Anisotropic carrier transport properties of highly aligned oligophenylenevinylenes in organic field-effect transistors

Organic field-effect transistors (OFETs) based on highly aligned oligo-p-phenylenevinylenes (5P4Vs) were fabricated and their anisotropic carrier transport properties were investigated to compare intermolecular charge transport via the pi-pi interaction of phenylenevinylene units and intramolecular charge transport via the conjugated oligomeric chains of 5P4V. The absorption spectra of the 5P4V layer, under irradiation of parallel and perpendicularly polarized light along the rubbing direction, showed that the dichroic ratio was 6.2 at the peak wavelength of 346 nm. The strong optical-absorption anisotropy indicates the production of well-aligned 5P4Vs along the rubbing direction. The field-effect mobility in a current flow perpendicular to the rubbing direction is larger by a factor of 2.7 compared to that parallel to the rubbing direction. These results indicate that the charge transport via pi-pi interaction of phenylenevinylene units is greater than the charge transport via conjugated oligomeric chains of 5P4V.