Daytime Sub-Ambient Radiative Cooling with Vivid Structural Colors Mediated by Coupled Nanocavities.

Daytime radiative cooling is a promising passive cooling technology for combating global warming. Existing daytime radiative coolers usually show whitish colors due to their high broadband solar reflectivity, which is not suitable for aesthetic demands and effective display. It is challenging to produce high-cooling performance materials with vivid colors because colors are often produced by the absorption of visible light, decreasing net cooling power. In this work, we design a series of colorful multilayered radiative coolers (CMRCs) consisting of an optimized selective emitter for cooling and coupled nanocavities for structural coloration, which can successfully delicately balance the trade-off between the chromaticity and cooling performance. By judiciously designing the geometric parameters and manipulating the coupling effect inside the coupled nanocavities, our coolers show sub-ambient cooling performance and a larger color gamut (occupying 17.7% sRGB area) than reported ones. We further fabricate CMRCs and demonstrate that they have temperature drops of 3.4-4.4 °C on average based on outdoor experiments. These CMRCs are promising in thermal management of electronic/optoelectronic devices and outdoor facilities.