where r is a uniform random number between 0 and 1. This process is simulated for 1.0 ns for each KMC simulation run. All simulations were performed at 300 K. Exciton diffusion coefficients were calculated by first performing 1000 independent KMC runs and computing mean square displacement of the exciton ⟨r 2 (t)⟩. Each KMC run for a given crystal were performed for fixed values of energetic disorder and reorganization energy (see Supplementary Information S1). The diffusion coefficients was then calculated as: