Field-effect transistor characteristics and microstructure of regioregular poly(3-hexylthiophene) on alkylsilane self-assembled monolayers prepared by microcontact printing

Molecular orientation of regioregular poly(3-hexylthiopene) (P3HT) on self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) prepared by microcontact printing (μCP) are investigated using grazing-incidence X-ray diffraction and field-effect measurements. Spin-coated P3HT films on OTS SAMs fabricated by the μCP method are less oriented and exhibit lower diffraction intensity than those prepared by conventional liquid phase deposition (LPD). In spite of the lower crystallinity, the field-effect mobility in P3HT film on μCP-OTS is almost the same as that on LPD-OTS. This result is attributed to the lower density of trapping centers in P3HT films on μCP-OTS, which is manifested by the lower subthreshold swing of transistor characteristics of P3HT films on μCP-OTS.