Charge carrier drift velocity is typically described in terms of charge carrier mobility μ, which is carrier velocity per unit electric field. In the disorder formalism, mobility is given by:P. M. Borsenberger and D. S. Weiss, "Organic photoreceptors for xerography" (Marcel Dekker: New York, 1998)

where C is a constant, kB is the Boltzmann constant, E is the electric field, T is the temperature, σ is the parameter that characterizes DOS distribution (and diagonal, or energetic, disorder), and Σ is a parameter that characterizes off-diagonal, or positional, disorder.

Use the slider on the right to see how the dynamics of formation of the space-charge field changes with values of μ (charge carrier mobility) from 10-8 cm2/(Vs) to 10-6 cm2/(Vs) (typical for photorefractive polymer composites). As the mobility μ increases, the space-charge field Esc forms faster.O. Ostroverkhova and K. D. Singer, J. Appl. Phys. 92, 1727 (2002) The reason Esc2, and not Esc, is plotted as a function of time on the figure is because diffraction efficiency measured in Four-Wave-Mixing experiments at low applied electric fields E0 is proportional to Esc2 and therefore, dynamics of Esc2 can be directly related to that of experimentally measured diffraction efficiency.

« Back Next »