of the current where carriers move with the constant average velocity to the opposite electrode, and then a sharp drop of the current when carriers begin to arrive at the collecting electrode (see Fig. \[fig-transient\]). There is a standard parameter $$\label{W}
    W=\frac{t_{1/2}-t_0}{t_{1/2}},$$ which is typically used to describe the spreading of the carrier packet, here $t_{1/2}$ is a time for the transient to decay to the half of the plateau value $I_p$ and $t_0$ is the time of crossing the asymptotes drawn to the plateau and the decaying tail of the transient [@Bassler:15; @Borsenberger:9; @Borsenberger:4289; @Borsenberger:967]. For the normal diffusive transport $W\propto \frac{\Delta x}{vt}\propto t^{-1/2}\propto L^{-1/2}$, here $L$ is the thickness of the transport layer. Hence, the investigation of the thickness dependence of $W$ gives a direct possibility to discriminate between the normal diffusive and anomalous nondispersive transport: if $W(L)\propto L^{-1/2}$, then we have a diffusive behavior, and if $W(L)$ decays more slowly, then the diffusivity does not exist and we have the case of the anomalous diffusion.

![Typical photocurrent transient for the nondispersive transport regime (solid line). Broken lines show how to calculate drift times $t_0$ and $t_{1/2}$.[]{data-label="fig-transient"}](figure7.eps){width="3in"}

Amorphous organic materials having localized states where there is an experimental 