Topological Carbon Quantum Rings With Near‐Unity Photoluminescence for Efficient Sky‐Blue Electroluminescence

Carbon quantum dots (CQDs) are promising environmentally benign emitters for next‐generation optoelectronic devices, yet aggregation‐caused quenching (ACQ) fundamentally limits their solid‐state emission efficiency. Existing strategies primarily rely on surface or morphological modifications, while the role of topology in regulating exciton behavior remains largely unexplored. Here, we report a topological design strategy to suppress ACQ by constructing carbon quantum rings with a closed‐loop conjugated architecture. Guided by symmetric molecular precursors, the ring formation process is elucidated by combined mass spectrometry and density functional theory (DFT) calculations, revealing a thermodynamically driven evolution from planar oligomers to curved and ultimately closed‐loop structures. This unique topology intrinsically suppresses intermolecular π–π coupling and non‐radiative decay, while enabling exciton confinement within a rigid conjugated framework. As a result, the carbon quantum rings exhibit a near‐unity photoluminescence quantum yield of 99.5% in solution and 58.9% in solid‐state films. When integrated into electroluminescent devices, efficient sky‐blue emission is achieved with a low turn‐on voltage of 2.8 V, a maximum luminance of 1020 cd m −2 , and an external quantum efficiency of 3.4%. This work establishes topology as a fundamental design parameter for carbon‐based emitters and provides a general strategy for overcoming ACQ in sustainable optoelectronic materials.