ROLE OF THE SEMICONDUCTOR INSULATOR INTERFACE IN THE CHARACTERISTICS OF PI-CONJUGATED-OLIGOMER-BASED THIN-FILM TRANSISTORS

Thin-film transistors (TFT) were made with various pi-conjugated oligomers, including an oligothiophene series (from terthienyl up to octithienyl) and two linear polyacenes, tetracene and pentacene. Furthermore, various inorganic and organic insulators have been used. The devices were characterized by measuring the drain current as a function of the source-drain bias for various source-gate voltages, which allow the determination of the field-effect mobility, mu(FET). As expected, mu(FET) increases as the conjugation length of the oligomer increases. Importantly, the mobility also appears to be very dependent on the nature of the isolating layer, which shows that the charge transport of the device is predominantly governed by the properties of the semiconductor-insulator interface.