Hybrid films of VO2 nanoparticles and a nickel(II)-based ligand exchange thermochromic system: excellent optical performance with a temperature responsive colour change

It is well known that excellent optical performance is a vital factor of vanadium dioxide (VO2) thermochromic films. Except for optimizing the properties of VO2 itself as most researchers have been focusing on, hybridizing has been verified to be an effective way to substantially improve the solar regulation efficiency (ΔTsol) and luminous transmittance (Tlum) of the thermochromic films. Therefore, a nickel(II)-based ligand exchange thermochromic system (NLETS), which contains nickel(II), 2,2-dimethylpropane-1,3-diol ((CH3)2C(CH2OH)2) and bromide, is selected in this paper to be combined with VO2 nanoparticles forming a hybrid film. Compared with a pure VO2 film, this novel scheme demonstrates a 127% increase (from 8.02% to 18.19%) in ΔTsol at a rather high Tlum (Tlum,l = 73.36% and Tlum,h = 68.71%). What is more, since the intrinsic colour change of the NLETS from colourless to blue, the hybrid film presents an evident temperature responsive colour change: from yellow to green, which is crucial for exhibition, publicity and promotion of thermochromic products.

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