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−PT 3 P, 3 ), 5,5‘ ‘‘-bis(4- n -perfluorooctylphenyl)-2,2‘:5‘,2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene (DFO−PT 4 P, 4 ), and 1,4-bis[5-(4- n -perfluorooctylphenyl)-2-thienyl]benzene (DH−PTPTP, 5 ). These systems have been characterized by 1 H and 19 F 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 ∼10 - 6 to ∼ 0.1 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 ∼10 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.