Abstract
In order to develop a high quality EL display, highly efficient phosphors, optical design for thin-film multi-layers and improvenent of driving technique are required. In this paper, we proposed a capacitance coupled photo-conductive layer combined with an conventional EL device, and improved characteristics of hysterisis effects will be discussed by employing an SPICE simulation technique. In results, (a)the range of dark resistance adopted to the photo-conductive layer becomes wide by optimizing the coupling capacitance, (b)writing voltage is drastically reduced, and (c)simple and strict adjustment of writing and erasing voltage are possible. These effects will be attributed to the reduction of impedance mismatching between EL layer and photo-conductive layer. In addition, we found a kind of semi-stable operational mode existed around the normal mode, in which the several times of light-emissions are continuously repeated even after a pair of writing voltage pulse was removed. Detail analysis showed that the luminance increases monotonically with increasing the writing voltage, which may be a new memory effect and expected for the application to analog gray scale capability.
