Effects of Thermal Annealing Upon the Morphology of Polymer-Fullerene Blends
Bettinger, Christopher J.
Toney, Michael F.
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AbstractGrazing incidence X-ray scattering (GIXS) is used to characterize the morphology of poly(3-hexylthiophene) (P3HT)-phenyl-C61-butyric acid methyl ester (PCBM) thin film bulk heterojunction (BHJ) blends as a function of thermal annealing temperature, from room temperature to 220 °C. A custom-built heating chamber for in situ GIXS studies allows for the morphological characterization of thin films at elevated temperatures. Films annealed with a thermal gradient allow for the rapid investigation of the morphology over a range of temperatures that corroborate the results of the in situ experiments. Using these techniques the following are observed: the melting points of each component; an increase in the P3HT coherence length with annealing below the P3HT melting temperature; the formation of well-oriented P3HT crystallites with the (100) plane parallel to the substrate, when cooled from the melt; and the cold crystallization of PCBM associated with the PCBM glass transition temperature. The incorporation of these materials into BHJ blends affects the nature of these transitions as a function of blend ratio. These results provide a deeper understanding of the physics of how thermal annealing affects the morphology of polymer-fullerene BHJ blends and provides tools to manipulate the blend morphology in order to develop high-performance organic solar cell devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
CitationVerploegen E, Mondal R, Bettinger CJ, Sok S, Toney MF, et al. (2010) Effects of Thermal Annealing Upon the Morphology of Polymer-Fullerene Blends. Advanced Functional Materials 20: 3519–3529. Available: http://dx.doi.org/10.1002/adfm.201000975.
SponsorsThis publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics, Award No KUS-C1-015-21, made by King Abdullah University of Science and Technology (KAUST). We also acknowledge support from the Global Climate and Energy Program (GCEP) and the Stanford Center for Polymer Interfaces and Macromolecular Assemblies (CPIMA). EV would like to thank the Eastman Kodak Corporation and the Kodak Fellows Program for support. CJB was funded by a Ruth L. Kirschstein NIH fellowship (Grant # 1F32NS064771-01). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The authors would like to thank Stefan Mansfeld for providing the WxDiff software package for GIXS data analysis.
JournalAdvanced Functional Materials