Afterglow of Dual‐Confined Carbon Dots Ranging from Blue to Near‐Infrared

Abstract Comprehensive research into afterglow emission in the near‐infrared (NIR) region of carbon dots (CDs) is currently lacking. In this study, highly efficient multicolor CDs are synthesized with fluorescence from blue to NIR using Rhodamine 6G. Boron oxide (B 2 O 3 ) is employed as a matrix for encapsulating and confining the CDs, inhibiting triplet exciton quenching. Furthermore, structural rigidity is enhanced due to the formation of carbon‐boron (C─B) covalent bonds between CDs and B 2 O 3 , achieving tunable afterglow emission ranging from 463 to 722 nm with lifetimes up to 801 ms. The green–yellow afterglow composite exhibits an impressive quantum yield up to 37.67% while demonstrating thermally activated delayed fluorescence (TADF). Thus, this composite is coated onto a blue alternating‐current light‐emitting diode (BAC‐LED) to fabricate a white AC‐LED, which is successfully prepared with Commission Internationale de L'Eclairage (CIE) at coordinates of (0.32, 0.34), accompanied by the color rendering index (CRI) reaching 81.1. The bright afterglow compensates for zero‐point flickering in the BAC‐LED, resulting in stable and gentle emission. The potential applications of these luminescent materials in optoelectronic devices are undoubtedly widened by this remarkable advancement.