The thermochromic characteristics of ITO/VO2 composite films on SiO2 nanospheres

As a promising thermochromic material for smart windows, VO 2 -based films have received extensive attention. To enhance the luminous transmittance ( T lum ) of thermochromic smart windows without seriously affecting the solar modulation efficiency (Δ T sol ), this paper prepared VO 2 films by rapid thermal annealing of sputtered vanadium thin films on an ordered SiO 2 nanosphere array, and then the ITO as antireflection layer was deposited on VO 2 film by reactive magnetron sputtering. The surface morphology, crystal structure and optical transmittance of the films were characterized by Scanning Electron Microscopy, X-ray diffraction and UV–VIS–NIR spectrophotometer, respectively. The SiO 2 nanospheres provide continuous refractive index gradient, while the deposition of the ITO antireflection layer creates conditions for thin film interference, thereby synergistically reducing surface reflection in the VO 2 -based smart window. Compared with the planar VO 2 thin film ( T lum , 39.1%), the ITO/VO 2 /SiO 2 composite structure can significantly increase the T lum from 39.1 to 55.5%, an increase of nearly 16.4%, while the Δ T sol is basically unchanged. The results provide an effective strategy for improving the performance of smart windows.