Metal-Insulator-Semiconductor Field-Effect-Transistors based on Dihexyl-
quaterthiophene (DH4T), has been realized. Unlike conventional MISFET, these devices work
through the modulation of an accumulation layer at the semiconductor-insulator interface. An
analytical model that describes the operation of organic thin-film-transistors based on a simple
trap distribution, with a single shallow trap level located between the valence-band edge and
the Fermi level, has been used to determine some microscopic parameters such as the
mobility, the density of traps and the corresponding level of traps.