High Electron Mobility in Solution-Cast and Vapor-Deposited Phenacyl−Quaterthiophene-Based Field-Effect Transistors:  Toward N-Type Polythiophenes

New carbonyl-functionalized quaterthiophenes, 5,5' ''-diperfluorophenylcarbonyl-2,2':5',2' ':5' ',2' ''-quaterthiophene [DFCO-4T], 5,5' ''-diphenyl-2,2':5',2' ':5' ',2' ''-quaterthiophene [DPCO-4T], and a polymer having the same basic motif as DFCO-4T, poly{1,4-bis[(3'-n-octyl-2,2'-dithiophene)carbonyl]-2,3,5,6-tetrafluorobenzene} [P(COFCO-4T)], have been synthesized, characterized, and the crystal structures of the molecules determined. Field-effect transistors fabricated with vapor-deposited and solution-cast films of DFCO-4T exhibit very high Ion:Ioff current ratios (up to 108) and electron mobilities up to approximately 0.51 and approximately 0.25 cm2.V-1.s-1, respectively. Solution-cast blends of P(COFCO-4T) and DFCO-4T (1:1 weight ratio) exhibit an electron mobility of approximately 0.01 cm2.V-1.s-1 (Ion:Ioff = 104).