Organic Thin-Film Transistors Based on Blends of Poly(3-hexylthiophene) and Polystyrene with a Solubility-Induced Low Percolation Threshold

Abstract

We have demonstrated that organic thin-film transistors based on blends of poly(3-hexylthiophene) (P3HT) and polystyrene (PS) with high performance and low percolation threshold can be facilely fabricated by changing the solubility of solvent and the aging time of the precursor solution. The structural analysis reveals that these benefits arise from the improvements of both the crystallinity and connectivity of P3HT phase in the blend. In the case of crystallinity, we found that because of the solubility-aging-induced formation of ordered precursors, the molecular ordering of the poly(3-hexylthiophene) phase in the blend films increases, and thus the electronic properties of field-effect transistors (FETs) based on these films are significantly improved. For the connectivity, we found that either bilayered structure or highly connected P3HT nanofibrillar network could form in the blend by changing the solubility of the solvent. Both structures are extremely beneficial to keeping connectivity of active channels and thus keeping the charge-transport properties at low semiconductor content. By optimizing the conditions, the devices based on P3HT/PS blend films containing only 1 wt % P3HT can still show field-effect mobility as high as 1 × 10−2 cm2V−1 s−1, which is comparable with that obtained from the pristine P3HT film.