Crystalline structures in organic semiconductors for high-performance OTFT applications

We have investigated crystalline structures in organic semiconducting thin films with regioregular poly(3-alkyl thiophene)s, pentacene, and oligofluorene-thiophene derivatives, using grazing-incidence X-ray diffraction and atomic force microscopy. We found that crystalline morphologies and molecular orientation in these thin films strongly affect electric characteristics of these film-based organic thin-thin transistors (OTFTs). Specifically, in solution- and vacuumdeposited films, preferentially perpendicular orientation of π-conjugated crystalline planes with respect to dielectric substrates require results in high-performance charge mobility in the OTFT devices.