Interpretation of photocurrent transients in amorphous semiconductors

This paper reviews recent work in the development and improvement of techniques to determine the energy distribution of localised states (DOS) in semiconductors from their transient photocurrent (TPC) response, in a multi-trapping context. We first outline the development of general transform-based techniques, which may be applied to cases in which carriers are replenished from device contacts, where both trapping and release processes are significant. We then outline the development of a `post-transit' analysis restricted to situations in which carriers are extracted at contacts, where only carrier release processes are significant. In both cases we demonstrate that by eliminating approximations previously employed to aid computational stability we can achieve analytical DOS spectroscopies capable of much finer energy resolution, without significant loss of stability. The techniques described are applied to experimental photocurrent decay data on a-Si:H. A200; D140; P180; T28