Flexible Quantum-Dot Color-Conversion Layer Based on Microfluidics for Full-Color Micro-LEDs

Investigation and comparison of the influence of modified DBR and yellow color filters for quantum dot color conversion-based micro LED applications

This study compares how a modified distributed Bragg reflector (DBR) and yellow color filter (Y-CF) increase the color purity, viewing angle, and brightness of the quantum dot color conversion layer (QDCC) for micro-LED displays. We designed and built a 53-layer high-performance modified DBR with almost total blue leakage filtering (T %: 0.16 %) and very high G/R band transmittance (T %: 96.97 %) for comparison. We also use a Y-CF that filters blue light (T %: 0.84 %) and has good G/R band transmittance (T %: 94.83 %). Due to DBR's angle dependency effect, the modified DBR/QDCC structure offers a remarkable color gamut (117.41 % NTSC) at the forward viewing angle, but this rapidly diminishes beyond 30°. The Y-CF/QDCC structure retains 116 % NTSC color at all viewing angles. Because of its consistent color performance at all viewing angles, sufficient brightness, and outstanding color gamut, the Y-CF/QDCC structure is the best option for contemporary QDCC-based micro-LED displays.

Current Confinement Effect on the Performance of Blue Light Micro-LEDs with 10 μm Dimension

The current confinement effect on the micro-LED (μLED) with a 10 μm dimension was simulated using SpeCLED software. In this study, three p-contact sizes were considered: 2 μm × 2 μm, 5 μm × 5 μm, and 8 μm × 8 μm dimensions for μLEDs with a 10 μm dimension. According to the simulation data, the highest external quantum efficiency (EQE) of 13.24% was obtained with a 5 μm × 5 μm contact size. The simulation data also showed that the μLEDs with narrow contact sizes experienced higher operating temperatures due to the current crowding effect. The experimental data revealed a red-shift effect in narrow contact sizes, indicating higher heat generation in those devices. As the contact sizes increased from 2 to 8 μm, the turn-on voltage decreased due to lower equivalent resistance. Additionally, the leakage current increased from 44 pA to 1.6 nA at a reverse voltage of -5 V. The study found that the best performance was achieved with a contact ratio of 0.5, which resulted in the highest EQE at 9.95%. This superior performance can be attributed to the better current confinement of the μLED compared to the μLED with a contact ratio of 0.8, resulting in lower leakage current and improved current spreading when compared to the μLED with a contact ratio of 0.2.

Microfluidic static droplet generated quantum dot arrays as color conversion layers for full-color micro-LED displays

This paper presents an easy and intact process based on microfluidics static droplet array (SDA) technology to fabricate quantum dot (QD) arrays for full-color micro-LED displays. A minimal sub-pixel size of 20 μm was achieved, and the fluorescence-converted red and green arrays provide good light uniformity of 98.58% and 98.72%, respectively.