Micro-light-emitting diodes (micro-LEDs) with outstanding performance are promising candidates for next-generation displays. To achieve the application of high-resolution displays such as meta-displays, virtual reality, and wearable electronics, the size of LEDs must be reduced to the micro-scale. Thus, traditional technology cannot meet the demand during the processing of micro-LEDs. Recently, lasers with short-duration pulses have attracted attention because of their unique advantages during micro-LED processing such as noncontact processing, adjustable energy and speed of the laser beam, no cutting force acting on the devices, high efficiency, and low cost. Herein, we review the techniques and principles of laser-based technologies for micro-LED displays, including chip dicing, geometry shaping, annealing, laser-assisted bonding, laser lift-off, defect detection, laser repair, mass transfer, and optimization of quantum dot color conversion films. Moreover, the future prospects and challenges of laser-based techniques for micro-LED displays are discussed.

Deep-ultraviolet (DUV) sterilization technology using DUV-LEDs has attracted considerable attention owing to its portability, eco-friendliness, high potency, and broad-spectrum sterilization. This study compiles the developments of recent DUV sterilization research. Recent works have investigated DUV sterilization from the perspective of device improvement and principle investigation: one employed a novel epitaxial structure to optimize the performance and fabrication cost of DUV-LEDs and realized potent virus disinfection effects for various respiratory RNA viruses, and another work explained the disinfection phenomenon of SARS-CoV-2 and its variants (Delta and Omicron) in a cryogenic environment. These studies have contributed significantly to the development of DUV sterilization.

The evolution of next-generation cellular networks is aimed at creating faster, more reliable solutions. Both the next-generation 6G network and the metaverse require high transmission speeds. Visible light communication (VLC) is deemed an important ancillary technology to wireless communication. It has shown potential for a wide range of applications in next-generation communication. Micro light-emitting diodes (μLEDs) are ideal light sources for high-speed VLC, owing to their high modulation bandwidths. In this review, an overview of μLEDs for VLC is presented. Methods to improve the modulation bandwidth are discussed in terms of epitaxy optimization, crystal orientation, and active region structure. Moreover, electroluminescent white LEDs, photoluminescent white LEDs based on phosphor or quantum-dot color conversion, and μLED-based detectors for VLC are introduced. Finally, the latest high-speed VLC applications and the application prospects of VLC in 6G are introduced, including underwater VLC and artificial intelligence-based VLC systems.The evolution of next-generation cellular networks is aimed at creating faster, more reliable solutions. Both the next-generation 6G network and the metaverse require high transmission speeds. Visible light communication (VLC) is deemed an important ancillary technology to wireless communication. It has shown potential for a wide range of applications in next-generation communication. Micro light-emitting diodes (μLEDs) are ideal light sources for high-speed VLC, owing to their high modulation bandwidths. In this review, an overview of μLEDs for VLC is presented. Methods to improve the modulation bandwidth are discussed in terms of epitaxy optimization, crystal orientation, and active region structure. Moreover, electroluminescent white LEDs, photoluminescent white LEDs based on phosphor or quantum-dot color conversion, and μLED-based detectors for VLC are introduced. Finally, the latest high-speed VLC applications and the application prospects of VLC in 6G are introduced, including underwater VLC and artificial intelligence-based VLC systems.

Augmented reality (AR) and virtual reality (VR) are two novel display technologies that are under updates. The essential feature of AR/VR is the full-color display that requires high pixel densities. To generate three-color pixels, the fluorescent color conversion layer inevitably includes green and red pixels. To fabricate such sort of display kits, inkjet printing is a promising way to position the color conversion layers. In this review article, the progress of AR/VR technologies is first reviewed, and in succession, the state of the art of inkjet printing, as well as two key issues — the optimization of ink and the reduction of coffee-ring effects, are introduced. Finally, some potential problems associated with the color converting layer are highlighted.Augmented reality (AR) and virtual reality (VR) are two novel display technologies that are under updates. The essential feature of AR/VR is the full-color display that requires high pixel densities. To generate three-color pixels, the fluorescent color conversion layer inevitably includes green and red pixels. To fabricate such sort of display kits, inkjet printing is a promising way to position the color conversion layers. In this review article, the progress of AR/VR technologies is first reviewed, and in succession, the state of the art of inkjet printing, as well as two key issues — the optimization of ink and the reduction of coffee-ring effects, are introduced. Finally, some potential problems associated with the color converting layer are highlighted.

We propose a flexible white-light system for high-speed visible-light communication (VLC) applications, which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode (LED) on a flexible substrate pumping green CsPbBr3 perovskite quantum-dot (PQD) paper in nanostructure form and red CdSe QD paper. The highest bandwidth for CsPbBr3 PQD paper, 229 MHz, is achieved with a blue micro-LED pumping source and a high data transmission rate of 400 Mbps; this is very promising for VLC application. An 817 MHz maximum bandwidth and a 1.5 Gbps transmission speed are attained by the proposed semipolar blue micro-LEDs. The proposed flexible white light system and the high-bandwidth PQD paper could pave the way for VLC wearable devices.

A promising approach for the development of effective full-color displays is to combine blue microLEDs (μLEDs) with color conversion layers. Perovskite nanocrystals (PNCs) are notable for their tolerance to defects and provide excellent photoluminescence quantum yields and high color purity compared to metal chalcogenide quantum dots. The stability of PNCs in ambient conditions and under exposure to blue light can be improved using a SiO2 coating. This study proposes a device that could be used for both display and visible light communication (VLC) applications. The semipolar blue μLED array fabricated in this study shows a negligible wavelength shift, indicating a significant reduction in the quantum confined Stark effect. Owing to its shorter carrier lifetime, the semipolar μLED array exhibits an impressive peak 3 dB bandwidth of 655 MHz and a data transmission rate of 1.2 Gb/s corresponding to an injection current of 200 mA. The PNC–μLED device assembled from a semipolar μLED array with PNCs demonstrates high color stability and wide color-gamut features, achieving 127.23% and 95.00% of the National Television Standards Committee standard and Rec. 2020 on the CIE 1931 color diagram, respectively. These results suggest that the proposed PNC–μLED device is suitable for both display-related and VLC applications.

With regard to micro-light-emitting diodes (micro-LEDs), their excellent brightness, low energy consumption, and ultra-high resolution are significant advantages. However, the large size of traditional inorganic phosphors and the number of side defects have restricted the practical applications of small sized micro-LEDs. Recently, quantum dot (QD) and non-radiative energy transfer (NRET) have been proposed to solve existing problems. QDs possess nanoscale dimensions and high luminous efficiency, and they are suitable for NRET because they are able to nearly contact the micro-LED chip. The NRET between QDs and micro-LED chip further improves the color conversion efficiency (CCE) and effective quantum yield (EQY) of full-color micro-LED devices. In this review, we discuss the NRET mechanism for QD micro-LED devices, and then nano-pillar LED, nano-hole LED, and nano-ring LED are introduced in detail. These structures are beneficial to the NRET between QD and micro-LED, especially nano-ring LED. Finally, the challenges and future envisions have also been described.

Red-green-blue (RGB) full-color micro light-emitting diodes (μ-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN μ-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar μ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200A/cm2 injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar μ-LEDs’ emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020).

Full-color displays based on micro light-emitting diodes (μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring (NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al2O3 layer was deposited on the sidewall of NR-μLEDs, which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.