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Regio- and conformational isomerization critical to design of efficient thermally-activated delayed fluorescence emitters

Lookup NU author(s): Kenneth Etherington, Jamie Gibson, Dr Thomas Northey, Professor Thomas PenfoldORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

Regio- and conformational isomerization are fundamental in chemistry, with profound effects upon physical properties, however their role in excited state properties is less developed. Here two regioisomers of bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide, a donor–acceptor–donor (D–A–D) thermally-activated delayed fluorescence (TADF) emitter, are studied. 2,8-bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide exhibits only one quasi-equatorial conformer on both donor sites, with charge-transfer (CT) emission close to the local triplet state leading to efficient TADF via spin-vibronic coupling. However, 3,7-bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide displays both a quasi-equatorial CT state and a higher-energy quasi-axial CT state. No TADF is observed in the quasi-axial CTemission. These two CTstates link directly to the two folded conformers of phenothiazine. The presence of the low-lying local triplet state of the axial conformer also means that this quasi-axial CT is an effective loss pathway both photophysically and in devices. Importantly, donors or acceptors with more than one conformer have negative repercussions for TADF in organic light-emitting diodes.

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Author(s): Etherington MK, Franchello F, Gibson J, Northey T, Santos J, Ward JS, Higginbotham HF, Data P, Kurowska A, Dos-Santos PL, Graves DR, Batsanov AS, Dias FB, Bryce MR, Penfold TJ, Monkman AP

Publication type: Article

Publication status: Published

Journal: Nature Communications

Year: 2017

Volume: 8

Online publication date: 13/04/2017

Acceptance date: 19/02/2017

Date deposited: 18/04/2017

ISSN (print): 2041-1723

Publisher: Nature Publishing Group

URL: https://doi.org/10.1038/ncomms14987

DOI: 10.1038/ncomms14987

Data Access Statement: http://dx.doi.org/10.17634/153015-2

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