Tailoring Phase Transition in Poly(3-hexylselenophene) Thin Films and Correlating Their Crystalline Polymorphs with Charge Transport Properties for Organic Field-Effect Transistors

Poly(3-hexylselenophene) (P3HS) carries attractive advantages over their close analogue poly(3-hexylthiophene) (P3HT), including a stronger intermolecular interaction, a better interchain charge hopping, and a narrower bandgap. However, P3HS is much less studied compared to P3HT. Herein, we report on intriguing reversible phase transition between two different crystalline polymorphs (i.e., form I and II) in P3HS thin films with different molecular weights enabled by alternating thermal and solvent vapor annealing. More importantly, the phase transition kinetics and mechanism as well as the associated changes on molecular packing structures were also scrutinized. The correlation between different P3HS crystalline polymorphs and the resulting field-effect mobilities was explored for the first time. Our study provides an insight into P3HS crystallization and phase transition, thus entailing the use of polyselenophene-based materials for a wide range of optoelectronic applications.