OLEDs: Expert Guide

What’s an LED?
Light-emitting diodes (LEDs) are small devices capable of producing their own light when an electrical current passes through them. They are far more energy efficient and durable than lightbulbs, and don’t generate excess heat or require a filament to work. They also use less power than liquid crystal display (LCD) screens which need a constant backlight to shine through the pixels that make up the screen. You can find LEDs in everyday items such as torches, digital alarm clocks, watches and remote controls.
 
What does the ‘O’ in OLED stand for?
The ‘O’ in OLED stands for organic. An organic, carbon-based film is sandwiched within two conductors (an anode and a cathode), and is supported by a base material called a substrate. A light source is generated whenever an electrical current passes through. In a non-organic LED, the layer between the two conductors isn’t flexible, so the organic carbon-based film is the key for OLEDs – it enables them to be razor-thin, ultra-light, super-bright and flexible, which means that they can be used in a number of innovative devices from bendy screens to bright, crystal-clear TVs and even see-through displays.
 
How does an OLED TV create light and pictures?
"An OLED display produces its own light from the individual pixels or elements actually on the display,” explains Peter Hainsworth, technical marketing manager of Sony’s audio division. “It’ll only take whatever energy it requires to produce whatever light or colour it needs on that display. Therefore, a dark picture draws no power while a fully white picture draws maximum power. With an LCD, the backlight is on all the time.”

There are different types of OLEDs, each best suited to a specific application. Sony (www.sony.co.uk) tends to use the ‘top-emitting’ OLED to produce very bright displays – light bounces off a reflective substrate (the base material), generating very bright light. However, a ‘transparent’-type OLED lets light pass through the entire device so that see-through pictures can be displayed.
 
How are OLEDs similar to natural phenomena?
Creatures such as fireflies also generate their own light but they achieve this through a biochemical reaction (chemical oxidation), whereas OLEDs produce their own light after an electrical current is generated. “While they achieve the same results, they do so by different means. But the roots for OLED are firmly planted in the natural world,” said Hainsworth.
 
What else could OLEDs be used for?
The list is a long one. Prototypes of transparent OLEDs, which let you see through the screen like a window while images are being displayed on the surface, have already been produced by companies such as Samsung (www.samsung.co.uk). Potentially, these could be used as satellite navigation devices on car windscreens, enabling people to see the road in front of them as well as the route they’re following. Hainsworth also suggests using them in window displays, so you can display a moving advert while letting customers see the product being sold behind it.

Sony and Samsung have also demonstrated prototypes of bendy screens at various trade shows, such as the Consumer Electronics Show (CES) - you can find clips on YouTube (http://www.youtube.com/watch?v=NcAm3KihFho).

This ability to have a flexible screen should encourage creativity and innovation. Displays could, for example, be used in clothing, and a television screen could reach a new level of portability once it’s possible to roll it up, pop it in a handbag and take it on holiday with you! General Electric (GE) is already taking inspiration from newspaper production lines to produce ‘rolls’ of OLEDs (http://www.grcblog.com/?p=247). “Imagine wallpaper that lights up,” General Electric suggests on its Global Research website (www.ge.com/research).
 
What other advantages do OLEDs have?
OLEDs are capable of producing light that is far brighter than that of other displays. A typical flat-screen television may quote a contrast ratio of 50,000:1. This is a measurement of the dynamism between the darkest and the brightest part of a display. However, Sony’s 11-inch OLED TV, the Bravia XEL-1, quotes a contrast ratio of 1,000,000:1. “It’s just a figure, but when you see the screen and a photograph displayed on it, the realism is quite incredible,” claimed Hainsworth.

OLED screens are also incredibly light; Sony’s television weighs just 2kg. They also have a wider viewing angle than LCDs (about 170 degrees). This is a measurement of how far round you can sit to the side of a screen while still being able to view a clear image.
 
What are the drawbacks?
At the moment, OLEDs are very expensive to produce because the economies of scale aren’t there to support mass production. The good news is that prices will eventually decrease once quick and efficient ways of producing the displays are established – however, the speed with which this happens will depend on initial demand.
 
 
OLED DEVICES CURRENTLY ON THE MARKET
Because of the high production cost, the current OLED screens available on the market are quite small, but their tiny power consumption means they are handy for mobiles, digital cameras, MP3 players and other portable devices. In the UK, Sony’s Bravia XEL-1, costs a whopping £3,500. Sony’s forthcoming X-Series Walkmans are currently available to pre-order, costing around £214 on Amazon for the 16GB model – again, not cheap. LG plans to ramp up OLED TV production by 2011.