Color-converted micro-LED displays consist of a mono-color micro-LED array and color conversion materials to achieve full color, while relieving the burden of epitaxial growth of three-color micro-LEDs. However, it usually suffers from low efficiency and color crosstalk due to the limited optical density of color conversion materials. With funnel-tube array, the optical efficiency of the color-converted micro-LED display can be improved by ~3X, while the crosstalk is eliminated. After optimization of the tapper angle, the ambient contrast ratio is also improved due to higher light intensity.

Nowadays, displays are ubiquitous in our daily lives. Long-time exposure to a display’s unnatural light could influence the user’s circadian rhythm, especially at night. Here, we propose a four-color micro-light-emitting diode (LED) display to achieve low circadian action for nighttime uses. Specifically, we evaluate the RGBW-type (red, green, blue, and white) and RYGB-type (red, yellow, green, and blue) micro-LED displays in terms of circadian effect and color gamut coverage. With the addition of an extra white subpixel, it was found that the circadian effect at night can be reduced dramatically, but the color gamut remains unchanged. However, with an additional yellow subpixel, both the circadian effect and color gamut were found to improve. Finally, we simulated the circadian illuminance of real image contents for different displays. In comparison with existing liquid crystal displays, organic LED displays, and RGB (red, green, blue) micro-LED displays, the proposed four-primary-color micro-LED displays can significantly reduce the circadian effect at night.

The “Patterned-Liquid-Crystal for Novel Displays” is a Special Issue focused on new insights and explorations in the field of liquid crystals arranged in a periodic patterned way