Efficient Generation of Model Bulk Heterojunction Morphologies for   Organic Photovoltaic Device Modeling
  Kinetic Monte Carlo (KMC) simulations have been previously used to model and understand a wide range of behaviors in bulk heterojunction (BHJ) organic photovoltaic devices, from fundamental mechanisms to full device performance. One particularly unique and valuable aspect of this type of modeling technique is the ability to explicitly implement models for the bicontinuous nanostructured morphology present in these devices. For this purpose, an Ising-based method for creating model BHJ morphologies has become prevalent. However, this technique can be computationally expensive, and a detailed characterization of this method has not yet been published. Here, we perform a thorough characterization of this method and describe how to efficiently generate controlled model BHJ morphologies. We show how the interaction energy affects the tortuosity of the interconnected domains and the resulting charge transport behavior in KMC simulations. We also demonstrate how to dramatically reduce calculation time by several orders of magnitude without detrimentally affecting the resulting morphologies. In the end, we propose standard conditions for generating model morphologies and introduce a new open-source software tool. These developments to the Ising method provide a strong foundation for future simulation and modeling of BHJ organic photovoltaic devices that will lead to a more detailed understanding of the important link between morphological features and device performance. 
Michael C. Heiber and Ali Dhinojwala
cond-mat.mtrl-sci