Enhanced passive radiative cooling coating with Y2O3 for thermal management of building

Passive daytime radiative cooling (PDRC), a green cooling technology with energy-free consumption, has demonstrated great potential in solving global warming and other problems. Dielectric particles embedded in polymers are considered efficient radiative cooling strategies devoted to solving the problems of the complex preparation process and low cooling efficiency. However, the high ultraviolet ray (UV) absorption or low refractive index of dielectric materials results in their low solar scattering. Herein, we propose a simple and efficient method to prepare a radiative cooling coating consisting of yttrium oxide (Y2O3) and polydimethylsiloxane (PDMS). The PDMS/Y2O3 radiative cooling film was fabricated according to the theoretically optimized particle size, volume fraction, and coating thickness. The result indicated that the randomly distributed Y2O3 nanoparticles were employed in PDMS to enhance the scattering efficiency of sunlight. The solar reflectance and “atmospheric window” emissivity of the PDMS/Y2O3 film was about 94.52% and 93.4%. Outdoor cooling tests exhibited that the PDMS/Y2O3 hybrid film could achieve sub-ambient radiative cooling of 7.4 °C under solar irradiation of 1132 W/m2. In comparison, commercial white paint was 1.8 °C higher than ambient temperature. Consequently, the film is promising for large-scale applications in green buildings, cold chain logistics, photovoltaic fields, modern agricultural production, and other fields.