Synergistic Rigidity‐Enhancement and Electron‐Rich Systems Engineering Robust Carbon Dots‐Based ultra‐Narrowband NIR Emitters for LEDs with Superior Operational Stability

Herein, we report the controllable synthesis of carbon dots (CDs) with high color purity, narrow full width at half maxima (FWHM) of 29, 32 and 39 nm, and near‐infrared emission at wavelengths of 683, 695 and 704 nm. Structural characterization, transient absorption, and temperature‐dependent dynamics were investigated to elucidate the narrowband mechanism. Our results demonstrate that the high symmetry and substantial conjugation of the graphitic core enhance material rigidity with minimal exciton‐capturing defects. The high pyrrole N content increases the conjugated electron delocalization, promoting radiative recombination of confined electrons and holes, thereby reducing FWHM. In addition, the large exciton binding energy, weak electron‐phonon coupling, and simple radiative dynamics of the CDs further contribute to their ultra‐narrow emission bandwidths. The CDs exhibit exceptional photo and thermal stabilities in extremely acidic or alkaline conditions and various organic solvents. No quenching or peak broadening is observed at high CD concentrations, rendering these materials suitable for applications in high‐performance optoelectronic devices. Excitingly, CD‐based light‐emitting diodes (LEDs) can operate stably at a maximum current of 2000 mA and retain more than 94% of its performance for 150 h at 300 mA. LEDs utilizing these narrowband CDs provide high‐color purity displays and specific steady‐state lighting applications.