Bias induced change in effective mobility of polymer transistors

Abstract

Changes in the mobility, induced by an extended application of a gate bias, are reported in polythiophene TFTs. The gate-induced decrease in mobility is a different mechanism from the threshold shift that has been studied previously. The mobility decrease is not associated with trapped holes, is irreversible by low-temperature annealing, has a strong temperature dependence, and depends on the number of times the gate is switched as well as the duration of the gate bias. The effect exhibits both as an increase in series resistance and as a change in bulk mobility. The thermal activation of the process suggests an energy barrier to a new physical structure which is too stable to reverse. A possible mechanism for structural changes is proposed, based on the electrostrictive effect.