Constructing Organic Electroluminescent Material with Very High Color Purity and Efficiency Based on Polycyclization of the Multiple Resonance Parent Core

Abstract Multiple resonance thermally activated delayed fluorescence (MR‐TADF) compounds have set off an upsurge of research because of their tremendous application prospects in the field of wide color gamut display. Herein, we propose a novel MR‐TADF molecular construction paradigm based on polycyclization of the multiple resonance parent core, and construct a representative multiple resonance polycyclic aromatic hydrocarbon (MR‐PAH) based on the para ‐alignment of boron and nitrogen atoms into a six‐membered ring ( p ‐BNR). Through the retrosynthesis analysis, a concise synthesis strategy with wide applicability has been proposed, encompassing programmed sequential boron esterification, Suzuki coupling and Scholl oxidative coupling. The target model molecule BN‐TP shows green fluorescence with an emission peak at 523 nm and a narrow full‐width at half‐maximum (FWHM) of 34 nm. The organic light‐emitting diode (OLED) employing BN‐TP as an emitter exhibits ultrapure green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.26, 0.70), and achieves a maximum external quantum efficiency (EQE) of 35.1 %.