Role of Side‐Chain Branching on Thin‐Film Structure and Electronic Properties of Polythiophenes |
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Authors: | Scott Himmelberger Duc T. Duong John E. Northrup Felix P. V. Koch Bryan S. Beckingham Natalie Stingelin Stefan C. B. Mannsfeld Alberto Salleo |
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Affiliation: | 1. Materials Science and Engineering, Stanford University, Stanford, CA, USA;2. Palo Alto Research Center, Palo Alto, CA, USA;3. Department of Materials, Eidgen?ssische Technische Hochschule (ETH), Zürich, Zurich, Switzerland;4. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA;5. Centre for Plastic Electronics, Imperial College London, London, UK;6. Center for Advancing Electronics Dresden, Dresden University of Technology, Dresden, Germany |
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Abstract: | Side‐chain engineering is increasingly being utilized as a technique to impact the structural order and enhance the electronic properties of semiconducting polymers. However, the correlations drawn between structural changes and the resulting charge transport properties are typically indirect and qualitative in nature. In the present work, a combination of grazing incidence X‐ray diffraction and crystallographic refinement calculations is used to determine the precise molecular packing structure of two thiophene‐based semiconducting polymers to study the impact of side‐chain modifications. The optimized structures provide high‐quality fits to the experimental data and demonstrate that in addition to a large difference in interchain spacing between the two materials, there exists a significant disparity in backbone orientation as well. The calculated structures are utilized in density functional theory calculations to determine the band structure of the two materials and are shown to exhibit a dramatic disparity in interchain dispersion which accounts for the large observed difference in charge carrier mobility. The techniques presented here are meant to be general and are therefore applicable to many other highly diffracting semicrystalline polymers. |
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Keywords: | organic semiconductors polymers structures thin films X‐ray diffraction |
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