Dependencies of field effect mobility on regioregularity and side chain length in poly(alkylthiophene) films

Carrier mobilities in poly(3-alkylthiphene) cast films have been studied by means of fabricating a field effect transistor (FET) at the field range of (0.3-1.6)x 10(4) V/cm. It is found that the regioregurality is markedly ef fective to the mobilities than the side chain length. The FET mobility of t he regioregular poly(3-hexylthiophene), PHT is approximately 3x10(-3) cm(2) /Vs which is larger than that of regiorandom PhT by 3 orders of magnitude. The mobility of regioregular poly(3-dodecylthiophene), PDDT is 8 x10(-4) cm (2)/Vs and is also 3 orders of magnitude larger than that of regiorandom PD DT. The mobilities of regioregular ones decrease, however, those of regiora ndom ones increase at higher fields. Time FET mobilities are nearly same to the mobilities estimated by the time of flight method. These results have been discussed taking the regularity of the main chain and the length of si de chain into consideration.