Abstract
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 3.0×10-4 cm2 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 π-overlapped lamellar structure. The quasi-one-dimensional anisotropy of the present device is ascribed to a weak π–π stacking structure due to a flat-on-like orientation of MEH-PPV confirmed by atomic force microscopy.