CHARGE-TRANSPORT IN OLIGOTHIOPHENE FIELD-EFFECT TRANSISTORS

Temperature-and electric-field-dependent mobility measurements of poly crystalline alpha-sexithiophene thin films, which form the active laye r in field-effect transistors, are reported and are found to be strong ly sample dependent. In samples with significant charge trapping, the mobility at temperatures greater than 50 K occurs by thermally activat ed hopping. There is a correlation between the extent of charge trappi ng and the magnitude of the field-effect mobility. In most samples, th e field-effect mobility at temperatures less than 40 K is approximatel y temperature independent, but with an absolute value that is sample d ependent. If the effects of trapping are neglected, the mobility in th ese field effect transistors possesses two main components: a nearly t emperature-independent component and a temperature activated component .