Full-color micro-LED displays with cadmium-free quantum dots patterned by photolithography technology.

A full-color display consisting of red and green photoluminescence cadmium-free quantum dots (QDs) as the color conversion material and excited by a 68×68 blue micro-LED flip chip array mounted on an active-matrix driving board was completed in this study. The QD photoresist (QDPR) lithography technology was reported in detail, and it has been proven to be a stable process route. The suitable thickness of 12±1µm of the QDPR and black matrix was proposed to reduce the light cross talk between different sub-pixels. The thickness of the common color filter of 1-2 µm was made successfully between the quantum dot film and the cover glass, which can greatly reduce the leakage of blue backlight and decrease the quantum dots excitation by the ambient light, as well as improve the color gamut and color purity of the display panel. In addition, the high red and green light conversion efficiency reaches up to 78.1% and 296.5%, respectively, and the screen display can reach 98.8% NTSC on the CIE 1931 chromaticity. Representative RGB monochromatic pictures were displayed successfully and ≤0.04 viewing angle deviation of the display was measured precisely.