Enhancing vertical assembly of Dot-LEDs for display application using metal chelate coordination chemical linkers

The chemical linker assembly technique for dot-LEDs described in this study offers practical solutions to critical challenges in micro-LED display production, such as high costs, low yield in mass transfer processes, and high cost of micro-LED chips. Dot-LEDs feature a cylindrical structure with a diameter ranging from 0.75 to 1.35 μm and an aspect ratio of 1.1∼1.2 for height to diameter. We introduce a viable approach using N-(carboxymethyl)-N-(11-mercaptoundecyl)glycine (gly-thiol) chemical linkers for the face-selective vertical assembly of dot-LEDs. The size scale of dot-LED enables solution assembly processes when manufacturing pixels. By bonding the Au surface of the p-GaN face to the bottom Au electrodes using the chelate bond of Au-gly-thiol-Zn²⁺-gly-thiol-Au, we intend to enhance the face-selective vertical assembly. The process involves forming two chelate coordination bonds of Zn²⁺ ion surrounded by a gly-thiol-treated dot and bottom electrodes, achieving over 60 % efficiency in face-selective vertical assembly. We achieved bright and uniform dot-LED electroluminescence devices, with a peak external quantum efficiency (EQE) of 8.1 % at 3.4 V and a luminance of 22,387 cd/m² at 9.0 V. Our findings suggest substantial improvements in the assembly and efficiency of micro-nano-scale dot-LED displays, providing a display platform technology for their application in future display systems.