With the rapid advancement of technology, Mini/Micro-LED technology is gradually leading the new transformation in the display industry. In a recent interview with the China Lighting Electrical Appliance Magazine public account, Dr. Guo Weijie, Assistant Professor at Xiamen University, delved into the current state and development prospects of Mini/Micro-LED technology, with a particular focus on the multiple technical challenges faced by Micro-LED in its commercialization process. Professor Guo believes that technological bottlenecks represent both challenges and opportunities. Additionally, he warns that emerging devices, such as AR glasses, have a far greater impact on the eyes than traditional lighting, urging researchers to focus on light health while pursuing the industrialization of these technologies to ensure sustainable development and user safety.
Mini/Micro-LED: Leading the Technological Revolution
Mini-LED and Micro-LED differ significantly in terms of chip size, manufacturing processes, and specific application scenarios, though they are often discussed together in many technical forums and industry topics. This is because both are part of the ongoing effort to miniaturize LED chips, driving LED technology toward array-based applications and enabling independent control of each display unit, thereby significantly enhancing the display’s fineness and flexibility.
Currently, Mini-LED technology has gradually replaced traditional LED backlighting in LCD TVs, achieving fine-tuned dynamic backlighting through high-density, small-pitch designs, significantly improving dynamic contrast in LCD displays. Micro-LED technology, however, is more cutting-edge, using micron-level LED chips as sub-pixels in displays, demonstrating significant advantages in brightness, contrast, and color gamut.
In terms of size, Mini-LED chips typically range from 50 to 200 micrometers, whereas Micro-LED chips are smaller than 50 micrometers. In terms of chip structure, Mini-LED retains the epitaxial substrate for flip-chip bonding, a simpler process that is more cost-effective; whereas Micro-LED requires the removal of the epitaxial substrate, which makes the process more complex.
Professor Guo notes that while some view Mini-LED as a transitional technology that will eventually be replaced, it has already demonstrated distinct advantages in backlighting and certain specific fields, achieving commercialization. Micro-LED, however, is better suited for applications requiring high resolution and fine control, such as high-end displays and wearable devices. Professor Guo emphasizes that these two technologies each excel in different contexts and should not simply be viewed as replacements.
The Multiple Challenges in Micro-LED Commercialization
While Micro-LED has more potential advantages in terms of performance, it still faces numerous technical and cost challenges that must be overcome before it can be widely commercialized. From one perspective, cost issues are essentially technical challenges. Professor Guo points out that whether in the seamless display technology route or the AR (Augmented Reality) display technology route, creating a complete Micro-LED display system requires many precise steps—each of which is crucial and presents hidden challenges.
For the seamless display technology route, the primary challenge is the mass transfer technology of Micro-LED chips. This involves transferring millions or even tens of millions of tiny Micro-LED chips accurately onto a driving substrate, ensuring that each chip is arranged precisely and that the brightness and wavelength consistency are maintained after powering on. This is an extremely challenging system engineering task that requires high precision, as well as continuous improvements in the efficiency and yield of the mass transfer process to reduce costs.
Epitaxial growth technology is another critical factor limiting the development of Micro-LED technology. During the epitaxial growth process, strict control over the growth conditions is required to ensure the consistency of the LED chip’s brightness and wavelength.
Moreover, sidewall defects during the Micro-LED chip manufacturing process also significantly impact Micro-LED performance. As the chip size decreases, quantum efficiency declines. To overcome this issue, innovation in epitaxial structure, etching technology, and post-processing is required to improve the chip’s quantum efficiency.
When it comes to the driving substrate, the traditional structure does not fully match the characteristics of the LED chips. The wavelength of the emitted light from LED chips shifts with changes in driving current and temperature, necessitating the development of specialized driving substrate solutions to accommodate the unique working characteristics of LED chips. This task requires a comprehensive understanding of driver circuit design, chip characteristics, and manufacturing processes.
In terms of the optical-electrical properties of Micro-LEDs, due to their extremely small size, traditional probe testing methods can no longer meet the requirements. Therefore, there is an urgent need to develop non-contact electrical performance testing technologies that can precisely measure the performance of Micro-LED chips. However, no mature technology has yet been widely applied in actual production, making it another bottleneck in the development of Micro-LED technology.
For the AR display technology route, Micro-LED faces process challenges arising from further miniaturization. To achieve higher pixel density, Micro-LED chip sizes must be reduced to 4 micrometers or even smaller. This presents greater demands on epitaxial growth and chip processing technologies. Ensuring brightness and wavelength consistency for each small chip in the same area of the epitaxial wafer, while ensuring reliable long-term operation at high brightness, is an important direction for current technological research.
Regarding full-color AR display technology, multiple technical routes are currently being explored. Some methods include making red, green, and blue Micro-LED screens separately and then coupling them, or adding red and green quantum dots to blue Micro-LED chips for fluorescent conversion to achieve the three primary colors, or integrating the three colors into one chip via vertical stacking. However, each of these methods has its own limitations.
Despite these challenges, Professor Guo, who is also involved in Mini/Micro-LED research, remains optimistic, stating that all challenges represent opportunities. For researchers, this field offers numerous challenges but also abundant opportunities.
Light Health Issues That Cannot Be Overlooked
Currently, smart homes mainly use smartphone apps to control home appliances. Professor Guo believes that with the development of smart homes and the Internet of Things (IoT), Mini/Micro-LED technology will have even greater development prospects. Major tech giants such as Apple, Meta (formerly Facebook), and Google have jointly envisioned using AR glasses as a new interface for human-computer interaction in the future. Although the performance of these devices is still not at an ideal level, there has been a promising start.
AR glasses typically use RGB (red, green, blue) narrow-band light spectra to display images. Additionally, AR glasses require eye-tracking, where infrared light modules project infrared light onto the eye, and infrared cameras track the gaze. This also introduces additional infrared light exposure to the eyes. Since this light enters the eyes via near-eye displays, it is narrow-band and intense, resulting in higher stimulation and impact on the eyes. Therefore, during the development of Mini/Micro-LED technology, it is necessary to collaborate with experts in the lighting field to incorporate healthy lighting principles and ensure that new technologies provide superior visual experiences while also achieving healthy displays.
About the Interviewee
Dr. Guo Weijie is an Assistant Professor at the College of Electronic Science and Technology, Xiamen University. He is also the Deputy Secretary-General of the Fujian Optoelectronics Industry Association and a member of the Optical Display Professional Committee of the China Optical Engineering Society. He specializes in the cutting-edge fields of semiconductor lighting and applications, particularly in Mini/Micro-LED, AR eye-tracking, and non-visual effects of visible light. His research achievements have earned him multiple awards, including the Second Prize of Fujian Provincial Science and Technology Progress Award (1st author) and the First Prize of the China Light Industry Federation Science and Technology Progress Award (2nd author). He has also led numerous projects funded by national and provincial science foundations and industry commissions.
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