Harnessing Thin-Film Polymorphism via Regulating Conjugated Polymer-Solvent Interactions for Organic Field-Effect Transistors.

Zheng, Hao; Guo, Yanan; Guan, Yan; Wu, Bingjie; Shi, Lina; Xu, Qiming; Lin, Zhiqun; Peng, Juan · Nano Lett · 2026

basic_science · Level V

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Abstract

Tailoring the polymorphism of conjugated polymers is a promising strategy to enhance the performance of optoelectronic devices. However, a comprehensive understanding of the formation and transformation mechanisms of these polymorphisms remains limited. Herein, we correlate, for the first time, thin-film polymorphisms of poly(3-hexylselenophene) (P3HS) with their solution-state polymer-polymer and polymer-solvent interactions by quantifying the second virial coefficient (<i>A</i><sub>2</sub>). P3HS exhibits weak aggregation in toluene, where <i>A</i><sub>2</sub> is positive and polymer-solvent interactions dominate. The fast toluene evaporation kinetically traps these weak aggregates in polymorph I in the film. In contrast, P3HS aggregates strongly in <i>p</i>-xylene, where <i>A</i><sub>2</sub> is negative and polymer-polymer interactions prevail. The slower evaporation of <i>p</i>-xylene promotes the formation of polymorph II. P3HS polymorphs greatly affect their charge transport characteristics, with higher mobility observed in polymorph I. This study highlights a direct connection among different molecular interactions, solution aggregates, and thin-film polymorphisms of conjugated polymers.