Colored Radiative Cooling Structure Managing Full Solar Spectrum via Near-Infrared Reflection and Photoluminescence

Colored radiative cooling (CRC) offers an attractive alternative for surface and space cooling with preserving the aesthetics of the object. However, it is still deficient on CRC structure with vivid and ample color display, sophisticated performance investigation, retention of properties, functionality, and structural flexibility all at once. Thus, to manage the entire solar spectrum, a colored cooling structure comprising a NIR-reflective bottom layer and top colored layer with phosphor-embedded polymer matrix is proposed. The structure is paintable, vivid and ample colored, hydrophobic, and UV and water-resistant. In the daytime outdoor measurement, the structure exhibited lower temperature than their control group using commercial white paint by 4.7^oC, 7.2^oC, and 7.4^oC, for red, orange, and yellow color, respectively. After precise time-tracing temperature validation between the theory and the experiment, CRC performance enhancement from NIR reflection and PL effect was thoroughly analyzed and up to 16.1^oC of temperature reduction was achieved for orange color. Furthermore, experiments of hydrophobicity infusion and exposure to UV and DI water verified the durability of the colored cooling structure. Also, flexible film-type colored cooling structure was demonstrated using different bottom reflective layer such as silver thin film and porous aluminum oxide particle embedded poly(vinylidene fluoride-co-hexafluoropropylene), allowing a numerous materials sets of the colored cooling structure for vivid colored, functional, and durable CRC.