Abstract
Over the past few decades, many efforts have been put to optimize the properties of electroluminescent devices such as electroluminescence (EL) panel, organic light emitting diode (OLED), flat panel display, EL lamps, etc. In this chapter, the authors provide a comprehensive review of the state-of-the-art research activities related to EL phenomena, the principle of electroluminescence, different types of EL, fabrication of devices, studies on novel electroluminescent materials, their characteristics and potential applications. The authors begin with a historical background of electroluminescence, description of its structure, working principle and parameters with mechanism. They discuss the experiments determining the electrical, optical, and physical properties of the powder as well as thin film EL cells. The recent progress on the improvement of their characteristics and finding novel structures, such as the latest achievements in using various semiconductor nanostructures in polymer matrix as emitting layer in EL devices, are summarized.
TopElectroluminescence Devices
The electroluminescence (EL) devices include light emitting diodes, which are discrete devices that produce light when a current is passed through a p-n junction of a semiconductor, as well as EL displays (ELDs) which are matrix-addressed devices that can be used to display text, graphics, and other computer images. EL is also used in lamps and backlights. EL lamps are low power and emit a soft light without any irritating glare (Figure 1). They are invariably thin, almost like ribbons or sheets of paper, and they can be produced in a variety of colors. EL provides a cool, continuous, even light that can be shaped into stripes, strips, and geometric figures (Figure 2). Strips can run for several meters, with only one connection to a power source. Shapes can be illuminated with different colors and with flashing, animated effects. The EL panels are lamps, which radiate gently, without glare, and can be used for lighting purpose.
Figure 1. An electroluminescent nightlight in operation (uses 0.08 W at 230 V, and dates from 1960; lit diameter 59 mm)
Figure 2. Animated effects include flash or blinking where one or more lamps light up intermittently. When done in sequence, the human eye will detect movement in an image.