[HDTVTest] Samsung To Begin QD-OLED "Trial Production" Later This Year - Page 5 - Overclock.net - An Overclocking Community

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[HDTVTest] Samsung To Begin QD-OLED "Trial Production" Later This Year

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post #41 of 46 (permalink) Old 05-15-2019, 11:23 AM
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Quote: Originally Posted by Asmodian View Post
Is it? Do we know what Samsung is using and have any data on its stability under real conditions?

Micro-LED is pretty stable but inorganic compounds are not inherently more stable than organic ones just because they are inorganic. I have done lots of inorganic chemistry with compounds that are highly unstable and lots of organic chemistry with compounds that are very stable. Very tiny spots that get hot can easily react with almost anything, inorganic as much as organic.

That Samsung is planning to use blue OLED (the least stable color) tells me that they do not have stable blue dots. This may be because they simply cannot make reliable dots that small but it is also possible they don't have something stable enough at that size and power levels.

It has to be very stable too, if it is going to last as tiny quantum dots instead of a bulk subpixel like OLED.
The semiconductor materials used in inorganic LEDs certainly are more stable than those used in OLEDs. Like, orders of magnitude more stable. An OLED will show measurable degradation (loss of brightness) after hundreds or thousands of hours, depending on applied current. Inorganic LEDs show stability through hundreds OF thousands of hours.

The quantum dots themselves are simply nanoparticles, a stable crystalline material of very small size so that the electrons start to get constrained by the dimensions of the crystal and start doing weird quantum mechanical things. The electronic band structure of the material changes, which changes its absorption and emission characteristics, direct vs indirect band gaps, and other optically useful features.

Nanoparticle fabrication is quite well understood, and not hard to do with the right processes. Uniformity is key, as you're often using the same material for each kind of quantum dot, but controlling the size allows you to change the properties. A blue-to-green downconverter will be a different size of nanoparticle than a blue-to-red downconverter, for example, so it's important to get the size consistent if you want well-defined colors.

The nanoparticles are not consumed or depleted by their optical interactions. The electrons simply move from one set of energy states to another set of energy states, and go back again after they reradiate the new light. There is no chemical process involved, nor any transfer of material, only the excitation levels of the electrons are changing.

The reason they use blue is that blue can get downconverted to green and red because blue is a shorter wavelength, and therefore higher energy. Upconversion, creating a photon of higher energy than the ones that excited the atom, is considerably harder and requires much more specific material properties. The efficiency is also awful because upconversion has to be a multi-photon absorption, which is considerably less probable than the single-photon absorption required for downconversion.
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post #42 of 46 (permalink) Old 05-15-2019, 10:54 PM - Thread Starter
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Quote: Originally Posted by Mand12 View Post
The nanoparticles are not consumed or depleted by their optical interactions. The electrons simply move from one set of energy states to another set of energy states, and go back again after they reradiate the new light. There is no chemical process involved, nor any transfer of material, only the excitation levels of the electrons are changing.
No chemical processes are supposed to happen when OLEDs emit light either, merely electrons and holes moving around similar to how they do in semiconductors. That said I admit this process does seem a lot more likely to go wrong over time compared to micro-LEDs, gallium nitride is really very stable, but I am not sure a 4K micro-LED display will ever be affordable. This QD-OLED is not micro-LED anyway and no one is planning on ramping up micro-LED production any time soon.

Doing this to any inorganic "stable crystalline material" is not guaranteed to be consequence free, especially in the presence of oxygen. Everyone seems to think any inorganic display would automatically not burn in like LCDs, but LCDs don't burn in because the light source for each pixel is always on for the same amount of time. Any self emissive display will burn in. It might be an order of magnitude slower with very stable materials but it still will, unlike classic LCDs. There is no way around this.

Quote: Originally Posted by Mand12 View Post
The reason they use blue is that blue can get downconverted to green and red because blue is a shorter wavelength, and therefore higher energy. Upconversion, creating a photon of higher energy than the ones that excited the atom, is considerably harder and requires much more specific material properties. The efficiency is also awful because upconversion has to be a multi-photon absorption, which is considerably less probable than the single-photon absorption required for downconversion.
Right, the QDs down convert photons, they are not generating light from electricity. Samsung is effectively using blue OLED subpixels as individual backlights the same way LG uses their white subpixels. The efficiency of a blue OLED + QD downconversion to get red and green is probably better than a white OLED + filter, but this doesn't help burn in except insofar as you can run the screen at lower power for the same brightness.

A brighter/more efficient OLED with true RGB subpixels would be great but burn in could be worse if Samsung's blue OLED subpixels are less stable than LG's white ones. We need to wait and see.

Last edited by Asmodian; 05-15-2019 at 10:59 PM.
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post #43 of 46 (permalink) Old 05-16-2019, 05:49 AM
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It's not just one order of magnitude slower, and that matters a lot.

The organic molecules in OLEDs simply break down with applied current. I can't remember the specifics, but it's an easily measurable phenomenon. Comparable degradation in inorganic semiconductor LEDs is basically nonexistent. They don't care whether or not oxygen is present.
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post #44 of 46 (permalink) Old 05-16-2019, 06:25 AM
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Quote: Originally Posted by Asmodian View Post
... but I am not sure a 4K micro-LED display will ever be affordable. This QD-OLED is not micro-LED anyway and no one is planning on ramping up micro-LED production any time soon.
That is why Samsung is hedging their bets on the display market by using 3 new techs as the way forward. Once they know the clear winner, they will focus on that




Apple is already moving forward with mass production on MicroLED for Apple Watch, and is significantly into development and nearing production of a panel they will be using for the iPhone.
Other companies are planning mass production of panels soon.

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post #45 of 46 (permalink) Old 05-16-2019, 06:52 AM
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MicroLED works well for small screens. Doing it on the scale of a TV simply takes up too much real estate. You don't need it to be particularly micro, pixel sizes on a 4k TV are still pretty large, but it's simply that volume of silicon that is going to make it very pricey. A 75" TV is about fifty 200cm wafers' worth of area to cover.
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post #46 of 46 (permalink) Old 05-17-2019, 03:30 PM
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Quote: Originally Posted by ryder View Post
monitor tech has been so incredibly frustrating.

granted there are good panels out right now, but so many of us are waiting to build our dream PC because of a lack of 4k 120hz+ oled 24-32" monitors.
Whats frustrating to me is hpow everyone abandoned 3D. 3D is and was awesome especially on LGs passive tech. Hell even some of the old Vizio TVs had great 3D

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