Spin‐Flip‐Restricted Multiple‐Resonance Emitters for Extended Device Lifetime in Indolocarbazole‐Based Blue Organic Light‐Emitting Diodes

Abstract

Abstract In this study, a multiple‐resonance (MR) core structure is developed 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 stabilizes the triplet energy of the fused ICz emitters and narrows the full‐width‐at‐half maximum (<20 nm). In addition, the emitters exhibit higher exciton stability than conventional boron‐based MR emitters. The fused ICz‐based blue fluorescent device exhibits a high external quantum efficiency of 7.2%, a blue index of 68.6 cd A−1 at a Commission internationale de l'éclairage y coordinate (CIEy) 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.

Keywords

• blue emitter
• device lifetime
• fluorescence
• multiple‐resonance effect
• narrow emission