A 3D porous polymer film designed for efficient passive radiative cooling

Passive daytime radiative cooling (PDRC) technique can cool objects without energy consumption by reflecting sunlight and radiating heat into the cold outer space through atmospheric transparent windows (ATW). Here, 3D porous polydimethylsiloxane (P-PDMS) films with excellent radiative cooling properties were fabricated using citric acid monohydrate (CAM) templates. Integrating with high sunlight reflectance (78.6%) and great thermal emissivity (99.4%) in ATW, the test was performed in an outdoor environment with an average solar radiation of 715.09 W/m2. The maximum temperature of P-PDMS film is reduced to 15.4℃, and in the actual roof application test, P-PDMS film also show excellent passive radiant cooling performance of 8.3℃ cooling in the house. The 3D-porous structure plays an important role in improving solar reflectivity and IR emissivity. Combined with efficient DRC capabilities and mass production compatibility, this work brings a new paradigm for the preparation of cooling devices with potential commercial applications in sustainable energy-free cooling.