Y‐Shaped Pyrene‐Based Aggregation‐Induced Emission Blue Emitters for High‐Performance OLED Devices

The proposed concept of aggregation-induced emission (AIE) has offered an efficient strategy to design high-performance luminescent materials. Herein, three blue emitters containing a pyrene core decorated with either triphenylamine or tetraphenylethylene units are presented. The designed compounds Py-TPA and Py-2TPE are AIE or active materials with blue emission from 464 to 478 nm in the solid state, whereas Py-2TPA is not. Moreover, the enhanced thermal stability of compounds Py-TPA and Py-2TPE allows for their utilization as emitter layers for the fabrication of blue organic light-emitting diode (OLED) devices. The devices exhibit excellent electroluminescence emission with maximum lambda(max em) in the range 456-482 nm with a maximum external quantum efficiency of 7.27%, high exciton utilization efficiency (77.3%), and low turn-on voltage (<= 3.1 V), as well as low-efficiency roll-off. Theoretical calculations reveal that the high exciton utilization efficiency (n(r)) originates from the triplet excitons at T-2 to the lowest single excited (S-1) state via a reverse intersystem crossing process following the principle of the "hot exciton" mechanism. This article not only provides powerful evidence revealing the advantages of pyrene-based AIEgens for OLED applications, but also offers a new approach for designing pyrene-based "hot exciton" materials for next-generation OLEDs.