Thermopower of Pentacene Thin-film Transistors

The mechanism of conduction in organic thin-film transistors remains poorly understood, though it is generally thought that conduction occurs via hopping in a disordered band tail. Thermopower in principle can give additional information about the density of states D(E), and the dependence of the mobility on D(E); such information can be used to discriminate between various conduction mechanisms. We report for the first time measurements of the thermopower of pentacene thin films on SiO$_{2}$/Si in a field-effect transistor configuration as a function of charge carrier density and temperature. This work was supported by the Laboratory for Physical Sciences.