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Screen Tech is Enough to Send You Dotty

From the Printware Blog on Tuesday 21st February 2017

Samsung SUHD Quantum Dot Exhibition

Samsung have recently announced significant advances to their Quantum Dot screens that could allow even more colour shades than OLED equivalents – over 1 billion of them. With such a number of colours available could it give Samsung screens the richest viewing experience available?

The short answer is: potentially. However, there are many more factors at play here and the answer, I'm afraid, is not a straightforward one. We still have to take backlights, NITS and viewing angles into consideration, as well as the fact that there are two generations of Quantum Dots to account for...

When organic-LED (OLED) screens were developed they were able to blow away the competition by side-stepping an important feature of other screens: the backlight.

Contrast this with traditional LED screens - which are actually LCD displays with an LED backlight. Even where a pixel is black, there is still a light source operating behind it meaning perfect blackness cannot be achieved. In OLEDs the colour filter and light source are one so each pixel can be switched off completely to emit zero light. This gives the 'perfect' blacks that allow for high contrast ratios.

On the other hand, Samsung quantum dot display (or QD-LED) technology, uses photoluminescent particles that measure an infinitesimal 2 to 10 nm across. To put this into contrast, our DNA measures just 1nm in diameter. Blue quantum dots are the smallest, then greens and finally reds are the ‘largest’, which seems odd to say given that they are over a thousand times smaller than a human hair. At these sizes, a huge amount of quantum dots can be used in any visible pixel size to realise a rich spectrum of colours.

These quantum dots produce colour when they are exposed to a blue LED backlight. This stimulates a group of quantum dots in multivarious combinations to generate the specific pixel colour desired with a huge range of control. Samsung have claimed that this system can produce the mind-boggling range of colours and at twice the brightness (1,500 - 2000 NITs) of OLED displays due to the pureness of the green, red and blue emitted by their quantum dots.

Despite this, Quantum Dot technology does not have everything its own way. They still require exposure to photons - i.e. a light source - to emit their own light. As such, they do not function without a backlight and this is where OLEDs have the advantage.

The answer to this may already be in the pipeline, but we may be forced to wait a while for it. The next generation of quantum dots could potentially avoid the need for a backlight and exceed the capabilities of OLED screens, assuming of course that OLEDs do not advance dramtically in the interim.

Samsung have revealed that they are working on quantum dots that are electroluminescent, rather than photoluminescent. What that means is that the substance can be induced to emit light not through exposure to another light source, but exposure to an electrical charge. Not only would this be highly energy efficient, it would avoid the need for a backlight in the same manner as OLED technology. By simply not turning pixels ‘on’ these could be used to create areas of perfect black on the screen.

Samsung Quantum Dot Display at ISE 2017Also, having just one layer of these QLEDs to produce the image would create a far wider viewing angle in common with the OLED equivalents. If this is achievable as Samsung say it is, it would put both technologies on an equal footing. The only question that would remain is if the OLEDs could be advanced to produce the same colour range and brightness as a quantum dot display.

We should have plenty of time to anticipate and speculate over the arrival of the QLEDs, as these will not be available for a couple of years at least. In the meantime it will be interesting to see if QD-LEDs begin to break the dominance of OLED screens.

At ISE 2017 Samsung announced that Quantum Dot Digital Signage will launch soon. Keep an eye on our commercial screens section for more developments.

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