Oled Displays and Lighting

Explains the fundamentals and practical applications of flat and flexible OLEDs for displays and lighting

Organic light-emitting diodes (OLEDs) have emerged as the leading technology for the new display and lighting market. OLEDs are solid-state devices composed of thin films of organic molecules that create light with the application of electricity. OLEDs can provide brighter, crisper displays on electronic devices and use less power than conventional light-emitting diodes (LEDs) or liquid crystal displays (LCDs) used today. This book covers both the fundamentals and practical applications of flat and flexible OLEDs.

Key features:

• Covers all of the aspects necessary to the design and manufacturing of OLED displays and lighting.
• Explains the fundamental basic technologies and also related technologies which might contribute to the next innovation in the industry.
• Provides several indications for future innovation in the OLED industry.
• Includes coverage of OLED vacuum deposition type and solution type materials.

The book is essential reading for early career engineers developing OLED devices and OLED related technologies in industrial companies, such as OLED device fabrication companies.

Preface ix

1 History of OLEDs 1

References 10

2 Fundamentals of OLEDs 12

2.1 Principle of the OLED 12

2.2 Fundamental Structure of the OLED 14

2.3 Features of the OLED 15

3 Light Emission Mechanism 17

3.1 Fluorescent OLEDs 17

3.2 Phosphorescent OLEDs 19

3.3 Thermally Activated Delayed Fluorescent OLEDs 21

3.4 Energy Diagram 21

3.5 Light Emission Efficiency 23

References 24

4 OLED Materials 25

4.1 Types of OLED Materials 26

4.2 Anode Materials 27

4.3 Evaporated Organic Materials (Small Molecular Materials) 29

4.3.1 Hole Injection Materials 29

4.3.2 Hole Transport Materials 32

4.3.3 Emitting Materials and Host Materials in Fluorescent Emission Layer 33

4.3.4 Emitting Materials and Host Materials in Phosphorescent Emission Layer 34

4.3.5 Emitting Materials and Host Materials in TADF Emission Layers 42

4.3.6 Electron Transport Materials 43

4.3.7 Electron Injection Materials and Cathodes 45

4.3.8 Charge-Carrier and Exciton Blocking Materials 46

4.3.9 N-Dope and P-Dope Materials 49

4.4 Solution Materials 50

4.4.1 Polymer Materials 50

4.4.2 Dendrimers 61

4.4.3 Small Molecules 69

4.5 Molecular Orientation of Organic Materials 70

References 71

5 OLED Devices 75

5.1 Bottom Emission, Top Emission, and Transparent Types 75

5.2 Normal and Inverted Structures 79

5.3 White OLEDs 81

5.4 Full-Color Technology 84

5.4.1 RGB-Side-by-Side 87

5.4.2 White + CF 87

5.4.3 Blue Emission with Color Changing Medium (CCM) 88

5.5 Micro-Cavity Structure 89

5.6 Multi-Photon OLED 91

5.7 Encapsulation 94

5.7.1 Thin Film Encapsulation 99

5.7.2 Desiccant Technologies 100

References 100

6 OLED Fabrication Process 103

6.1 Vacuum Evaporation Process 103

6.1.1 Mask Deposition 104

6.1.2 Three Types of Evaporation Methods 104

6.1.3 Ultra-High Vacuum 105

6.2 Wet Processes 107

6.3 Laser Processes 114

References 115

7 Performance of OLEDs 117

7.1 Characteristics of OLEDs 117

7.2 Lifetime 120

7.2.1 Storage Lifetime 121

7.2.2 Driving Lifetime 121

7.3 Temperature Measurement of OLED Devices 124

References 126

8 OLED Display 127

8.1 Features of OLED Displays 128

8.2 Types of OLED Displays 128

8.3 Passive-Matrix OLED Display 130

8.4 Active-Matrix OLED Display 132

8.4.1 TFT Circuit Technologies 133

8.4.2 TFT Device Technologies 137

8.4.3 Commercialized and Prototype AM-OLED Displays 139

References 144

9 OLED Lighting 147

9.1 Appearance of OLED Lighting 147

9.2 Features of OLED Lighting 148

9.3 Fundamental Technologies of OLED Lighting 152

9.4 Light Extraction Enhancement Technologies 154

9.5 Performance of OLED Lighting 159

9.6 Color Tunable OLED Lighting 159

9.7 Application of OLED Lighting – Products and Prototypes 161

References 164

10 Flexible OLEDs 166

10.1 Early Studies of Flexible OLEDs 166

10.2 Flexible Substrates 167

10.2.1 Ultra-Thin Glass 168

10.2.2 Stainless Steel Foil 171

10.2.3 Plastic Films 172

10.3 Flexible OLED Displays 174

10.3.1 Flexible OLED Displays on Ultra-Thin Glass 176

10.3.2 Flexible OLED Displays on Stainless Steel Foil 176

10.3.3 Flexible OLED Displays on Plastic Film 177

10.4 Flexible OLED Lighting 181

10.4.1 Flexible OLED Lighting on Ultra-Thin Glass 182

10.4.2 Flexible OLED Lighting on Stainless Steel Foil 184

10.4.3 Flexible OLED Lighting on Plastic Films 184

10.5 Toward the Flexible 186

References 186

11 New Technologies 189

11.1 Non-ITO Transparent Electrodes 189

11.1.1 Conducting Polymer 190

11.1.2 Stacked Layer Using Ag 194

11.1.3 Silver Nanowire (AgNW) 195

11.1.4 Carbon Nanotube (CNT) 196

11.2 Organic TFT 197

11.3 Wet-Processed TFT 198

11.4 Novel Wet-Processed or Printed OLED 201

11.5 Roll-to-Roll Equipment Technologies 203

11.6 Quantum Dot 204

References 206

Index 209

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