TechReport (UK)

LED or OLED?

For a number of years now, most domestic TVs have used display technology based upon Liquid Crystal Displays (LCDs) backlit with Light Emitting Diodes (LEDs).

LCDs do not produce light of their own accord – they can only allow it to pass or block it, so they need a light source behind them (along with colour filters to produce the whole colour spectrum) to be able to display a visible picture. This was originally provided by the use of flat fluorescent tubes – the same technology as used in CCFL domestic lighting. More recently, LED technology has allowed more controllable, brighter lighting, whilst requiring less power and offering a longer lifetime.

The latest development in TV display technology, however, is Organic LEDs (OLEDs).

These are tiny LEDs which can be mounted in huge numbers on a substrate and switched on and off individually (in much the same way as the pixels of an LCD).

Their big advantage over LCDs, however, is that each OLED produces its own light, so there is no need for backlighting with an OLED screen (although peak brightness levels cannot match those of current LCD / LED displays).

This also makes the overall construction of an OLED TV much simpler (albeit the OLEDs are much more expensive to make initially), so leading to much slimmer Tvs:

Other advantages include very fast response times, very high contrast (from the blackest blacks to the whitest whites), very low power consumption, excellent viewing angles, the ability to mount OLEDs on completely flexible surfaces and their use allows the TV to be both very thin and light:

                                                                 OLED TV                                                   LED / LCD TV

(Observe the much greater level of detail visible in the shadows in the left-hand image, but the much higher peak brightness in the right-hand one).

This all sounds great, so why are there still only a relatively small number of TVs utilising this technology? For one very big reason – price.

OLED technology has been around for a long time now, but until recently was reserved only for small, specialist displays. It is now a common technology in mobile phone displays (which are, of course, relatively small), but low production yields (the proportion of usable to non-usable product) mean that larger screen is very expensive to make when compared to its LCD equivalent (which have had years to improve their production yields).

It is also fair to say that the ‘jury is out’ at present on the longevity of these displays – there has simply not been enough time to fully prove their reliability when in regular use, but tests suggest that current OLED products will degrade faster than LED/ LCD displays (albeit this will probably not impact upon the usual replacement cycle for this type of product).

What can be said, however, is that OLED production techniques are sure to improve over the next few years, so costs will come down, longevity will improve and with all their other obvious advantages it seems almost inevitable that they will supplant the LCD / LED displays that currently dominate the market.

In the mean-time, if you simply have to have the most amazing picture on your TV and money really is no object, then by all means plump for an OLED model – at present, LG and Panasonic are the main manufacturers offering OLED ranges.

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