Monte Carlo simulation of the time dependence of geminate recombination

The time dependence of recombining geminate pairs in a hopping system has been simulated as a function of the initial pair separation r0, the anisotropy of the diffusion constant, the dimensionality, the concentration of hopping sites and the final-step recombination velocity. It is found that the decay of the recombination rate R follows a power law, R ∼ t-x, with x ≥ 3/2. Both the exponent x and the initial onset of the recombination rate depend on r0 and the dimensionality. In the time domain of experimental relevance, significant deviations from the asymptotic form of the analytic solution of Hong and Noolandi are found. The introduction of anisotropy in the carrier mobility yields a multiplicity of decay rates. On the other hand, if the final recombination step is hindered by an energy barrier, the recombination kinetics ultimately become exponential.