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March 5, 2024

What Apple’s MicroLED Decision Means for 8K

Last week, Apple was all over the news with reports that it had cancelled its long standing self-driving car project. But a less widely reported story has big potential implications for the future of displays including 8K TVs.

There were reports that Apple had stopped its planned use of microLED technology in a future Apple Watch. The news was effectively confirmed, when AMS Osram reported that it had lost a big customer for a new microLED fab that it was building in Malaysia. The shares of AMS Osram fell 45% on the news.  

Why Did Apple Consider MicroLEDs?

First, why did Apple plan to switch from OLED to microLED in the first place? OLEDs are the current displays in all the Apple Watch models. However, microLED has seemed for some time a very attractive potential display technology. LEDs have typically had much higher efficiency than OLEDs and that gives the potential for higher brightness. Perhaps more importantly in the case of the Watch application, it means a longer battery life with less requirement for re-charging. MicroLEDs also have high speed and great colour, but then so do OLEDs. They also have long lifetimes Apple started to seriously invest in microLED ten years ago when it bought Luxvue, and its total investment is put at $3 billion.

MIcroLEDs are similar to the LEDs that we see around us, but are very, very small. Eric Virey of Yole Group, an expert analyst on this technology, has previously compared the size of microLEDs of this type to house dust or pollen! LEDs are made, like other semiconductors, by depositing layers onto a wafer using epitaxy. Rather than silicon, LEDs are usually made on sapphire wafers, but these are expensive, so unless you make the LEDs extremely tiny (less than 50 microns per side or right down to less than 10), you simply can’t make them cheap enough for display use as you need millions. An 8K display needs around 100 million LEDs (one for each red, green and blue sub-pixel) and even a 4K/UltraHD display needs 25 million or so.

This chart from Yole highlights that microLEDs are around the size of pollen

Key to keeping the cost down is to be able to remove the epi layers from the wafer so that the wafer can be re-used. But there are several real challenges to making a full display. First, the LEDs have to be distributed across the display precisely and with good performance. That is very hard to do very quickly, and you have to be extremely quick if you want to compete with the low cost of LCDs and OLEDs.

Secondly, the LEDs themselves will not all be perfect, or even the same in color and efficiency, so you have to be able to control the quality. The quality control process for big LED displays has the same challenge and it is one of the reasons for the high cost of these and the huge variance in cost between the best and the cheapest. Again, it’s hard to do this quickly and cheaply enough to compete with LCD and OLED.

Thirdly, when you get below 10 microns per edge (when the cost gets more attractive as you get more LEDs per wafer), side wall defects in the LEDs can have a very significant impact on the efficiency of the LEDs and the advantage compared to OLED reduces. There is a lot of research working going on to try to solve this problem in R&D Labs, but it is a big challenge.

Fourthly, the materials and manufacturing process used for blue LEDs is different from that of red and green LEDs. That has implications for the manufacturing processes, but also for the drive electronics which need to be different for the two types. One way around this is to use all blue LEDs with a colour conversion material such as quantum dots (QDs). However, the QDs have to be on the LED itself, which gets very hot and that makes designing a good conversion material difficult. Phosphors can be used, but they tend to be less efficient at very small particle sizes.

Finally, there is not an established supply chain or an industry standardized manufacturing process for microLEDs. There are many different approaches being tried so there is no cost reduction in materials and equipment yet, based on industry scale.

What is the Killer App for MicroLED?

It might be thought that the clear advantages of LED would eventually mean that it could take over every application. LCDs did this, driving out PDPs and other technologies, until OLEDs improved. The reality of the cost challenges of microLEDs is that the only early markets open would be those where OLED and LCD did not currently meet all the needs. One area is in very large TVs of more than 100″ diagonal where a modular approach using LED can reach sizes that LCDs and OLEDs cannot.

The second area of opportunity is in displays that really, really need better battery life and, ideally, where there were fewer pixels to have to deal with. Watches seemed to be such a market and in Apple, the microLED industry seemed to have a champion that was able and prepared to invest in the technology. Apple also had a marketing approach that allowed it to command premium prices for better products. Apple has in the past paid higher prices for components than others dared. That’s ideal for a new technology. You start at the premium end and gradually enter more of the market as volume increases, costs decline and supply chains mature.

Back in September 2023, Yole Group said that these conditions meant that Apple was acting as the incubator for the industry. Now that Apple has switched off the incubator, the industry will face more and more challenges.

The challenge for microLED now is that it has always been tough to compete with the existing technologies which are a ‘moving target’. When microLED became a strong focus for research some years ago, there seemed to be a lot of major advantages over OLED, in particular, in efficiency, lifetime and brightness. But OLED has not stood still and even a couple of years ago it was acknowledged by many in microLED that the idea of displacing OLED in smartphones had probably disappeared. Since then we have seen continued improvements in OLED to boost lifetimes, efficiency and brightness. There is a very strong roadmap of OLED materials and architectures that will make it very tough to displace.

What Does This Mean for 8K?

MicroLED may well have a place in the future for very large displays of 100″ and above and companies such as Samsung are developing these TVs, albeit at very high prices. Moving to 8K is likely to be a real challenge, though.

Historically, LCD prices have been largely based on the area of the display, not so much on the resolution. A bigger display costs more, but higher resolution does not add so much cost because many of the materials are similar. LED displays, on the other hand, have tended to be priced ‘per pixel’. It is often a surprise to buyers of large LED-based video walls that the costs for higher resolution can rise very dramatically for a similar sized display with higher resolution.

At the moment, the focus for many LCD-based TV makers is to match the visual quality of OLED-based sets while exploiting the lower costs and huge supply chain for LCD. To do that, much of the engineering and product development effort currently is on miniLED backlights which are starting to really challenge the look of OLEDs in store. MiniLED-based LCD TVs can also develop higher brightness than OLED TVs.

In the longer term, once miniLED costs have come further down and the technology has further matured, we believe that LCD makers and their customers that make TV will return to the advantage that they have in costs for higher resolution that they have over OLEDs and re-emphasize 8K. For microLED, the near future is looking very uncertain in the light of Apple’s decision.

Update

After we published this article several commentators have said that they are not convinced that Apple has stopped its microLED developments and that it may have just decided to change supplier. Apple is notoriously secretive about its plans so it looks as though it will be a while before the truth is clear. However, even if Apple is just ‘changing horses’. the change will mean, we would have thought, a significant delay to plans to introduce microLED. We may find out more at DIsplay Week in May!

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