Emission of dispersed-type inorganic EL devices with frequency-variable high-voltage oscillation circuit

摘要

Dispersed-type inorganic electroluminescent (EL) devices composed of a transparent electrode, a phosphor, a dielectric, and a back electrode were prepared under various conditions using a zinc sulfide (ZnS)-based phosphor. Additionally, a voltage/frequency variable circuit was designed. A compact high-voltage/frequency variable circuit including three modules for boosting, frequency conversion, and voltage conversion was designed. A 140 V-pp voltage and a frequency in the range of 270 Hz to 2.4 kHz can be controlled by this circuit. The emission has begun to be observed at a voltage about 60 V-pp and a frequency of 400 Hz, at a voltage about 40 V-pp and a frequency of 1.4 kHz, 2.4 kHz, respectively. The emission intensity increased with an increase in frequency; emission with a wavelength of 450 nm was strongly influenced by the frequency. The luminescence and the electrical properties were affected by the preparation conditions including device structures, dispersion of ZnS:Cu, and Cl particles because of the current path generated by defects in the EL cell.