Nanoporous Thermochromic VO2 Films with Low Optical Constants, Enhanced Luminous Transmittance and Thermochromic Properties

Nanoporous thermochromic VO2 films with low optical constants and tunable thicknesses have been prepared by polymer-assisted deposition. The film porosity and thickness change the interference relationship of light reflected from the film-substrate and the air-film interfaces, strongly influencing the optical properties of these VO2 films. Our optimized single-layered VO2 films exhibit high integrated luminous transmittance (Th-lum,Th-l = 43.3%, = T-lum,T-h 39.9%) and T-sol,T-h modulation (Delta T-sol = 14.1%, from T-sol,T-I = 42.9% to T-sol,T-h = 28.8%), which ae comparable to those of live layered TiO2/VO2/TiO2/VO2/TiO2 films 45%, T-lum/l = 45% T-lum/h = 42% and Delta T-sol = 12%, from T-sol,T-l = 52% to T-sol/h = 40%, from Phys. Status Solidi A, 2009, 206, 2155-2160.). Optical calculations suggest that the performance could be further improved by increasing the porosity.