Quantum dots (QDs) become a possible candidate for the next generation of display due to its narrow emission spectrum and tunable color by simply changing the particles size. The emission spectrum of QDs is narrow with high color saturation value, which makes QDs applicable in displays as the color conversion layer. QDs color conversion (QDCC) layers can dramatically improve the color saturation performance of most display technologies, including liquid crystal display (LCD), mini/micro-LED, and OLED. The QDCC technology replaces the traditional color filter with QDs film, comprising patterned red, green, and blue QDs arrays at the subpixel level. These subpixels absorb incoming blue or UV light and convert it into a high purity red, green or blue color. There are numerous benefits from...[ Read more ]

Quantum dots (QDs) become a possible candidate for the next generation of display due to its narrow emission spectrum and tunable color by simply changing the particles size. The emission spectrum of QDs is narrow with high color saturation value, which makes QDs applicable in displays as the color conversion layer. QDs color conversion (QDCC) layers can dramatically improve the color saturation performance of most display technologies, including liquid crystal display (LCD), mini/micro-LED, and OLED. The QDCC technology replaces the traditional color filter with QDs film, comprising patterned red, green, and blue QDs arrays at the subpixel level. These subpixels absorb incoming blue or UV light and convert it into a high purity red, green or blue color. There are numerous benefits from this method using QDs for color conversion, including greater device efficiency as much less light is lost to color filter.

However, different types of displays may need QDCC films with different patterns. Traditionally, for the fabrication of QDCC containing RGB color in subpixel pattern, photolithography is commonly applied. But photolithography and mold casting methods require evaporation, sputtering, mask fabrication, and etching. All these demands high level infrastructure equipment and increase the production cost. In this way, the inkjet printing method offers a new way to enable quicker prototyping and iteration cycles at a cheaper cost. For the inkjet printing method, only the necessary materials are dispensed and placed on the surfaces without contacting the sample. Overall, the inkjet printing method minimizes material waste and sample containment or damage. Thus, in this thesis research, the inkjet printing method is applied to print QDs for color conversion applications.

There exist inherent challenges to overcome in inkjet printing high resolution QDs. QDs layers need to be deposited with high qualities in order to realize high resolution and uniform light emitting display. Thus, inkjet printing QDs has been widely investigated. Once it is jetted from the nozzle, the interaction between QDs droplets and the substrate can form a uniform pixel. However, the coffee-ring effect remains one of the main challenges in printing QDs to the desired high performance QDs-display applications. The chosen approach to control the QDs layer morphology is critical in achieving high-performance, low-cost, large scale, and full-color, pixel displays. All of these steps require extensive evaluation of the QDs ink design and the optimization of the printing process to implement inkjet printing of QDs layers. This thesis reports the high resolution QDs printing with optimized polymer ink in three aspects, namely, studying the stability of ink droplet generation process, the positioning of and interaction of droplets on the printing substrate, and the process study of solid 3D printing. Through the detailed studies on polymer ink recipes and inkjet parameters, inkjet printing uniform and high resolution QDs films are achieved with superior optical properties which are evidenced by relevant analysis and characterization.