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Synthesis and solar cell applications of semiconducting polymers based on vinylene-bridged 5-alkoxy-6-fluorobenzo[c][1,2,5]thiadiazole (FOBTzE)
To improve the strong aggregation behavior and molecular orientation of the previously reported polymer PFE4T with vinylene-bridged 5,6-difluorobenzo[ c ][1,2,5]thiadiazole (FBTzE), we designed and synthesized a vinylene-bridged 5-alkoxy-6-fluorobenzo[ c ][1,2,5]thiadiazole (FOBTzE) moiety as a nove...
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Published in: | Polymer journal 2023-04, Vol.55 (4), p.405-415 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | To improve the strong aggregation behavior and molecular orientation of the previously reported polymer
PFE4T
with vinylene-bridged 5,6-difluorobenzo[
c
][1,2,5]thiadiazole (FBTzE), we designed and synthesized a vinylene-bridged 5-alkoxy-6-fluorobenzo[
c
][1,2,5]thiadiazole (FOBTzE) moiety as a novel electron acceptor unit and its copolymer
PFOE4T
. By installing a strong electron-donating alkoxy group into the FBTzE framework instead of an electron-withdrawing fluorine atom, the highest occupied molecular orbital (HOMO) energy level of the resulting polymer
PFOE4T
was found to be ca. 0.1 eV higher than that of the previously reported polymer
PFE4T
but comparable to that of typical difluorobenzothiadiazole-based polymers. On the other hand, the introduction of alkoxy side chains reduced the strong aggregation tendency and changed the molecular orientation of the polymers from edge-on to bimodal orientation, providing a uniform polymer blended film with PC
61
BM and enhancing carrier transport. These results indicate that the fabricated
PFOE4T
/PC
61
BM-based solar cells exhibited a power conversion efficiency of 4.52% with a high fill factor (FF) of 0.68. However, because
PFOE4T
still has strong aggregation and low solubility, the
PFOE4T
/PC
61
BM blended film formed a large phase separation, resulting in limited short-circuit current density (
J
sc
) and PCE.
Vinylene-bridged 5-alkoxy-6-fluorobenzo[
c
][1,2,5]thiadiazole (FOBTzE) as a novel acceptor unit and its copolymer
PFOE4T
were designed and synthesized. The incorporation of an electron-donating alkoxy group instead of a fluorine atom prevented strong aggregation tendency and changed the molecular orientation of the polymers from edge-on to bimodal orientation, which was expected to provide uniform thin-film with PC
61
BM and promoted carrier transport. However, since
PFOE4T
has still strong aggregation ability and low solubility, the
PFOE4T
/PC
61
BM blended film formed a large phase separation, resulting in a power conversion efficiency of only 4.52%. |
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ISSN: | 0032-3896 1349-0540 |
DOI: | 10.1038/s41428-022-00706-z |