Understanding Packing of New Compounds for Inexpensive Solar Panels

We perform molecular dynamics simulations to investigate the structure of two kinds of molecules that could be used in high-efficiency organic solar cells. We consider a branched molecule (ITIC) and polymer (PTB7) and measure their spatial correlations and dynamics as a function of temperature and density. Using radial distribution functions to measure local correlations we identify a density threshold above which both types of molecules become too entangled to rearrange. We find increased spatial correlations at lower temperatures when densities are below the entanglement threshold and fundamentally different molecular packings of the branched ITIC molecules versus the more linear PTB7 molecules that can more easily align. Our findings provide insight into the molecular packings that could correlate with better charge transport in organic solar cells and inform strategies for more efficient and informative future simulations.