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

Abstract

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.