Efficient and Long‐Lived Blue OLEDs by Space‐Confined Triplet Scavenging Modulation in Terminal Emitters

ABSTRACT Blue organic light‐emitting diodes (OLEDs) incorporating multiple‐resonance (MR) emitters have achieved exceptional color purity and external quantum efficiencies (EQEs), yet their operational stability remains limited by triplet accumulation on terminal emitters (TEs). In this study, we report a space‐confined triplet‐scavenging strategy that spatially couples an anthracene‐based triplet‐scavenging unit to the MR core while electronically decoupling them. This architecture enables efficient triplet dissipation without disturbing the intrinsic singlet emission of the MR‐core. Therefore, the proposed BCzBN‐SF1An preserves narrowband blue emission and high photoluminescence quantum yield, while exhibiting an enlarged singlet‐triplet splitting and suppressed delayed emission, consistent with triplet scavenging effect. In hyperfluorescent (HF) OLEDs, BCzBN‐SF1An exhibits a maximum EQE of 22.2% with a significantly reduced efficiency roll‐off. Notably, the device lifetime is extended to 127 h at LT 80 , a threefold improvement over the parent BCzBN‐based device, without sacrificing color purity or efficiency. Transient electroluminescent measurements further reveal suppressed charge trapping and the elimination of delayed emission from TEs, highlighting the synergistic roles of triplet scavenging and optimized charge carrier dynamics. This work demonstrates comprehensive insights into carrier/exciton dynamics, along with an effective molecular design paradigm for simultaneously achieving high efficiency and long operational lifetime in blue HF‐OLEDs through precise triplet exciton management.