Radiative Cooling of Outdoor Electronic Devices by Polyimide Fiber Films Fabricated via an Electrospinning-Electrospray Process

Radiative cooling materials have attracted extensive research interest due to their unique characteristics of zero energy consumption and minimized carbon footprint. However, the design and manufacture of radiative cooling materials for outdoor electronic devices remain to explore. In this study, a silica/fluorinated polyimide fiber film was particularly designed and fabricated for the radiative cooling of outdoor electronic devices. The film was prepared by an electrospinning-electrospray process with hexafluoroisopropylidene, diaminobiphenyl, and silica as raw materials. Composed of polyimide nanomicrometer fibers and polyimide-silica bead-like particles, the prepared film delivered an average solar reflectivity of 94.29% and an average mid infrared emissivity of 93.12%. Especially, the film exhibited high emissivity in the band of 6-16 μm, where the emission of electronic devices is relatively concentrated. Under direct sunlight, the radiative cooling film achieved a temperature 30.6 and 9.4 °C cooler than the commercial polyimide films and commercial high reflective coatings, respectively. The film also cooled a smartphone in high load operation under sunlight by 3.6-4.1 °C. The findings of this work provide new insight into the research and development of radiative cooling materials for outdoor electronic devices.