Integration of Through‐Space Conjugation of Adjacent Arene with Nitrogen/Carbonyl Framework for Narrowband Emission

Organic luminescent materials featuring noncovalent through‐space conjugation (TSC) have attracted considerable attention. However, the presence of multiple vibrational energy levels and weak spatial electron delocalization typically results in broad emission peaks for TSC‐based emitters, significantly impeding their extensive application in optoelectronic technologies. Herein, two TSC emitters, TSFQ‐TRZ and TSFQ‐Ph, were synthesized by integrating a fused nitrogen/carbonyl skeleton with adjacent arene 2,4,6‐triphenyl‐1,3,5‐triazine (TPTRZ) and phenyl group segments, through a rigid spiro spacer. These emitters exhibited narrow emissions, with full widths at half‐maximum of 19 nm and 25 nm, respectively. Experimental and theoretical investigations unveiled that the TPTRZ segment introduces steric hindrance while simultaneously suppressing molecular vibrations via intramolecular interactions—a key factor in achieving narrow emissions. Leveraging this narrow blue emission, electroluminescent devices employing TSFQ‐TRZ as the emitter achieved an impressive maximum external quantum efficiency of 26.7%, which further increased to 28.2% when sensitized by phosphorescent emitter. This work demonstrates highly efficient, narrowband emissions from TSC‐based emitters, thereby expanding their potential applications in the electroluminescence field.