Dual-Mechanism Synergistic Enhancement of Room-Temperature Phosphorescence in Carbazole Derivatives.

Small-molecule phosphorescent materials feature high chemical purity and tailorable luminescence, yet aggregation-caused quenching (ACQ) and poor thermal stability remain critical bottlenecks. Herein, we designed and synthesized a series of carbazole-based derivatives (K-CN, K-Br₂, K-Cl, K-Br), these compounds bear heavy-atom substituents (-Br, -Cl) and rigid skeletons to enhance spin-orbit coupling for efficient intersystem crossing. The rigid carbazole backbone suppresses non - radiative decay, and the optimized molecular structure avoids quenching. Exhibiting relatively extended phosphorescent afterglow durations (0.6-3 s) and long phosphorescence lifetimes (τp: 4.2-177.3 ms) at 77 K. Doping these compounds into a PMMA matrix yields composite materials with significantly enhanced room-temperature phosphorescence. K-CN stands out with the longest lifetime (177.3 ms) and room-temperature phosphorescent afterglow (2 s), and favorable energy level gaps (S₁-T₅ ≈ 0.158 eV) via TD-DFT calculations, and hold great potential for applications in optoelectronic devices such as organic light-emitting diodes (OLEDs).