Achieving High‐Efficiency and Stable Narrowband Organic Electroluminescence via Synchronously Activating Hot‐Exciton and Triplet–Triplet Annihilation Processes in Multi‐Resonance Emitters

ABSTRACT Achieving efficient and stable narrowband organic light‐emitting diodes (OLEDs) is critical for ultra‐high‐definition displays, but the long‐lived triplet excitons in emissive layer could reduce operation lifetimes of the devices due to their potential chemical bond cleavage. Herein, we designed two dual‐function modified multi‐resonance (MR) emitters with anthracene and benzonitrile group, namely BN‐An‐PCN and BNO‐An‐PCN, for introducing low‐triplet energy level and constructing multiple triplet‐exciton harvesting channels. These two MR emitters not only maintain their inherent narrowband‐emission properties, but also exhibit combined hot‐exciton and triplet‐triplet annihilation characteristics, which would be beneficial to efficient utilization and recycling of triplet exciton in electroluminescence process. By introducing sensitization technique, the OLEDs fabricated with both molecules as dopants achieve excellent maximum external quantum efficiencies. Moreover, the operational half‐lifetime at 1000 cd m −2 initial luminance of the BN‐An‐PCN‐based device is 4.2‐fold longer than that of its unmodified parent‐structure‐based counterpart.​ These results suggests that the rational design of the triplet energy levels distribution could effectively enhance the operational stability of the devices, and the dual‐function modification strategy is feasible for improving the performance of classical MR emitters.