Surface and interface engineering for VO2 coatings with excellent optical performance: From theory to practice

Known as smart windows, energy-efficient thermochromic coatings on architectural glasses have attracted great attention due to the modulation ability of solar irradiation in response to change of ambient temperature. As the most promising thermochromic inorganic substance, vanadium dioxide (VO2)-based smart windows have been widely investigated over the past few decades. However, pricey preparation process and poor optical performance (including low luminous transmittance as well as solar modulation efficiency) still limit its commercialization process. To date, various strategies have been proposed to tackle these issues. These studies have been mainly focused on antireflection, which are supposed to have enormous potential to make a further breakthrough in improving light transmission. Meanwhile, the localized plasmon surface resonance of the VO2 NPs has been gradually applied to boost solar regulation efficiency of smart windows. In this review, the basic principles of antireflection and thermochromism of coatings for smart windows are firstly discussed. Then, the state-of-the-art VO2-based thermochromic coatings fabrication strategies through aqueous process for improving the visible transparency and modify thermochromic performance, especially surface engineering techniques, are reviewed in detail. Afterwards, since the assessment of the thermochromic coatings' control ability to thermal radiation is vital for their practical application, multiform energy-saving measurements are presented Finally, the current challenges and perspectives of VO2-based coatings in energy-efficient smart windows are discussed.