Aggregation control in natural brush-printed conjugated polymer films and implications for enhancing charge transport

Gang Wang, Wei Huang, Nicholas D. Eastham, Simone Fabiano, Eric F. Manley, Li Zeng, Binghao Wang, Xinan Zhang, Zhihua Chen, Ran Li, Robert P. H. Chang, Lin X. Chen, Michael J. Bedzyk, Ferdinand S. Melkonyan, Antonio Facchetti, Tobin J Marks

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Abstract

Shear-printing is a promising processing technique in organic electronics for microstructure/charge transport modification and large-area film fabrication. Nevertheless, the mechanism by which shear-printing can enhance charge transport is not well-understood. In this study, a printing method using natural brushes is adopted as an informative tool to realize direct aggregation control of conjugated polymers and to investigate the interplay between printing parameters, macromolecule backbone alignment and aggregation, and charge transport anisotropy in a conjugated polymer series differing in architecture and electronic structure. This series includes (i) semicrystalline hole-transporting P3HT, (ii) semicrystalline electron-transporting N2200, (iii) low-crystallinity hole-transporting PBDTT-FTTE, and (iv) low-crystallinity conducting PEDOT:PSS. The (semi-)conducting films are characterized by a battery of morphology and microstructure analysis techniques and by charge transport measurements. We report that remarkably enhanced mobilities/conductivities, as high as 5.7×/3.9×, are achieved by controlled growth of nanofibril aggregates and by backbone alignment, with the adjusted R2 (R2adj) correlation between aggregation and charge transport as high as 95%. However, while shear-induced aggregation is important for enhancing charge transport, backbone alignment alone does not guarantee charge transport anisotropy. The correlations between efficient charge transport and aggregation are clearly shown, while mobility and degree of orientation are not always well-correlated. These observations provide insights into macroscopic charge transport mechanisms in conjugated polymers and suggest guidelines for optimization.

Original languageEnglish
Pages (from-to)E10066-E10073
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number47
DOIs
Publication statusPublished - Nov 21 2017

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Keywords

  • Natural brush-printing
  • Polymer charge transport
  • Polymer aggregation
  • Polymer alignment
  • Shear effects

ASJC Scopus subject areas

  • General

Cite this

Wang, G., Huang, W., Eastham, N. D., Fabiano, S., Manley, E. F., Zeng, L., Wang, B., Zhang, X., Chen, Z., Li, R., Chang, R. P. H., Chen, L. X., Bedzyk, M. J., Melkonyan, F. S., Facchetti, A., & Marks, T. J. (2017). Aggregation control in natural brush-printed conjugated polymer films and implications for enhancing charge transport. Proceedings of the National Academy of Sciences of the United States of America, 114(47), E10066-E10073. https://doi.org/10.1073/pnas.1713634114