Thin paints for durable and scalable radiative cooling

Passive daytime radiative cooling (PDRC) is environment-friendly without energy input by enhancing the coating's solar reflectance (R¯solar) and thermal emittance (ε¯LWIR) in the atmosphere's long-wave infrared transmission window. However, high R¯solar is usually achieved by increasing the coating's thickness, which not only increases materials' cost but also impairs heat transfer. Additionally, the desired high R¯solar is vulnerable to dust pollution in the outdoors. In this work, a thin paint was designed by mixing hBN plates, PFOTS, and IPA.R¯solar = 0.963 andε¯LWIR = 0.927 was achieved at a thickness of 150 μm due to the high backscattering ability of scatters. A high through-plane thermal conductivity (∼1.82 W m−1 K−1) also can be obtained. In addition, the porous structure coupled with the binder PFOTS resulted in a contact angle of 154°, demonstrating excellent durability under dust contamination. Outdoor experiments showed that the thin paint can obtain a 2.3 °C lower temperature for sub-ambient cooling than the reference PDRC coating in the daytime. Furtherly, the above-ambient heat dissipation performance can be enhanced by spraying the thin paint on a 3D heat sink, which was 15.7 °C lower than the reference 1D structure, demonstrating excellent performance for durable and scalable PDRC applications.