Photocurrent probe of field-dependent mobility in organic thin-film transistors

Abstract

We demonstrate the application of photocurrent modulation spectroscopy in characterizing the performance of organic thin-film transistors. This technique provides a consistent framework to extract the mobility and density of free-carriers from experimental data without relying on assumed models of transport. Applying this technique to pentacene thin-film transistors shows that the mobility increases as ∼Vg1∕3, inconsistent with the prediction of hopping transport. The free-carrier density is approximately 1∕2 of the expected capacitive charge, and the mobility increases monotonically with the free carrier density, consistent with the trap and release model of transport.