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Title
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Impact of the donor polymer on recombination via triplet excitons in a fullerene-free organic solar cell
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Author
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Abstract
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| The greater chemical tunability of non-fullerene acceptors enables fine-tuning of the donor-acceptor energy level offsets, a promising strategy towards increasing the open-circuit voltage in organic solar cells. Unfortunately, this approach could open an additional recombination channel for the charge-transfer (CT) state via a lower-lying donor or acceptor triplet level. In this work we investigate such electron and hole back-transfer mechanisms in fullerene-free solar cells incorporating the novel molecular acceptor 2,4-diCN-Ph-DTTzTz. The transition to the low-driving force regime is studied by comparing blends with well-established donor polymers P3HT and MDMO-PPV, which allows for variation of the energetic offsets at the donor-acceptor interface. Combining various optical spectroscopic techniques, the CT process and subsequent triplet formation are systematically investigated. Although both back-transfer mechanisms are found to be energetically feasible in both blends, markedly different triplet-mediated recombination processes are observed for the two systems. The kinetic suppression of electron back-transfer in the blend with P3HT suggests that energy losses due to triplet formation on the polymer can be avoided, regardless of favorable energetic alignment. |
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Language
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English
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Source (journal)
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Physical chemistry, chemical physics / Royal Society of Chemistry [London] - Cambridge, 1999, currens
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Publication
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Cambridge
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The Royal Society of Chemistry
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2019
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ISSN
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1463-9076
[print]
1463-9084
[online]
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DOI
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10.1039/C9CP03793D
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Volume/pages
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21
:41
(2019)
, p. 22999-23008
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ISI
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000492992600030
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Pubmed ID
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31599899
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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