Bilayer processing for an enhanced organic-electrode contact in ultrathin bottom contact organic transistors

A bilayer lift-off process has been employed to fabricate optimal electrode contact geometry for statistical characterization of ultrathin organic thin-film transistors (OTFTs). For over 100 p-channel ultrathin (12 ML) copper phthalocyanine (CuPc) OTFTs, the bilayer photoresist lift-off process increased the field effect mobility by two orders of magnitude, decreased the contact resistance by three orders of magnitude, increased the on/off ratio by one order of magnitude, and the threshold voltage was decreased by a factor of three compared to conventionally processed devices. The generality of the method was validated by fabricating OTFTs in four different phthalocynaines and CuPc OTFTs with eight different channel thicknesses.