Department of Chemistry, Northwestern University, Evanston, IL 60208.
The Materials Research Center, Northwestern University, Evanston, IL 60208.
Proc Natl Acad Sci U S A. 2017 Nov 21;114(47):E10066-E10073. doi: 10.1073/pnas.1713634114. Epub 2017 Nov 6.
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 () semicrystalline hole-transporting P3HT, () semicrystalline electron-transporting N2200, () low-crystallinity hole-transporting PBDTT-FTTE, and () 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 () 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.
剪切印刷是一种有前途的有机电子加工技术，可用于微结构/电荷输运修饰和大面积薄膜制造。然而，剪切印刷增强电荷输运的机制尚不清楚。在这项研究中，采用了一种使用天然刷子的印刷方法，作为一种信息工具，实现了共轭聚合物的直接聚集控制，并研究了打印参数、大分子主链取向和聚集以及电荷输运各向异性之间的相互作用在一系列具有不同结构和电子结构的共轭聚合物中。该系列包括（）半晶态空穴传输聚合物 P3HT、（）半晶态电子传输聚合物 N2200、（）低结晶度空穴传输聚合物 PBDTT-FTTE 和（）低结晶度导电聚合物 PEDOT:PSS。通过一系列形貌和微观结构分析技术以及电荷输运测量对（半）导电薄膜进行了表征。我们报告说，通过控制纳米纤维聚集物的生长和大分子主链的取向，可以实现显着提高的迁移率/电导率，高达 5.7×/3.9×，与聚集和电荷输运之间的调整（）相关性高达 95%。然而，尽管剪切诱导的聚集对于增强电荷输运很重要，但仅主链取向并不能保证电荷输运各向异性。显然显示了高效电荷输运与聚集之间的相关性，而迁移率和取向度并不总是很好相关。这些观察结果提供了对共轭聚合物中宏观电荷输运机制的深入了解，并为优化提供了指导。
