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

Vanadium dioxide (VO 2 ) is an ideal thermochromic material for “smart window” which can reduce energy consumption of air conditioning in modern architectures. However, the application of VO 2 -based smart window is always limited by the poor luminous transmittance ( T lum ), low solar regulation efficiency (Δ T sol ) and unsightly brown color. According to previous researches, compositing has been approved to be an effective method to solve all of above issues for VO 2 -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 VO 2 nanoparticles for enhanced performance. The composite film demonstrates ultrahigh optical properties : Δ T sol  = 27.0%, which is 1.91 times higher than that of pure VO 2 film (14.1%) at a rather high T lum ( T l, lum  = 65.9% and T h, lum  = 55.3%) with little loss of visible light at high temperature (Δ T lum  = 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 VO 2 -based smart window.