Nonlinear charge injection in organic field-effect transistors

Transport properties of a series of poly(3-hexylthiophene) organic field-effect transistors with Cr, Cu, and Au source/drain electrodes were examined over a broad temperature range. The current-voltage characteristics of the injecting contacts are extracted from the dependence of conductance on channel length. With reasonable parameters, a model of hopping injection into a disordered density of localized states, with emphasis on the primary injection event, agrees well with the field and the temperature dependence of the data over a broad range of temperatures and gate voltages.