Flexible Dual-Layer Fabric Based on AlPO4 Hollow Microspheres toward Daytime Radiative Cooling

Radiative cooling provides a supplement to traditional active energy-intense cooling. Recently, photonic designs have emerged to realize efficient daytime radiative cooling (DRC) based on high emission in the mid-infrared and reflectance in the solar spectrum. However, such technologies tend to be costly and suffer from complex processes, which significantly limit their application. Herein, a polyvinylidene difluoride/polyvinylpyrrolidone-(hollow aluminum phosphate microspheres) (PVDF/PVP-(H-AlPO4)) dual-layer composite fiber film was prepared via a straightforward and cost-effective microfluidic electrospinning technique, combining multieffect cooling, including thermal isolation, solar reflection, and a self-pumping process. The incorporation of hollow aluminum phosphate microspheres (H-AlPO4) in the polymer matrix enhances the mechanical properties and overall scattering ability. Promisingly, the PVDF/PVP-(H-AlPO4) dual-layer composite fiber film ensures the desired DRC performance, achieves a high emissivity of 91.46% in the atmospheric window, and reflects 94.76% of the solar radiation. In outdoor environments under 605 W/m2 solar radiation, the dual-layer composite fiber film obtains an average 3.1 °C subambient cooling temperature, with the highest cooling temperature reaching 6.4 °C. We believe that this study not only provides an efficient method for preparing DRC fiber films with photonic structures but also offers a potential solution for the design of radiative cooling materials and lays a solid foundation for its practical application.