Journal Advanced Science Date 2024.08.29 Abstract In this study, we developed a multiple-resonance (MR) core structure with a spin-flip-restricted emission mechanism based on a fused indolo[3,2,1-jk]carbazole (ICz) framework as emitters to improve the lifetime of blue organic light-emitting diodes. The molecular skeleton modulation approach applied to the conjugated π-system effectively stabilized the triplet energy of the fused ICz emitters and narrowed the full-width-at-half maximum (<20 nm). In addition, the emitters exhibited higher exciton stability than conventional boron-based MR emitters. The fused ICz-based blue fluorescent device exhibited a high external quantum efficiency of 7.2%, a blue index of 68.6 cd A？1 at a Commission internationale de l'？clairage (CIEy) coordinate of 0.075, and a device lifetime 1.8 times longer than that of a boron-based emitter. In addition, a phosphor-sensitized fluorescent device based on the ICz emitter exhibited an improved external quantum efficiency of 20.6% with a CIEy coordinate of 0.076. Reference N DOI N Prev LIST Next