Charge Transport Anisotropy due to Interfacial Molecular Orientation in Polymeric Transistors with Controlled In-Plane Chain Orientation

• Published in: Applied physics express 2012-02, Vol.5 (2), p.021602-021602-3
• Main Authors: Watanabe, Shun-ichiro, Tanaka, Hisaaki, Kuroda, Shin-ichi, Toda, Akio, Tomikawa, Haruki, Nagano, Shusaku, Seki, Takahiro
• Format: Article
• Language: English
• ISSN: 1882-0778; 1882-0786
• DOI: 10.1143/APEX.5.021602

We report charge transport anisotropy of ultrathin-film transistors of poly[2-methoxy-5-(2$'$-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with controlled in-plane chain orientation prepared by a modified Langmuir--Blodgett method. The field-effect mobility of a five-monolayer transistor reached $3.0\times 10^{-4}$ cm 2 V -1 s -1 with a large anisotropy ratio of about 7.5 between parallel and perpendicular chain orientations. This is in sharp contrast to a nearly two-dimensional mobility anisotropy of the previously reported ultrathin poly(3-hexylthiophene) transistors having a $\pi$-overlapped lamellar structure. The quasi-one-dimensional anisotropy of the present device is ascribed to a weak $\pi$--$\pi$ stacking structure due to a flat-on-like orientation of MEH-PPV confirmed by atomic force microscopy.