Hot‐Exciton Mechanism and AIE Effect Boost the Performance of Deep‐Red Emitters in Non‐Doped OLEDs

Abstract Luminescent materials possessing a “hot‐exciton” mechanism and aggregation‐induced emission (AIE) qualities are well‐suited for use as emitting materials in nondoped organic light‐emitting diodes (OLEDs), particularly in deep‐red regions where their ground state and singlet excited state surfaces are in proximity, leading to the formation of multiple nonradiative channels. However, designing molecules that artificially combine the hot‐exciton mechanism and AIE attributes remains a formidable task. In this study, a versatile strategy is presented to achieve hot‐exciton fluorescence with AIE property by increasing the first singlet excited (S₁) state through modulation of the conjugation length of the newly created acceptor unit, matching the energy level of high‐lying triplet (T_n) states, and enhancing exciton utilization efficiency by employing suitable donor moieties. This approach reduces the aggregation‐caused quenching (ACQ) in the aggregate state, resulting in the proof‐of‐concept emitter DT‐IPD, which produces an unprecedented external quantum efficiency (EQE) of 12.2% and Commission Internationale de I'Eclairage (CIE) coordinates of (0.69, 0.30) in a deep‐red non‐doped OLED at 685 nm, representing the highest performance among all deep‐red OLEDs based on materials with hot‐exciton mechanisms. This work provides novel insights into the design of more efficient hot‐exciton emitters with AIE properties.