OLED display technology

OLED displays are getting bigger,
cheaper and more efficient, but how long until the technology replaces LCD
altogether? We go behind the screens and take a closer look.
IT’S TAKEN A long time, but OLED televisions are finally starting to arrive in UK shops. The technology has been lauded as the future of TV for years, but high prices, complex production processes and lifespan concerns have held it back from the High Street. There is also a problem with the longevity of blue LEDs, with manufacturers struggling to make them last as long as the red and green versions.

Manufacturers have been working hard to overcome these problems, and things are beginning to change, but with the existing LCD technology so heavily entrenched, it’s going to be an uphill battle for OLED. In order to understand what impact OLED will have on TVs in the near future, we’ve broken down the technology to see what all the fuss is about.

OLED display technology

In the simplest terms, Organic Light Emitting Diodes (OLEDs) sandwich an organic semiconductor between two electrodes (an anode and a cathode), which emit light as a current is passed between them. The OLED is 100    to 500 nanometres thick, or roughly 200 times thinner than a human hair. The brightness intensity depends on the current applied.

OLEDs aren’t rigid and must be attached to a substrate before they can be used in a display. This substrate can be made from glass, clear plastic or foil, depending on what the screen will be used for. If the substrate is opaque or reflective, it’s known as a Top-emitting structure, letting light exit in just one direction. This is the kind most commonly used for TVs, smartphones and other traditional displays. Transparent structures use a transparent substrate to let out light in both directions. These are used for Heads-up Displays (HUDs).

There are two competing OLED technologies, produced by arch-rival South Korean giants Samsung and LG. Samsung uses RGB OLED pixels, comprising red, green and blue sub-pixels. The blue sub-pixels are 1.5x larger than the others as they are less efficient, and are run at a lower brightness. This compensates for the fact that the blue OLED sub-pixels age faster than the other two sub-pixel colours. Production costs are reportedly higher than those of competing OLED designs due to the size of the laser required to produce the substrate.

LG, meanwhile, has its WOLED technology, which uses a combination of red, green and blue OLEDs to generate a white light source.
Each of these light sources is placed across four sub-pixels. Three of these sub-pixels have coloured filters to produce red, green and blue light, while a fourth pixel is left white, which helps make the display brighter.

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On paper, OLED represents the ideal middle ground between the plasma and LCD technology currently powering our screens. The main advantage of OLED displays is that they do not require a backlight. LCD displays use backlights to illuminates the entire screen, and liquid crystals block this light when black is required. However, some light leaks through, which can lead to washed-out greys instead of deep blacks. Even more expensive LCD models, which use local dimming to split the backlight into different zones, can’t create perfect blacks.

Plasma panels can produce incredibly deep blacks, but they use a lot of power to produce bright whites. OLED displays are more energy-efficient, even more so than LCD screens. Plasma panels can’t be economically produced in sizes smaller than 32in, either, meaning the technology isn’t suitable for smartphones or laptops. This hugely reduces the economies of scale for the technology.

OLED displays also have superior viewing angles to LCDs. There’s no visible colour shift, even when you’re sitting at almost 90° to the screen. OLEDs also have near-instantaneous response times, which are up to one hundred times faster than a typical LCD panel.

OLED panels are thinner, lighter and more flexible than both LCD and plasma displays.
Because the substrates are made from plastic rather than glass, they can be bent into shapes as well as laid flat, allowing for curved TVs like Samsung’s S9C.

Finally, OLEDs will get easier to produce. As they are basically plastics, OLEDs can be made into large, thin sheets that are cut to size for specific screens. Once manufacturing processes are streamlined, OLEDs will drop in price.
COUNTING THE COST At present, manufacturing costs for OLED TVs are much higher than for LCD or plasma displays, and the yield Is low. Costs could drop as much as 36 per cent in 2014, but that will still mean paying almost five times as much for an OLED TV as an LCD set.

Currently, you can buy only curved OLED sets from Samsung and LG in the UK. When asked why there’s no standard OLED TV on sale yet, LG claimed “the curved screen looks wider and delivers a more realistic experience free of image distortion, regardless of where you look”. Samsung stated, “Our new 55 OLED TV is curved because we wanted to offer a special experience. It helps distinguish OLED technology from other TVs at retail.’’

In short, OLED is so expensive that a design statement was required to turn heads and open the biggest wallets. It’s still some way off becoming the standard for new TVs, but with both Samsung and LG working hard on improving the technology, we will hopefully see affordable sets in the next three years.

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