Influence of the contact metal on the performance of n -type carbonyl-functionalized quaterthiophene organic thin-film transistors

Organic thin-film transistors using 5, 5 -diperfluorohexylcarbonyl- 2, 2′: 5′, 2″: 5″, 2 -quaterthiophene (DFHCO-4T) as the electron conducting organic semiconductor are fabricated and the performance of these transistors with different top-contact metals is investigated. Transistors with Au source-drain top contacts attain an apparent saturation mobility of 4.6 cm²/V s, whereas this parameter is 100 times lower for similar transistors with Al/LiF top contacts. We explain this lower performance by the formation of a thin interfacial layer with poor charge injection properties resulting from a redox reaction between Al and DFHCO-4T.