The trapping rate γT depends on the charge carrier mobility μ and the carrier capture cross-section and is electric field dependent (due to electric field-dependent mobility). Although charge trapping in photorefractive materials is very important, the exact mechanism of trapping process is not well understood. For example, the dependence of the trapping rate on the trap depth is not known at present.

In most organic materials, the approximation of a single trap level is an oversimplification, and at least two kinds of traps (let us call them "shallow" and "deep", with the latter characterized with a lower detrapping rate) are needed to describe space-charge field dynamics.O. Ostroverkhova and K. D. Singer, J.Appl. Phys. 92, 1727 (2002) Use the slider on the right to see how the dynamics of the space charge field formation change if the number of shallow traps is fixed at 1017 cm-3, and the number of deep traps is varied.

When developing materials for applications, the trap depth, which determines the detrapping rate &beta, is one of the factors that determines whether the material is suitable for a particular application, as discussed here.

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