Has The Golden Age Of Mini LED, Micro LED And Quantum Dot Come?

- Jan 13, 2021-

The LED family products used in displays, AR/VR, automobiles and TVs are constantly innovating. Can all these innovative products be commercially available?

Many LED technologies have made major breakthroughs, and each market segment has its own advantages, disadvantages and maturity. MiniLED, micro LED and quantum dots all have a great impact on the existing LED technology, but, so far, a careful observation of each market segment shows that most of them have not yet reached the stage of profitable large-scale commercial use.

Mini LEDs

As a light source for backlighting, mini LED means a larger number of LEDs, but smaller than the LEDs currently used, enabling thinner displays and improving local contrast, similar to OLEDs. In automotive applications, it meets the industry's requirements for high contrast and brightness, surface fit and durability. Mini LEDs are easy to manufacture in existing fabs, and mass production and chip bonding accuracy can be easily achieved.

But mini LED still faces some challenges. For smart phone applications, mini LEDs face a strong opponent of OLED, which is downgraded to only be used in high-end market segments due to their cost performance. Direct-type mini LEDs can achieve local dimming; they can be used for curved displays, and the resulting TV cost is expected to be about 20% to 30% lower than the OLED version. However, as the number of LEDs used increases, heat dissipation problems also arise. In addition, more local dimming areas require a greater number of LEDs, thereby increasing the number of ICs. Therefore, it increases the cost to improve the performance, which is a major challenge for mini LEDs.

Micro LEDs

In contrast, micro LED is more breakthrough than mini LED in terms of performance, technology and basic structure. Micro LED is comparable to existing OLED technology in terms of response time and viewing angle, but is better than OLED in terms of brightness, durability and power consumption.

"From the perspective of display designers or OEMs, this technology has not yet taken shape," said Eric Virey, senior technology and market analyst at Yole Développement. "Even if the remaining problems are solved, a supply chain must be established. Therefore, although we may see some impressive micro LED products in the next few years, the number must be limited. Large-scale realization Commercial use will take at least two to three years. At that time, competing technologies such as OLED or electroluminescent quantum dots will also develop. Performance is one aspect, but cost compatibility is more important."

With the advancement of technology, micro LEDs have a reliable way to reduce costs and can compete in high-end markets for various applications, such as TVs, augmented reality (AR), virtual reality (VR) and wearable devices. In the field of smart phones, the cost of OLED drives the micro LED to reach its technological limit in terms of chip size.

Plessey Semiconductors is a supplier that has made significant progress. The company’s micro LED display for earphones achieves 10 times the resolution, 100 times the contrast ratio, and 1,000 times the brightness compared to traditional OLEDs, while power consumption is only half of OLED. In 2019, Plessey also demonstrated its first AR/VR glasses equipped with micro LEDs at CES. Vuzix has planned to abandon the use of OLED in its next-generation smart glasses and instead adopt Plessey's micro LED technology.

Quantum dots

There are three quantum dot technologies at different stages of development:

Color conversion quantum dots are a kind of "plug and play" technology that Samsung uses in its "QLED" TV products, and Vizio also has applications in its "P-Quantum" series of products. This technology adds a layer of quantum dot film to the backlight of the LCD display. The quantum dots can convert the blue light source from the LED into purer blue, green and red light, thereby improving the color gamut, display energy efficiency and/or brightness.

Electroluminescent quantum dots or EL-QDs are more breakthroughs. There is no color conversion process from LED to quantum dots.

QD-OLED combines OLED and QD color conversion, using blue OLED pixels to excite patterned quantum dots located on top of the OLED to convert red and green pixels. Compared with the OLED technology using color filters, it achieves better brightness and efficiency at a lower cost.

