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

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.