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Lookup NU author(s): Dr Yang Cao, Dr Julien EngORCiD, Professor Thomas Penfold
This is the authors' accepted manuscript of an article that has been published in its final definitive form by American Chemical Society, 2019.
For re-use rights please refer to the publisher's terms and conditions.
Thermally activated delayed fluorescence (TADF) has shown great potential as a mechanism for harvesting low-lying triplet excited states in organic molecules and is therefore of great interest in the context of organic electronics, especially organic light emitting diodes (OLEDs). Herein we study the mechanism for triplet harvesting in triquinolonobenzene (TQB), which instead of relying upon the well-established donor-acceptor (D-A) scheme uses excited-state intramolecular proton transfer (ESIPT). We demonstrate that upon photoexcitation into the lowest singlet excited state the proton is transferred within 20 fs, suggesting it plays little role in triplet harvesting which occurs on the nano- to micro-second timescale. However, TQB exhibits multiple low-lying triplet states that are strongly coupled along this proton transfer coordinate. The majority of these states favour the structure prior to proton transfer (TQB-TA) and this means that the proton transfer dynamics (3TQB-TA->1TQB-TB) plays a crucial role in triplet harvesting. This mechanism yields an energy gap in good agreement with that reported experimentally and is consistent with previous photophysical characterisation. Finally, a discussion upon extending this understanding into a device context is also presented.
Author(s): Cao Y, Eng J, Penfold TJ
Publication type: Article
Publication status: Published
Journal: Journal of Physical Chemistry A
Year: 2019
Volume: 123
Pages: 2640-2649
Print publication date: 04/04/2019
Online publication date: 08/03/2019
Acceptance date: 08/03/2019
Date deposited: 10/03/2019
ISSN (print): 1089-5639
ISSN (electronic): 1520-5215
Publisher: American Chemical Society
URL: https://doi.org/10.1021/acs.jpca.9b00813
DOI: 10.1021/acs.jpca.9b00813
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