Title Page
Abstract
Contents
Chapter 1. Introduction 13
1.1. An Overview of Organic and Quantum Dot Light-Emitting Diodes 13
1.2. Challenges of QLEDs and OLEDs: Previous Patterning Techniques 18
1.3. A Common Layer Structure for Full-Color Displays 23
1.4. Outline of Thesis 27
Chapter 2. QD-Organic Hybrid LEDs Using a Red QD Common Layer 29
2.1. Experimental Details 30
2.1.1. Materials 30
2.1.2. Device fabrication 34
2.1.3. Characterization 35
2.2. Material Selection and Structure Engineering 38
2.3. Fabrication Scheme of Hybrid LED Using the QDCL 42
2.4. Electrical Characteristics 44
2.5. EL Spectra and Color Coordinates 51
2.6. Hybrid LED Demonstration 57
2.7. Summary 59
Chapter 3. QD-Organic Hybrid LEDs Using an Organic Blue Common Layer 60
3.1. Experimental Details 61
3.1.1. Materials 61
3.1.2. Device Fabrication 64
3.1.3. Characterization 65
3.2. Material Selection and Structure Engineering 66
3.3. Fabrication Scheme of Hybrid LED Using the BCL 70
3.4. Electrical Characteristics 72
3.5. EL Spectra and Color Coordinates 78
3.6. Analysis on the Origin of Performance Enhancement 82
3.7. Hybrid LED Demonstration 86
3.8. Summary 88
Chapter 4. Conclusion 89
Bibliography 92
Publication 98
초록 102
Table 2.1. Summary of EL characteristics of devices. 54
Table 2.2. CIE color coordinates of OLED without or with the QDCL obtained at 10 mA/cm². 56
Table 3.1. Summary of device performances. 81
Table 3.2. Fitting parameters of the TREL decay responses of devices. 85
Figure 1.1. Various applications of OLED displays. 15
Figure 1.2. (a) Schematics of QD and (b) QDs dispersed in solvents with different sizes. 16
Figure 1.3. Various display applications demanding high-resolution. 18
Figure 1.4. Full-color device configuration using conventional QLEDs or OLEDs. 19
Figure 1.5. Previously introduced QLED patterning techniques: (a) contact printing [42], (b) transfer printing [43], (c) photolithography [44], and (d) inkjet printing. 20
Figure 1.6. Schematic illustration of the FMM on a steel frame. 22
Figure 1.7. Comparison of pixel array density of full-color OLED display patterned with FMMs (a) before and (b) after adopting the red common layer. 25
Figure 1.8. Comparison of sub-pixel sizes of full-color OLED display patterned with FMMs (a) before and (b) after adopting the red common layer. 25
Figure 2.1. The CIE standard color matching functions. 37
Figure 2.2. The TEM images of (a) ZMO NPs and (b) InP/ZnSe/ZnS red QDs, and the chemical structures of (c) CBP, (d) Ir(ppy) 3, and (e) BCzVBi. 39
Figure 2.3. The PL spectra of light-emitting materials. 41
Figure 2.4. Energy level diagram of the materials used in this work. 41
Figure 2.5. Schematic illustrates of full-color hybrid LED fabrication process adopting QDCL structure. This full-color device consists of red QLED and green... 43
Figure 2.6. The cross-sectional TEM images of the red QLED, and green and blue OLEDs: (a) device R, (b) GH, and (c) BH. 46
Figure 2.7. The electrical performances of the devices with or without the HBL: (a) current density-voltage, (b) luminance-voltage, and (c) EQE-current density. 48
Figure 2.8. (a) Current density-voltage characteristics of the HODs of green- and blue-emitting OLEDs with or without the HBL. (b) A schematic illustration of hole... 49
Figure 2.9. Current density-voltage characteristics of the EODs of green- and blue- emitting OLEDs with or without the QDCL. 50
Figure 2.10. The EL spectra of (a) green-emitting and (b) blue-emitting OLEDs with or without the HBL. The spectrum of red-emitting QLED is plotted together for... 52
Figure 2.11. The EL spectra, normalized EL spectra, and corresponding CIE color coordinates of device GH ((a), (c), and (e)) and BH ((b), (d), and (f)) at various... 53
Figure 2.12. (a) The EL spectra of green- and blue-emitting OLEDs without the QDCL, and device R. (b) The CIE color coordinates, and color space consist of... 55
Figure 2.13. Scheme for full-color hybrid LED demonstration using QDCL architecture in a (a) ITO-patterned glass substrate: deposition of (b) ETL, (c) QDCL,... 58
Figure 2.14. A photograph of QD-organic hybrid LED demonstrated in a single substrate adopting QDCL. Device was driven at 1 mA/cm² . 58
Figure 3.1. TEM images of the (a) CdSe/CdZnS and (b) CdZnSeS@ZnS QDs, and the chemical structure of (c) BCBP (host) and (d) BCzVBi (dopant). 67
Figure 3.2. The absorption and PL spectra of diluted QD solution with the PL spectrum of BCzVBi dissolved in toluene. 69
Figure 3.3. The energy level diagram of used materials in this chapter. 69
Figure 3.4. A schematic illustration of the fabrication process for the full-color hybrid device with red and green-emitting QLED sub-pixels and a blue-emitting OLED sub-pixel. 71
Figure 3.5. The cross-sectional TEM images of the red and green QLEDs, and blue OLED: (a) device RC, (b) GC, and (c) B. 73
Figure 3.6. The current density-voltage characteristics of (a) QLEDs and OLED, and EODs with or without the BCL containing (b) red and (c) green QDs. 75
Figure 3.7. (a) The luminance-voltage and (b) EQE-current density characteristics of the device without or with the BCL. 77
Figure 3.8. (a) The EL spectra of the QLEDs and OLED observed at 10 mA/cm² and (b) corresponding CIE coordinates and color space covered by them. The solid and... 79
Figure 3.9. The EL spectra, normalized EL spectra, and corresponding CIE color coordinates of device RC ((a), (c), and (e)) and GC ((b), (d), and (f)) at various... 80
Figure 3.10. TREL decay characteristics of (i) red-emitting QLEDs (device R and RC) at 633 nm and (ii) green-emitting QLEDs (device G and GC) at 527 nm. (b)... 84
Figure 3.11. (a) EL spectra of the device GC' obtained at 10 mA/cm², (b) the TREL decay characteristics of the device B and GC' observed at 449 nm, and (c) a... 84
Figure 3.12. Scheme for full-color hybrid LED demonstration using BCL architecture in a (a) ITO-patterned glass substrate: deposition of (b) HIL/HTL, (c)... 87
Figure 3.13. A photograph of QD-organic hybrid LED demonstrated in a single substrate adopting BCL. Device was driven at 1 mA/cm². 87