Novel sunlight-driven Cu7S4/VO2 composite films for smart windows

Abstract

As a promising inorganic thermochromic material, VO₂ can achieve modulation in the near-infrared band without affecting the visible light transmittance, and thus has been widely used in smart windows. However, VO₂-based thermochromic smart windows still face challenges for real-world applications, such as high phase transition temperatures and poor optical properties. In this paper, a solar-driven and high-performance VO₂-based thermochromic smart window composite film was prepared by combining Cu₇S₄, a photothermal material, with traditional VO₂ film through simulation and experiment. Its visible light transmittance in low and high temperature environments is T_lum,l = 60.8% and T_lum,h = 55.9%, and the solar modulation ability is as high as ΔT_sol = 12.3%. The composite film could be heated to 72 °C by infrared light irradiation and maintain excellent photothermal heating effects even after 100 cycles of heating and cooling. Due to its excellent photothermal and solar radiation regulation performances, the composite film can be widely used in smart windows.