What exactly is different between the quantum dots found in the old Sony W900a, a KS8000 and the 2017 Samsung QLEDs?
Joule's post has good illustrations for this:
Found it:
http://www.avsforum.com/nanosys-quantum-dots-at-ces-2017/
2016/17 TVs
(IFA/Summer) 2018 TVs ------- this will likely be the tech used for the next 3-4 years
True QLED ---- ~ 5 years away
Traditional Color Filters that LCD and OLED displays use work by
blocking light.
Think of them like a piece of colored glass that you put in front of a white light source. To output red light, it has to block all green and blue light (and every other color in the visible spectrum).
This is very inefficient, and also limits the color gamut since these color filters are imperfect and produce an impure red / green / blue light.
That's why you probably won't see any displays using color filters that are able to cover the entire BT.2020 color gamut.
Quantum Dots work by
transforming high-energy light to lower-energy light.
So you can take blue light, and with the right QD material, transform it into very specific green or blue light - or any other color for that matter - and this is a very efficient process.
There's also been talk of starting with higher-energy ultraviolet light to further improve efficiency.
Previous Quantum Dot displays (top) used a blue backlight, transformed into very pure white light by the quantum dot enhancement film (much purer than "white" LEDs), which was then passed through color filters to create red, green, and blue.
The high-end 2018 QD displays should be eliminating the QDEF and traditional color filters entirely (middle).
In the place of color filters, they are going to allow the blue backlight to pass through, and there is going to be red / green quantum dot material in place of the color filters.
So rather than red / green / blue being created from filtering out white light, red / green are going to be created by transforming blue light directly into red / green emitters.
And that's another key point about this technique. Not only is it far more efficient - which enables wider color gamuts, higher light output, and lower power consumption - it moves the emitter to the very front of the display stack, which should greatly improve viewing angles (and potentially uniformity).
Looking forward, the future would be QD-LED displays, which are likely going to be µLED displays using quantum dot patterned LEDs. Rather than having quantum dot color filters, they will be emitting red / green / blue light directly.