Helically chiral multiresonant thermally activated delayed fluorescent emitters and their use in hyperfluorescent organic light-emitting diodes

• Published in: Chemical science (Cambridge) Vol. 15; no. 41; pp. 16917 - 16927
• Main Authors: Wang, Jingxiang, Chen, Dongyang, Moreno-Naranjo, Juan Manuel, Zinna, Francesco, Frédéric, Lucas, Cordes, David B, McKay, Aidan P, Fuchter, Matthew J, Zhang, Xiaohong, Zysman-Colman, Eli
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 18.09.2024; The Royal Society of Chemistry
• Subjects: Benzonitrile; Chemistry; Chirality; Circular polarization; Emission; Emitters; Enantiomers; Fluorescence; Light emitting diodes; Narrowband; Organic light emitting diodes; Photoluminescence; Quantum efficiency; Stability; Toluene
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d4sc03478c

Chiral multiresonant thermally activated delayed fluorescence (MR-TADF) materials show great potential as emitters in circularly polarized (CP) organic light-emitting diodes (CP-OLEDs) owing to their bright and narrowband CP emission. Here, two new chiral MR-TADF emitters BuPh-BN and DPA- BuPh-BN possessing intrinsically helical chirality have been synthesized and studied. The large steric interactions between the -butylphenyl groups not only induce the helical chirality but also provide a notable configurational stability to the enantiomers. Racemic mixtures of BuPh-BN and DPA- BuPh-BN show narrowband emission at 490 and 477 nm with full-width at half maximum (FWHM) of 25 and 28 nm and photoluminescence quantum yields, , of 85 and 54% in toluene. The separated enantiomers of BuPh-BN and DPA- BuPh-BN show symmetric circularly polarized luminescence (CPL) with respective dissymmetry factors | | values of 1.5 × 10 and 0.9 × 10 . The hyperfluorescence organic light-emitting diodes (HF-OLEDs) with BuPh-BN and DPA- BuPh-BN acting as terminal emitters and 2,3,4,5,6-penta-(9 -carbazol-9-yl)benzonitrile (5CzBN) as their assistant dopant exhibited, respectively, maximum external quantum efficiencies (EQE ) of 20.9 and 15.9% at 492 and 480 nm with FWHM of 34 and 38 nm. This work demonstrates a strategy for developing intrinsically helically chiral MR-TADF emitters possessing significant configurational stability, which can be used in HF-OLEDs.