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A display is an electronic component or subsystem used to convert electrical signals into visual imagery in real time suitable for direct interpretation by a human observer. Until recently, the cathode ray tube (CRT) has been the main source of displays. During the last twenty years, it has been determined that alternatives to CRT displays need to found. One of the alternatives was the introduction of flat-panel displays. The term 'flat-panel display' is more of a concept than a specific entity. It is a display which is flat and light and may not require a great deal of power. A flat-panel display is often defined in terms of the ideal display, that being: thin form, low volume, even surface, having high resolution, high contrast, sunlight readable, color, low power, and being solid-state, light weight, and low cost. This is easy to conceive but difficult to deliver. The objective is to develop displays with as many desirable characteristics as possible. Flat-panel displays are basically of two types: the light valve type (that needs an external source of light such as a backlight or arc-lamp) and the emissive type (that generate light at the display surface). The light emitting diode (LED) display is of the emissive type. Inorganic LED and electroluminescent (EL) displays have been in use for more than 25 years in one form or the other because of their 'inherent' ruggedness and operation over extremely wide temperature ranges. Because of certain limitations of inorganic materials (such as cost, power, and color), LED displays do not dominate the high information content flat- panel display market. A recent discovery of polymer and other organic materials has changed LED prospects. It may now be possible to make organic LED displays that are inexpensive, low-power, and at the same time provide high resolution and full color. If present research objectives are met, organic LEDs may revolutionize the flat-panel display market. This paper addresses the various aspects of organic LED technology with particular reference to its useful characteristics, and the technology challenges. The pace of research accomplishments indicate that it will be some years yet before OLEDs succeed in the market place as product components.
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