| Organic light-emitting display(OLED) are thin, lightweight, flat, viewing angle, have a large surface area, and may be made flexible and bendable, is considered to be one of the most noteworthy technologies in the 21 st century. Full color and large area of panel display are important objectives of the development of OLED. The fabrication process by red, green and blue(RGB) OLEDs can be made side-by-side in order to obtain a full-color display. Currently, small molecule RGB color patterning is done by vacuum depositting red, green and blue materials through a pre-patterned shadow mask, typically made of a thin metal sheet which is widely known as fine metal mask(FMM) technology. However, the technique has several inherent limitations. These limitations include mask deformation, difficulties in mask-to-substrate overlay alignment, and the waste of organic materials. The development of maskless color patterning approaches, in which the RGB color patterning can be done without the use of shadow masks, can offer significant advantages. Inkjet printing is one of the color patterning processes without masks. The advantages of ink-jet printing lie in the accurate and convenient deposition of a wide range of functional materials in a large area at low cost, and the possibility of delivering extremely small volume solution with almost no waste of the materials. In addition, ink-jet printing can be utilized in automated fabrication process allowing selective patterning. How to achieve uniform solid films from the ink-jet printed inks is one of the biggest challenges for ink-jet printing process. The most commonly observed phenomenon is a coffee ring-like surface profile after solvent evaporation, showing that most of the solute is pushed to the edge of the droplet. Various approaches have been explored to reduce the coffee ring effect, such as controlling the ambient humidity, mixing different solvents, adjusting the substrate’s temperature, modifying the substrate’s surface energy, adding the surfactant, and making special-shaped solute particle, etc. In contrast to conjugated polymers, solution- processed OLEDs based on organic small molecules possess some advantages, such as excellent reproducibility of chemical synthesis and high purity of small molecules. However, the studies focused on tuning the solution of the emissive layer in order to obtain good film morphology issues was rarely concerned.In addition to the polymer and small molecules luminescent materials, QDs have exhibited size- and composition-tunable luminescent properties, high photo-luminescence quantum yield, good stability, solution-processing and printed films from ink, which make them promising in applications for light-emitting devices. Currently, the performance of the QD-LEDs does not meet the requirement of the large-area display devices, therefore the device architectures and the charge-transporting materials used for QD-LEDs need to be optimized.The original works are given as follows:1. We obtained printable small molecule solutions and found that the viscosity is an important factor for stable ink-jet printed inks, for Jetlab2 inkjet printing equipment, dilute solution above or at 1cp viscosity can be printed steadily. The line printing process by an ink-jet printer is successfully developed to deposit the solution-processable small molecule on hole injection layer. To achieve uniform surface profile of the printed line, an inward Marangoni flow has to be created to match the outward capillary flow in a mixed solvent ink. By adjusting the volume ratio, the film’s surface profile is changed from concave to flat to convex by the combination effect of the surface tension gradient and the viscosity of the solution. With 10-30 vol% DMA in the mixed solvent, a flat film surface is obtained. It’s found that the line width of the printed line is controlled by the contact angle. It’s suggested that the SFE of PEDOT: PSS and PEI substrates might be too high to form a balance flow for the ink, and a high outward flux is created resulting in the coffee ring profile. On the contrary, the SFE of ZnO and PVK is small enough for the ink to form a balance flow, which creates the flat line surface. As the red and green materials(1 b and 1 c) soluble in the same solvent, the changing trend of line printing films are completely different. It’s revealed that the direction of the Marangoni flow could not be predicted by only the pure solvents’ surface tensions.2. We introduce several pixel structures of substrate for inkjet printing processing OLEDs and designed a kind of linear pixel structure. OLEDs based on inkjet printing small molecules electroluminescent 1c and 1b are manufactured. The luminous efficiency of ink-jet printing device are slightly lower than spin coating devices, means that the inkjet printing film quality still needs to be further improved. Futhermore, a 3 inch 120 ppi blue PLED display plane were fabricated via line printing technology, the line printed PLED display presents uniform matrix emission without defect or dead pixel.3. We studied different hole transport layer materials influence on core/shell type quantum dot light emitting devices, found that HOMO energy levels of organic hole transport layer material was the main factors influencing the QD-LED device performance. By optimizing the annealing temperature of quantum dots film and the ZnO NPs film, the QD-LED devices performance were improved. This was induced by the enhancement of quantum dots electronic transmission which improved by the increasing of annealing temperature. Finally, we explored inkjet printing quantum dot light emitting layer of QD-LED technology and obtained printable red light quantum dots ink printing in atmosphere. The printed QDs films on PVK present a weak coffee ring, the line width is 220 μm, respectively. A QD-LED device.
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