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

Abstract

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 (∼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 × 10⁻³ cm² V⁻¹ s⁻¹ using only 2 wt% P3HT composition. The maximum FET mobility of 7.86 × 10⁻³ cm² V⁻¹ s⁻¹ with the on/off ratio of 10⁵ 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.