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 have heavy - atom substituents (–Br, –Cl) and a rigid structure to enhance spin orbit coupling for efficient intersystem crossing. The rigid carbazole backbone suppresses non - radiative decay, and the optimized molecular structure avoids quenching. which exhibit relative extended phosphorescent afterglow durations (0.6-3 s), and long phosphorescence lifetimes ( τ _p : 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. which hold great potential for applications in optoelectronic devices such as organic light-emitting diodes (OLEDs).