Photocarrier Mobility in Regioregular Poly(3-hexylthiophene) Studied by the Time of Flight Method

Abstract
The carrier mobility in the regioregular poly(3-hexylthiophene)(PHT) film has been studied by means of the time of flight (TOF) method using a sandwich-type cell of indium tin oxide(ITO)/PHT (cast film)/Al. The response of the photocurrent exhibits a dispersive character; however, the clear kink associated with the transit time of the carrier is observed. The drift mobility of holes is determined to be 4 ×10-4 cm2/V·s and almost independent of the field > 105 V/cm at room temperature. This is the largest TOF mobility in poly(3-alkylthiophene) reported to date. It is also found that the activation energy of the mobility is 88 meV and almost independent of the field. The results are discussed taking various transport models into consideration.