Multi-shape VO2 nanoparticle stacking structure film with positive luminous modulation for smart window

Vanadium dioxide (VO2)-based thermochromic smart window show excellent promise for energy-saving and have been extensively researched. However, the performance of smart windows is restrained by the VO2 film negative modulation with luminous transmittance. Unfortunately, there has been no breakthrough in exploring negative modulation mechanism for VO2 thin nanofilm until now. In this work, we propose a novel structure design consisting of densely packed VO2 nanostructure over glass based on rectangular and circular nanoparticles array structure. The preparation process involves the magnetron sputtering and low-pressure annealing technique, which is well-suited for the glass substrate. According to optical measurements, the luminous transmittance modulation (ΔTlum = 1.86 %) was significantly increased compared to the continuous vanadium oxide film. Simultaneously, leading to the solar modulation (ΔTsol = 8.35 %) and luminous transmittance (Tlum = 57.18 %@30 °C) also were improved, which can be ascribed to the absorption between lager and small nanoparticles in the luminous when VO2 is in rutile state. The mechanisms are investigated by localized surface plasmon resonance theoretical analyses and numerical simulations. Our novel approach offers a promising solution for constructing energy-efficient VO2-based smart windows.