Scalable and paint-format microparticle–polymer composite enabling high-performance daytime radiative cooling

Radiative cooling, a process in which the Earth maintains a near-constant temperature despite significant solar flux, is a promising technology with no requirement of any input energy for sub-ambient cooling as well as no emission of greenhouse gas. Here, we demonstrate a paint-format microparticle–polymer composite with a low fabrication cost, simple structure, and high radiative cooling performance. Harnessing intrinsic optical properties of aluminum oxide and silicon oxide particles with large energy bandgaps and complementary IR emission properties within the atmospheric transparency window, the proposed radiative cooling paint has an extremely low solar absorptivity of 0.032 and strong IR emission of 0.935 in the atmospheric transparency window. Furthermore, many outdoor measurements proved the RC paint provided high-performance radiative cooling effect for comparison with commercial white paint even in hot summer season detrimental for daytime raditaive cooling, enabling the practical use of radiative cooling.