Marin-Beloqui, J.M. orcid.org/0000-0003-1762-5595, Congrave, D.G., Toolan, D.T.W. orcid.org/0000-0003-3228-854X et al. (6 more authors) (2023) Generating long-lived triplet excited states in narrow bandgap conjugated polymers. Journal of the American Chemical Society, 145 (6). pp. 3507-3514. ISSN 0002-7863
Abstract
Narrow bandgap conjugated polymers are a heavily studied class of organic semiconductors, but their excited states usually have a very short lifetime, limiting their scope for applications. One approach to overcome the short lifetime is to populate long-lived triplet states for which relaxation to the ground state is forbidden. However, the triplet lifetime of narrow bandgap polymer films is typically limited to a few microseconds. Here, we investigated the effect of film morphology on triplet dynamics in red-emitting conjugated polymers based on the classic benzodithiophene monomer unit with the solubilizing alkyl side chains C16 and C2C6 and then used Pd porphyrin sensitization as a further strategy to change the triplet dynamics. Using transient absorption spectroscopy, we demonstrated a 0.45 ms triplet lifetime for the more crystalline nonsensitized polymer C2C6, 2–3 orders of magnitude longer than typically reported, while the amorphous C16 had only a 5 μs lifetime. The increase is partly due to delaying bimolecular electron–hole recombination in the more crystalline C2C6, where a higher energy barrier for charge recombination is expected. A triplet lifetime of 0.4 ms was also achieved by covalently incorporating 5% of Pd porphyrin into the C16 polymer, which introduced extra energy transfer steps between the polymer and porphyrin that delayed triplet dynamics and increased the polymer triplet yield by 7.9 times. This work demonstrates two synthetic approaches to generate the longest-lived triplet excited states in narrow bandgap conjugated polymers, which is of necessity in a wide range of fields that range from organic electronics to sensors and bioapplications.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2023 The Authors. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | Conjugated polymers; Palladium; Polarons; Polymers; Pyrroles |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 21 Feb 2023 12:15 |
Last Modified: | 21 Feb 2023 12:15 |
Status: | Published |
Publisher: | American Chemical Society (ACS) |
Refereed: | Yes |
Identification Number: | 10.1021/jacs.2c12008 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:196601 |