White Light AC Electroluminescent Displays

Abstract

Alternating Current Electroluminescence (ACEL)was measured in orange and blue phosphors and a mixture of them in a ratio of 2: 1. The phosphor, dielectric and top silver electrodes were prepared by screen printing. Nowadays ACEL is presented on the market as the only technique for quick and easy preparation of large area, low cost electroluminescent panels by the means of material printing. From the optical microscope images, we could conclude that the radiation of blue phosphor dominates over the orange one. These results are confirmed in the absolute irradiance spectra. Moreover, using samples, based on phosphor stripes leads to a decrease of the total irradiance, but, on the other hand, the uniformity of the emitted EL light is improved. Printing of striped active layer is preferred from the point of view of achieving more uniformly distributed light. The summarized fitting parameters show that driving frequency around 300 Hz will produce white light with reasonable intensity and with values of x, y coordinates higher than 0.31. The somewhat lower intensity of the emitted light can be improved by setting higher driving AC voltage. The voltage tested in this work was set to be constant at 250 Vpp.