Effect of Polymorphism, Regioregularity and Paracrystallinity on Charge Transport in Poly(3-hexylthiophene) [P3HT] Nanofibers

Abstract

We investigate the relationship between molecular order and charge-transport parameters of the crystalline conjugated polymer poly(3-hexylthiophene) (P3HT), with a particular emphasis on its different polymorphic structures and regioregularity. To this end, atomistic molecular dynamics is employed to study an irreversible transition of the metastable (form I′) to the stable (form I) P3HT polymorph, caused by side-chain melting at around 350 K. The predicted side-chain and backbone–backbone arrangements in unit cells of these polymorphs are compared to the existing structural models, based on X-ray, electron diffraction, and solid-state NMR measurements. Molecular ordering is further characterized by the paracrystalline, dynamic, and static nematic order parameters. The temperature-induced changes of these parameters are linked to the dynamics and distributions of electronic coupling elements and site energies. The simulated hole mobilities are in excellent agreement with experimental values obtained for P...