Improving molecular structure in polythiophene thin films by solvent dipping post-treatment

We systematically studied a simple post-treatment method for improving the structural and electrical characteristics of dip-coated poly(3-hexylthiophene) (P3HT) thin films through direct dipping into a solvent. The molecular structure and electrical and optical properties of the P3HT thin films were greatly influenced by the solubility parameter differences between P3HT and the post-treatment solvents. The post-treatment with xylene substantially improved the crystallinity and enhanced the electrical properties in the P3HT thin film, although film thickness decreased. Through optimization of the solubility parameter differences between P3HT and post-treatment solvents, device performance was improved by an appropriate combination of reduced film thickness and improved molecular structure.