Light Extraction and Shaping Technique for Micro-LED Displays (Invited)

Reviewartikel, 2025

Significance Micro-LED displays have excellent performance, such as high brightness, high resolution, vivid colors, long lifespan, and fast response speed. They are expected to become disruptive display technology following liquid crystal display (LCD) and organic light emitting diode (OLED), especially in fields like micro-projection, near-eye displays, and others. However, these fields urgently require display devices with high light efficiency and good directivity. The light extraction efficiency and beam shaping of Micro-LEDs have become pressing challenges for researchers and industry. Light extraction technologies, such as Micro-LED sidewall repair, surface random roughening, and surface photonic crystal technology, have been developed. For beam shaping, there are Micro-LED beam modulation designs based on structures like microlenses, metasurfaces, and resonant cavities. Due to these technologies, Micro-LEDs can be effectively used in near-eye display applications. Progress In this study, we have reviewed and analyzed many Micro-LED-related design solutions. We summarize the advantages and disadvantages of these options and discuss aspects related to manufacturing design, process costs, material selection, etc. Through comparison, it can be concluded that photonic crystal technology is effective in improving the light extraction efficiency of Micro-LEDs. However, there are some drawbacks, such as difficulty in obtaining a directional light source, the challenges of manufacturing photonic crystals, and the high production costs. Microlens technology performs well in light field control, but its effect on Micro-LED light extraction efficiency is not significant. Metasurface technology presents high processing difficulty and costs, but it offers significant beam-shaping effects. Resonant cavity structures can effectively enhance light extraction efficiency and achieve precise beam shaping in Micro-LEDs. However, their implementation faces substantial challenges in fabrication process and structural design complexity. Sidewall repair and rough surface technologies are more effective in improving Micro-LED light extraction efficiency. These classic examples help us better understand and study Micro-LED technology. Conclusions and Prospects With the development of Micro-LED technology, we believe that costs will be reduced soon. Micro-LED development is expected to usher in a breakthrough. Surface roughening and sidewall passivation technologies also have room for improvement. The Micro-lens array is easier to realize at the process level. Metasurface technology, photonic crystal technology, micro-cavity structures, and other research areas are experiencing a development boom. In the application of Micro-LED displays, they can be combined with artificial intelligence (AI) technology. We can use AI algorithms to design and optimize structures. Additionally, AI can improve accuracy and reduce labor costs, to realize the application of “AI+ Micro-LED Display”. AI algorithms can automatically identify and repair wafer defects in Micro-LED manufacturing. They can also analyze chip position deviations during mass transfer and adjust process parameters in real-time to improve yields. In terms of user demand analysis, AI optimizes color calibration, brightness adjustment, and other parameters of Micro-LED displays to enhance the immersive experience of AR/VR devices. In the field of visible light communication integration, “AI+ Micro-LED Display” can simultaneously realize display and high-speed optical communication functions, such as pulse-width modulation. The in-depth application of AI technology provides more possibilities for Micro-LED display products. Through natural language processing technology, users can interact more intelligently with devices using voice commands. However, there are also challenges to the adaptability of AI technology. AI model training requires a large amount of manufacturing data, but the lack of a data-sharing mechanism between enterprises limits the universality of the algorithm. Additionally, the technical standards for Micro-LED combined with AI have not been unified, which may lead to compatibility issues and a lack of mature software. Hardware ecosystems may also limit the expansion of application scenarios. In addition, quantum dot materials offer high color purity and saturation, which makes them highly suitable for Micro-display applications. Micro-LED light extraction and beam shaping technologies can be combined with quantum dots and other innovations to achieve high-efficiency, full-color displays. As research progresses, we believe that these technical challenges can be overcome, thus paving the way for the more widespread market adoption of Micro-LED technology.