Organic electroluminescence (EL) is moving from a simple curiosity in laboratories to the reality of commercial use. The day will soon arrive when high-quality green EL displays find practical usage. Charge-injection-type EL involves the combination of positive and negative charge carriers injected from electrodes in contact with an organic thin film. The occurrence of EL through bipolar charge injection into organic solids was clarified for single crystals of anthracene and related compounds in the 1960s. Few new developments in physics exist today for organic EL. However worldwide enthusiasm for charge-injection-type EL, which started in the mid-1980s, has been increasing rapidly. The motivation for this renewed interest is straightforward. High-efficiency surface emission across the whole visible spectral range can be obtained easily, and prospects now exist for full-color flat-panel-display technology.Since the demonstration of high-performance EL devices made of multilayers of vacuum-sublimed dye films by Tang and VanSlyke, much progress has occurred in the research and development of EL devices made from molecular materials. A variety of molecular materials such as vacuum-sublimed dye films, fully π-conjugated polymers, polymers with chromophores orr skeletal chains, or side chains, and polymer-dispersed dye films can be used for EL devices.Among a variety of EL devices, multilayer-structure versions made of vacuum-sublimed dye films exhibit the best performance. Application-oriented research in the development of high-quality flat-panel displays has been performed during the past 10 years, mainly in Japan's private-sector laboratories.
