Fig. 1 Schematic diagram of the full-chain development of VO2-based smart window

Fig. 2 Element doping of VO2 (a) Comparison of the optical hysteresis at 2000 nm of VO2 film and W-doped VO2 film[9]; (b) Transmittance hysteresis loops at λ=2000 nm for V1-xMoxO2 films[10]; (c) Temperature dependent transition hysteresis loops for the pure and Mg-doped VO2 films grown on ZnO substrates[14]

Fig. 3 Multilayer film structure design (a) 3D surface image of the luminous transmittance (Tlum, lt) calculation of the Cr2O3/VO2 (80 nm)/SiO2 multilayer structure on the thickness design of Cr2O3 (bottom layer) and SiO2 (top layer); (b) Transmittance spectra (350-2600 nm) at 25 (solid lines) and 90 ℃ (dashed lines) for the CVS structures with various thicknesses of SiO2 layers[26]; (c) Schematic illustration of H2O/VO2 film; (d) Transmittance spectra of VO2 films with and without H2O layer[24]; (e) Schematic illustration of SA/Glass/TVT structure; (f) Transmittance spectra in visible-NIR region at room temperature (25 ℃) and 95 ℃ of SA/Glass/TVT structure[25]. SA: SiO2/AZO (300 nm)/Glass Colourful figures are available on website

Fig. 4 VO2 microstructure design (a) Schematic illustration of the as-prepared 3DOM (3D Ordered Macroporous) VO2 (M) film; (b) Photographs of the VO2(M) films on glass slides; (c) Optical transmittance spectra of the VO2 (M) films with 3DOM structures[31]; (d) Schematic of fabrication route for nanoporous VO2 films; (e) Optical photograph of the nanoporous VO2 films on quartz; (f) Transmittance spectra of the nanoporous VO2 films[32]

Fig. 5 (a) Experimental flow chart for the synthesis of VO2@ZnO core-shell structure nanoparticles, (b)TEM image of VO2@ZnO core-shell structure nanoparticle; (c) Optical transmittance spectra at 20 and 80 ℃ of uncoated VO2 film and VO2@ZnO film; (d) Solar regulation efficiency (ΔTsol), luminous transmittance (Tlum), and durability at constant temperature (60 ℃) and humidity (90%) of different VO2-based smart window coatings[36]; (e) Schematic illustrations of four types of sample[39]

Fig. 6 Flexible films and their preparation flow chart (a) Schematic illustration of the fabrication process for the SWNTs/VO2/mica hierarchical film; (b) Thin VO2/mica film showing excellent flexibility[45]; (c) Schematic illustration of the graphene-supported VO2 film[46]

Fig. 7 Color control of VO2 (a) Pure hydrogel thin film at room temperature (25 ℃); (b) VO2/hydrogel hybrid at room temperature (25 ℃) and (c) 35 ℃[47]; (d) Model of the VO2 film comprising periodic silver-nanodisk array; (e) Re?ection images of the pattern at 20 and 80 ℃, respectively[52]; (f) Photographs of pure IL-Ni-Cl complexes film, pure VO2 nanoparticles film, and VO2/IL-Ni-Cl composite film at 20 (left) and 80 ℃ (right)[48]