A Boron, Nitrogen, and Oxygen Doped π-Extended Helical Pure Blue Multiresonant Thermally Activated Delayed Fluorescent Emitter for Organic Light Emitting Diodes That Shows Fast k RISC Without the Use of Heavy Atoms

• Published in: Advanced materials (Weinheim) 2024-06, Vol.36 (26), p.e2402289
• Main Authors: Weerasinghe, Rangani Wathsala, Suresh, Subeesh Madayanad, Hall, David, Matulaitis, Tomas, Slawin, Alexandra M Z, Warriner, Stuart, Lee, Yi-Ting, Chan, Chin-Yiu, Tsuchiy, Youichi, Zysman-Colman, Eli, Adachi, Chihaya
• Format: Article
• Language: English
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202402289

Narrowband emissive multiresonant thermally activated delayed fluorescence (MR-TADF) emitters are a promising solution to achieve the current industry targeted color standard, BT.2020, for blue color without using optical filters, aiming for high efficiency organic light-emitting diodes (OLEDs). However, their long triplet lifetimes, largely affected by their slow reverse intersystem crossing rates, adversely affect device stability. In this study, a helical MR-TADF emitter (f-DOABNA) has been designed and synthesized. Because of its π-delocalized structure, f-DOABNA possesses a small singlet-triplet gap, ΔE , and displays simultaneously an exceptionally faster reverse intersystem crossing rate constant, k , of up to 2 × 10 s and a very high photoluminescence quantum yield, Φ , of over 90% in both solution and doped films. The OLED with f-DOABNA as the emitter achieved a narrow deep-blue emission at 445 nm (full width at half-maximum of 24 nm) associated with CIE coordinates of 0.150, 0.041, and showed a high maximum external quantum efficiency, EQE , of ∼20%. This article is protected by copyright. All rights reserved.