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Preface xi 1 History and Introduction of QDs and QDLEDs 1
1.1 Preparation Route of Quantum Dots 3
1.2 Light-Emitting Characteristics of Quantum Dots 3
1.2.1 Particle Size and Emission Color 3
1.2.2 Quantum Dot Optical Property 4
1.2.2.1 Quantum Surface Effect 4
1.2.2.2 Quantum Size Effect 4
1.2.2.3 Quantum Confinement Effect 5
1.2.2.4 Quantum Tunnelling Effect 5
1.2.2.5 Quantum Optical Properties 6
1.2.3 Core-Shell Structure of QDs 8
1.2.4 Continuously Gradated Core-Shell Structure of QDs (cg-QDs) 12
1.2.5 Typical QDs Materials 14
1.2.5.1 II-VI Semiconductor QDs 16
1.2.5.2 IV-VI Semiconductor QDs 17
1.2.5.3 II 3 -v 2 Semiconductor QDs 17
1.2.5.4 Ternary I-III-VI 2 Chalcopyrite Semiconductor QDs 17
1.2.5.5 Single Element-Based Semiconductor QDs 17
1.3 Application of Quantum Dots on Display Devices 18
1.3.1 The Basic Structure of QDLED 18
1.3.2 Main Factors Affecting QDLED Light Emission 19
1.3.2.1 Auger Recombination (AR) 19
1.3.2.2 Fluorescence Resonance Energy Transfer 21
1.3.2.3 Surface Traps and Field Emission Burst 22
1.3.3 History of QDLED Development 22
1.4 Conclusion and Remarks 27 References 28 2 Colloidal Semiconductor Quantum Dot LED Structure and Principles 33
2.1 Basic Concepts 33
2.1.1 Color Purity 33
2.1.2 Solution Processability 34
2.1.3 Stability 35
2.1.4 Surface States of Quantum Dots 36
2.1.5 Energy Levels and Energy Bands 36
2.1.6 Metals, Semiconductors, and Insulators 37
2.1.7 Electrons and Holes 38
2.1.8 Fermi Distribution Function and Fermi Energy Level 39
2.1.9 Schottky Barrier 39
2.1.10 Energy Level Alignment 40
2.2 Colloidal Quantum Dot Light-Emitting Devices 40
2.2.1 The Basic Structure of QDLED 41
2.2.2 The Working Principle of QDLED 43
2.2.3 Operating Parameters of QDLED 44
2.2.3.1 Turn-on Voltage 44
2.2.3.2 Luminous Brightness 44
2.2.3.3 Luminous Efficiency 44
2.2.3.4 Luminescence Color 45
2.2.3.5 Luminous Lifetime 45
2.2.3.6 QDLED Device Fabrication Process 48 References 48 3 Synthesis and Characterization of Colloidal Semiconductor Quantum Dot Materials 51
3.1 Background 51
3.2 Synthesis and Post-processing of Colloidal Quantum Dots 53
3.2.1 Direct Heating Method and Hot Injection Synthesis Method 53
3.2.1.1 Hot-Injection Method 54
3.2.1.2 Direct Heating Method 55
3.2.2 Precursor Chemistry 56
3.2.3 Ligating and Non-ligating Solvents 56
3.2.4 Mechanism of Nucleation and Growth of Colloidal Quantum Dots 58
3.2.5 Size Distribution Focus and Size Distribution Scatter 59
3.2.6 Crystalline Species-Mediated Growth and Orientation of Nanocrystals Attachment Growth 60
3.2.7 Synthesis Methods and Band Gap Regulation Engineering of Nuclear-Shell Quantum Dots 61
3.2.7.1 Non-alloyed Core-Shell Quantum Dots 63
3.2.7.2 Alloy Core-Shell Quantum Dots 64
3.2.8 Surface Chemistry of Colloidal Quantum Dots 65
3.2.8.1 Covalent Bond Classification Method 65
3.2.8.2 Entropic Ligands 66
3.3 Material Characterization 66
3.3.1 Ultraviolet-Visible (UV-Vis) Absorption and Fluorescence Spectra 67
3.3.2 Nuclear Magnetic Resonance Spectroscopy 69
3.3.3 Fourier Transform Infrared Spectroscopy (FTIR) 71
3.3.4 X-Ray Photoelectron Spectroscopy (XPS) 74
3.3.5 Transmission Electron Microscopy 76
3.3.6 Small-Angle X-Ray Scattering and Wide-Angle X-Ray Scattering 76
3.3.7 X-Ray Diffractometer 77
3.3.8 X-Ray Absorption Fine Structure Spectra 78
3.3.9 Measurement of Fluorescence Quantum Yield 79
3.4 Conclusion and Outlook 79 References 81 4 Red Quantum Dot Light-Emitting Diodes 87
4.1 Background 87
4.2 Red Light Quantum Dot Materials 88
4.2.1 Materials 89
4.2.2 Quantum Dot Structure Design and Optimization 90
4.2.3 Surface Ligands 91
4.2.4 Core-Shell Structure 94
4.2.5 Alloy Core-Shell Structure 96
4.3 Red QDLED Devices 97
4.3.1 Red QDLED Device Architecture Development 97
4.3.2 Common Device Structures 99
4.4 Conclusion and Outlook 102 References 104 5 Green Quantum Dot LED Materials and Devices 111
5.1 Background 111
5.2 Commonly Used Luminescent Layer Materials in Green QDLEDs 120
5.2.1 Discrete Core/Shell Quantum Dots 120
5.2.2 Alloyed Core/Shell Quantum Dots 121
5.2.3 Core/Multilayer Shell Quantum Dots 121
5.3 Development of Device Structures for Green QDLEDs 122
5.4 Factors Affecting the Performance of Green QDLEDs 125
