Efficient daytime radiative cooling films originating from controllable multi-scattering effect

Passive radiative cooling technology has received extensive attention as an environmentally friendly cooling solution. However, existing radiative coolers often suffer from complexities in preparation and high costs, limiting their practical applications. Here, a novel porous structure with randomly distributed microspheres is fabricated in a low-cost and simple method known as solvent volatilization-induced phase separation, employing polyvinylidene fluoride (PVDF) and monodispersed SiO2 microspheres. Utilizing the regulation of parameters such as the size of the pores and microspheres, controllable multi-scattering of light by the microstructures is achieved. The porous PVDF/SiO2 film, with an average solar reflectance of 93.8% and an average atmospheric window emissivity of 0.958, is self-supporting and exhibits excellent flexibility and mechanical strength. When applied to closed and windowed models, the porous PVDF/SiO2 film effectively lowers the internal temperatures by an average of 7.0 °C and 4.6 °C in summer, respectively, and by an average of 6.7 °C and 4.4 °C in spring. This work provides a viable strategy for achieving efficient radiative cooling and improving building energy management in a simple, cost-effective, and scalable manner.