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The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation

Yifan Dong, Hyojung Cha, Jiangbin Zhang, Ernest Pastor, Pabitra Shakya Tuladhar, Iain McCulloch, James Durrant Orcid Logo, Artem A. Bakulin

The Journal of Chemical Physics, Volume: 150, Issue: 10, Start page: 104704

Swansea University Author: James Durrant Orcid Logo

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DOI (Published version): 10.1063/1.5079285

Abstract

Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization of open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite of this, the carrier dynamics and relative energies of the key...

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Published in: The Journal of Chemical Physics
ISSN: 0021-9606 1089-7690
Published: 2019
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URI: https://cronfa.swan.ac.uk/Record/cronfa49706
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first_indexed 2019-03-26T12:24:07Z
last_indexed 2019-04-09T13:04:22Z
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spelling 2019-04-08T14:36:46.4747216 v2 49706 2019-03-25 The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation f3dd64bc260e5c07adfa916c27dbd58a 0000-0001-8353-7345 James Durrant James Durrant true false 2019-03-25 MTLS Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization of open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite of this, the carrier dynamics and relative energies of the key states controlling the photophysics of these systems are still under debate. Herein, we report an in-depth ultrafast spectroscopic study of a representative OPV system based on a polymer donor PffBT4T-2OD and a small-molecule NFA EH-IDTBR. Global analysis of the transient absorption data reveals efficient energy transfer between donor and acceptor molecules. The extracted kinetics suggest that slow (∼15 ps) generation of charge carriers is followed by significant geminate recombination. This contrasts with the “reference” PffBT4T-2OD:PC71BM system where bimolecular recombination dominates. Using temperature-dependent pump-push-photocurrent spectroscopy, we estimate the activation energy for the dissociation of bound charge-transfer states in PffBT4T-2OD:EH-IDTBR to be 100 ± 6 meV. We also observe an additional activation energy of 14 ± 7 meV, which we assign to the de-trapping of mobile carriers. This work provides a comprehensive picture of photophysics in a system representing new generation of OPV blends with a small driving force for charge separation. Journal Article The Journal of Chemical Physics 150 10 104704 0021-9606 1089-7690 31 12 2019 2019-12-31 10.1063/1.5079285 https://www.repository.cam.ac.uk/handle/1810/290537 COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University 2019-04-08T14:36:46.4747216 2019-03-25T15:49:55.3380449 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering Yifan Dong 1 Hyojung Cha 2 Jiangbin Zhang 3 Ernest Pastor 4 Pabitra Shakya Tuladhar 5 Iain McCulloch 6 James Durrant 0000-0001-8353-7345 7 Artem A. Bakulin 8
title The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
spellingShingle The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
James Durrant
title_short The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
title_full The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
title_fullStr The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
title_full_unstemmed The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
title_sort The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation
author_id_str_mv f3dd64bc260e5c07adfa916c27dbd58a
author_id_fullname_str_mv f3dd64bc260e5c07adfa916c27dbd58a_***_James Durrant
author James Durrant
author2 Yifan Dong
Hyojung Cha
Jiangbin Zhang
Ernest Pastor
Pabitra Shakya Tuladhar
Iain McCulloch
James Durrant
Artem A. Bakulin
format Journal article
container_title The Journal of Chemical Physics
container_volume 150
container_issue 10
container_start_page 104704
publishDate 2019
institution Swansea University
issn 0021-9606
1089-7690
doi_str_mv 10.1063/1.5079285
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
url https://www.repository.cam.ac.uk/handle/1810/290537
document_store_str 0
active_str 0
description Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization of open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite of this, the carrier dynamics and relative energies of the key states controlling the photophysics of these systems are still under debate. Herein, we report an in-depth ultrafast spectroscopic study of a representative OPV system based on a polymer donor PffBT4T-2OD and a small-molecule NFA EH-IDTBR. Global analysis of the transient absorption data reveals efficient energy transfer between donor and acceptor molecules. The extracted kinetics suggest that slow (∼15 ps) generation of charge carriers is followed by significant geminate recombination. This contrasts with the “reference” PffBT4T-2OD:PC71BM system where bimolecular recombination dominates. Using temperature-dependent pump-push-photocurrent spectroscopy, we estimate the activation energy for the dissociation of bound charge-transfer states in PffBT4T-2OD:EH-IDTBR to be 100 ± 6 meV. We also observe an additional activation energy of 14 ± 7 meV, which we assign to the de-trapping of mobile carriers. This work provides a comprehensive picture of photophysics in a system representing new generation of OPV blends with a small driving force for charge separation.
published_date 2019-12-31T04:00:54Z
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score 11.037056

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