Morphology and field-effect transistor characteristics of semicrystalline poly(3-hexylthiophene) and poly(stearyl acrylate) blend nanowires

The morphology and charge transport characteristics of semicrystalline poly(3-hexylthiophene) (P3HT) and semicrystalline poly(stearyl acrylate) (PSA) or amorphous poly(methyl methacrylate) (PMMA) with various blending ratios were systematically investigated using different solvents. The P3HT-PSA films prepared from CH2Cl2 formed well-defined P3HT nanowires with an average diameter of 30 nm, which was larger than that (similar to 14 nm) of the P3HT-PMMA films, as evidenced by TEM and AFM. The P3HT-PSA nanowire based field effect transistors (FET) could achieve a high hole mobility of 3.2 x 10(-3) cm(2) V-1 s(-1) using only 2 wt% P3HT composition. The maximum FET mobility of 7.86 x 10(-3) cm(2) V-1 s(-1) with the on/off ratio of 10(5) was obtained in the 10 wt% P3HT-PSA blends, which were higher than those of pristine P3HT and P3HT-PMMA devices. The semicrystalline PSA probably facilitated large P3HT crystallites and led to high FET mobility. Also, the P3HT-PSA FET devices showed lower percolation threshold and better ambient stability than the P3HT-PMMA devices. These results indicated that the crystalline non-conjugated polymers played a critical role in the charge transport and air stability of FETs based on conjugated polymer blends.