Two-step molding of polymer coating for efficient daytime radiative cooling

Abstract

Passive daytime radiative cooling has great potential for energy conservation and sustainable development. Polymer-based radiative cooling materials have received much attention due to their excellent cooling performance and scalable potential. However, the use of large amounts of organic solvents, the long cycle time, and the complexity of the preparation process have limited their development. Herein, we report a two-step cold-press sintering method for the preparation of a polymer radiative cooler, which is free of organic solvents. For demonstration, a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) coating with a solar reflectance of 97.4% and an emissivity of 0.969 within the atmospheric window is prepared, which can achieve a sub-ambient cooling phenomenon with a temperature reduction of 4.8 °C. Besides, the maximal radiative cooling power of 50.2 W/m² is also obtained under sunlight. After the implementation of the proposed sintered PVDF-HFP coating in buildings, more than 10% of annual energy consumption can be saved in China. This work proposes a simple, environmentally friendly, and scalable processing method for the preparation of radiative cooling materials, facilitating the large-scale application of radiative cooling technology.