Simple evaluation of dynamic disorder effects on exciton transport

Exciton transport in molecular materials is usually well described by Fermi's golden rule within the Condon approximation. However, when collective or molecular vibrations are thermally accessible, dynamic disorder effects have a sizable impact on the predicted exciton transfer rates and need to be considered for quantitative evaluation. In this work, we derive an analytic expression for the distribution of the electronic couplings that gives direct access to averaged quantities without the need to perform explicit calculations for a distribution of structural conformations. The distribution of exciton couplings and transfer rates obtained by this simple model in the study of singlet exciton transfer in the crystal naphthalene are in very good agreement with the data generated from molecular dynamics.