Samsung MicroLED displays

I thought the next big thing in TVs was gonna be MicroLED, a technology with all of the advantages of OLED and none of the downsides. It was gonna be sweet, but I was wrong. Samsung recently announced that they are ceasing all LCD production by the end of the year and investing eleven billion dollars in OLED, but with quantum dots? Quantum dots don't go with OLEDs, why would you even want that? Why didn't they do this already then?

To learn more, we talked to nanosys, a company that actually makes the majority of the world’s quantom dots, who gave us absolutely fascinating answers to all of these questions and more. Quantum dots can make OLEDs better in three key ways: more accurate colors, higher brightness, which is great for HDR, and wider viewing angles. Sound familiar? Great because that's exactly the same benefits that quantum dots have been bringing to LCDs for years now.

But the way that Samsung's going to use them on OLEDs is different from anything that we've seen before. Look at this nanosys road map for 2018, it's divided into three sections which we can think of as present, near future, and not so near future. Here in the present, all quantum dot displays are LCDs with quantum dot enhancement films. What Samsung's planning with their QD display OLEDs is in the near future, second half of 2021 to be exact, but COVID so.

Then in the far future we've got wacky microLED competitors that are neither LCD nor OLED, but we'll save that for later. To help us understand this road map and the tech that could be in your next TV, let's start with a quick primer on why quantum dots are useful in the first place.

Quantum dots are molecule sized spheres of nano semiconductor materials that emit light if you provide them with energy and they behave differently according to their size, so if you shine a high energy photon like a blue light, at a quantum dot that's seven nanometers wide, it'll glow red. Shine the light on a three nanometer dot, and it'll glow green. The best part is nanosys can vary their output in one nanometer steps. So they get to be really picky about what color shines out. Blue? That's just what I wanted.

So quantum dots allow a display to load true red or true green and that's not just an opinion. You can tell by looking at the wave form of the light. For comparison, here is a typical LCD back light unit, these lights don't actually shine white, and they shine blue. As you can see here. Then their treated with a yag phosphor so that it all mixes into white, but you see how narrow that blue light is? The industry uses a measure called full width half max. It's the width of the wave half way up it's amplitude. So our blue LED has a full width half max of about twenty to thirty nanometers right here. The yag portion on the other hand, well that is a big wide one hundred nanometer less containing contaminating colors like pink, orange, and teal.

That's a problem. The white light from the source then passes through color filters at the displays sub pixels to separate the light into red, green, and blue. Now these filters themselves have a pretty loose definition for each color, so what ends up hitting your eye, inevitably goes through this game of telephone. Garbage in, garbage out.

But what if we made our white light using a blue back light with red and green quantum dots? Well now, everything has a full width half max of just thirty nanometers, then when the color filters take say red, they only get red, not, you know, orange or something. Now we get really accurate output, something that's good enough for color professionals in print or content creation or for a high quality HDR gaming monitor since HDR specs require wide color gamuts in addition to very high contrast.

But it kinda makes you wonder. If you start with pure red, green, and blue, why do you even need the color filters? Ah ha, so this is the different between phase one and phase two of the nanosys road map. The new quantum dot OLEDs that Samsung's making don't use quantum dot enhancement films like we've seen on every quantum dot display so far. Instead they have quantum dot inkjet printed onto the panel substrate itself. These displays then don't have color filters, they just have quantum dot color conversion and the difference in wording there is deliberate.

A filter stops all of the colors of light that you don't want and keeps the color that you do, but that's a waste of light and therefore energy. Conversion with quantum dots takes all of the light and converts it into the desired color with an efficiency or quantum yield, man that's sci-fi marketing term if I ever saw one, greater than 95%.

So with this new knowledge, let's go back to the three ways that quantum dots will make OLEDs better.

Number one, they will have more accurate colors, because quantum dots have slightly narrower full width half max's than the current OLED solution.

Number two, the brightness will be higher because more of the emitted light will be allowed to pass through instead of being blocked.

And number three, they will have wider viewing angles because quantum dots are just plain better at scattering light evenly in all directions than the around 50 degrees that current OLEDs give you before the colors turn to shift.

So that's what's happening, but why is it happening now? Samsung's been using quantum dots and making the worlds best OLEDs screens for smart phones for years now. I mean, didn't they already have all the ingredients? Does anybody know why they didn't just put them together?

Samsung's amoled phone displays are RGB OLEDs, while the big screen TVs that LG makes are WOLED. No one's been able to scale RBG OLEDs beyond small screen sizes like this because of manufacturing limitations. And Samsung's inexperience making big screen OLEDs, means they have to play catch up in terms of addressing geometry because the driver I see on the edge of the display are so far away from the pixels in the sender.

They also have to figure out exactly how to make an OLED using a lone blue phosphor. Ideally the blue light wouldn't have to be converted, avoiding any efficiency loss at all but for that to happen it has to be the right blue, royal blue. It's difficult because unlike quantum dots, these phosphors are complex, organic materials that are doped with your opium and other rare earth materials and you can't sort these millions of molecules after the fact, you can only control the manufacturing. The rumor right now is that Samsung will be targeting the DCIP3 color gamut using a mix blue emitter without conversion.

Then there's the manufacturing side, the color converting quantum dots have to be imprinted onto the display substrate. That means that not only does the inkjet printing for color filter in a large splays need to be possible, which only happened recently, but the quantum dots themselves need to be integrated into inks that don't clog the inkjet nozzles, can be printed at open air rather than in a vacuum, and can be cured using standard manufacturing methods. Seems expensive, I'm not gonna throw it.

I personally cannot wait to get my hands on these QD OLED displays so get subscribed so you don't miss that. But what about that far future section of the road map? Well this is where things get really sci-fi. Quantum dot electro luminescent or QDEL displays. Sounds kinda dumb but QLED was already taken I guess, so door. Remember how quantum dots shine when you put energy into them? Well that energy doesn't have to be a shining light, you could power them with electricity. Here, the quantum dots themselves would form the pixels, simplifying the technology stack and because quantum dots aren't as sensitive as OLEDs, they don't need to be manufactured in vacuum chambers with walls as thick as a battleships.

That enables manufacturing that is so much simpler that it could reap other breakthroughs like truly flexible substrates that can fold entire radius' that we've seen so far or devices so cheap and so thin that your wallpaper could be a display. That tech is actually in the lab today with research by nanosys customers happening all over the world. So then what are we waiting for? Well the limiting factor right now is lifetime, particularly of the blue and green quantum dots. The problem has to do with non radiative recombination pathways. In layman's terms, if you put energy into a device and not all of it turns into light, the rest is either creating heat or breaking chemical bonds. That's a problem.