The Role of Solvents’ Dielectric Constants in the Delicate Interplay between Microstructure and Optical Properties of Poly (3-Hexylthiophene) Thin Films

In order to gain a deeper understanding of the interplay between microstructure and functional properties of conducting polymers such as their optical behaviors, precise control of the structure formation methods of such polymers is of great importance. This work concerns the study of the role of solvents on the formation of different structures and how the resultant structural features affect the functional optical properties of a model Poly (3-hexylthiophene) conjugated system. Thin films of P3HT have been formed from solvents of different polarities and the structural features of the resultant films studied using optical microscopy and XRD technique. The photo-physical characteristics have been studied using UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. We report that the nature of polymer structure and thus the resultant optical properties greatly depend on the solvent polarity and their dielectric constants rather than their solubility power. We have asserted that the solvent polarities have their fingerprints in the resultant film crystallinities, grain sizes, optical photoluminescence and the optical band gaps and by extension on the opto-electronic device applications