ZnS蒸着膜の光電特性(II)D. C. E. L

抄録

In this paper the results of investigation of the radiation waveforms and the temperature dependence of light intensity with direct current bias of thin evaporated films of ZnS; Cu, Mn, Cl phosphors are reported. Equations relating the brightness (B) with voltage, current and power of direct current electroluminescence (D. C. E. L) are obtained. The brightness was strongly dependent on the total current through the sandwich type cell and showed a linear relationship to power, and hence we may conclude that the efficiency of the E. L. cell remains constant. Equations for brightness may be expressed as follows: B=A₁ exp (-c₁/√V) at room temperature, B=A₂T₂ exp (-c₂/T) above 250°K. Here V is the applied voltage, T is the absolute temperature of the cell, and A₁, A₂, C₁, C₂ are constants. It is seen that (B) is practically independent of T at low temperatures. From these results, it is considered that the excitation mechanism of D. C. E. L can be explained by the tunneling effect of electrons at low temperatures, whereas at high temperatures the effect of Schottky emission must be considered. It was also found that the direct excitation of Mn center due to the electrons injected into phosphor film from the negative electrode are responsible for the E. L. effect of the film.