Influence of donor and acceptor domain sizes and their mesoscopic ordering on exciton dynamics are investigated as a function of energetic disorder in three-dimensional blend morphologies of bulk heterojunction solar cells (BHJ-SCs). Several BHJ-SC geometries, including bilayer, evenly distributed, graded, and ordered morphologies, are used in this investigation to estimate the exciton’s fundamental properties, such as dissociation probability, average number of hops, mean displacement, average dissociation time, and diffusion coefficient as a function of energetic disorder. This study uses an exponential distribution of exciton lifetimes to simulate realistic photocarrier dynamics. Simulation results suggest that the exciton dissociation efficiency estimated using the exponential lifetime model is over 13.5% smaller than that estimated using the constant exciton lifetime model, especially in blends with low energetic disorder. Monte Carlo (MC) simulation results of exciton diffusion coefficients agree reasonably well with the reported experimental values. It is observed that higher energetic disorder increases exciton recombination in larger phase-separated domains. On the basis of the simulation results, exciton dynamics can be classfied into low and high energetic disorder regimes. These exciton dynamics simulation results provide guidance to engineer blend morphology to enhance exciton dissociation efficiency.