Cost effective 24-h radiative cooler with multiphase interface enhanced solar scattering and thermal emission

Passive radiative cooling is an emerging energy-free pathway that radiates the emission of heat from the earth to cold space (3 K) through an atmosphere transparent window (7–14 µm). Recently, this technology has attracted great interest in residential and industrial applications. However, critical challenges remain for 24-h radiative cooling due to the unwanted solar heating effect in the daytime. The complex manufacturing process and high price also result in a cost barrier for large-scale applications. Here, an easy-prepared and cost-effective radiative cooler (RC) was processed which consists of polydimethylsiloxane (PDMS) and SiO2 microspheres based on cellulose nanofibers (filter paper) with a backing silver (Ag) mirror for mass production. This whitish hybrid material exhibited high reflectance of 91% in the AM 1.5 solar spectrum (0.2–2.5 µm) and high thermal emissivity of 90% in the atmospheric window, which was enhanced by the randomized multiphase interfaces. Moreover, it can accomplish 24-h continuous outdoor cooling with an efficient average temperature reduction of 5 °C, especially 6.5 °C in the nighttime. Overall, this work provided a new approach to promote 24-h radiative cooling as a next-generation green energy technology.