Frequency dependence of the charge carrier mobility in DH4T

The charge carrier mobility in bulk samples of α,ω-dihexylquaterthiophene has been determined as a function of temperature using the Pulse-Radiolysis Time-Resolved-Microwave-Conductivity and Thin Film Transistor (TFT) techniques. The mobility values obtained at room temperature were 0.01 cm 2 /Vs for both methods However upon cooling to 150 K the FET mobility decreases by an order of magnitude whereas the TRMC mobility remains almost constant. This behaviour is interpreted as an effect of the frequency of the electric field that is used in the experiments and could be described theoretically using an over-the-barrier hopping model for the mobility.