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 I_on:I_off currents ratios (>10⁷). DHCO-4T is the first organic material exhibiting excellent ambipolar transport (μ_e/μ_h up to 0.1/0.01 cm² V^-1 s^-1, (I_on:I_off)_e/(I_on:I_off)_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.