Synthesis and characterization of diperfluorooctyl-substituted phenylene-thiophene oligomers as n-type semiconductors. Molecular structure-film microstructure-mobility relationships, organic field-effect transistors, and transistor nonvolatile memory elements

A new series of mixed phenylene-thiophene oligomers with terminal n-perfluorooctyl groups has been synthesized. These compounds are 2,5-bis(4-n-perfluorooctylphenyl)-thiophene (DFO-PTP, 1), 5,5'-bis(4-n-perfluorooctylphenyl)-2,2'-bithiophene (DFO-PTTP, 2), 5,5-bis(4-n-perfluorooctylphenyl)-2,2':5',2-terthiophene (DFO-PT3P, 3), 5,5'-bis(4-n-perfluorooctylphenyl)-2,2':5',2:5,2'-quaterthiophene (DFO-PT(4)tP, 4), and 1,4-bis[5-(4-n-perfluorooctylphenyl)-2-thienyl]benzene (DH-PTPTP, 5). These systems have been characterized by H-1 and F-19 NMR, elemental analysis or HRMS, optical absorption and emission spectroscopies, differential scanning calorimetry, and thermogravimetric analysis. Vacuum-deposited films were characterized by optical absorption and emission spectroscopy, X-ray diffraction, scanning electron microscopy, and field effect transistor measurements. As thin films, all of the fluorinated compounds are n-type semiconductors with carrier mobilities ranging from similar to10(-6) to similar to0.1 cm(2) V-1 s(-1), depending on the substrate deposition temperature. Furthermore, these films exhibit very large current I-on:I-off ratios (up to similar to10(7)) due to substantially suppressed off-currents. Particularly interesting is straightforwardly synthesized DFO-PTTP (2), which displays a combination of high mobility, high current I-on:I-off ratio, and reversible, tunable, and stable memory effects.