Submicron Quantum Dot Pixel Arrays Based on Electrophoretic Deposition for Light Emitting Diode = 전기영동 증착을 이용한 발광 소자용 1 μm 미만의 양자점 픽셀 배열

다국어 초록 (Multilingual Abstract)

Displays that are indispensable things in our lives, have developed in the direction of getting thinner, higher resolution, and richer colors. For this reason, many researchers has studied the quantum dot light emitting diode (QD-LED) which has high color purity and an ultra-thin structure that does not require a backlight. However, the technology for arraying quantum dots (QDs) for an ultra high resolution of over 2,000 ppi suitable for virtual reality (VR) devices is insufficient. Here in, I demonstrate that a new method to array the QDs in ultra high resolution which has not been reached by any technology and manufactured and evaluated a QD-LED with this QD array. For this purpose, the ligands of QDs were modified to be suitable for EPD and dispersed in water and QDs could be effectively arranged only in the pixel region through the difference in surface energy. By using electrophoretic deposition (EPD), not only a full color array of 2 μm × 6 μm sub-pixels, but also a monochromatic array of 0.5 μm width was made, thereby successfully fabricating the QD array of less than 1 μm. Here, optimal process conditions were derived using Taguchi method to uniformly deposit QDs. In addition to QDs, the zinc oxide (ZnO) layer, which is the electron injection layer (EIL) and electron transport layer (ETL), was also manufactured by EPD to avoid cross talk issues. Thus, from the EIL to the QD layer, only one photo lithography and solution process were used. The fabricated QD-LED of over 2,000 ppi achieved an external quantum efficiency of 6.31%, which showed superior performance than the toluene based conventional QD EL device, demonstrating the superiority of the QD array using EPD. In addition, it has a great meaning by showing high performance even though the resolution was kept differently from the other processes that made large pixels due to the difficulty of the process when fabricating the electroluminescence device. The proposed EPD process enables QD arrays regardless of substrate materials such as transparent substrates, opaque substrates, and flexible substrates, so, it is applicable to various industries like televisions, mobile devices, flexible displays, and transparent displays. In particular, it is expected that the era of realistic VR without screen door effect will be opened by producing of ultra high resolution displays.

목차 (Table of Contents)

• Abstract ix
• Chapter 1. Introduction
• 1.1 Quantum Dot Display 1
• 1.2 Literature Reviews of Quantum Dot Array 4
• 1.3 Motivation of Current Work and Overview 10
• Chapter 2. Principle of Electrophoretic Deposition and Simulation
• 2.1 Principle of Electrophoretic Deposition 27
• 2.2 Analysis of Electrophoretic Deposition by Simulation 32
• Chapter 3. Ultra High Resolution Quantum Dot Arrays by Electrophoretic Deposition
• 3.1 Process of Quantum Dot Arrays by Electrophoretic Deposition 42
• 3.2 Process Optimization with Taguchi Method 44
• 3.3 Results of Ultra High Resolution Quantum Dot Array 48
• 3.4 Summary 51
• Chapter 4. Application of Quantum Dot Array : Quantum Dot Light Emitting Diode
• 4.1 Fabrication of Quantum Dot Light Emitting Diode 89
• 4.2 Characterization Methods of Quantum Dot Light Emitting Diode 93
• 4.3 Performance of Quantum Dot Light Emitting Diode 95
• 4.4 Summary 99
• Chapter 5. Conclusion 113
• Reference 117
• 국문 초록 127