How OLED Works

The earliest solid-state light-producing device to hit the market was the Light-Emitting Diode, or LED. This semiconductor device was found to emit a bright light when current was passed through it. Being solid-state, it lacked a filament to burn-out and so it was seen to be a very reliable, long lasting light source. Soon all manner of displays appeared using this technology, most of which were alpha-numeric. They showed up on our wrist-watches, our radio dials, and even our automobile dashboards. In the middle 1970s, Sony started using LEDs in very large screen TV monitors for stadiums, auditoriums and concert halls, but they were never able to make an LED-based video display that was practical for home use because of the size and power requirements of the then current LED technology. It took a passive system, the LCD, to make the breakthrough to home and office electronics. LCD is a very low-power technology and the individual pixel size is a function of manufacturing processes so it lends itself to a myriad of tasks and screen resolutions. Unfortunately, LCD is non-emissive, that is to say that it doesn't produce any light in and of itself, but merely controls the amount of light that actually reaches our eyes from a supplied light source located behind the screen. The need for a flat, uniformly bright back-light over the entire screen area has made the low-power characteristics of the LCD somewhat moot. The backlight accounts for most of the power budget in these displays. That's why your digital camera batteries go flat so quickly when you use the LCD viewfinder.

What is needed is an emissive technology that has low power consumption and that can be made with manufacturing techniques akin to those producing LCD screens. In other words, instead of individual LED devices, this technology needs to be producible as a continuous film containing all three primary additive colors (Red, Green, Blue) in a matrix containing as many pixels as are needed for the application in question. OLED meets these requirements by placing a series of organic thin films between two transparent electrodes. An electric current causes these films to produce a bright light. By using semiconductor technology, each pixel can be addressed individually thus controlling the patterns of light and color which combine to form a picture

The organic process used in OLED is called electrophosphorescence and is a biological phenomenon that has been noted and wondered at for eons. Fireflies, plankton, and many sea creatures all possess this characteristic naturally. But it's only in the last few years that researchers have been able to synthesize it non-biologically.

Even though these OLED panels are made up of several layers of doped fluorocarbon polymers, the result is a system which is very thin, usually less than 0.5 thousandths of a millimeter thick. These OLEDs produce self-luminous displays that do not require backlighting and can operate at very low current with only 2-10 volts. These thin displays can be made flexible, and have a wide viewing angle of up to 170 degrees.

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