Mass transfer, detection and repair technologies in micro-LED displays

Micro-light emitting diode (micro-LED) is an emerging display technology with excellent performance of high contrast, low power consumption, long lifetime, and fast response time compared with the current display (e.g., liquid crystal and organic LED (OLED)). With technological advantages, micro-LED holds promise to be widely applied in augmented reality (AR), flexible screens, etc. and is thus regarded as the next generation of display technology. In the process flow of micro-LED, the step known as mass transfer that requires transferring millions of micro-LEDs from a growth substrate to a display plane, is one of the key challenges limiting the commercialization of micro-LED from laboratory. Worldwide academic and industrial efforts have been devoted to developing mass transfer strategies with purposes of improving yield and reducing cost. Herein we review three main categories of mass transfer technologies for micro-LED display (pick-and-place, fluid self-assembly and laser-enabled advanced placement) and the coupled detection and repair technologies after transfer. Discussions and comparisons have been provided about the underlying general principle, history, and representative parties, advantages, and disadvantages (yield/efficiency/cost) of these technologies. We further envision the application prospect of these transfer technologies and the promise of the future display of micro-LED.