High‐Temperature‐Induced Fused Polycyclic Aromatic Multiple Resonance Emitters Exhibiting Narrowband and Pronounced Red‐Shifted Emission

作者：Xilin Mu, Lin Wu, Zhizhi Li, Denghui Liu, Deli Li, Hengxuan Qi, Jiuyan Li, Shi‐Jian Su, Yubo Zhou, Siyao Wu, Wei Li, Ziyi Ge · 发表于：Small · 年份：2025 · DOI：10.1002/smll.202411961 · 被引用次数：12 · 研究领域：Organic Light-Emitting Diodes Research、Luminescence and Fluorescent Materials、Perovskite Materials and Applications

Abstract Synthetic methodology is a fundamental framework for preparing functional materials, significantly advancing their development. Herein, a novel 6π electrocyclization reaction is unexpectedly discovered that promotes further ring closure in materials derived from multi‐resonance thermally activated delayed fluorescence (MR‐TADF) compounds, known for their narrow emission. By simply raising the reaction temperature, this process significantly red‐shifts the emission peak of the target material while effectively narrowing its emissive width and greatly enhancing its optoelectronic performance. Utilizing this method, the newly synthesized MR‐TADF substrate material GCz‐4B2 is successfully converted into the target compound GCz‐4B1. Compared to GCz‐4B2, the emission peak of GCz‐4B1 exhibited a redshift of 26 nm while concurrently achieving a significant reduction in its full width at half‐maximum (FWHM) value and corresponding shoulder intensity. Notably, the photoluminescence quantum yield (PLQY) of GCz‐4B1 reached 95.1%, compared to only 85.6% for GCz‐4B2. This enhancement can be attributed to the increased rigidity from the further ring closure reaction, which reduced unfavorable vibrational relaxation processes and improved PLQY values. Furthermore, OLEDs based on GCz‐4B1 attained a maximum external quantum efficiency (EQE max ) of 28.0%, with a small FWHM value of 19.4 nm, significantly surpassing that of devices derived from GCz‐4B2.