Haftstellenfüllung bei Feldanregung elektrolumineszenter Zinksulfidphosphore

Abstract

Traps of electroluminescent ZnS-phosphors can be filled by field excitation at low temperatures as is indicated by thermoluminescence. Shape and light sum of the resulting glow curves are similar to those produced after very feeble UV-excitation. Regarding the same luminance of the phosphor the efficiency of the trap filling by field excitation was found to be only a small fraction of that by UV-excitation. The time dependence of field induced trap filling can be expressed by an exponential law. The voltage as well as the frequency dependence of the trap filling differs from that of the luminescence intensity. The results can be explained by the fact that electroluminescence excitation only occurs in small parts of the crystallites. It is supposed that the saturation of trap filling in these areas is achieved within a short time whereas trap filling in the bulk is performed by a slow diffusion process.