Controlling morphology and microstructure of conjugated polymers via solution-state aggregation

The macroscopic functions and properties of conjugated polymers depend on their microcosmic morphology and microstructure in the solid state. However, such morphology and microstructure from molecules to solid states are complicated. Therefore, it is a significant challenge to reveal the relationship among molecular structures to the complex microstructure and finally to device functions. This review focuses on the formation, behavior, and evolution of solution-state aggregation of conjugated polymers, which can influence and even determine the solid-state morphology and microstructure, ultimately clarifying the relationship between the microstructure and the properties of conjugated polymers. The critical role of solution-state aggregation is highlighted from a theoretical understanding of molecular interactions between polymer chains (conjugated backbones and/or flexible side chains) and solvent molecules. We highlight the recent progress on high-performance polymer-based devices through the solution-state aggregation strategy. Furthermore, we summarize the challenges and essential research direction on the solution-state aggregation, which will be addressed and established in the future. Therefore, an in-depth understanding of polymer aggregation will advance the development of high-performance conjugated polymers in various functional devices.