Bias-induced change in effective mobility observed in polymer transistors
Changes in the mobility induced by an extended application of a gate bias are reported in polythiophene thin film transistors. The gate-induced decrease in mobility is unrelated to the previously studied threshold shift effect that arises from trapped holes. The mobility decrease has a strong temperature dependence, is irreversible by low temperature annealing, 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.
Street, R. A. Bias-induced change in effective mobility observed in polymer transistors. Physical Review B. 2008 April 15; 77 (16): 165311.