Realization of high luminous transmittance and solar modulation ability by thermochromic VO2-based induced transmittance filter (ITF)

This paper presents a novel thermochromic induced transmittance filter (ITF) based on VO2 films. The ITF structure enables high transmittance in the short wavelength range with wide rejection at longer wavelengths, which meets the requirements of thermochromic VO2 for the metal-insulator transition. Thus, the VO2-based ITFs are designed and fabricated based on the induced transmittance effect, and a graded-index material TiO2 is initially adopted for the simplified structure of VO2-based ITF comparing standard ITFs. The VO2-based ITF's properties are characterized systematically and compared with those of VO2 films. Favorable results of crystallinity, surface roughness, hydrophobicity, the thermal hysteresis width, and pleasant appearance color are achieved in these VO2-based ITFs. Moreover, luminous transmittance T-lum (380-780nm) of 48.8% and a solar modulation ability Delta T-sol of 6.2% are achieved with an ideal spectrum shape in the VO2-based ITF, which provides a highly efficient solution to improve thermochromic VO2 films and related field. Published under license by AIP Publishing.