Evolution in morphology and structure of poly(3-hexylthiophene) blending with liquid crystals under magnetic field treatment

The morphology, crystalline structure as well as the charge transport properties of poly(3-hexylthiophene) (P3HT) binary blends with 4-cyano-4'-pentyl-terphenyl (5CT) and 5,5″-dioctyl-2,2':5′2″-terthiophene (8TTP8) liquid crystals after magnetic field treatment were investigated. The P3HT is immiscible with 5CT and 8TTP8, and they crystallized in their own regions. The 8TTP8 containing thiophene rings exhibited stronger interactions with P3HT than the 5CT containing phenyl rings. The liquid crystals can self-assemble to ordered patterns under the low-intensity magnetic field of 1 T, but the P3HT show of no response to the magnetic field as revealed by polarized optical microscope (POM). The magnetic field facilitates the formation of dendritic crystals in smaller size for the liquid crystals, as well as the appearance of P3HT nanofibers in higher density for the P3HT blends with liquid crystals as revealed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The magnetic field facilitates the π-π stacking of P3HT chains to form more nanowires and induce the crystallization and orientation of liquid crystals to form different crystal forms as confirmed by the grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis. Moreover, the magnetic field could also improve the hole mobility of both pristine P3HT and its blends with 5CT and 8TTP8 liquid crystals, in addition to the power conversion efficiency of P3HT:LCs:PCBM.