Exciton diffusion dynamics with dissipation in organic molecular semiconductors

Exciton diffusion governs energy transport in organic molecular crystals and limits the performance of optoelectronic devices. Accurate simulation requires capturing correlated electron-nuclear motion, yet existing approaches rely on empirical treatments. Here we derive a representation-free dissipation correction for exciton dynamics from the exact factorization formalism, in which a dimensionless factor ξ quantifies dissipation through the ratio of quantum and classical nuclear momentum. Within a classical path framework, ξ is obtained from site energy fluctuations in molecular dynamics non-empirically. The exciton Hamiltonian is constructed using a semiempirical approach to describe local excitations and excitonic couplings in large systems. Applications to anthracene, perylenetetracarboxylic diimide, and quinoid merocyanine reproduce distinct exciton transport regimes ranging from localized hopping to more delocalized transport, demonstrating that an account for dissipation is essential for realistic exciton dynamics.