Controlled Crystallization of Conjugated Polymer Films from Solution and Solvent Vapor for Polymer Electronics

• Published in: Advanced functional materials Vol. 27; no. 1; pp. np - n/a
• Main Authors: Schulz, Gisela L., Ludwigs, Sabine
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2017
• Subjects: Absorption spectroscopy; Addition polymerization; Agglomeration; Annealing; conjugated polymers; Copolymers; Crystallization; Electronic devices; Electronic properties; in‐situ absorption spectroscopy; Materials science; Morphology; Nucleation; Oligomers; Optical properties; organic electronics; polymer crystallization; Polymer films; Polymeric films; Polymers; Polymorphism; solvent vapor annealing; Solvents; Superstructures; Surface layer; Texture
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201603083

Over the years, solution‐processable conjugated oligomers and polymers have proven to be very promising for application in organic electronic devices. In addition to tuning the chemical structure of the materials, the role of morphology has been identified as a key parameter in determining device performance. Conjugated polymers are typically semicrystalline in nature consisting of both crystalline and amorphous domains giving rise to a wealth of superstructures. In comparison to classical non‐conjugated semicrystalline polymers, they bear the additional advantage of absorbing light. This makes UV‐vis absorption spectroscopy an excellent tool to monitor polymer aggregation and crystallization in‐situ both in solution and in films. With this feature article we point out the delicate interplay between solution processing and the obtained morphology in polythiophenes and low bandgap copolymers. Subtle changes in the preparation protocol lead to significant changes in textures and also give rise to polymorphism. Solvent vapor annealing and solution crystallization are highlighted as tools to control the nucleation and growth processes in semicrystalline polymer films. Structure‐function relationships between morphological, optical and electronic properties are demonstrated. Spherulitic superstructures are obtained via controlled nucleation and growth processes in conjugated polymer films, as evidenced by in‐situ monitoring of optical absorption. Pre‐aggregation in solution and solvent vapor annealing are discussed as excellent methods to reduce nucleation densities and to tune textures and polymorphism.