2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion

• Published in: Nature materials Vol. 15; no. 8; pp. 896 - 902
• Main Authors: Kang, Keehoon, Watanabe, Shun, Broch, Katharina, Sepe, Alessandro, Brown, Adam, Nasrallah, Iyad, Nikolka, Mark, Fei, Zhuping, Heeney, Martin, Matsumoto, Daisuke, Marumoto, Kazuhiro, Tanaka, Hisaaki, Kuroda, Shin-ichi, Sirringhaus, Henning
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2016; Nature Publishing Group
• Subjects: 136/117; 140/146; 639/301/1005/1007; 639/301/119/998; 639/301/357/995; Biomaterials; Charge carrier capture; Charge transport; Coherence; Condensed Matter Physics; Conducting polymers; Crystals; Diffusion; Dopants; Materials Science; Microstructure; Nanotechnology; Optical and Electronic Materials; Polymers; Semiconductor doping; Semiconductors; Solid state
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4634

Doping is one of the most important methods to control charge carrier concentration in semiconductors. Ideally, the introduction of dopants should not perturb the ordered microstructure of the semiconducting host. In some systems, such as modulation-doped inorganic semiconductors or molecular charge transfer crystals, this can be achieved by spatially separating the dopants from the charge transport pathways. However, in conducting polymers, dopants tend to be randomly distributed within the conjugated polymer, and as a result the transport properties are strongly affected by the resulting structural and electronic disorder. Here, we show that in the highly ordered lamellar microstructure of a regioregular thiophene-based conjugated polymer, a small-molecule p-type dopant can be incorporated by solid state diffusion into the layers of solubilizing side chains without disrupting the conjugated layers. In contrast to more disordered systems, this allows us to observe coherent, free-electron-like charge transport properties, including a nearly ideal Hall effect in a wide temperature range, a positive magnetoconductance due to weak localization and the Pauli paramagnetic spin susceptibility. Small molecules diffusing into a thin film of thiophene-based conjugated polymers act as p-type dopants without altering the ordered microstructure of the film. As a result, free-electron-like charge transport is also observed at high doping levels.