The morphology of active layers in the bulk heterojunction (BHJ) solar cells is critical to the performance of organic photovoltaics (OPV). Currently, there is limited information for the morphology from transmission electron microscopy (TEM) techniques. Meanwhile, there are limited approaches to predict the morphology /efficiency of OPV. Here we use Dissipative Particle Dynamics (DPD) to determine 3D morphology of BHJ solar cells and show DPD to be an efficient approach to predict the 3D morphology. Based on the 3D morphology, we estimate the performance indicator of BHJ solar cells by using graph theory. Specifically, we study poly (3-hexylthiophene)/[6, 6]-phenyl-C61butyric acid methyl ester (P3HT/PCBM) BHJ solar cells. We find that, when the volume fraction of PCBM is in the region 0.4 ∼ 0.5, P3HT/PCBM will show bi-continuous morphology and optimum performance, consistent with experimental results. Further, the optimum temperature (413 K) for the morphology and performance of P3HT/PCBM is in accord with annealing results. We find that solvent additive plays a critical role in the desolvation process of P3HT/PCBM BHJ solar cell. Our approach provides a direct method to predict dynamic 3D morphology and performance indicator for BHJ solar cells.

We combine atomistic simulation with mesoscale simulation to predict the morphology of bulk heterojunction (BHJ) solar cells. We show that good morphology is formed for weight fraction of PCBM in the region of 0.41–0.62 for poly(3-hexylthiophene)/[6,6]-phenyl-C61 butyric acid methyl ester BHJ solar cells, which agrees with experimental results. Our simulation results indicate that the enhanced phase separation is achieved by increasing the temperature, which is consistent with transmission electron microscopy results. We find that Flory-Huggins parameter (χ) > 1 is required for phase separation and good morphology. Our simulation method is useful for predicting the morphology of BHJ polymer solar cells.