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Drift-Diffusion Modeling of the Effects of Structural Disorder and Carrier Mobility on the Performance of Organic Photovoltaic Devices

Benjamin Y. Finck* and Benjamin J. Schwartz†

  • Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, USA

  • *bfinck@chem.ucla.edu
  • †schwartz@chem.ucla.edu
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Phys. Rev. Applied 4, 034006 – Published 21 September, 2015

DOI: https://doi.org/10.1103/PhysRevApplied.4.034006

Abstract

We probe the effects of structural disorder on the performance of organic photovoltaic (OPV) devices via drift-diffusion modeling. We utilize ensembles of spatially disordered one-dimensional mobility profiles to approximate the three-dimensional structural disorder present in actual devices. Each replica in our ensemble approximates one high-conductivity pathway through the three-dimensional network(s) present in a polymer-based bulk heterojunction solar cell, so that the ensemble-averaged behavior provides a good approximation to a full three-dimensional structurally disordered device. Our calculations show that the short-circuit current, fill factor, and power conversion efficiency of simulated devices are all negatively impacted by the inclusion of structural disorder, but that the open-circuit voltage is nearly impervious to structural defects. This is in contrast to energetic disorder, where previous studies found that spatial variation in the energy in OPV active layers causes a decrease in the open-circuit voltage. We also show that structural disorder causes the greatest detriment to device performance for feature sizes between 2 and 10 nm. Since this is on the same length scale as the fullerene crystallites in experimental devices, it suggests both that controlling structural disorder is critical to the performance of OPV devices and that the effects of structural disorder should be included in future drift-diffusion modeling studies of organic solar cells.

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Phys. Rev. Applied 4, 034006– Published 21 September, 2015
  • Received 22 April 2015
Article part of CHORUS

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