Hot-Exciton-Involved Dual-Channel Stepwise Energy Transfer Enabling Efficient and Stable Blue OLEDs with Narrow Emission and High Luminance.

Marching toward next-generation ultrahigh-definition and high-resolution displays, the development of high-performance blue organic light-emitting diodes (OLEDs) with narrow emission and high luminance is essential and requires conceptual advancements in both molecular and device design. Herein, a blue organic emitter is reported that exhibits hot-exciton and aggregation-induced emission characteristics, and use it as a sensitizer in the proposed triplet-triplet annihilation (TTA)-assisted hot-exciton-sensitized fluorescence (HSF) device, abbreviated THSF. Results show that through dual-channel stepwise Förster and Dexter energy transfer processes, the THSF system can simultaneously enhance exciton utilization, accelerate exciton dynamics, and reduce the concentration of triplet excitons. The smooth management of excitons makes the overall performance of the THSF device superior to the control TTA fluorescence and HSF devices. Furthermore, a high-performance narrowband blue (CIEx,y = 0.13, 0.12) OLED is achieved using a two-unit tandem device design, providing an excellent maximum external quantum efficiency of 18.3%, a record-high L90% (the luminance where the ƞext drops to 90% of its peak value) of ≈20 000 cd m-2, and a long half-lifetime at 100 cd m-2 initial luminance of ≈13 256 h. These results showcase the great potential of the THSF strategy in realizing efficient and stable blue OLEDs with narrow emission and high luminance.