The future is bright for OLEDs

Currently, Liquid Crystal Display (LCD) is THE technology of choice for almost every one of the world's mobile handset manufacturers. And, as the technology has matured and chrominance and luminance has improved, LCD TVs are also very popular.
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However, as we all know and have experienced, LCD displays are still very hard to see in bright sunlight or other well-lit circumstances and the displays soon drain battery power. That's why several other types of display technologies are currently being developed and tested around the world. And, one day, one of them might be good enough and cheap enough to replace the current leader.

Among the technologies now under development are Qualcomm's MEMS-based (that's Micro-Electro-Mechanical Systems, by the way) "mirasol" display that is even now being introduced in some clamshell handsets where the screen is relatively well-protected. The San Diego, California-headquartered company has also announced plans to open a mirasol display factory in Taiwan during 2009. So there's change afoot.

Another alternative display technology - and one that is rather more of an outsider - is E-Ink, as used in Amazon's Kindle. It's tough and doesn't use much power but its colour representation is very poor while the refresh rate is very slow.

One of the best-placed challengers is the OLED or Organic Light Emitting Diode. The technology is proven, constantly improving and, when in mass production, economies of scale will make them cheap.

Even so, the LCD is very well entrenched and all alternative display technologies, including OLEDs, presently cost more to manufacture. And whilst that differential may well erode over time, the sheer numbers of displays used in the telecoms industry means that minimal prices differences for an individual display become major impediments to the deployment of new technologies in mass quantities.

As the name suggests Organic Light Emitting Diodes work via an electroluminescent layer containing a polymer that allows the depositing on it of organic compounds. These are quickly and simply printed on in rows and columns and the resulting matrix forms a colour display.

While current OLEDs emit less light per area than inorganic solid-state based LEDs they do not require a backlight to function. and so they need a much smaller power source. The absence of a backlight also means a that OLEDs are much thinner than an LCD panel.

The OLED manufacturing process is radically different from that used for LCDs and can easily be printed onto any suitable substrate via an inkjet printer or even via traditional screen printing technologies.

What's more they can be printed onto flexible substrates allowing for potential new applications such as roll-up displays and can even be embedded in fabrics.

Additionally, because OLEDs emit light directly rather than through an intermediary process, they can provide a greater range of colours than LCDs, are brighter and the viewing angle is far better - the displays look bright, clear and undistorted even from a 90 degree viewing angle something that LCDs don't.

And, as those of you with LCD TV sets will know, because the technology uses backlighting it cannot represent true black only a poor approximation that is often and all to evidently a deep blue.

LCDs also have to use polarising filters and this results in the inevitable loss of some 50 per cent of the luminance emitted by the backlight whilst colour filters reduce the brightness of the display even further. Finally, OLEDs have a significantly faster response time than LCD displays.

Given these benefits one might wonder why OLEDs aren't already ubiquitous. Well, believe it or not, the technology also has some drawbacks. To start with the organic materials in the displays degenerate over time and lose chrominance. In other words, colours fade.

Indeed blue hues are particularly subject to degeneration and the working life of a blue OLED is 14,000 hours - that's 5 years for a display running for 8 hours a day. whilst LCDs last much, much longer, achieving an average of 60,000 hours.

However, that said, companies such as Toshiba and Panasonic have recently invented ways to double the lifespan of OLEDS and the technology's proponents (of whom there are ever-increasing numbers) say it will inevitably beat out LCD in the long term - but not for a while yet.

Overall though, the future's bright, the future's OLEDs.

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BY Martyn Warwick
Source：TELECOMTV

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