Electrical Signature of Ultrasound-Induced Anisotropic Self-Assembly of Poly(3-Hexylthiophene) (P3HT) during Channel Formation

We probed ultrasound irradiation-induced structural ordering of poly(3-hexylthiophene) (P3HT) chains during solidification of a sonicated P3HT solution by monitoring the temporal evolution of the electrical and spectroscopic signals. We observed a peak source-drain current in the test devices during the electrical channel formation, followed by a significant decrease, which has not been observed in the pristine P3HT solution as the solvent evaporates. Through P3HT concentration-dependent gated-sheet conductance and in-situ Raman spectroscopy measurements during channel formation, we found that the competition between aggregation of the disentangled P3HT chains in solution by sonication and the concentration-dependent chain interactions with solvent evaporation led to a distinct electrical signature in the channel formation of the sonicated P3HT film compared to that of the pristine P3HT. The finding provides insights into new opportunities through optimization between the thermodynamic and kinetic considerations in designing pre-deposition treatments for enhanced charge transport.