In-Situ thermochromic mechanism of Spin-Coated VO2 film

In this paper, we assess the applicable possibility of spin-coated VO2 film via a series of in-situ techniques to determine the reliability of its optical properties in thermochromic process. The phase transition and optical properties of the thin film were characterized by in-situ x-ray diffraction, temperature-dependent Raman spectroscopy and spectroscopic ellipsometry techniques, respectively. The spin-coated VO2 thin film is composed of uniform spherical nanoparticles, but it does not affect the thermochromic performance in respect to the films fabricated by deposition methods. The as-fabricated film is monoclinic phase (M) at room temperature. When the temperature reaches 75 °C, the VO2 film changed into rutile-phase (R) with high extinction coefficient in infrared wavelength, indicating good thermochromic properties at infrared region for potential thermal irradiation management. This phase is partially transited to M−phase from 75 to 45 °C as mixed phases and then to pure M−phase in cooling process. The results indicate that once the spin-coated VO2 film transits into R-phase at high temperature, it will keep the high infrared wavelength absorption state to screen the overheating of the internal space down to 45 °C. Our work provides a theoretical and experimental basis of spin-coated VO2 films for intelligent thermal management applications.