Colored emitters with silica-embedded perovskite nanocrystals for efficient daytime radiative cooling

Daytime radiative cooling is an innovative way to counter the temperature increase caused by solar exposure inside buildings, cars, and industries without consuming energy. To improve the radiative cooling performance, the light-to-heat energy conversion through solar reflection should be minimized, while the heat radiation in the wavelength range of 8–13 µm (atmospheric window) should be maximized. In this work, colored emitters for daytime radiative cooling are fabricated with silica-embedded perovskite nanocrystals, which can be colored with high light-to-photon conversion in the solar spectrum instead of light-to-heat conversion, and coated onto a highly mid-IR-radiative white emitter. The fabricated white, green, and red emitters for daytime radiative cooling exhibit sub-ambient cooling temperatures of 4.2, 3.6, and 1.7 °C, respectively, in outdoor measurements. Additionally, the enhancement of the daytime cooling performance by the light-photon conversion is proven through the comparison experiments and numerical calculation. These colored emitters for radiative cooling are more aesthetically pleasing than conventional white- and metallic-colored surface emitters, and are expected to diversify the applications for daytime radiative cooling.