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 films. They can function efficiently as light-emitting layers 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.