EL Technology Overview White Paper

This paper will review the electrical and optical properties of both monochrome and color electroluminescent (EL) displays. A simple electrical model for thin film electroluminescent (TFEL) device operation will be presented and used to describe the luminance and power consumption of TFEL devices. The basic material characteristics desirable for EL phosphors will be described. Progress in the development of monochrome and color EL displays will be presented including TFEL and Active Matrix EL devices and phosphors.

The phenomenon of electroluminescence (EL) is the non-thermal conversion of electrical energy into luminous energy. There are two classes of EL devices. In the familiar light emitting diode (LED) devices, light is generated by electron-hole pair recombination near a pn junction. Commercial LEDs have been fabricated from inorganic materials like GaAs, but recently there has been significant progress with the development of organic LED devices (OLEDs). This paper, however, will focus on the other class of EL devices in which the light is generated by impact excitation of a light emitting center (called the activator) by high energy electrons in materials like ZnS:Mn. The electrons gain their high energy from an electric field, and thus, this type of EL is often called high field electroluminescence. This review will focus on high field thin film electroluminescent (TFEL) devices. In these devices it is the behavior of the majority carriers (the electrons) that predominately determine the device physics.