Vanadium dioxide-1, 4-bis(benzoxazol-2-yl)naphthalene composite films and their thermochromic and photoluminescent property

Vanadium dioxide (VO₂) is an ideal thermochromic material for smart window which can be used to adjust the indoor temperature in summer. However, the application of the VO₂-based smart window coatings is practically restricted by several problems such as the inherently unpleasant brown-yellow color. In this work, the VO₂-organic fluorescent molecule bilayer composite films were fabricated by using 1, 4-bis(benzoxazol-2-yl)naphthalene (KCB) and W-doped VO₂ nanoparticles. After absorbing the ultraviolet light from sunlight, the KCB layer emits cyan fluorescence to make the composite film light blue or cyan in color, successfully modifying the brown-yellow color of the pure VO₂ films on glass. The composite films have the solar regulation efficiency ΔT_sol of greater than 9% and the luminous transmittance T_lum higher than 73%, and good anti-ultraviolet property as well. These features should be highly beneficial for the practical application of the VO₂-based films for smart windows.