Samsung Display (Samsung Display) recently confirmed that it is developing large-scale QD-OLED panels for TVs, which are a combination of quantum dots and OLED technology. It uses a blue OLED backlight behind the quantum dot film layer, which can provide higher brightness, a wider color range, and may reduce production costs. However, Samsung recently announced the establishment of an investment review committee in April 2019, which will be responsible for making decisions on Samsung’s plans to produce QD-OLED TV panels. If the plan is approved, mass production is expected to start at the end of 2020 or early 2021. The question is, Samsung plans to start trial production in 2019, so is this plan a normal operation plan or a somewhat delayed plan?

In addition, in the field of micro LEDs, Plessey has cooperated with Nanoco Technologies to apply Nanoco's cadmium-free quantum dot (CFQD) semiconductor nanoparticle technology to reduce the pixel size of monolithic micro LED displays. Plessey integrated Nanoco CFQD quantum dots into selected areas of the blue LED wafer to add red and green light. This reduces the smallest pixel size today by an incredible 87%. This process can provide smaller, higher-resolution micro LED displays for AR/VR devices, watches and mobile devices, while enhancing color rendering and energy efficiency.

Is it feasible to do things separately?

According to the differences in various LED technologies, and the extent to which these technologies need to be transformed from existing materials, processes and supply chains, only cooperation is the most effective way to achieve faster development and cost reduction. "Partnerships are critical to innovation and product development, especially in overcoming key technological bottlenecks," said Roger Chu, research associate. "If there is no partnership, those niche frontier technologies may not develop successfully."

Roger also said: “At present, it is generally believed that once micro LED chips and mass transfer technology are ready, manufacturers can successfully produce micro LED displays. In fact, micro LED technology is not yet mature, and in different manufacturing processes Still facing many bottlenecks. Therefore, manufacturers in related fields must work together and invest more in technology development."

Yole's Virey also expressed the same opinion in the OLED and EL-QD fields. "OLED or EL-QD materials are dispersed in ink and printed on the backplane of transistors. We see that many independent quantum dot material companies are developing their own materials, and many leading display manufacturers, such as Samsung, TCL Or BOE is not only working hard on its own development, but also cooperating with independent materials companies. Collaboration is essential. Each material needs to be manufactured accurately in order to work well with all other components."

Virey further pointed out that the manufacturing process and basic architecture of micro LEDs are completely different. The two industries of LED and display are combined, and there are few common points. Processes and tools do not yet exist. The establishment of a complete supply chain requires collaborative work among LED manufacturers, tool manufacturers, display manufacturers, and various micro LED start-ups. These start-ups are often pioneers in developing some key technologies.

A recent example of cooperation is the recent announcement by the EV Group and Plessey to introduce high-performance GaN-on-silicon (GaN-on-Si) monolithic micro LED technology to the mass market for AR applications.

Innovation brings surprises

According to Virey, he has seen at least two surprises in the industry so far. "In the past two to three years, micro LED has transformed from a'crazy idea that will never work' into a reliable display technology candidate. Think about it: to produce an 8K micro LED TV, nearly 1 assembly is required. A micro LED the size of a billion bacteria has an accuracy of 1 μm. There can be no mistake, and it must be completed within a few minutes to live up to its cost."

Virey added: "When the industry first discussed this idea, the best assembly technology on the market may take months or years to assemble a TV. Now, various companies have developed many massively parallel transmissions. And the assembly method, which makes micro LED closer and closer to reality. Of course, there are still many challenges in the future, but this is no longer a crazy idea."

He also talked about Samsung's QD-OLED technology. "Frankly speaking, I don’t think anyone took it seriously 18 months ago, but by then Samsung might have already established its first fab. The feasibility of such a speed stems from the fact that Samsung has already invested a lot of time. And money are used to enable the two major technologies required for QD-OLED: OLED and quantum dots. When Samsung realized that they could be combined into the third technology, it had already made great progress in these two technologies. ."

There are still many challenges, but the LED market is developing rapidly. Many companies, including Apple, Plessey, Samsung, AU Optronics, etc., are constantly advancing. Many prototypes and new features will be released in the short term, but from the perspective of display designers or OEMs, some patience is still required.

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