Non-exponential electroluminescence decay of ZnS: Mn films prepared by electron beam evaporation

Abstract

Non-exponentialities of the decay curve of a.c. thin-film electroluminescence devices are explained by applying the Yokota Tanimoto (Y-T) equation. In applying the equation it is assumed that the distributions of donors and acceptors are non-uniform; the concentrations increase from the bottom to the top of an active layer. Electron-spin resonance (ESR) measurements of the active layers indicate that the concentrations of isolated Mn²⁺ ions, Mn²⁺ pairs and Mn²⁺ triples in the layer agree approximately with those of donors and acceptors used in the Y-T equation to obtain a good fit to the measured decay curves, where the Mn²⁺ triples are assumed to work as the acceptors (i.e. quenchers), and the isolated Mn²⁺ ions and the Mn²⁺ pairs as the donors (i.e. luminescent centres).