Photocarrier mobility in regioregular poly(3-hexylthiophene) studied by the time of flight method

The carrier mobility in the regioregular poly(3-hexylthiophene)(PHT) film h as been studied by means of the time of flight (TOF) method using a sandwic h-type cell of indium tin oxide(ITO)/PHT (cast film)/Al. The response of th e photocurrent exhibits a dispersive character, however, the clear kink ass ociated with the transit time of the carder is observed. The drift mobility of holes is determined to be 4 x 10(-4) cm(2)/V-s and almost independent o f the field > 10(5) V/cm at room temperature, This is the largest TOF mobil ity in poly(3-alkylthiophene) reported to date. It is also found that the a ctivation energy of the mobility is 88 meV and almost independent of the fi eld. The results are discussed taking various transport models into conside ration.