Facile J-aggregate formation in the friction-transferred oriented thin-films of non-regiocontrolled poly(3-hexylthiophene)

Abstract

The molecular aggregation and ordering in polymer semiconductors critically influence their optoelectronic properties; yet, controlling these features in non-regiocontrolled (NR) polymers remains a challenge due to their inherent steric disorder. In this study, we demonstrate a targeted solvent-free approach to induce high-coherence J-aggregation in NR-poly(3-hexylthiophene) (NR-P3HT) thin films using the friction transfer method. While NR-P3HT typically adopts a disordered or weak H-aggregate configuration, we show that applying a mechanical shear specifically at the liquid crystalline (LC) transition temperature (∼110 °C) overcomes the kinetic barriers to ordering. By systematically optimizing the applied load and substrate temperature, we achieved thin films with unprecedented vibronic spectral signatures, where the 0–0 transition dominates (A00 > A01), indicative of J-aggregate behavior and extended intrachain coherence. This structural evolution was corroborated by polarized absorption spectroscopy, Raman shifts, and x-ray diffraction, which revealed a transition from face-on to edge-on orientation, with enhanced backbone planarity. These findings establish that the synergistic coupling of thermal activation at the LC transition with a mechanical shear can unlock highly ordered, J-aggregate morphologies in low-cost, amorphous polymers, offering a sustainable route to high-performance organic electronics.