OLED Display Fundamentals and Applications

Takatoshi Tsujimura is General Manager of the Konica Minolta Inc. He received an SID award for the development of the world's largest 20-inch OLED prototype and also received SID Fellow award for the development of 100% NTSC white + color filter technology. He has worked for Kodak and IBM and is an SID executive. Dr. Tsujimura was selected as one of the "10 best engineers/researchers in the 10 best Japanese companies" by Nikkei Electronics magazine.

• About the Author xiPreface xiiiSeries Editor’s Foreword to the Second Edition xv1 Introduction 1References 52 OLED Devices 72.1 OLED Definition 72.1.1 History of OLED Research and Development 72.1.2 Luminescent Effects in Nature 82.1.3 Difference Between OLED, LED, and Inorganic ELs 112.1.3.1 Inorganic EL 112.1.3.2 LED 112.2 Basic Device Structure 122.3 Basic Light Emission Mechanism 142.3.1 Potential Energy of Molecules 142.3.2 Highest Occupied and Lowest Unoccupied Molecular Orbitals (HOMO and LUMO) 152.3.3 Configuration of Two Electrons 172.3.4 Spin Function 202.3.5 Singlet and Triplet Excitons 202.3.6 Charge Injection from Electrodes 242.3.6.1 Charge Injection by Schottky Thermionic Emission 252.3.6.2 Tunneling Injection 282.3.6.3 Vacuum-Level Shift 282.3.7 Charge Transfer and Recombination 292.3.7.1 Charge Transfer Behavior 292.3.7.2 Space-Charge-Limited Current 292.3.7.3 Poole–Frenkel conduction 322.3.7.4 Recombination and Generation of Excitons 332.4 Emission Efficiency 362.4.1 Internal/External Quantum Efficiency 362.4.2 Energy Conversion and Quenching 372.4.2.1 Internal Conversion 372.4.2.2 Intersystem Crossing 372.4.2.3 Doping 382.4.2.4 Quenching 402.4.3 Outcoupling Efficiency of OLED Display 422.4.3.1 Light Output Distribution 422.4.3.2 Snell’s Law and Critical Angle 432.4.3.3 Loss Due to Light Extraction 442.4.3.4 Performance Enhancement by Molecular Alignment 452.5 Lifetime and Image Burning 462.5.1 Lifetime Definitions 462.5.2 Degradation Analysis and Design Optimization 472.5.3 Degradation Measurement and Mechanisms 502.5.3.1 Acceleration Factor and Temperature Contribution 502.5.3.2 Degradation Mechanism Variation 502.6 Technologies to Enhance the Device Performance 512.6.1 Thermally Activated Delayed Fluorescence 512.6.2 Other Types of Excited States 532.6.2.1 Excimer and Exciplex 532.6.2.2 Charge-Transfer Complex 532.6.3 Charge Generation Layer 54References 563 OLED Manufacturing Process 613.1 Material Preparation 613.1.1 Basic Material Properties 613.1.1.1 Hole Injection Material 613.1.1.2 Hole Transportation Material 623.1.1.3 Emission Layer Material 623.1.1.4 Electron Transportation Material and Charge Blocking Material 633.1.2 Purification Process 673.2 Evaporation Process 683.2.1 Principle 683.2.2 Evaporation Sources 723.2.2.1 Resistive Heating Method 723.2.2.2 Electron Beam Evaporation 753.2.2.3 Monitoring Thickness Using a Quartz Oscillator 763.3 Encapsulation 793.3.1 Dark Spot and Edge Growth Defects 793.3.2 Light Emission from the Bottom and Top of the OLED Device 803.3.3 Bottom Emission and perimeter sealing 813.3.4 Top Emission 823.3.5 Encapsulation Technologies and Measurement 833.3.5.1 Thin-Film Encapsulation 843.3.5.2 Face Sealing Encapsulation 873.3.5.3 Frit Encapsulation 883.3.5.4 WVTR Measurement 883.4 Problem Analysis 913.4.1 Ionization Potential Measurement 913.4.2 Electron Affinity Measurement 923.4.3 HPLC Analysis 933.4.4 Cyclic Voltammetry 94References 964 OLED Display Module 994.1 Comparison Between OLED and LCD Modules 994.2 Basic Display Design and Related Characteristics 1014.2.1 Luminous Intensity, Luminance, and Illuminance 1014.2.1.1 Luminous Intensity 1014.2.1.2 Luminance 1024.2.1.3 Illuminance 1034.2.1.4 Metrics Summary 1044.2.1.5 Helmholtz–Kohlrausch Effect 1064.2.2 OLED Current Efficiencies and Power Efficacies 1064.2.3 Color Reproduction 1094.2.4 Uniform Color Space 1154.2.5 White Point Determination 1164.2.6 Color Boost 1194.2.7 Viewing Condition 1204.3 Passive-Matrix OLED Display 