Fabrication and optical performance research of VO2/SiO2/VO2 composite spherical structure films

Abstract

Vanadium dioxide ( V O 2 ) is an ideal thermochromic smart window material for its infrared optical properties accompanied by reversible semiconductor-to-metal phase transition. However, it is still faced with insufficient solar energy modulation efficiency and low luminous transmittance. In order to further improve the thermochromic performance of V O 2 thin film, we proposed a V O 2 / S i O 2 / V O 2 composite spherical structure film composed of a V O 2 / S i O 2 microsphere antireflection structure and V O 2 single-layer film structure. This composite spherical structure film can form a Fabry–Perot cavity-like structure when V O 2 changes to a metal state at high temperature, which can enhance the absorption of near-infrared light. The solar energy modulation efficiency and visible light transmittance were improved simultaneously compared to a single-layer film microsphere structure with the same V O 2 thickness. The solar energy modulation efficiency was improved from 3.11% to 7.65% by increasing the difference in transmittance between the semiconductor phase and the metal phase, and the luminous transmittance was enhanced from 51.53% to 57.23% at the optimized top thickness of 25 nm and bottom thickness of 54 nm. This optical study of composite structure film will lay a foundation for the application of V O 2 film in thermochromic smart windows.