Simulation of the polarization current of geminate pairs in an organic material with Gaussian disorder

The time-dependent photocurrent caused by the transient polarization of geminate pairs by an electric field after a short generation pulse is numerically simulated by the Monte Carlo method within Gaussian-disorder models. The photocurrent decreases almost steadily in the case of a rather wide spread of initial separations; however, due to the Coulomb interaction of “twins”, the photoconductivity approaches its limiting value (free charge current) much faster than the full separation of pairs. However, the transient polarization of geminate pairs by an electric field contributes to the photoconductivity for a rather long time to affect experimental results, i.e., the photocurrent-decay law. Incorrect conclusions about the nature of recombination in a given material can be obtained, if the geminate-pair polarization current is neglected.