Thermochromic VO2 films with periodic meshes for smart windows: Analysis of optical properties

Abstract

VO2 films with periodic meshes demonstrate the potential for application in smart windows. In this contribution, we theoretically study light propagating through meshed VO2 films and identify three distinct optical phenomena, compared to their flat counterparts. The diffraction effect appears over the whole wavelength range from visible to infrared, contributing to an excellent luminous transmission (Tlum) beyond 60% and a relatively high solar transmission (Tsol) for broad geometry configurations. Local resonances arising from edge effect at the upper edge of the meshes and Wood’s anomaly enable to drop Tsol in the infrared range for the condition above the critical temperature, which is desirable for improving the solar spectral modulation (ΔTsol). However, they either tend to couple a larger part of the resonant light into the meshes or are within a few discrete wavelengths only. Consequently, the transmission drop for VO2 above the critical temperature is limited and thus results in a moderate ΔTsol.