Organic Light Emitting Diode
Organic Light Emitting Diode is a scalable nano level emerging technology in Flat Panel Displays and as a White Light Source with efficient features. This paper focuses on OLED structure, principle aspects, fabrication methodology and different techniques to replace current white light sources like Incandescent bulbs, Fluorescent tubes, and even display techniques like Liquid Crystal Displays, Plasma technologies. OLEDs can be fabricated using Polymers or by small molecules. OLED matrix displays offer high contrast, wide viewing angle and a broad temperature range at low power consumption. These are Cheaper, Sharper, Thinner, and Flexible. An OLED is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes. Generally, at least one of these electrodes is transparent. There are two main families of OLED s: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a Light-emitting Electrochemical Cell or LEC, which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. Active-matrix OLED s (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes. An OLED display works without a backlight. Thus, it can display deep black levels and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions such as a dark room an OLED screen can achieve a higher contrast ratio than an LCD, whether the LCD uses cold cathode fluorescent lamps or the more recently developed LED backlight. Due to its low thermal conductivity, an OLED typically emits less light per area than an inorganic LED. OLEDs are used in television screens, computer monitors, small, portable system screens such as mobile phones and PDA s, watches, advertising, information, and indication.
OLEDs are also used in large-area light-emitting elements for general illumination. OLED s have a potential of being white-light sources that are •Bright, power-efficient and long lived, by emitting pleasing white light •Ultra-thin, lightweight, rugged, and conformable
OLEDs are energy conversion devices (electricity-to-light) based on Electroluminescence. Electro-luminescence is light emission from a solid through which an electric current is passed. OLEDs are more energy-efficient than incandescent lamps. The luminous efficiency of light bulbs is about 13 - 20 lm/W but the latest experimental green emitting OLEDs already have luminous efficiency of 76 lm/W, though at low luminance. The development is on track for OLEDs to effectively compete even with fluorescent lamps, which have the luminous efficiency of 50 - 100 lm/W. One big advantage of OLEDs is the ability to tune the light emission to any desired color, and any shade of color or intensity, including white. Achieving the high Color Rendition Index (CRI) near 100 (the ability to simulate the most pleasing white color, sunlight), is already within the reach of OLEDs. Another advantage of OLEDs is that they are current-driven devices; where brightness can be varied over a very wide dynamic range and they operate CRT is still continuing as top technology in displays to produce economically best displays. The first best look of it is its Cost. But the main problems with it are its bulkiness, Difficulties in Extending to Large area displays as per construction. Even though Liquid Crystal Displays have solved one of problem i.e. size, but it is not economical. So in this present scenario the need for a new technology with both these features combined leaded to invention of OLED.OLED which is a...
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