Radiative cooling performance of fluorinated polyimide composite films for electronic devices with broadband mid-infrared emission enhanced by BaHPO₄/SiO₂ particles

Fluorinated PI film integrates with BaHPO 4 /SiO 2 particles to form a Janus structure. • The film achieves 96.94% solar reflectivity and 94.70% MIR emissivity (6-16 μm). • Outdoor test shows 13 and 22 °C lower than commercial coatings and standard paints. • The film is flexible, durable, self-cleaning, and flame-retardant. Radiative cooling offers a promising passive strategy for thermal management of electronic devices; however, achieving the combination of high solar reflectivity, broadband mid-infrared (MIR) emissivity, and robust mechanical performance remains challenging. In this work, a fluorinated polyimide (PI)-based composite film with enhanced radiative cooling capability is developed via electrospinning followed by vacuum-assisted filtration. By incorporating BaHPO₄ and SiO₂ particles into a fibrous PI matrix, a gradient-structured composite is formed, enabling synergistic spectral regulation. The best-performing film exhibits a high average solar reflectivity of 96.94% (0.25-2.5 μm) and a strong broadband MIR emissivity of 94.70% (6-16 μm), matching the thermal radiation characteristics of typical electronic devices. The fabrication strategy also improves interfacial bonding, resulting in a tensile strength of 17.15 MPa. Experimental evaluations using a simulated electronic device demonstrate significant cooling performance, with temperature reductions of 13 °C and 22 °C compared to commercial high-reflectivity coatings and conventional paints, respectively. Additional tests confirm excellent flexibility, wear resistance, flame retardancy, hydrophobicity, and weather stability. This study provides a scalable approach to engineering high-performance radiative cooling films for energy-efficient thermal management of electronic systems operating under both indoor and outdoor conditions.