Advances in color-converted micro-LED arrays

The development of a full-color micro-display at the Industrial Technology Research Institute (ITRI) was reviewed in this study. The blue micro-display with 960 × 540 pixel arrays and 1984 PPI resolution is demonstrated on a CMOS active matrix addressing circuit. Different methods of fabricating such a micro-panel are developed to overcome the limitation in mass transfer. For the device size ranging from 5-100 micrometers, low-current external quantum efficiency of 10%-14% can be obtained. To achieve a full-color scheme, we adapt color-conversion layer design and use colloidal quantum dots as the illuminating material. A full-color array on a transparent substrate of 170 PPI resolution was demonstrated with a large-area blue LED backlight. The red and green pixels were fabricated by a photolithography process and had a size of 30 μm. The FWHM of 21 and 28 nm and the quantum yield of 28% and 41% for the green and red pixels, respectively, were measured by a 2D spectroradiometer. With superior color provided by quantum dots, it shows a wide color gamut that can fill 87% of Rec. 2020 color space. © 2020 The Japan Society of Applied Physics.