Twisted Multi‐Boron Topological <i>π</i> ‐Extension Enables Narrowband Deep‐Blue Multi‐Resonance Thermally Activated Delayed Fluorescence Emitters

Abstract

ABSTRACT Heteroatom‐fused ring systems featuring topological architectures represent a powerful platform for engineering molecular properties. Herein, we report two topology‐engineered heteroaromatic emitters, BO‐DPAB3 and BO‐DPAB4. Through precise modulation of the number, ratio, and spatial arrangement of B, N, and O heteroatoms, a twisted π‐conjugated framework with finely tuned electronic structure was constructed. The controllable multi‐boron π‐extension enables multidirectional electron delocalization while preserving localized excited‐state characteristics. The rigid twisted topology minimizes structural relaxation and weakens intermolecular interactions, thereby reducing aggregation‐caused quenching and enabling narrowband deep‐blue emission at 453 and 449 nm with a full‐width at half‐maximum (FWHM) of 24 and 20 nm, respectively. Notably, organic light‐emitting diode (OLED) devices based on the symmetric tetraboron emitter BO‐DPAB4 achieve a maximum external quantum efficiency (EQE max ) of 30.1% and a Commission Internationale de l’Éclairage (CIE) coordinate of (0.138, 0.073). This work establishes twisted multi‐boron topological π‐extension as an effective molecular design paradigm for developing deep‐blue emitters with high efficiency and color purity.