How to control the dipole orientation of organic emitters is a challenge in the field of organic light-emitting diodes (OLEDs). Herein, a linear thermally activated delayed fluorescence (TADF) molecule, PhNAI-PMSBA, bearing a 1,8-naphthalimide-acridine framework was designed by a double-site long-axis extension strategy to actively control the dipole orientation. The horizontal ratio of emitting dipole orientation of PhNAI-PMSBA reaches 95%, substantially higher than that of isotropic emitters (67%). This unique feature is associated with the intrinsically horizontal molecular orientation of PhNAI-PMSBA and the good agreement between its transition dipole moment direction and molecular long axis. The PhNAI-PMSBA-based OLED achieves an ultrahigh optical outcoupling efficiency of 43.2% and thus affords one of the highest red electroluminescence with an external quantum efficiency of 22.3% and the Commission International de l’Eclairage 1931 coordinates at around (0.60, 0.40).

在有机发光二极管（OLED）领域中，如何控制有机发射器的偶极取向是一个挑战。本文中，通过双位点长轴延伸策略设计了带有1,8-萘二甲酰亚胺-Ph啶骨架的线性热激活延迟荧光（TADF）分子PhNAI-PMSBA，以主动控制偶极子取向。PhNAI-PMSBA的发射偶极子取向的水平比达到95％，大大高于各向同性发射器的水平（67％）。此独特功能与PhNAI-PMSBA的固有水平分子取向以及其跃迁偶极矩方向和分子长轴之间的良好一致性相关。基于PhNAI-PMSBA的OLED实现43的超高光学输出耦合效率。