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Multiplying the efficiency of red thermally activated delayed fluorescence emitter by introducing intramolecular hydrogen bond.
- Source :
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Chemical Engineering Journal . Nov2022, Vol. 448, pN.PAG-N.PAG. 1p. - Publication Year :
- 2022
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Abstract
- [Display omitted] • Three TADF emitters were synthesized by finely modifying the acceptor units. • The donor–acceptor intramolecular hydrogen bond is formed in TPA-APm. • TPA-APm exhibits both twofold higher k F and an order of magnitude lower k nr. • TPA-APm-based red OLEDs achieved multiply increasing efficiency >20%. As one of the three primary colors, red organic light-emitting diodes (OLEDs) are indispensable in practical applications. However, red emitters are generally subject to severe non-radiative exciton loss due to their narrow energy gap. In this work, three new thermally activated delayed fluorescence (TADF) emitters were developed, namely 4-(acenaphtho[1,2-b]quinoxalin-9-yl)-N,N-diphenylaniline (TPA-AP), 4-(acenaphtho[1,2-b]pyrido[2,3-e]pyrazin-10-yl)-N,N-diphenylaniline (TPA-APy), and 4-(acenaphtho[1,2-b]pyrazino[2,3-e]pyrazin-9-yl)-N,N-diphenylaniline (TPA-APm), employing a series of finely modified acenaphtho[1,2-b]quinoxaline (AP) derivatives as acceptor units. Among three TADF emitters, an intramolecular hydrogen bond is formed between the donor (D) and acceptor (A) units in TPA-APm. Consequently, the overlap of the frontier molecular orbitals (FMOs) of TPA-APm can increase appropriately, and the fluorescence radiative rate (k F) of TPA-APm is nearly twofold than that of TPA-AP and TPA-APy. Furthermore, the non-radiative decay rate (k nr) of TPA-APm is less than that of TPA-AP and TPA-APy by an order of magnitude, which is attributed to the improved molecular rigidity caused by intramolecular hydrogen bond. As a result, TPA-APm-based OLEDs achieved a multiplied external quantum efficiency (EQE) of 21.1% with the electroluminescence peak at 590 nm, comparing to only 7.0% and 11.5% for the TPA-AP-based and TPA-APy-based devices, respectively. These results demonstrate appropriate intramolecular hydrogen bond can suppress the influence of non-radiative decay by simultaneously enhancing molecular rigidity and facilitating the fluorescence process, and have great potential in the design of efficient red TADF emitters. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 13858947
- Volume :
- 448
- Database :
- Academic Search Index
- Journal :
- Chemical Engineering Journal
- Publication Type :
- Academic Journal
- Accession number :
- 158671889
- Full Text :
- https://doi.org/10.1016/j.cej.2022.137717