A field-effect transistor has been fabricated from polymer materials by printing techniques. The device characteristics, which show high current output, are insensitive to mechanical treatments such as bending or twisting. This all-organic flexible device, realized with mild techniques, opens the way for large-area, low-cost plastic electronics.

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In order to analyze the correlation between charge transport and structural properties in conjugated oligomers, sexithiophene, 6T, was substituted by hexyl groups, both on the terminal a positions (a,cvDH6T) and as pendant groups in the ß position (ß,ß' 6 ). Structural characterizations by X-ray diffraction show that vacuum-evaporated thin films of 6T and , consist of layered structures in a monoclinic arrangement, with all-trans planar molecules standing on the substrate. When compared to 6T, , 6 is mainly characterized by a very large increase of molecular organization at the mesoscopic level, evidenced by a much longer range ordering. Electrical characterizations indicate that the conductivity of , 6 is largely anisotropic, with a ratio of 120 in favor of the conductivity parallel to the substrate plane, i.e. along the stacking axis. The charge carrier mobility, determined on field-effect transistors fabricated from these conjugated oligomers, also shows an increase by a factor of 25 when passing from 6T to , 6 , reaching a value of 5 X 10-2 cm* 12 3V-1 s-1. In contrast, ß,ß' 6 presents very low conductivity and mobility, the latter being below detection limit. These results are attributed to the self-assembly properties brought by alkyl groups in the a,w position.

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