Transforming Polymorphs via Meniscus-Assisted Solution-Shearing Conjugated Polymers for Organic Field-Effect Transistors

Abstract

The ability to tune polymorphs of conjugated polymers affords a robust platform for investigating the processing-structure-property relationship. However, simple and generalizable routes to polymorphs have yet to be realized. Herein, we report a viable meniscus-assisted solution-shearing (MASS) strategy to effectively modulate polymorphs (i.e., polymorphs I and II) of poly(3-butylthiophene) (P3BT) and scrutinize the correlation between the two different polymorphs and charge transport characteristics. Specifically, polymorph II exists solely in drop-cast P3BT films. Intriguingly, confined shearing of P3BT renders efficient transformation of polymorph II to I. The kinetics of polymorph transformation associated with the changes in molecular packing and thus photophysical properties are elucidated. The resulting organic field-effect transistors reveal a strong correlation of device performance to attained polymorphs and crystal orientations of P3BT. Such polymorph transformation via the convenient MASS technique can be readily extended to other conjugated polymers of interest. This study highlights the robustness of MASS in regulating polymorphs of conjugated polymers to interrogate their interdependence of processing, structure, and property for a wide range of optoelectronic applications.

Keywords: charge transport; crystal orientation; meniscus-assisted solution shearing; organic field-effect transistors; polymorph transformation; polythiophene.