Fluorescent Colored Passive Radiative Cooling Based on Carbon Dots for Cooling Power Recovery

ABSTRACT Passive radiative cooling (PRC) technology enables efficient thermal management through high solar reflectance and thermal emission within the atmospheric infrared window. However, conventional radiative coolers predominantly exhibit white or silver appearances due to stringent solar reflectance requirements, thereby limiting their aesthetic appeal. Although colored radiative coolers incorporating conventional pigments have been reported, they invariably suffer from solar absorption that significantly compromises cooling performance. Recent advances have explored photoconversion materials to mitigate cooling power losses via photoluminescence, primarily employing semiconductor quantum dots, perovskites, and phosphorescent dyes. However, most of these materials present critical limitations including environmental toxicity, high cost, synthesis complexity, and poor photostability. Carbon dots (CDs) provide a viable alternative as a low‐cost, eco‐friendly photoluminescent material which can deliver tunable coloration through visible absorption while simultaneously recovering the cooling power. Herein, we demonstrate a CD‐based colored passive radiative cooler (CD‐CPRC) with a bilayer structure that consists of a highly reflective hierarchically porous PRC ceramic and a CD‐polymer composite, with two types of CDs enabling conversion of either ultraviolet or visible light, respectively. Our field tests demonstrate that both CD‐CPRCs attain lower temperatures than non‐emitting pigment‐based radiative coolers, with a maximum temperature reduction of 4.2°C during midday. These findings showcase the potential of the CD‐CPRC as an efficient, feasible, eco‐friendly, and scalable technology for advancing next‐generation thermal management skins in smart cities.