Hopping Transport and Voltage Induced Metal-Insulator Transition in Polythiophene Field Effect Transistors

Abstract

ABSTRACTWe have studied the carrier transport in regio-regular polythiophene field effect transistors (FETs) by four-probe measurements of the steady-state channel conductance from room temperature to 4.2 K. At high gate voltage (constant total carrier density, n = 5×1012 cm−2) and at low temperatures, we demonstrate that the gate voltage and source-drain voltage combine to induce the insulator-to-metal transition. In the insulating regime, the carrier transport is well described by phonon assisted hopping in a disordered Fermi Glass (with Coulomb interactions between the hopping charge carrier and the charge left behind). At the highest gate voltages and at sufficiently high source-drain voltages, the data imply a zero-temperature transition from disordered insulator to metal.