Enhancement of carrier mobilities in poly(3-methylthiophene) by an electrochemical doping

A combination of potential-step chronocoulometry and in situ conductivity measurement leads to a successful evaluation of mobilities of positive charge carriers in poly(3-methylthiophene) at room temperature over a wide range of a doping level from 0.02 to 23%. A carrier mobility of 2 × 10−5 cm2 V−1 s−1 at a lightly doped region compares well with the one obtained with the time-of-flight technique. The mobility starts to increase at around 0.1% doping level and it reaches 0.13 cm2 V−1 s−1. The drastic mobility enhancement over four orders of magnitude provides a strong indication that a conduction mechanism is switched from a hopping to metallic transport.