White-Light-Emitting Materials for Organic Electroluminescent Devices

White emission is important for applying organic EL devices to full-color flat panel display and backlight for liquid crystal display. In order to obtain white emission, the use of a light-emitting material which shows the white emission by itself is advantageous for these applications because of its high reliability and productivity. A chelate-metal complex such as zinc bis(2-(2-hydroxyphenyl) benzothiazolate) ($Zn(BTZ)_{2}$ was known to emit white light with a broad electroluminescence. In this study, the electroluminescent characteristics of $Be(BTZ)_{2}$ and $Mg(BTZ)_{2}$, as well as $Zn(BTS)_2$ were investigated using organic electroluminescent devices with the structure of ITO/TPD/ $Be(BTZ)_{2}$, $Mg(BTZ)_{2}$, or $Zn(BTZ)_{2}/Al$. It was found that the device containing $Be(BTZ)_{2}$ showed the highest power efficiency.