Charge separation and geminate recombination in sensitized photoconducting polymers

Dynamics of charge pair photogeneration and recombination in sensitized photoconducting polymers was analysed by means of Monte Carlo simulations of the charge migration in the cubic lattice framework by taking into account the diagonal and off-diagonal disorder. On the basis of the experimental data, which indicate that the mean time of initial charge separation is on the subpicosecond time scale while the random hopping of charges in the geminate recombination process is of a few orders of magnitude slower, the mechanism, by suggesting correlated oscillations of the environment polarisation as a positive feedback in the unrelaxed charge transfer state, is suggested. By assuming wide initial hole distribution over the separation distance it has been demonstrated that faster recombination in the films with higher concentration of the sensitizer can be related to the dynamic scattering of the unrelaxed charge carrier by the sensitizer molecules in the course of the initial separation process.