Passive daytime radiative cooling materials toward real-world applications

Passive daytime radiative cooling (PDRC) is an emerging cooling technique of a sunshine-exposed terrestrial surface by dissipating excessive heat into the deep-cold outer space. It is a passive technique without fuel consumption and paves a promising way to overcome the issues of energy shortage and environmental pollution at the global scale. In the contemporary era, highly developed nanophotonic engineering allows spectrally precise emissivity/reflectivity of a thermal surface, significantly improving a PDRC structure's cooling power. Furthermore, scalable manufacturing techniques have also been successfully developed for PDRC material preparation at affordable costs, promoting their practical implementations. However, a comprehensive review of PDRC materials for real-world applications is still lacking. This work begins with the fundamentals of PDRC, continues with the power enhancement and scaling up process of PDRC materials, boosts with the advances of three typical types of scalable PDRC materials, including films, textiles, and bulk materials, and ends with an outlook that addresses the limitations and challenges on PDRC materials for extensive real-world applications. This review can help scientists and engineers carry forward the design and implementation of PDRC materials, promote the mitigation of global issues such as scorching and water shortage, and make the planet healthier and more comfortable.