Following the crystal growth of anthradithiophenes through atomistic molecular dynamics simulations and graph characterization

While organic semiconductors (OSC) offer distinctive features for several electronic and optical technologies, questions remain as to how the chemistries of the molecular building blocks impact material nucleation and growth and the resulting solid-state packing arrangements that are critical to semiconductor performance. Here we demonstrate a combined molecular dynamics (MD) simulation and graph characterization approach to follow the crystallization of anthradithiophene (ADT), a rigid, π-conjugated molecule used in OSC. Notably, ADT presents particular challenges as molecular synthesis leads to two isomeric structures wherein the sulfur atoms are syn or anti with respect to each other. Using our combined approach, we demonstrate how these molecular-scale differences impact the nucleation and growth of crystallites, starting from the gas phase through a condensed liquid (melt) to the solid state. The resulting systems, which are comprised of several crystalline/aggregate regions, are then thermally annealed, with the resulting thermal properties showing good consistency with experiment. The computational framework discussed here provides opportunities for robust and fast examination of the dynamics of the nucleation and growth of crystalline OSC.