Improved phase separation in polymer solar cells by solvent blending |
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| Authors: | Christian Kästner Burhan Muhsin Andreas Wild Daniel A M Egbe Silke Rathgeber Harald Hoppe |
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| Institution: | 1. Institute of Physics, Ilmenau University of Technology, , Ilmenau, 98693 Germany;2. Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University of Jena, , Jena, 07743 Germany;3. Linz Institute for Organic Solar Cells, Johannes Kepler University Linz, , Linz, 4040 Austria;4. Institute for Natural Sciences, Physics Department, University Koblenz‐Landau, , Koblenz, 56070 Germany |
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| Abstract: | The effect of solvent blending on the performance of an anthracene‐containing poly(p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene) backbone‐based donor polymer with asymmetrically substituted branched 2‐ethylhexyloxy and methyloxy side‐chains in bulk heterojunction solar cells is reported. This copolymer yields relatively high open‐circuit voltages with fullerene‐based electron acceptors. We systematically studied the thin‐film blend morphology and solar cell performance as a function of solvent composition (chlorobenzene to chloroform ratio) and polymer to 6,6]‐phenyl C61‐butyric acid methylester (PCBM) ratio. We combined photophysical investigations with atomic force microscopy and grazing incidence wide‐angle X‐ray scattering to elucidate the solid‐state morphology in thin films. In the investigated polymer system, the blend morphology becomes independent of the supporting solvent for high PCBM concentrations. Deposition from solvent blends rather than from pure chlorobenzene facilitates the beneficial phase separation between polymer and PCBM, leading to improved charge transport properties (short‐circuit currents) at lower PCBM concentrations. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 868–874 |
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| Keywords: | atomic force microscopy (AFM) blending GiWAXS photophysics thin films |
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