Hollow Cylindrical Micro-LEDs: Enabling High-Brightness Quantum Dots-Based Color Conversion for Full-Color Displays

We present a hollow cylindrical Micro-LED design, enabling high-brightness quantum dot (QD)-based full-color Micro-light-emitting diode (Micro-LED) displays. This design, featuring a two-step-mesa structure and an outer reflective electrode, precisely controls emission angles. Redirecting LED light horizontally optimizes QD interaction by extending the effective path length while suppressing blue light leakage through hollow size enlargement, avoiding thicker QD layers or color filters. Notably, QD integration via inkjet printing significantly reduces fabrication costs. Our 100 μm diameter hollow Micro-LEDs with QDs achieve luminance exceeding 10K nits for green and 9.6K nits for red at 37 A/cm2 current density. They also exhibit minimal blue light leakage, with 5.3% leakage to green and 2.1% leakage to red light emissions. Our approach realizes remarkable color conversion efficiency, achieving 37.7% for red and 41.7% for green emissions. These results demonstrate the potential to advance full-color Micro-LED displays through cost-effective manufacturing solutions.