Issue 7, 2022

Isomeric thermally activated delayed fluorescence emitters based on a quinolino[3,2,1-de]acridine-5,9-dione multiple resonance core and carbazole substituent

Abstract

The color purity of the pixels is an essential indicator in organic light-emitting diode (OLED) commercial displays. Since the two important parameters of high color purity and efficiency can be achieved simultaneously, multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters have achieved rapid development. Recently, there has been a lot of research work on connecting various donor (D) moieties to the existing MR core, but few studies on how the linking moiety affects the efficiency of MR-TADF emitters. To figure out the influence of substituents on the MR-TADF system, we developed three isomers QAOCz1, QAOCz2, and QAOCz3, which are constructed with the same moieties of 3,11-diphenylquinolino[3,2,1-de]acridine-5,9-dione and 9-phenyl-9H-carbazole (PhCz) by different site connections. Through reasonable adjustments of the substitution site, the donor–acceptor (D–A) interaction of the isomers gradually weakened and molecular rigidity gradually increased. As a result, their singlet–triplet energy gap (ΔEST) gradually decreased and their photoluminescence quantum yield (PLQY) gradually rose. QAOCz3 with the weakest D–A interaction successfully achieves a much higher PLQY of 98.9% and a smaller ΔEST of 0.16 eV. The QAOCz3 based OLED not only realizes the best maximum external quantum efficiency (EQE) of 21.1% but also has the narrowest full-width at half maximum (FWHM) of 40 nm. This work shows that weakening the D–A interaction between the substituents and the MR core by a spacer group is of great significance for the construction of efficient MR-TADF emitters.

Graphical abstract: Isomeric thermally activated delayed fluorescence emitters based on a quinolino[3,2,1-de]acridine-5,9-dione multiple resonance core and carbazole substituent

Supplementary files

Article information

Article type
Research Article
Submitted
07 Dec 2021
Accepted
22 Feb 2022
First published
26 Feb 2022

Mater. Chem. Front., 2022,6, 966-972

Isomeric thermally activated delayed fluorescence emitters based on a quinolino[3,2,1-de]acridine-5,9-dione multiple resonance core and carbazole substituent

J. Liu, S. Zou, X. Chen, S. Yang, Y. Yu, M. Fung, Z. Jiang and L. Liao, Mater. Chem. Front., 2022, 6, 966 DOI: 10.1039/D1QM01588E

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