Technological Breakthroughs in Chip Fabrication, Transfer, and Color Conversion for High‐Performance Micro‐LED Displays

Abstract

The implementation of high‐efficiency and high‐resolution displays has been the focus of considerable research interest. Recently, micro light‐emitting diodes (micro‐LEDs), which are inorganic light‐emitting diodes of size <100 µm2, have emerged as a promising display technology owing to their superior features and advantages over other displays like liquid crystal displays and organic light‐emitting diodes. Although many companies have introduced micro‐LED displays since 2012, obstacles to mass production still exist. Three major challenges, i.e., low quantum efficiency, time‐consuming transfer, and complex color conversion, have been overcome with technological breakthroughs to realize cost‐effective micro‐LED displays. In the review, methods for improving the degraded quantum efficiency of GaN‐based micro‐LEDs induced by the size effect are examined, including wet chemical treatment, passivation layer adoption, LED structure design, and growing LEDs in self‐passivated structures. Novel transfer technologies, including pick‐up transfer and self‐assembly methods, for developing large‐area micro‐LED displays with high yield and reliability are discussed in depth. Quantum dots as color conversion materials for high color purity, and deposition methods such as electrohydrodynamic jet printing or contact printing on micro‐LEDs are also addressed. This review presents current status and critical challenges of micro‐LED technology and promising technical breakthroughs for commercialization of high‐performance displays.

The micro-LED roadmap: status quo and prospects

“…We have been working on micro-LED mass transfer and tested many solutions. Currently, there is no single transfer method that can cover all applications [162,172,175,180,[188][189][190]. For example, small size high density could use stamping transfer; large size display might prefer fluid transfer or laser-induced forward transfer; direct bonding might be suitable for micro-display.…”

Recent advances in polyaniline-based micro-supercapacitors

“…143–145 During the fabrication of MSCs, photolithography can be rationally employed to fabricate both patterned current collectors and patterned electrodes with high precision (usually in the magnitude of micrometers or sub-micrometers). 78,146 In most cases, this approach is elaborately combined with other technologies, such as pyrolysis, 118 electrochemical polymerization, 105 and photochemical reduction, 119 for the fabrication of MSCs. Vacuum filtration is a commonly used routine to remove the solvent from a mixed dispersion or colloidal solution.…”

Development and Isolation of Dot LEDs for Display Applications through Electrochemical Etching and Sonochemical Separation

“…[11][12][13][14] Therefore, highefficiency micro LED display technology has made it possible to create micro-LED televisions or augmented reality (AR) displays through the assembly of micro-LED modules or the mass transfer of individual micro-LEDs. [15][16][17][18][19] However, despite the advantages that micro-LED display technology offers over TFT-LCD and AM-OLED displays, its high production costs and material expenses remain obstacles to its widespread application, particularly for home-use televisions and smart glasses. To make micro-LED displays more accessible, the cost of producing high-resolution displays should be significantly reduced, and individual micro-LED chips should become more affordable.…”