Printing quantum dot color conversion layer in etch pits using EHD technology based on mini-LED

The rapid development of display technologies has boosted the demand for efficient and high-resolution color conversion techniques. However, conventional approaches such as photolithography and inkjet printing are constrained by limitations in pixel size and material compatibility, making it difficult to meet the demands of industrialization. Due to the low luminescence efficiency of the red quantum dot (QD) material, an innovative quantum dot color conversion (QDCC) layer structure was proposed in this study. The red QD film was prepared in pixel pits below the glass surface using electrohydrodynamic inkjet printing, thus integrating the QD film into the glass substrate. This results in a more vivid and accurate full-color display. The results indicate that the fabricated QDCC layer achieves a pixel size of 216 × 116 μm2, with a maximum external quantum efficiency (EQE) of 5.81% and a luminance of 1 315 205 cd/m2. To improve the performance of the device, the transparent photoresist used for leveling between the LEDs was substituted with a black photoresist. Although the EQE changes to 3.93% and the luminance changes to 1 206 038 cd/m2, the color coordinates move closer to the red region, changing from (0.4396, 0.2089) to (0.4786, 0.2258). This innovative method significantly not only reduces the thickness and weight of the display but also improves its color performance. This research lays the foundation for high-performance displays, paving the way for ultra-thin and energy-efficient display technologies.