Theoretical analysis of the drift and diffusion of charge carriers in thin layers of organic crystals

The influence of diffusion on the current shape in the time-of-flight (TOF) experiment under conditions of the quasiequilibrium transport has been considered. An analytical expression for the transient current density has been obtained for the case of the reflecting front electrode. The expression has been found to be in a better agreement with the Monte-Carlo numerical modeling than the usual expression based on the standard convection-diffusion equation. We found an estimate of the minimum layer thickness for a flat plateau appearance on TOF current transients.