High‐Lying Triplet Exciton‐Mediated Multi‐Channel Sensitization Strategy for Efficient and Stable Blue Organic Light‐Emitting Diodes

ABSTRACT The development of blue organic light‐emitting diodes (OLEDs) remains constrained by simultaneously achieving high luminous efficiency and operational stability. Herein, we systematically explore the electroluminescent performances and exciton dynamics of blue OLEDs employing the hot‐exciton material PAC and the multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitter v ‐DABNA. Direct doping of v ‐DABNA into PAC enables efficient Förster resonance energy transfer (FRET) but causes severe triplet quenching due to the low triplet energy of PAC, resulting in limited device efficiency. To resolve this issue, we propose a high‐lying triplet (T n )‐mediated multi‐channel sensitization (HTEMS) strategy, which integrates the ultrafast high‐lying reverse intersystem crossing characteristics of the hot‐exciton material with spatial segregation of exciton recombination and emission domains. This design effectively suppresses triplet energy back‐transfer while enables efficient FRET and T n ‐mediated Dexter energy transfer. An impressively high external quantum efficiency to 15.0% with trivial roll‐off was achieved by integrating triplet–triplet annihilation exciton recycling strategy. Further deuteration engineering prolonged lifetime (LT90, the luminance dropped to 90% of initial value at 1000 cd m −2 ) to among the highest values of v ‐DABNA‐based devices, with CIE y < 0.20. This work overcomes the intrinsic efficiency–stability trade‐off in blue emission, offering a robust strategy for high‐performance blue OLEDs.