MicroLED displays could replace LCDs and OLEDs in big-screen TVs in the not-too-distant future, if manufacturing challenges can be overcome.
MicroLEDs are part of an emerging display technology that has the potential to replace LCDs and OLEDs in big-screen TVs in the not-too-distant future. MicroLED displays can provide the same perfect black as OLEDs, but without the danger of burn-in, as well as higher brightness than any other display technology. While simple in concept, manufacturing TVs using microLEDs presents some challenges that are just now beginning to be overcome in a meaningful way.
As their name suggests, microLEDs are microscopic-scale versions of the same LEDs being used today in a plethora of applications and are based on the same gallium nitride technology. MicroLED dimensions are less than 100µm, or about two orders of magnitude smaller than a conventional LED die. Some microLEDs are as small as 3µm on a side. Research into the use of microLEDs for devices like smartwatches and virtual-reality headsets, both of which are small, low-energy applications, has been ongoing for a number of years. But creating a flat-panel display for a big-screen TV requires many, many more LEDs; for example, nearly 25 million, one red, blue, and green LED for each pixel, would be required for a 4K, 3840×2160 pixel display.
The sets of red-green-blue microLEDs are grouped into modules that are then integrated to form the display. The modules, which themselves may contain millions of microLEDs, must be manufactured and then transferred onto the display backplane without damage. It’s no surprise that the biggest challenge in the manufacturing process is the verification of each LED individually to identify failed units that are then replaced using specialized pick-and-place equipment. While the test and repair process may take on the order of several hours, the process of transferring the microLEDs onto the backplane can take days or even weeks.
Another manufacturing challenge involves the smaller gap between pixels due to the physical size limitations of associated circuitry. This limitation dictates how small the overall dimensions of a microLED display can be, directly impacting the potential market because most consumers want smaller TVs rather than wall-size displays that cost more and take up more space.
The inclusion of quantum dots is being explored as a way to reduce manufacturing complexity. One strategy being considered is to replace a red-green-blue combination pixel with a pixel containing three blue LEDs, one of which would include a red quantum dot and the other a green quantum dot. This approach could potentially increase overall efficiency as well.
There are, however, distinct advantages associated with microLED displays. The diagram below, while not to scale, illustrates the increased simplicity and reduced thickness of a microLED display compared to LCD or OLED.
Because no color filtering is required, another attractive feature of microLEDs is increased brightness as compared to OLEDs. For example, while the HDR standard for OLED TVs is 540 nits, commercially available microLED-based TVs are expected to be able to provide around 4000 nits, with even higher levels possible as the technology advances.
MicroLED lifespan is also expected to be significantly improved over OLED-based products, primarily because no organic materials are needed. Lifespan estimates are as high as 100,000 hours, and while it’s certainly theoretically possible, the degree to which this will be achieved remains to be seen.
MicroLEDs are expected to become the standard technology for big-screen displays with shipment volumes of over 15 million microLED TVs by 2026, according to IHS Markit. Samsung has devoted significant resources to this technology and for the third year in a row has featured wall-size microLED displays at CES.
Samsung envisions microLED displays for uses other than just watching TV. Long life and low power requirements would make it possible for the device to be always on, displaying, for instance, a virtual fishtank or window, headlines, weather, or a personal calendar when not in use as a TV or monitor. Apple is also exploring the use of microLEDs for its smartwatch, although there is currently no known timeframe for release to market. Other electronics manufacturers are working on microLED-based products as well, including LG and Sony.
—Yoelit Hiebert has worked in the field of LED lighting for the past 12 years and has experience in both the manufacturing and end-user sides of the industry.