Passive daytime radiative cooling (PDRC) is an emerging energy-free cooling technology, which can weaken our dependence on energy-consuming air-conditioning requirements. Though the advance in micro/nanostructure PDRC materials achieves excellent sub-ambient cooling performance, the majority of them are facing a huge challenge in terms of practical large-scale applications owing to complicated preparation methods and high costs. Herein, combining a low-cost polymer matrix with inorganic dielectric particles, a hierarchically porous composite (HPC) film with a micro/nanostructure and adjustable spectral properties is developed through a flexible phase-inversion-based method. The HPC-film exhibits a strong solar reflectivity (∼98.26%) and infrared emissivity (∼97.56%), thus realizing a sub-ambient average cooling temperature of ∼9.1 °C and effective radiative cooling power of ∼87.2 W m−2 under a solar irradiance of ∼890 W m−2. As a proof of concept, we demonstrate that the proposed cooler is capable of delaying ice melting by four times compared with the pristine case due to the remarkable radiative cooling performance, which provides inspiration for developing a scalable and sustainable pathway of ice protection and preservation. Overall, the multiple advantages of the facile and flexible manufacturing technique, excellent stability and repeatability in this study promise potentially valuable applications in passive radiative cooling.
