Micro-LED Displays vs LCD and OLED

This posting examines the advantages of micro-LED displays technology vs established LCD and OLED solutions.

Micro-LEDs are essentially LED light sources we use now for lighting purposes, but with dimensions less than 100 um. Shrinking LED die dimensions causes some bad consequences (harder to handle, efficiency drop due to larger ratio of sidewalls to lighting area, etc.), but also brings a lot of exciting opportunities to enhanced performance and build new devices and applications. One of the most important application for the technology is their use in micro-LED displays.

LCD displays have gone a long way from very expensive and heavy to pretty thin, quite large (up to 65”), and affordable. Moreover, the latest enhancements of brightness and color using Quantum Dots technology and improved backlighting made LCDs almost as good as the next emerging display technology – OLEDs.  Still, LCDs are “passive” display technology, meaning, it does require external light source to illuminate the screen. Moreover, use of polarizers to control liquid crystal pixels reduces the light transmission and screen brightness, also makes these displays not energy efficient. LCDs are not compatible with flexible (or foldable) substrates and barely applicable to curved substrates.

OLED technology overcomes these LCD deficiencies by being self-emissive (does not need backlighting), brighter, much thinner, lighter and more power efficient. Moreover, after a long development cycle and struggle to overcome lifetime problems related to high sensitivity to environment, OLED technology lately came out as a viable consumer product and even prices stated to fall to a reasonable consumer acceptance level, which provides some confidence of OLED devices capturing smartphones and TVs markets from LCD over the next few years.

So, what could the new micro-LED displays technology offer in order to capture the market from LCD and OLED displays? Well, apparently there are quite a few benefits they offer which would make micro-LEDs to shine in specific markets. micro-LED displays could beat LCD and OLEDs on the following performance parameters:

  • power consumption (50% less than even OLED),
  • higher light efficiency (at least double),
  • much higher contrast (few orders of magnitude!!!),
  • much faster response (an order of magnitude faster than OLED),
  • much larger operation temperature (from extreme cold to extreme hot),
  • no image retention (which is a killer for OLED display quality),
  • super-high brightness (orders of magnitude higher than OLED),
  • longer (indefinite?) lifetime, and
  • super-high resolution (again, orders of magnitude higher than OLED).

In addition, micro-LED technology opens the way to completely new opportunities for displays by hybridization: integrating micro-LED dies and other micro-elements (controllers microchips, IR light sources, sensors, etc.) on the same display substrates (flexible or rigid). And the last, but not the least, micro-LED technology is highly scalable. The size of display substrate, where micro-LED dies could be assembled, is limited to only the practical dimensions of some mechanical fixtures and robotic mechanisms.

Moreover, micro-LED dies could be assembled to a “tiles” or modules without bezels, so they could be stackable to any required display size.

In contrast, the LCD or OLED scalability is limited by issues with uniformity of depositions of liquid crystal and organic materials over large areas, which is not easy and practical, and cost-prohibitive.

Still, when you analyze the current device requirements it’s not obvious at all that we need so much better performance for real products in the market. In fact, when you place side-by-side the best LCD and OLED smartphones you may find it hard to distinguish which is which…

Well, apparently there are some display applications, which rely on this “extra” performance micro-LEDs can offer:

  1. Near-eye microdisplays, the hurt of Artificial Reality (AR) and Virtual Reality (VR) devices do really need that high brightness to display information clearly against a bright-lit background. Also, these devices, being in so proximity to the most sensitive light/image sensor in the World (human eye) require very high-resolution display technology with pixel sizes down to 1 um
  1. Similar enhanced brightness and contrast requirements would be very useful for automotive head-up displays (HUD)
  1. Enhanced brightness and low power consumption could be very attractive for smartwatches, smartphones and other wearable display devices.
  1. Large-size TVs, video walls, digital cinemas and digital signage & advertising display could be enabled using extraordinary scalability of micro-LED technology. Interestingly, in contrast with LCDs and OLEDs the cost of displays does not scale with the area, but only with the number of dies (pixels) used.
  1. Micro-LED (or in this case, mini-LEDs, which are slightly larger than micro-LED, 100-300 mm, but still much smaller than regular LED dies) could enhance performance of LCD displays if used in backlighting panels. The current backlighting technology is based on edge-lit waveguides, which are not as efficient as micro-LEDs, and limit ability to reduce TVs thickness. What’s even more attractive is an ability to enable local dimming using direct-micro-LED-lit LCD displays, which enhance contrast and overall picture quality.

Thus, the applications and devices above, hungry for light, scale and performance, and not reachable using LCD or OLED technology, could be the first consumers for upcoming micro-LED technology.

 

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