High‐Performance Non‐doped OLEDs with Nearly 100 % Exciton Use and Negligible Efficiency Roll‐Off

: Non-doped organic light-emitting diodes (OLEDs) possess merits of higher stability and easier fabrication than doped devices. However, luminescent materials with high exciton use are generally unsuitable for non-doped OLEDs because of severe emission quenching and exciton annihilation in neat films. Herein, we wish to report a novel molecular design of integrating aggregation-induced delayed fluorescence (AIDF) moiety within host materials to explore efficient luminogens for non-doped OLEDs. By grafting 4-(phenoxazin-10-yl)benzoyl to common host materials, we develop a series of new luminescent materials with prominent AIDF property. Their neat films fluoresce strongly and can fully harvest both singlet and triplet excitons with suppressed exciton annihilation. Non-doped OLEDs of these AIDF luminogens exhibit excellent luminance (ca. 100000 cd m-2 ), outstanding external quantum efficiencies (21.4-22.6 %), negligible efficiency roll-off and improved operational stability. To the best of our knowledge, these are the most efficient non-doped OLEDs reported so far. This convenient and versatile molecular design is of high significance for the advance of non-doped OLEDs.