Originally Posted by Asmodian
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.