Morphology and optoelectronic characteristics of organic field-effect transistors based on blends of polylactic acid and poly(3-hexylthiophene)

This study investigates the influence of the solvent used to prepare films of a poly(3-hexylthiophene) (P3HT) and poly(lactic acid) (PLA) blend on the morphology and charge transport mobility of field-effect transistors (FETs). Films prepared from CH 2 Cl 2 , a poor solvent for P3HT, tended to form well-defined nanowires, attributable to P3HT self-assembly via a solubility-induced process. This phenomenon resulted in a mobility of 5.30 × 10 −3 cm 2 (Vs) −1 and an on/off ratio of 3.23 × 10 3 in a CH 2 Cl 2 -solvent P3HT/PLA-blend system with a P3HT content of 10 wt%. Even a blend with 2 wt% P3HT exhibited a mobility of 1.76 × 10 −3 cm 2 (Vs) −1 . However, in blend systems where CHCl 3 solvent was employed in film preparation, the mobility decreased as the PLA content increased, and almost no electrical characteristics were exhibited at 50 wt% P3HT due to the isolated, spherical, phase-separated morphology of P3HT aggregation. Moreover, in CH 2 Cl 2 solvent systems, the mobility of the P3HT/PLA (10/90) blend decreased from 5.3 × 10 −3 cm 2 (Vs) −1 (in a glove box) to 3.7 × 10 −3 cm 2 (Vs) −1 (after 28 days of air exposure), whereas that of 100 wt% P3HT declined by approximately one order of magnitude. These results confirm that P3HT/PLA blends prepared from CH 2 Cl 2 solvent can be used to fabricate environmentally friendly, low-cost FETs with favorable air stability. The morphology and effects on the OFET performance of blends of various ratios of P3HT and insulating PLA using CHCl 3 and CH 2 Cl 2 as solvents were explored. It is demonstrated that a P3HT network structure within the PLA matrix could be induced using CH 2 Cl 2 . The one-dimensional nanowire morphology of these network structures may have provided an efficient pathway for OFET charge transport. These results confirm that P3HT/PLA blends in CH 2 Cl 2 solvent could be used to fabricate low-cost, green-polymer-blended FETs.