An Effective Design Strategy for Robust Aggregation‐Induced Delayed Fluorescence Luminogens to Improve Efficiency Stability of Nondoped and Doped OLEDs

Abstract Exploring molecular design strategy for efficient luminescent materials is of high academic and industrial significance. In this work, it is demonstrated that the introduction of the functional group 4‐(phenoxazin‐10‐yl)benzoyl to the conventional chromophores of carbazole‐substituted fluorene derivatives can generate robust luminogens with aggregation‐induced delayed fluorescence (AIDF), and subtle molecular structure modulation can result in prodigious differences in photoluminescence (PL) and electroluminescence (EL). The obtained new AIDF materials exhibit high thermal and electrochemical stabilities, but their PL quantum yields and delayed fluorescence can be altered greatly. In consequence, these luminogens show varied EL performances in nondoped organic light‐emitting diodes (OLEDs) with external quantum efficiencies (η ext ) ranging from 19.0% to 3.3%. In doped OLEDs, these luminogens can afford higher η ext values of 21.7−24.4% because of enhanced PL efficiencies and/or improved exciton recombination efficiencies. Noticeably, both nondoped OLEDs and doped OLEDs at high doping concentrations enjoy very small efficiency roll‐offs. These findings reveal that the proposed design strategy is feasible and applicable for constructing new AIDF luminogens for the fabrication of high‐performance OLEDs with greatly advanced efficiency stability.