Enhanced luminous transmittance of thermochromic VO2 thin film patterned by SiO2 nanospheres.

In this study, an ordered SiO₂ nanosphere array coated with vanadium dioxide (VO₂) has been fabricated to enhance transmittance with the potential application as an energy-efficient coating in the field of smart windows. SiO₂ arrays were formed using the methods of self-assembly, and VO₂ thin films were prepared by rapid thermal annealing (RTA) of sputtered vanadium films. VO₂@SiO₂ arrays were characterized by scanning electron microscopy, X-ray diffraction, a four- point probe, and UV-vis-NIR spectrophotometry. Compared with the planar films, the films deposited on 300 nm diameter SiO₂ nanospheres can offer approximately 18% enhancement of luminous transmission (T_lum) because the diameter is smaller than the given wavelength and the protuberance of the surface array behaves as a gradation of refractive index producing antireflection. The solar regulation efficiency was not much deteriorated. [ABSTRACT FROM AUTHOR]