Comment Articles

Organic LEDs

Rupert Goodwins AnchorDesk

Published: 01 Dec 2000 16:33 GMT

In many ways, they're ideal for the job. They can be made just like any other electronic component, can last for up to a million hours, generate little heat in operation and are efficient enough to be used in battery-operated devices.

Now they have a challenger. Organic LEDs, or OLEDs, have been growing quietly in the lab for the past twenty years. Electronically, they're similar to old fashioned LEDs -- put a low voltage across them and they glow. But that's as far as the similarity goes: instead of being made out of semiconducting metals, OLEDs are made from polymers, plastics or other carbon-containing compounds. These can be made very cheaply and turned into devices without all the expensive palaver that goes with semiconductor fabrication -- some of the original publicity said that they could be mixed up in tins like so much paint and just glooped out to make a display. That now looks somewhat optimistic, as OLEDs have proved rather sensitive to contamination, surface smoothness and other minutiae of production, but nevertheless the compounds do lend themselves to being printed or deposited in fine detail over large areas. In other words, they look natural candidates for cheap flat screen displays.

The market leader in flat screens today is, of course, the LCD. Even this is vulnerable to OLEDs' finer points. OLEDs are bright and viewable over a wide angle and, unlike many LCDs in today's market, OLEDs are self-luminous so need no external lighting. This means a display made with the new technology can be much thinner than an LCD -- prototypes under two millimetres in thickness have been shown -- and don't have the environmental drawbacks of backlights, which usually contain mercury. OLEDs are also far more efficient, as when they're turned off they don't take any power. A backlight is always on at full brightness, no matter how much of the LCD display in front of it is actually letting light through.