VO2-based colorful smart windows with self-cleaning function

Smart windows hold promise for mitigating energy demand for indoor heating or cooling. However, VO2-based thermochromic smart windows face challenges such as high phase transition temperature, limited window color options, and a lack of functional diversity. Herein, we investigated the colorful smart windows utilizing the tungsten-doped VO2 thin films with the phase transition temperature of approximately 23.5 °C. The surface color of these smart windows can be dynamically adjusted from brown to purple, cyan, yellow, and red by tuning the thickness of the wave-impedance matching layer of HfO2 film, resulted from the interference effect of the HfO2 layer and the underlying WxV1-xO2 layer. Moreover, the HfO2-coated WxV1-xO2 thin film with the HfO2 thickness of 132 nm demonstrates superior optical performance with a solar modulation ability of 9.35 %, the low-temperature luminous transmission of 36.81 %, and the high-temperature luminous transmission of 38.03 %. In addition, the incorporation of SiO2 nanoparticles into the HfO2-coated WxV1-xO2 thin films results in the superhydrophobic property with a water contact angle of 162.1° due to the formed rough surface, which is favor to the self-cleaning of the windows surface. •The phase transition temperature of VO2 thin films can be reduced to about 23.5 °C by the W doping.•The surface color of the smart window can be tuned by adjusting the thickness of the top HfO2 layer.•The smart window demonstrates superior superhydrophobic properties with a water contact angle of 162.1°.