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OLED(Organic Light Emitting Diode) A display technology that offers bright, colorful images with a wide viewing angle, low power, high contrast ratio and fast response time for sports and action movies. OLEDs are called "organic" because the emitting layers are based on carbon rather than silicon or gallium (see OLED Cross Section diagram below).
Although OLED is a different technology, it shares similarities with LCD (LED) TVs and earlier plasma sets. Like LCD screens, white OLED (WOLED) passes light through color filters. However, RGB OLED resembles plasma screens because the red, green and blue colors are intrinsically generated. Because OLEDs do not require backlights, the screens are ultra thin. OLEDs are also used for lighting (see OLED lighting and WOLED).
OLEDs can be transparent, enabling them to function in heads-up displays and as window shades that react to sunlight. OLED's color, speed, thinness, transparency and flexibility make it the display technology of the 21st century.
Passive and Active OLEDs
Passive matrix OLEDs appeared in cellphones and MP3 players in the 1990s, and active matrix OLEDs followed in 2003. Four years later, Sony introduced the first active matrix OLED TV (see image below). However, significant progress was made in the next five years, and LG and Samsung debuted 55" OLED TVs in 2012. See PHOLED, AMOLED, TOLED, OLED lighting and LED.
|First OLED TV - Only 11 Inches|
|In 2007, Sony's XEL-1 captivated audiences with intense colors, but few were sold due to its small 11" screen and whopping USD $2499 price. To enhance the thinness of the screen, it was separated from the tuner circuits. (Image courtesy of Sony Corporation.)|
|From 11 to 77 Inches|
|A huge difference in seven years. At CES 2014, several large-screen OLED HDTVs were unveiled, such as this curved 77" 4K TV from LG. See 4K TV.|
OLEDs Are Monolithic Devices
OLED screens consist of a series of carbon-based "organic" layers between electrical contacts (electrodes). Like LEDs, when electrons and holes combine in the organic layer, they emit photons. Unlike LCDs, which have separate layers, each OLED layer is deposited on the other, creating a monolithic unit. Commonly constructed on glass, OLEDs can also be fabricated on plastic and flexible films, such as the Flexible OLED (FOLED) from Universal Display Corporation.
|OLED Cross Section (Not to Scale)|
|The cathode layer can be reflective (OLED) or transparent (TOLED). OLEDs are made using small-molecule organic LEDs (SM-OLEDs) or less-expensive, lower-voltage and longer-lasting large-molecule polymer LEDs (PLEDs). For more details, see PHOLED. (Illustration courtesy of Universal Display Corporation, www.universaldisplay.com)|
|A Smartphone in Your Pen?|
|Flexible OLED screens like this are expected within a few years. (Image courtesy of Universal Display Corporation, www.universaldisplay.com)|