Photoluminescence in a disordered insulator: The trapped-exciton model

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Abstract
A simple phenomenological model of the electronic structure of the pseudogap of an amorphous semiconductor is considered, and used as the starting point for a systematic investigation of the processes that determine the nature of the photoluminescence. Many of the most striking features of these materials are shown to derive in a straightforward manner from the nature of the primary luminescing entity, a "trapped exciton" in which the hole is trapped in a localized gap state and the electron is bound to the hole by their mutual Coulomb attraction. Other important properties of the photoluminescence reflect the dynamics of the hopping motion of a charged carrier through a band of localized states.