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Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices

Zhang, Yiwei; Parnell, Andrew J.; Pontecchiani, Fabio; Cooper, Joshaniel F.K.; Thompson, Richard L.; Jones, Richard A.L.; King, Stephen M.; Lidzey, David G.; Bernardo, Gabriel

Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices Thumbnail


Authors

Yiwei Zhang

Andrew J. Parnell

Fabio Pontecchiani

Joshaniel F.K. Cooper

Richard A.L. Jones

Stephen M. King

David G. Lidzey

Gabriel Bernardo



Abstract

We demonstrate that the inclusion of a small amount of the co-solvent 1,8-diiodooctane in the preparation of a bulk-heterojunction photovoltaic device increases its power conversion efficiency by 20%, through a mechanism of transient plasticisation. We follow the removal of 1,8-diiodooctane directly after spin-coating using ellipsometry and ion beam analysis, while using small angle neutron scattering to characterise the morphological nanostructure evolution of the film. In PffBT4T-2OD/PC71BM devices, the power conversion efficiency increases from 7.2% to above 8.7% as a result of the coarsening of the phase domains. This coarsening process is assisted by thermal annealing and the slow evaporation of 1,8-diiodooctane, which we suggest, acts as a plasticiser to promote molecular mobility. Our results show that 1,8-diiodooctane can be completely removed from the film by a thermal annealing process at temperatures ≤100 °C and that there is an interplay between the evaporation rate of 1,8-diiodooctane and the rate of domain coarsening in the plasticized film which helps elucidate the mechanism by which additives improve device efficiency.

Citation

Zhang, Y., Parnell, A. J., Pontecchiani, F., Cooper, J. F., Thompson, R. L., Jones, R. A., …Bernardo, G. (2017). Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices. Scientific Reports, 7, Article 44269. https://doi.org/10.1038/srep44269

Journal Article Type Article
Acceptance Date Feb 7, 2017
Online Publication Date Mar 13, 2017
Publication Date Mar 13, 2017
Deposit Date Mar 17, 2017
Publicly Available Date Mar 29, 2024
Journal Scientific Reports
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 7
Article Number 44269
DOI https://doi.org/10.1038/srep44269

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http://creativecommons.org/licenses/by/4.0/

Copyright Statement
This work is licensed under a Creative Commons Attribution 4.0 International License. The images
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unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license,
users will need to obtain permission from the license holder to reproduce the material. To view a copy of this
license, visit http://creativecommons.org/licenses/by/4.0/
© The Author(s) 2017.





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