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Toward a better understanding of conjugated polymer blends with non-spherical small molecules: coupling of molecular structure to polymer chain microstructure

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Abstract

A major obstacle in the organic solar cell field is the inability to predict the relevant microstructural length scales that determine charge transport of the interpenetrating polymer/small molecule network based on the component chemical structures. This has led to a trial-and-error approach, which is extremely labor-intensive. This manuscript is our attempt to move toward forming a link between small molecule chemical structure and the morphological hierarchy of the blend. We focus on geometric motifs of small molecule organic semiconductors which have 2D, nonspherical 3D, and quasispherical 3D molecular orbital extent. We find that phase separation in these blends is a function of the molecular structure, and that the small molecule chemical structure is coupled to the crystallite orientation distribution of the polymer matrix. We further find that the ability of a molecule to form a network with a well-defined length scale of phase separation depends on the polymer persistence length.

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ACKNOWLEDGMENTS

GIXD measurements were performed at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by the U.S. Department of Energy, Office of Basic Energy Sciences; the authors would like to acknowledge Tim Dunn for his beamline support. We thank Stefan Mannsfeld (Dresden University of Technology, Germany) for providing software used to process GIXD images. GISAXS and REXS data were acquired at the Advanced Light Source at the Lawrence Berkeley National Laboratory also operated by the U.S. Department of Energy, Basic Sciences Division; the authors acknowledge Dr. Cheng Wang and Dr. Mike Brady for their beamline training and support. GISAXS data were calibrated and reduced using a MATLAB program written by Victoria Savikhin (Stanford University). Solvent-excluded volume and surface area calculations were performed by Cameron Pye (University of California, Santa Cruz) using Biovia’s Discovery Studio.

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  1. Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA, 95064, USA

    Michael Roders, Vincent V. Duong & Alexander L. Ayzner

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  1. Michael Roders
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Roders, M., Duong, V.V. & Ayzner, A.L. Toward a better understanding of conjugated polymer blends with non-spherical small molecules: coupling of molecular structure to polymer chain microstructure. Journal of Materials Research 32, 1935–1945 (2017). https://doi.org/10.1557/jmr.2016.490

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