Electrical conduction and degradation mechanisms in powder ZnS:Mn, Cu direct current electroluminescent devices

The electrical properties and degradation mechanisms in direct current electroluminescent (dc EL) ZnS: Mn,Cu powder devices have been investigated. The electrical characteristics of degraded devices were found to be substantially different from freshly prepared devices. The degradation mechanisms were explored by scanning electron microscopy (SEM) and it was found that the layer close to the positive electrode had undergone modifications due to Cu ion migration. The equivalent circuit is also analyzed and the effect of degradation on the values of its parameters is examined. Finally, a method to improve the maintenance characteristics is described.