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

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

来源：Proceedings of the National Academy of Sciences, 2017, 114(47): E10066-E10073.

DOI：10.1073/pnas.1713634114

• natural brush-printing
• shear effects
• polymer alignment
• polymer aggregation
• polymer charge transport

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 5.7x/3.9x, are achieved by controlled growth of nanofibril aggregates and by backbone alignment, with the adjusted R-2 (R-adj(2)) 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.

• 出版日期2017-11-21
• 单位西北大学