Fabrication of multifunctional coating with high luminous transmittance, self-cleaning and radiative cooling performances for energy-efficient windows

Abstract Due to the huge consumption of energy and shortage of resources, passive cooling is becoming an efficient way for saving energy with a function of reducing energy consumption. This work presents a multifunctional SiO2@TiO2/ZnO laminated coating with high luminous transmittance, self-cleaning capability and radiative cooling performance used for energy-efficient windows. SiO2@TiO2 nanospheres as an upper coating were designed as antireflection layer to achieve high luminous transmittance and degradation layer to achieve self-cleaning. While ZnO nanorods as an undercoat were designed as highly reflective layer to realize radiative cooling and support layer to stabilize upper layer. The bilayer coating exhibits excellent antireflective property for reducing 16% reflectivity in the visible region, thus increasing transmittance up to 73%. TiO2 behaves well on degradation of organic pollutants, as it can completely decompose organic matter within 3 h under UV radiation. This would have a positive impact on the self-cleaning ability of the as-fabricated laminated coating and further beneficial for increasing indoor brightness. Both infrared reflectance spectra and infrared thermal images provide valid evidence of high infrared reflectance and outstanding radiative cooling performance. The reflectivity of the laminated coating is 50.25% higher than that of the blank glass, so the temperature gets 4.5 °C reduction under the same radiation conditions. Therefore, SiO2@TiO2/ZnO laminated coating shows great potential in application of energy-efficient windows and may have an inspiration on developments of smart windows.