Self‐Host Thermally Activated Delayed Fluorescence Material with Aggregation‐Induced Emission Character: Multi‐Functional Applications in OLEDs

Abstract Thermally activated delayed fluorescence (TADF) materials that can exhibit high efficiencies in non‐doped organic light‐emitting diodes (OLEDs) are highly desired. On the base of a reference TADF molecule (4‐(9,9‐dimethylacridin‐10(9H)‐yl)phenyl)(phenyl)methanone (BP‐DMAC) containing benzoyl/acridine as acceptor/donor, 9‐phenyl‐9H‐3,9“‐bicarbazole (PBCz) is incorporated to the benzoyl side to design and develop a novel emitter, (4‐(9,9‐dimethylacridin‐10(9H)‐yl)phenyl)(9‐phenyl‐9H‐[3,9″‐bicarbazol]‐6‐yl)methanone (PBCz‐BP‐DMAC). The introduction of PBCz unit is proved to endow PBCz‐BP‐DMAC the additional self‐host feature, in addition to its original aggregation‐induced emission and TADF characters. As a result, the non‐doped OLED of PBCz‐BP‐DMAC exhibits sky‐blue emission with remarkable external quantum efficiency (EQE) of 23.0% and rather low efficiency roll‐off (6%) at a brightness of 1000 cd m⁻², while its doped device reveals a maximum EQE of 27.5%; the spectra and color coordinates of the doped and non‐doped devices are almost identical. It also acts as a host to sensitize green iridium phosphor (fac‐tris(2‐phenylpyridine) iridium(III), Ir(ppy)₃) with high EQE of 23.6%. More fascinatingly, the simplified single‐emitting‐layer all‐TADF white OLED utilizing PBCz‐BP‐DMAC as host emitter in combination with an orange TADF emitter (4CzTPN‐Ph) realizes a state‐of‐the‐art EQE of 20.6%. Evidently PBCz‐BP‐DMAC is one of the best sky‐blue TADF materials and exhibits multi‐functional applications in OLEDs with excellent performance.