Colored Cooler With Sandwich Structure for Sub‐Ambient Daytime Radiative Cooling

ABSTRACT Passive daytime radiative cooling offers a sustainable cooling strategy by simultaneously reflecting solar radiation and emitting thermal radiation through the mid‐infrared transparent window. However, the coolers that achieve sub‐ambient daytime cooling typically appear white or silver, limiting their use in applications where colored appearances are required. Herein, we report a colored cooler (CoCooler) with a sandwich structure that decouples visible coloration from near‐infrared solar heating. The CoCooler integrates a transparent polydimethylsiloxane emission layer, an inorganic‐colorant‐containing layer, an isolation layer, and a porous radiative cooling layer. The sandwich structure enables selective visible absorption for color generation, strong near‐infrared reflection to minimize solar heating, and broadband mid‐infrared emission for radiative heat dissipation. The red, yellow, and blue CoCoolers exhibit vivid color while maintaining high solar reflectance of 90.70%, 91.58%, and 89.89%, respectively, and high mid‐infrared emissivity of 0.982, 0.983, and 0.982. Under outdoor sunlight, the CoCoolers achieve sub‐ambient temperature drops of 3.7°C–5.4°C, and are 33.3°C–42.2°C cooler than the commercial‐colored paints with similar chromaticity. Building simulations further estimate an average energy savings of 23.8 MJ·m −2 and a CO 2 emission reduction of 11.7 k…