Improved field‐effect mobility in short oligothiophenes: Quaterthiophene and quinquethiophene

Organic field effect transistors (OFETs) made from quaterthiophene (4T) and quinquethiophene (5T) have been fabricated with greatly enhanced field‐effect mobilities. It is shown that the problem seems to lie in achieving efficient charge injection rather than in poor charge transport within the material. Dopping of the drain and source contacts with a thin layer of the electron acceptor TCNQ is demonstrated to improve charge injection in 4T devices. Other factors affecting performance are considered briefly.