Two kinds of poly(3-hexylthiophene) films with the same chemical compositions were subjected to a charge transport study in order to examine possible influences of film structures on mobilities of charge carriers. One film was electrochemically synthesized using 3-hexylthiophene as a monomer (as-grown film), and the other was prepared by dissolving the as-grow film in chloroform and then cast the polymer solution (cast film). Mobilities coincided well at the lowest (0.02%) and high (20%～30%) doping levels, irrespective of the film preparation methods. However, a clear difference was found between the two kinds of polymer films in the intermediate doping region. The mobility for the as-grown film was almost constant in the low doping region and then started to increase at 1% doping level, whereas the mobility for the cast film showed an initial decrease followed by a drastic increase with the doping level. These features of doping level vs. mobility plots are consistent with those observed earlier with electrochemically generated polythiophene and poly(3-methylthiophene) films and cast films of chemically synthesized poly(3-hexylthiophene)s and poly(3-octylthiophene)s. This finding demonstrates that the above features originate solely from the difference in structures of the polymer films.

Key words: poly(3-hexylthiophene), electrosynthesis, mobility