5.4.1 QD Ligand Effect 126
5.4.2 QD Core/Shell Structure 129
5.4.3 Optimization of the Device Structure 130
5.4.4 Other Strategies to Improve Device Performance 132
5.5 Summary and Outlook 134 References 135 6 Blue Quantum Dot Light-Emitting Diodes 141
6.1 Introduction 141
6.2 Blue Quantum Dot Luminescent Materials 143
6.2.1 Blue Quantum Dots Containing Cadmium 145
6.2.2 Cadmium-Free Quantum Dots 149
6.2.2.1 Quantum Dots Based on InP 149
6.2.2.2 Quantum Dots Based on ZnSe 151
6.2.2.3 Quantum Dots Based on Cu 153
6.2.2.4 Quantum Dots Based on AlSb 155
6.3 Optimization of Charge Transport Layer (CTL) 155
6.3.1 Hole Transport Layer 156
6.3.2 Electron Transport Layer 161
6.4 Device Structure 164
6.5 Summary 166 References 168 7 Near-Infrared Quantum Dots (NIR QDs) 173
7.1 Introduction of Near-Infrared Quantum Dots 173
7.2 Near-Infrared Quantum Dot Materials 174
7.2.1 Chalcogenide Lead Quantum Dots 176
7.2.2 Chalcogenide Cadmium Quantum Dots 177
7.2.3 Silicon Quantum Dots 178
7.3 Optimization of Near-Infrared Quantum Dot Materials 179
7.3.1 Regulation of Near-Infrared Quantum Dots by Ligand Engineering 179
7.3.2 Control of Near-Infrared Quantum Dots by Core/Shell Structure 180
7.3.3 Quantum Dots in the Matrix 181
7.4 Summary and Prospect 182 References 183 8 White QDLED 187
8.1 Generation of White Light 187
8.2 Quantum Dots for White LEDs 188
8.2.1 Yellow-Blue Composite White Light Quantum Dots 189
8.2.1.1 Cadmium-Containing Yellow Light Quantum Dots 189
8.2.1.2 Cadmium-Free Yellow Light Quantum Dots 189
8.2.2 Three-Base Color Quantum Dot Composite 193
8.2.3 Quantum Dots with Direct White Light Emission 197
8.3 Summary Outlook 200 References 203 9 Non-Cadmium Quantum Dot Light-Emitting Materials and Devices 207
9.1 Introduction 207
9.2 Quantum Dots and QDLED 208
9.2.1 InP 208
9.2.2 ZnSe 215
9.2.3 I-iii-vi 218
9.3 Methods for Optimizing QDLED Performance 222
9.3.1 Ligand Engineering 223
9.3.2 Shell Engineering 224
9.3.3 QDLED Device Structure Optimization 225
9.4 Summary and Outlook 227 References 230 10 AC-Driven Quantum Dot Light-Emitting Diodes 235
10.1 Principle of Luminescence of DC and AC-Driven QDLEDs 236
10.2 Mechanism of Double-Emission Tandem Structure of AC QDLEDs 239
10.2.1 Field-Generated AC QDLEDs 240
10.2.2 Half-Field to Half-Injection AC QDLEDs 242
10.2.3 AC/DC Dual Drive Mode QDLEDs 244
10.3 Optimization Strategies for AC QDLEDs 245
10.3.1 Optimization of the Field-Induced AC QDLED 247
10.3.1.1 Dielectric Layer Optimization 248
10.3.1.2 Quantum Dot Layer Optimization 250
10.3.2 Optimization of Half-Field-Driven Half-Injected AC QDLEDs 251
10.3.2.1 Charge Generation Layer Optimization 254
10.3.2.2 Tandem Structure 254
10.3.2.3 AC/DC Dual Drive Mode QDLED Optimization 255
10.3.3 Conclusion and Future Direction of AC-QDLED 256 References 257 11 Stability Study and Decay Mechanism of Quantum Dot Light-Emitting Diodes 259
11.1 Quantum Dot Light-Emitting Diode Stability Research Status 259
11.2 Factors Affecting the Stability of Quantum Dot Light-Emitting Diodes 261
11.2.1 Quantum Dot Light-Emitting Layer 261
11.2.2 Hole Transport Layer 263
11.2.3 Electronic Transport Layer 265
11.2.4 Other Functional Layers 267
11.3 Quantum Dot Light-Emitting Diode Efficiency Decay Mechanism 268
11.4 Aging Mechanisms of QDLEDs 271
11.4.1 Positive Aging 272
11.4.2 Negative Aging 273
11.4.3 Electron Transport Layer 274
11.4.4 Hole Transport Layer 275
11.4.5 QDs Layer 276
11.5 Characterization Technologies for QDLEDs 278
11.5.1 Transient Electroluminescence 279
11.5.2 Electro-Absorption (EA) Spectroscopy 281
11.5.3 In-Situ EL-PL Measurement 282
11.5.4 Differential Absorption Spectroscopy 283
11.5.5 Displacement Current Measurement DCM Technology 285
11.6 Outlook 286 References 287 12 Electron/Hole Injection and Transport Materials in Quantum Dot Light-Emitting Diodes 291
12.1 Introduction 291
12.2 Charge-Transport Mechanisms 292
12.3 Electron Transport Materials (ETMs) for QDLED 293
12.3.1 Metal-Doped ETMs 293
12.3.2 Metal Salt-Doped ETMs 296
12.3.3 Design of Composite Materials ETMs 296
12.3.4 Polymer-Modified ETMs 296
12.3.5 Inorganic Organic Hybrid ETMs 296
12.3.6 Double-Stacked ETMs 297
12.4 Electron Injection Materials for QDLED 299
12.5 Hole Transport Materials for QDLED 301
12.5.1 Doping of HTMs 305