ON THE RELATION BETWEEN FROZEN POLARIZATION AND ELECTROLUMINESCENCE OF ZNS CELLS
NATIONAL ELECTROTECHNICAL INST TURIN (ITALY)
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The kinetics of the decay of the Frozen Polarization FP shown by an Electroluminescent Cell ELC after excitation which a suitable waveform of electrical potential has been studied as a function of temperature between 7 C and 42.5 C. The order of the kinetics was evaluated as well as the thermal activation energy, which turned out to be around 2.5 EV. This figure corresponds closely to the ionization energy of Cu impurities in ZnSCu phosphor. The kinetics of the decay of the amount of light which an ELC gives out under excitation by a single linear voltage transient retarded on variable amounts with respect to a previous excitation were investigated. The latter consisted of a train of linear transients long enough to saturate the cell. The phenomenon has been followed from -44.5 C to 47.5 C, and again an activation energy has been found of roughly 1.5 ev. The connection between these two experiments and its possible implications are briefly discussed to cast some light on the mechanism of barrier injection of carriers in EL phosphors.