Facile J-Aggregate formation in the Friction-Transferred Oriented Thin-Films of Non-Regiocontrolled Poly(3-Hexylthiophene)

The molecular aggregation and ordering in polymer semiconductors critically influence their opto-electronic properties. In this study, we explore a sustainable, solvent-free approach to control aggregation behaviour in non-regioregular poly(3-hexylthiophene) (NR-P3HT) thin films using the friction transfer method. By systematically optimizing the thin film processing parameters like applied load, substrate temperature, and stage speed, we demonstrated the emergence of distinct vibronic spectral signatures, with particular focus on the 0-0 and 0-1 absorption feature. Notably, films fabricated under specific thermal and mechanical conditions exhibited dominant 0-0 peak intensities, indicative of J-aggregate-like behaviour owing to the enhanced intrachain ordering. This transition was corroborated by polarized absorption spectroscopy, Raman shifts, and X-ray diffraction, revealing improved molecular alignment, as well as extended p-conjugation. The results suggest that the liquid crystalline transition temperature, coupled with optimal shear stress, facilitates the self-assembly of initially disordered chains into more ordered domains. Findings of the present work not only impart a new insight pertaining to the implications of mechanical and thermal stimuli on synergistic modulation of aggregation and molecular packing but also highlight a green, scalable strategy for tailoring microstructure in organic semiconductors.