Thermochromic multilayer films of VO2 and TiO2 with enhanced transmittance

Thermochromic films of VO2, as well as multilayer films of VO2 and TiO2, were made by reactive DC magnetron sputtering. Spectrophotometrically measured transmittance and reflectance were used to determine optical constants pertinent to temperatures below and above a temperature-induced structural change at τc≈60 °C. We then used computations to optimize multilayer films for specific applications and, specifically, demonstrated that TiO2/VO2/TiO2 films could display a luminous transmittance significantly higher than that of bare VO2 films, and that TiO2/VO2/TiO2/VO2/TiO2 films could yield a large change of solar transmittance for temperatures above and below τc. Our data can serve as starting points for developing novel coatings for windows with superior energy efficiency.