Theory of Geminate Recombination as a Molecular Process

A molecular model of field-dependent photogeneration is presented. The model, diffusion on a lattice in a combined Coulomb and external dc field, is solved exactly. The solution for the quantum efficiency $\eta$ has a larger range of applicability than the continuum theory to which it can be compared in the infinite-sink case. It is shown that $\eta$ can vary greatly with small variation of key molecular parameters and that the high-field limit of $\eta$ is controlled by the same molecular properties which determine its field dependence.