Organic thin-film transistors based on carbonyl-functionalized quaterthiophenes: high mobility N-channel semiconductors and ambipolar transport.

New carbonyl-functionalized quaterthiophenes, 5, 5' ''-diheptanoyl-2,2':5',2' ':5' ',2' ''-quaterthiophene (DHCO-4T), 5, 5' ''-diperfluorohexylcarbonyl-2,2':5',2' ':5' ',2' ''-quaterthiophene (DFHCO-4T), and 2,7-[bis-(5-perfluorohexylcarbonylthien-2-yl)]-4H-cyclopenta[2,1-b:3,4-b']-dithiophen-4-one (DFHCO-4TCO) have been synthesized and characterized. Field-effect transistors fabricated with these materials exhibit high electron mobilities both in a vacuum (up to 0.6 cm2 V-1 s-1) and in air (up to 0.02 cm2 V-1 s-1) and very high Ion:Ioff currents ratios (>107). DHCO-4T is the first organic material exhibiting excellent ambipolar transport (mue/muh up to 0.1/0.01 cm2 V-1 s-1, (Ion:Ioff)e/(Ion:Ioff)h up to 107/108 for the same device) over a broad range of deposition temperatures. These materials are therefore promising for organic complementary circuits.