Efficient Daytime Radiative Cooling Cover Sheet with Dual-Modal Optical Properties

Daytime radiative cooling is an eco-friendly cooling technique that does not consume additional fuel and is a promising technology now being developed using various materials and methods. Existing radiative cooling emitters are typically in the form of multilayered or mixed thin films and photonic structures, which are difficult to apply in industrial fields. Moreover, the complicated processes and materials used increase the cost. Herein, a dual-modal radiative cooling emitter in the form of a cover sheet developed by electrospinning polyacrylonitrile (PAN) with alumina (Al₂O₃) and silica (SiO₂) nanoparticles is reported; it is an easily accessible and highly practical architecture that can be applied and used in daily life. Additionally, this radiative cooling cover sheet exhibits dual selective- and broadband-like optical properties in the IR region depending on the substrate characteristics for efficient cooling. The cooling power is numerically proven to be 89.51 W m⁻², and experimentally, a temperature drop of 9.67 °C could be measured on a daily car model.