Template-guided self-assembly of semiconducting polymers in crystallizable solvent-induced nanoconfinement

The morphology and chain orientation of conjugated polymer films strongly influence their charge transport properties. In this study, we investigate the solution crystallization behavior of semiconducting polymers in nanoconfinement generated using 1,3,5-trichlorobenzene (sym-TCB), a solvent additive that crystallizes at room-temperature. Solutions of a diketopyrrolopyrrole-bithiophene (pDPPBT) copolymer, poly(3-hexylthiophene) (P3HT), and other polymers were prepared in chloroform with varying concentrations of sym-TCB. Upon film casting, sym-TCB crystals directed the growth of polymer domains, resulting in spherulitic morphologies replicated from the solvent crystals. pDPPBT films exhibited predominantly edge-on chain orientation at the dielectric interface, whereas P3HT showed bimodal orientation: face-on alignment near the top film surface via epitaxial crystallization and edge-on alignment at the bottom interface. This crystallization behavior was also observed in other conjugated polymer systems. Notably, pDPPBT films with conductive domains templating the solvent crystals significantly enhanced field-effect mobility (∼5.60 cm² V^-1 s^-1), outperforming control films with randomly aligned fibrillar domains (1.60-2.40 cm² V^-1 s^-1). These findings demonstrate that solvent crystal-induced nanoconfinement enables precise control over multiscale polymer ordering, offering an effective strategy to enhance charge transport in organic thin-film transistors.