Study of highly concentrated ZnS:Mn ACTFEL devices

The electroluminescence (EL) of ZnS:Mn (ACTFEL) ac driven thin film electroluminescence devices shows that for Mn concentrations beyond 1 mol%, the characteristic yellow emission of the Mn2+ center gradually decreases, when red (R) and infrared (IR) emissions appear successively. Comparative studies of the temperature quenching of these emissions, and their excitation spectra in PL show energy transfer from excited Mn2+ to the centers associated with the R and IR bands. A discussion of the results leads to point out that the deexcitation process of Mn2+ centers can be related to a percolation problem. The nature of the R and IR centers is also discussed.