Structural and electrical characterization of processable bis-silylated thiophene oligomers

A new class of processable, chemically stable, and easily synthesized and purified alpha,omega-bis(dimethyl-tert-butylsilyl) oligothiophenes is described. Information on the solid-state properties was obtained by single crystal X-ray diffraction and CPMAS NMR spectroscopy. Molecular packing was characterized by a sandwich-type organization, with the molecular planes between adjacent layers along the stacking direction being exactly parallel. Vacuum-evaporated thin films of the tetramer, pentamer, and hexamer displayed field effect transistor activity, with charge mobilities increasing with the substrate deposition temperatures in the range 28-80 degrees C. The best FET performance was achieved with the pentamer which was characterized by an on/off ratio > 10(3), reproducibility, and a device stability in air of months.