VO2/Nickel-bromine-ionic liquid composite film for thermochromic application

Abstract

Vanadium dioxide (VO2) is an ideal thermochromic material for “smart window” which can reduce energy consumption of air conditioning in modern architectures. However, the application of VO2-based smart window is always limited by the poor luminous transmittance (Tlum), low solar regulation efficiency (ΔTsol) and unsightly brown color. According to previous researches, compositing has been approved to be an effective method to solve all of above issues for VO2-based smart window simultaneously. In this work, a new thermochromic ionic liquid (nickel-bromine-ionic liquid (or Ni-Br-IL, for short)) was synthesized and introduced to be composited with VO2 nanoparticles for enhanced performance. The composite film demonstrates ultrahigh optical properties: ΔTsol = 27.0%, which is 1.91 times higher than that of pure VO2 film (14.1%) at a rather high Tlum (Tl,lum = 65.9% and Th,lum = 55.3%) with little loss of visible light at high temperature (ΔTlum = 10.6%). Meanwhile, it can be observed the color change from light yellow to green clearly as the temperature rises. Such enhanced performance will benefit the publicity and application for VO2-based smart window.