Effortlessly Crafted, Superior Quality, and Mass-Producible Coatings Combining Backscattering and Surface Scattering for Passive Daytime Radiative Cooling

Passive daytime radiative cooling (PDRC) stands out as an eco-friendly, energy-independent cooling solution, which has emerged as a field of intense interest and extensive investigation. In this work, a low-thickness PDRC coating with an average solar reflectance of 93.7% and an average long-wave infrared emittance of 98.5% was developed by combining the backscattering of hollow silica microspheres (HSMs) with the surface scattering of TiO2. A finite element method simulation was conducted to verify that the HSMs enhance the backscattering performances. The synergistic interaction between the two fillers optimized their performance, leading to a high work efficiency and a significant reduction in the filler loading. Moreover, the coating demonstrated outstanding cooling performance in both indoor and outdoor tests. Under summer temperatures exceeding 38.9 °C, the temperatures of a wooden house model and a concrete slab were reduced by 5.0 and 6.3 °C, respectively. The coating featured simple industrial preparation, low cost, and the ability to produce in large volumes, thereby providing a viable path toward commercial and industrial scalability. This work offers a viable solution to the current challenges faced in the application of PDRC coatings.