Organic LEDs open up vast range of new possibilities

This article was written by Graham Norris and published by the Taiwan Journal on September 30, 2005. According to this article, one of the new technologies that might soon replace the currently popular liquid-crystal display (LCD) televisions is the organic light-emitting diode (OLED). Today, mostly monochromatic OLED displays can already be found in small gadgets such as mobile phones, personal digital assistants, MP3 players and car stereos.

According to this article, traditional LEDs are point sources of light whose emissive semiconductors are encased in little bulbs of glass. These LEDs are mostly used for lighting in electronic devices and as a graphics tool in signage and bulky outdoor displays.

By contrast, OLEDs are distributed light sources that consist of extended polymeric membranes that glow. They can be engineered to take the place of LCDs.

For example, LCD panels generally require a color-filter layer, an LED backlighting module, and a liquid-crystal layer to block or admit light from the module. However, in OLEDs, all these functions are combined in the same layer of plastic, which glows locally with the desired color when electrically stimulated. The result is that OLEDs are more energy-efficient and a lot cheaper to make than LCDs.

Specifically, an OLED consists of a substrate, an anode, two or more layers of polymeric material, and a cathode. Electricity passes between the anode and cathode and causes the sandwiched organic layer to emit light. The substrate is currently made of relatively rigid glass, but further research is being conducted on other substrate materials that will make OLEDs more flexible and easier to produce. Researchers have also improved the OLED manufacturing process significantly since they found a way to apply the organic material to the substrate evenly.

As in the LCD flat-panel industry, East Asian manufacturers such as those in Japan, South Korea and Taiwan are shaping up as the most aggressive competitors in the battle for the fast-growing OLED market.