Passive Daytime Radiative Cooling: From Sole Function to Multifunctionality

Passive daytime radiative cooling (PDRC), simultaneously reflecting sunlight and emitting infrared radiation heat to the cold outer, offers a promising alternative to traditional mechanical-based cooling in current electricity-intensive world. The continuously upgraded functional PDRC materials have further promoted the application of radiation cooling technology in real-world applications. This review explores the design evolution of PDRC materials, structures, and systems from sole-function to multifunctional designs, emphasizing their potential to achieve both high solar reflectance and strong thermal emittance for optimal cooling performance. Among them, multifunctional PDRC materials or systems with self-cleaning, fire-resistant, switchable, and evaporated-coupled characteristics are presented. Future challenges and opportunities for advancing PDRC materials are also discussed, aiming to guide the development of scalable solutions that can facilitate the large-scale production and application of this sustainable cooling technology.