where V i j is the exciton coupling parameter between molecules i and j, ∆E i j = E j -E i is the change in energy associated with energy transfer from molecule i to molecule j, λ is the reorganisation energy, h is the reduced Planck's constant, k b is Boltzmann's constant, and T is the absolute temperature. In the third step, the exciton is transferred to one of its neighbors j with probability