High‐Efficiency and Long‐Lifetime Narrowband Green MR‐TADF OLEDs Enabled by Distinct Molecular Design Strategies

ABSTRACT Narrowband green multi‐resonant thermally activated delayed fluorescence (MR‐TADF) emitters are essential for next‐generation BT.2020 OLED displays; however, achieving high efficiency and long operational lifetime remains a significant challenge. Herein, we demonstrate two complementary molecular design strategies that independently target device stability and efficiency through rational structural modulation. The stability‐oriented emitters, tBuICzBN‐Q and tBuICzBN‐DPPM, incorporate electron‐deficient heteroaromatic units to enhance molecular rigidity and suppress nonradiative decay, resulting in maximum external quantum efficiencies (EQEs) of up to 28.9% and operational lifetimes (LT 97 ) exceeding 2500 h at 1000 cd m −2 . Efficiency‐driven Ph‐NapBF emitter is designed to maximize oscillator strength and promote efficient energy transfer, delivering a record‐high EQE of 37.7%. Furthermore, top‐emission OLEDs exhibit BT.2020‐compliant green emission with CIE coordinates of (0.17, 0.79) and a current efficiency exceeding 277.2 cd A −1 . These results highlight the molecular design strategies can address the efficiency and lifetime limitations of narrowband green MR‐TADF.