A flexible and superhydrophobic PVDF-HFP@PVA bilayer enables high-performance radiative cooling and thermal management

Passive radiative cooling which dissipates heat from surfaces by reflecting sunlight and emitting radiation towards outer space, has garnered growing attention as an eco-friendly cooling strategy with zero-energy consumption. However, few studies focus on low-cost and multifunctional composite film fabricated by a straightforward and environmentally friendly method that is crucial for their large-scale applications. Herein, we introduce a facile, efficient, and scalable approach to fabricate a hydrophobic and polymer-dielectric poly (vinylidene fluoride)-hexafluoropropylene (P(VDF-HFP)@PVA hydrogel Janus film (DPP), exhibiting exceptional radiative cooling and thermal management capabilities for diverse practical applications. With the introduction of ZnO, DPP showcases the optical capability with a solar reflectance of ≈93 % and an infrared emittance of ≈96 %, endowing it with remarkable radiative cooling performance. The synergistic integration of hydrogel phase change and radiation cooling capabilities offered by the P(VDF-HFP) layer enables the DPP to achieve a subambient cooling of 8.62 °C under direct sunlight. Moreover, when applied to the thermal management of electronic devices and fruit preservation due to the phase change property, the DPP effectively reduced surface temperatures by 10 °C and 15.5 °C respectively. Its simplicity and versatility suggest that it could be widely adopted for daytime passive radiation cooling, thereby expanding its practical applications across various fields.