White-Emitting Thin-Film Electroluminescence Devices with SrS Phosphor Doubly Activated with Rare-Earth Ions

Abstract

Thin-film electroluminescence (TFEL) devices with SrS-based phosphor layers have been investigated to obtain white emissions by mixing emissions of two different rare-earth activators, and new white-emitting phosphor layers, except for SrS:Pr, Ce, have been developed. SrS:Sm, Ce and SrS:Nd, Ho phosphor layers show white El-emissions, whose color coordinates correspond to points in the white area on the CIE chromaticity diagram. The EL emissions of SrS:Pr, Ce, SrS:Nd, Ce, and SrS:Ho, Ce phosphor layers are not found in the white area, but are close to the area. Luminance of the emissions, for devices driven with a sinusoidal voltage of 5 kHz, are 200–750 cd/m², The three primary colors, red, green and blue, can be extracted from the emission of all these devices with color filters. Relative intensities of the three extracted colors are evaluated.