The Pixel Aspect Ratio Matters – on the Selection of QDCC Materials for Full-Color MicroLED Applications

The aspect ratio (width to thickness ratio) of the designed pixel pattern in the quantum dot color conversion (QDCC) layer is crucially important to the light extraction and the final performance of the microLED devices. Different level of resolution is required for different products ranged from low (as in public information display) to high (as in AR and VR), which results in different QDCC manufacture processes with different pixel configurations and material specifications. Based on simulation and practical experiments, only a high value of aspect ratio can ensure high light extraction for products of very high pixel resolution such as AR and VR, which requires QDs with higher blue light absorption coefficient to maintain a thin QDCC film thickness. For Iow–PPI process (≤ 200 PPI), IJP (inkjet printing) process is beneficial, while for high–PPI process (≥ 400 PPI), photolithography process is feasible. Both QD IJP ink for printing process and QD photoresist for photolithography process can provide products with color gamut higher than 90% BT2020, and their energy consumption can match the RGB-chip microLEDs.