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Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters

[Image: see text] Understanding the excited-state dynamics and conformational relaxation in thermally activated delayed fluorescence (TADF) molecules, including conformations that potentially support intramolecular through-space charge transfer, can open new avenues for TADF molecular design as well...

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Autores principales: Woon, Kai-Lin, Yi, Chih-Lun, Pan, Kuan-Chung, Etherington, Marc K., Wu, Chung-Chih, Wong, Ken-Tsung, Monkman, Andrew P.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2019
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493288/
https://www.ncbi.nlm.nih.gov/pubmed/32952765
http://dx.doi.org/10.1021/acs.jpcc.9b01900
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author Woon, Kai-Lin
Yi, Chih-Lun
Pan, Kuan-Chung
Etherington, Marc K.
Wu, Chung-Chih
Wong, Ken-Tsung
Monkman, Andrew P.
author_facet Woon, Kai-Lin
Yi, Chih-Lun
Pan, Kuan-Chung
Etherington, Marc K.
Wu, Chung-Chih
Wong, Ken-Tsung
Monkman, Andrew P.
author_sort Woon, Kai-Lin
collection PubMed
description [Image: see text] Understanding the excited-state dynamics and conformational relaxation in thermally activated delayed fluorescence (TADF) molecules, including conformations that potentially support intramolecular through-space charge transfer, can open new avenues for TADF molecular design as well as elucidate complex photophysical pathways in structurally complex molecules. Emissive molecules comprising a donor (triphenylamine, TPA) and an acceptor (triphenyltriazine, TRZ) bridged by a second donor (9,9-dimethyl-9-10-dihydroacridin, DMAC, or phenoxazine, PXZ) are synthesized and characterized. In solution, the flexibility of the sp(3)-hybridized carbon atom in DMAC of DMAC–TPA–TRZ, compared to the rigid PXZ, allows significant conformational reorganization, giving rise to multiple charge-transfer excited states. As a result of such a reorganization, the TRZ and TPA moieties become cofacially aligned, driven by a strong dipole–dipole attraction between the TPA and TRZ units, forming a weakly charge-transfer dimer state, in stark contrast to the case of PXZ–TPA–TRZ where the rigid PXZ bridge only supports a single PXZ–TRZ charge transfer (CT) state. The low-energy TPA-TRZ dimer is found to have a high-energy dimer local triplet state, which quenches delayed emission because the resultant singlet CT local triplet energy gap is too large to mediate efficient reverse intersystem crossing. However, organic light-emitting diodes using PXZ–TPA–TRZ as an emitting dopant resulted in external quantum efficiency as high as 22%, more than two times higher than that of DMAC–TPA–TRZ-based device, showing the impact that such intramolecular reorganization and donor–acceptor dimerization have on TADF performance.
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spelling pubmed-74932882020-09-16 Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters Woon, Kai-Lin Yi, Chih-Lun Pan, Kuan-Chung Etherington, Marc K. Wu, Chung-Chih Wong, Ken-Tsung Monkman, Andrew P. J Phys Chem C Nanomater Interfaces [Image: see text] Understanding the excited-state dynamics and conformational relaxation in thermally activated delayed fluorescence (TADF) molecules, including conformations that potentially support intramolecular through-space charge transfer, can open new avenues for TADF molecular design as well as elucidate complex photophysical pathways in structurally complex molecules. Emissive molecules comprising a donor (triphenylamine, TPA) and an acceptor (triphenyltriazine, TRZ) bridged by a second donor (9,9-dimethyl-9-10-dihydroacridin, DMAC, or phenoxazine, PXZ) are synthesized and characterized. In solution, the flexibility of the sp(3)-hybridized carbon atom in DMAC of DMAC–TPA–TRZ, compared to the rigid PXZ, allows significant conformational reorganization, giving rise to multiple charge-transfer excited states. As a result of such a reorganization, the TRZ and TPA moieties become cofacially aligned, driven by a strong dipole–dipole attraction between the TPA and TRZ units, forming a weakly charge-transfer dimer state, in stark contrast to the case of PXZ–TPA–TRZ where the rigid PXZ bridge only supports a single PXZ–TRZ charge transfer (CT) state. The low-energy TPA-TRZ dimer is found to have a high-energy dimer local triplet state, which quenches delayed emission because the resultant singlet CT local triplet energy gap is too large to mediate efficient reverse intersystem crossing. However, organic light-emitting diodes using PXZ–TPA–TRZ as an emitting dopant resulted in external quantum efficiency as high as 22%, more than two times higher than that of DMAC–TPA–TRZ-based device, showing the impact that such intramolecular reorganization and donor–acceptor dimerization have on TADF performance. American Chemical Society 2019-04-17 2019-05-16 /pmc/articles/PMC7493288/ /pubmed/32952765 http://dx.doi.org/10.1021/acs.jpcc.9b01900 Text en Copyright © 2019 American Chemical Society This is an open access article published under a Creative Commons Attribution (CC-BY) License (http://pubs.acs.org/page/policy/authorchoice_ccby_termsofuse.html) , which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
spellingShingle Woon, Kai-Lin
Yi, Chih-Lun
Pan, Kuan-Chung
Etherington, Marc K.
Wu, Chung-Chih
Wong, Ken-Tsung
Monkman, Andrew P.
Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title_full Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title_fullStr Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title_full_unstemmed Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title_short Intramolecular Dimerization Quenching of Delayed Emission in Asymmetric D–D′–A TADF Emitters
title_sort intramolecular dimerization quenching of delayed emission in asymmetric d–d′–a tadf emitters
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493288/
https://www.ncbi.nlm.nih.gov/pubmed/32952765
http://dx.doi.org/10.1021/acs.jpcc.9b01900
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