Enhancing thermally activated delayed fluorescence by fine-tuning the dendron donor strength
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Date
20/01/2022Author
Grant ID
812872
RPG-2016-047
EP/P010482/1
Metadata
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Thermally activated delayed fluorescence (TADF) relies on a small energy gap between the emissive singlet and the non-emissive triplet state, obtained by reducing the wavefunction overlap between donor and acceptor moieties. Efficient emission, however, requires maintaining a good oscillator strength, which is itself based on sufficient overlap of the wavefunctions between donor and acceptor moieties. We demonstrate an approach to subtly fine-tune the required wavefunction overlap by employing donor-dendrons of changing functionality. We use a carbazolyl-phthalonitrile based donor-acceptor core, 2CzPN , as a reference emitter, and progressively localize the hole density through substitution at the 3,6-positions of the carbazole donors ( Cz ) with further carbazole, (4-tert-butylphenyl)amine ( tBuDPA ) and phenoxazine ( PXZ ). Using detailed photoluminescence studies, complemented with Density Functional Theory (DFT) calculations, we show that this approach permits a gradual decrease of the singlet-triplet gap, ΔEST, from 300 meV to around 10 meV in toluene, yet we also demonstrate why a small ΔEST alone is not enough. While sufficient oscillator strength is maintained with the Cz- and tBuDPA-based donor dendrons, this is not the case for the PXZ-based donor dendron, where the wavefunction overlap is reduced too strongly. Overall, we find the donor-dendron extension approach allows successful fine-tuning of the emitter photoluminescence properties.
Citation
Duda , E , Hall , D , Bagnich , S , Carpenter-Warren , C L , Saxena , R , Wong , M Y , Cordes , D B , Slawin , A M Z , Beljonne , D , Olivier , Y , Zysman-Colman , E & Köhler , A 2022 , ' Enhancing thermally activated delayed fluorescence by fine-tuning the dendron donor strength ' , Journal of Physical Chemistry B , vol. 126 , no. 2 , pp. 552-562 . https://doi.org/10.33774/chemrxiv-2021-z10sw , https://doi.org/10.1021/acs.jpcb.1c05749
Publication
Journal of Physical Chemistry B
Status
Peer reviewed
ISSN
1520-6106Type
Journal article
Rights
Copyright © 2022 The Authors. Published by American Chemical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acs.jpcb.1c05749
Description
Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 812872 (TADFlife). SB acknowledges support from the German Science Foundation (392306670/HU2362). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11. DB is a FNRS Research Director. Y.O. acknowledges funding from the FRS-FNRS under the grant F.4534.21 (MIS-IMAGINE).Collections
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