Four‐Coordinate Boron Emitters with Tridentate Chelating Ligand for Efficient and Stable Thermally Activated Delayed Fluorescence Organic Light‐Emitting Devices

• Published in: Angewandte Chemie 2019-07, Vol.131 (27), p.9186-9192
• Main Authors: Li, Panpan, Chan, Hing, Lai, Shiu‐Lun, Ng, Maggie, Chan, Mei‐Yee, Yam, Vivian Wing‐Wah
• Format: Article
• Language: English
• Subjects: Acridine; Betriebsstabilität; Boron; Boron compounds; Carbazole; Carbazoles; Chelation; Chemistry; Diodes; Dreizähnige Liganden; Emitters; Fluorene; Fluorescence; Ligands; Organic light emitting diodes; Organische Leuchtdioden; Pyridines; Thermisch aktivierte verzögerte Fluoreszenz; Thin films; Vacuum; Vierfach koordiniertes Bor
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201903332

A new class of four‐coordinate donor‐acceptor fluoroboron‐containing thermally activated delayed fluorescence (TADF) compounds bearing a tridentate 2,2′‐(pyridine‐2,6‐diyl)diphenolate (dppy) ligand has been successfully designed and synthesized. Upon varying the donor moieties from carbazole to 10H‐spiro[acridine‐9,9′‐fluorene] to 9,9‐dimethyl‐9,10‐dihydroacridine, these boron derivatives exhibit a wide range of emission colors spanning from blue to yellow with a large spectral shift of 2746 cm−1, with high PLQYs of up to 96 % in the doped thin film. Notably, vacuum‐deposited organic light‐emitting devices (OLEDs) made with these boron compounds demonstrate high performances with the best current efficiencies of 55.7 cd A−1, power efficiencies of 58.4 lm W−1 and external quantum efficiencies of 18.0 %. More importantly, long operational stabilities of the green‐emitting OLEDs based on 2 with half‐lifetimes of up to 12 733 hours at an initial luminance of 100 cd m−2 have been realized. This work represents for the first time the design and synthesis of tridentate dppy‐chelating four‐coordinate boron TADF compounds for long operational stabilities, suggesting great promises for the development of stable boron‐containing TADF emitters. Fein abgestimmte Emission: Eine neue Klasse vierfach koordinierter fluor‐ und borhaltiger thermisch aktivierter Verzögerte‐Fluoreszenz(TADF)‐Emitter mit einem dreizähnigen 2,2′‐(Pyridin‐2,6‐diyl)diphenolat(dppy)‐Liganden wurde erfolgreich entwickelt und synthetisiert. Effiziente vakuumbeschichtete OLEDs mit hohen EQEs von 18.0 % und langen Halbwertszeiten von 12 733 Stunden wurden erreicht.