ability in near-infrared region, and the decreasing efficiency of V0.99W0.01O2 film can achieve to 20 K/at.%, which will greatly favor the practical application of VO2-based smart windows.
Graphical Abstract
Transmittance spectra for pure VO2 film in the range of 250–2500 nm and the recorded transmittance–temperature hysteresis loop in the range of 20–90 °C of the W-doping VO2 films after annealing at 500 °C for 30 min (middle inset).
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Acknowledgments
This work was financially supported by NSFC (Nos. 51372180, 51032005 and 51461135004), NSF of Hubei Province (No. 2013CFA008), the research funds of Guangxi Key Laboratory of Information Materials (No. 1210908-05-K), Doctoral Fund of Ministry of education priority development projects (No. 20130143130002) and the Key Technology Innovation Project of Hubei Province (No. 2013AEA005).
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Hu, L., Tao, H., Chen, G. et al. Porous W-doped VO2 films with simultaneously enhanced visible transparency and thermochromic properties. J Sol-Gel Sci Technol 77, 85–93 (2016). https://doi.org/10.1007/s10971-015-3832-z
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DOI: https://doi.org/10.1007/s10971-015-3832-z