Determination of localized state distributions from anomalously-dispersive transport data

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Abstract
A general relation is deduced between the density of localized states N(E) and the transient photocurrent I(t) for an amorphous semiconductor exhibiting trapcontrolled electronic transport. It is demonstrated that the waiting-time distribution functionψ(t) is related to I(t) through a Volterra integral equation, which may be solved numerically. The relative density of states N(E) may be deduced in a straightforward manner from ψ(t), using an approximation which should not introduce more than a small degree of distortion. The computational method is applied to the case of an exponential tail of localized states, and to a system with three discrete sets of trapping centres. Finally, the consequences of an incomplete knowledge of some of the system parameters are considered.