Strain alignment of conjugated polymers: Method, microstructure, and applications
Harry M. Schrickx, Pratik Sen, Nrup Balar, Brendan O’Connor
Abstract
Straining conjugated polymer films is an effective strategy for controlling molecular orientation. Aligning polymer chains within the film plane significantly influences both electrical and optical properties, thereby presenting avenues for improving electronic device performance and unlocking novel device functionalities. The unique anisotropic optoelectronic nature of these films opens up possibilities for enhanced charge mobility as well as innovative applications in optical sensing and light emission. A polymer film's response to strain also provides practical information on its mechanical properties and potential for implementation in flexible and stretchable applications. This review delves into the process of strain alignment of conjugated polymers, mechanical considerations, morphological analysis, and devices applications. The exploration begins with a concise overview of various polymer alignment processing methods, followed by an in-depth examination of strain alignment and transfer printing techniques employed in device fabrication. We then discuss molecular characteristics that support polymer ductility and strain alignment. Accurately characterizing the microstructure of aligned films is then reviewed. Finally, we present an overview of device demonstrations that have utilized strain-aligned conjugated polymer films.