Emerging colored and transparent radiative cooling: Fundamentals, progress, and challenges

The worsening energy crisis and global warming have intensified interest in passive daytime radiative cooling (PDRC) technology. This technology consumes no energy and can directly dissipate heat to outer space. Despite advancements in the cooling mechanism, material design, preparation technologies, and practical applications, the traditional white or silver appearance does not meet aesthetic and functional needs, and potential light pollution limits their development. Recently, colored and transparent PDRC materials have been developed, providing solutions that satisfy aesthetic and functional requirements while delivering impressive cooling performance. This review overviews these emerging materials and strategies for colored and transparent PDRC. First, the cooling mechanism of PDRC is examined from the optics and thermodynamic perspective, and the current experimental methods for radiative cooling performance and the current state of traditional white and silver PDRC are summarized. Next, the design strategies, cooling performance, and application areas of colored and transparent PDRC are discussed in detail, and the problems existing in each type of material design are comprehensively analyzed. Furthermore, the challenges and potential research directions for the next generation of highly efficient PDRC are explored. This review aims to inspire further in-depth research into colored and transparent PDRC technology and promote its application across various fields.