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

Abstract

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.

Ring‐Banded Spherulitic Crystals of Poly(3‐butylthiophene) via Controlled Solvent Evaporation

“…In general, semicrystalline non‐conjugated polymers such as polyolefins form spherulites from the melt. Solvent vapor annealing of conjugated polymer films enables control of the nucleation density to allow the formation of ordered spherulites . Interestingly, field‐effect transistors made from conjugated polymer spherulites displayed significant charge transport anisotropy …”

“…Solvent vapor annealing of conjugated polymer films enables control of the nucleation density to allow the formation of ordered spherulites. [16] Interestingly, field-effect transistors made from conjugated polymer spherulites displayed significant charge transport anisotropy. [17,18] Ring-banded spherulites are often reported in non-conjugated polymers.…”

Semiconducting Polymer Spherulites—From Fundamentals to Polymer Electronics

“…Copyright 2008, American Chemical Society. b) Setup for a more controllable adjustment of the vapor pressure used by Ludwigs et al . Reproduced with permission .…”

Exploiting physical vapor deposition for morphological control in semi‐crystalline polymer films

“…The studies are of tremendous importance for functional polymers, which enable a broad range of applications such as solar cells, transistors, non‐volatile memories, and sensors . Among all the applications, film morphology, arising from the complex semi‐crystalline nature of polymers, critically determines performance . For example, it is generally accepted that a higher extent of crystallinity in the active layer of semiconducting polymer thin films can enhance device efficiency and a longer lateral dimension of defect‐free crystalline lamellae can reduce gas permeability through polymer thin films .…”

“…[11][12][13] Among all the applications, film morphology, arising from the complex semi-crystalline nature of polymers, critically determines performance. [8,[14][15][16][17] For example, it is generally accepted that a higher extent of crystallinity in the active layer of semiconducting polymer thin films can enhance device efficiency [8,14,15,18] and a longer lateral dimension of defect-free crystalline lamellae can reduce gas permeability through polymer thin films. [11] Despite its significance, ways to drive polymer thin film crystallization into a desired morphology has not been fully understood or mastered, especially since the process is known to deviate from bulk crystallization.…”