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 own distinct aggregation-induced delayed fluorescence (AIDF) feature, and exhibit high photoluminescence efficiencies and short delayed fluorescence lifetimes in neat films. The RISC is conspicuously accelerated owing to 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 con-centration 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 sma...