Aggregation-Induced Delayed Fluorescence Luminogens with Accelerated Reverse Intersystem Crossing for High-Performance OLEDs

A fast reverse intersystem crossing (RISC) is of high importance for delayed fluorescence emitters in terms of increasing exciton utilization and suppressing efficiency roll-off. Herein, new robust luminogens comprised of carbonyl, phenoxazine, and chlorine-substituted carbazole derivatives are synthesized and characterized. They have distinct aggregation-induced delayed fluorescence (AIDF) features and exhibit high photoluminescence efficiencies and short delayed fluorescence lifetimes in neat films. The RISC is conspicuously accelerated because of their tiny singlet-triplet energy splitting and greatly enhanced spin-orbit coupling by heavy atom effect in neat in nondoped OLEDs, providing excellent maximum electroluminescence (EL) efficiencies of 20.4-21.7%, and can also perform outstandingly in doped OLEDs in a wide doping concentration range (5-90 wt %), affording impressive EL efficiencies of up to 100.1 cd A(-1), 104.8 lm W-1, and 29.1%, with small efficiency roll-off. These findings demonstrate the AIDF luminogens with fast RISC are promising candidates to fulfill various demands of production and application of OLEDs.