Amide (n, π*) Transitions Enabled Clusteroluminescence in Solid‐State Carbon Dots

Abstract Carbon dots (CDs) demonstrate great superiority in optoelectronic devices due to their tunable emission and photobleaching resistance properties. Although the fluorescence of CDs in solution has been extensively studied, their solid‐state fluorescence (SSF) mechanism still remains largely unexplored experimentally. Herein, solid‐state fluorescent CDs with unique clusteroluminescence (CL) generated from clusterization‐triggered emission are designed based on condensation between precursors with carboxyl and amino groups. The CDs demonstrate obvious concentration‐dependent fluorescence and quench‐resistant SSF, which is attributed to the activation of amide (n, π*) transition by the clusterization process. This sub‐luminophore is non‐luminescent at long wavelengths in isolated state, while it induces photoluminescence redshift via through‐space interaction in aggregated state. Besides, the SSF of CDs can be tuned from quenched to quenching‐resistant emission through amide formation, and the dominant fluorescent center of CDs solids is switchable from surface to edge state through amide passivation. Based on their long‐wavelength CL feature, high‐purity red light‐emitting diode devices exhibiting 656‐nm warm light are fabricated with the Commission Internationale de l´Eclairage (CIE) coordinates of (0.66, 0.34) and unchanged wavelength under different driving currents. These findings provide novel insights into the SSF mechanism of CDs and a universal strategy to construct fluorescent materials with tailored properties.