Colored passive daytime radiative cooling paints: From fundamentals to applications

Abstract

Passive daytime radiative cooling (PDRC) offers a sustainable approach to reducing the energy consumption and carbon emissions associated with cooling demands. Among various PDRC materials, paints are particularly attractive for real-world applications owing to their simple processing and compatibility with various substrates. However, most current PDRC paints are restricted to dull white or silver colors due to the requirement of high solar reflectance, limiting their use in aesthetically demanding scenarios such as building envelopes, vehicles, and solar photovoltaic modules. To address this limitation, colored passive daytime radiative cooling (CPDRC) paints have been developed to balance aesthetic appeal and cooling performance while maintaining practicality. Achieving this balance relies on rational spectral design, namely selective narrow-band absorption in the visible spectrum combined with high reflectivity in other parts of the solar spectrum. Building on this rationale, the fundamentals of CPDRC are firstly introduced and then design strategies tailored for paint systems are summarized, including material selection and structural optimization across different coloration mechanisms (chemical color, structural color, and photoluminescent color). Furthermore, solutions to specific practical requirements are discussed, focusing on the unique challenges and opportunities introduced by coloration. Finally, an outlook on the future development of CPDRC paints is offered.