A Novel Solution Process for the Synthesis of VO2 Thin Films with Excellent Thermochromic Properties

This article describes a novel and simple route to preparing VO2 thermochromic films by using a VOCl2 solution with poly(vinylpyrrolidone) (PVP) X-ray diffraction and Raman spectra showed that the VO2 films deposited with PVP consisted of a nearly pure monoclinic/rutile (M/R) phase Conversely, films prepared without PVP contained obviously impure crystalline phases The as-prepared films with PVP showed excellent optical properties compared to those prepared by common gas-phase methods. an integral visible transmittance of 54 5% and an IR reduction (change in transmittance) of 4 1 5 % at 2000 nm The phase-transition temperatures were adjusted from 69 to 54 degrees C by tungsten doping. Equipment analyses revealed that PVP plays two roles in the film Fort-nation First, it fundamentally acts as a film-forming promoter to improve physical gelation via interactions among oppositely charged carbonyl groups and amine groups of the polymer Second, the negatively charged carbonyl groups can interact with VO2+ to form a uniform mixed-gel film after solvent evaporation Thus. the addition of PVP can stabilize the solution and improve the as-prepared him quality and phase purity The current study suggests that the process has promise in applications of smart windows