1214.3.1 Structure 1214.3.2 Pixel Driving 1224.4 Active-Matrix OLED Display 1254.4.1 OLED Module Components 1254.4.2 Two-Transistor One-Capacitor (2T1C) Driving Circuit 1274.4.3 Ambient Performance 1364.4.3.1 Living Room Contrast Ratio 1364.4.3.2 Chroma Reduction Due to Ambient Light 1374.4.4 Subpixel Rendering 138References 1395 OLED Color Patterning Technologies 1435.1 Color-Patterning Technologies 1435.1.1 Shadow Mask Patterning 1435.1.1.1 Shadow Mask Process 1435.1.1.2 Blue Common Layer 1465.1.1.3 Polychromatic Pixel 1475.1.2 White+Color Filter Patterning 1485.1.3 Color Conversion Medium (CCM) Patterning 1495.1.4 Laser-Induced Thermal Imaging (LITI) Method 1495.1.5 Radiation-Induced Sublimation Transfer (RIST) Method 1515.1.6 Dual-Plate OLED Display (DOD) Method 1525.1.7 Other Methods 1535.2 Solution-Processed Materials and Technologies 1535.3 Next-Generation OLED Manufacturing Tools 1585.3.1 Vapor Injection Source Technology (VIST) Deposition 1585.3.2 Hot-Wall Method 1635.3.3 Organic Vapor-Phase Deposition (OVPD) Method 164References 1656 TFT and Driving for Active-Matrix Display 1676.1 TFT Structure 1676.2 TFT Process 1696.2.1 Low-Temperature Polysilicon Process Overview 1696.2.2 Thin-Film Formation 1726.2.3 Patterning Technique 1736.2.4 Excimer Laser Crystallization 1776.3 MOSFET Basics 1806.4 LTPS-TFT-Driven OLED Display Design 1836.4.1 OFF Current 1836.4.2 Driver TFT Size Restriction 1846.4.3 Restriction Due to Voltage Drop 1856.4.4 LTPS-TFT Pixel Compensation Circuit 1906.4.4.1 Voltage Programming 1906.4.4.2 Current Programming 1926.4.4.3 External Compensation Method 1936.4.4.4 Digital Driving 1946.4.5 Circuit Integration by LTPS-TFT 1976.5 TFT Technologies for OLED Displays 2006.5.1 Selective Annealing Method 2006.5.1.1 Sequential Lateral Solidification (SLS) Method 2006.5.1.2 Selective Annealing by Microlens Array 2006.5.2 Microcrystalline and Superamorphous Silicon 2026.5.3 Solid-Phase Crystallization 2056.5.3.1 MIC and MILC Methods 2056.5.3.2 AMFC Method 2056.5.4 Oxide Semiconductors 207References 2107 OLED Television Applications 2157.1 Performance Target 2157.2 Scalability Concept 2177.2.1 Relationship between Defect Density and Production Yield 2177.2.1.1 Purpose of Yield Simulation 2177.2.1.2 Defective Pixel Number Estimation Using the Poisson Equation 2177.2.2 Scalable Technology 2177.2.2.1 Scalability 2187.3 Murdoch’s Algorithm to Achieve Low Power and Wide Color Gamut 2197.3.1 A Method for Achieving Both Low Power and Wide Color Gamut 2197.3.2 RGBW Driving Algorithm 2217.4 An Approach to Achieve 100% NTSC Color Gamut With Low Power Consumption Using White + Color Filter 2247.4.1 Consideration of Performance Difference between W-RGB and W-RGBW Method 2247.4.1.1 Issues of White+Color Filter Method for Large Displays 2247.4.1.2 Analysis of W-RGBW Approach to Circumvent Its Trade-off Situation 2247.4.1.3 Design of a Prototype to Demonstrate That Low Power Consumption Can Be Achieved with Large Color Gamut 2297.4.1.4 Product-Level Performance Demonstration by the Combination of Scalable Technologies 230References 2338 New OLED Applications 2358.1 Flexible Display/Wearable Displays 2358.1.1 Flexible Display Applications 2358.1.2 Flexible Display Substrates 2358.1.3 Laser Liftoff Process 2368.1.4 Barrier Technology for Flexible Displays 2408.1.5 Organic TFTs for Flexible Displays 2418.1.5.1 Organic Semiconductor Materials 2428.1.5.2 Organic TFT Device Structure and Processing 2438.1.5.3 Organic TFT Characteristics 2458.2 Transparent Displays 2458.3 Tiled Display 2478.3.1 Passive-Matrix Tiling 2478.3.2 Active-Matrix Tiling 248References 2529 OLED Lighting 2559.1 Performance Improvement of OLED Lighting 2559.2 Color Rendering Index 2579.3 OLED Lighting Requirement 2599.3.1 Correlated Color Temperature (CCT) 2609.3.2 Other Requirements 2629.4 Light Extraction Enhancement of OLED Lighting 2629.4.1 Various Light Absorption Mechanisms 2629.4.2 Microlens Array Structure 2669.4.3 Diffusion Structure 2669.4.4 Diffraction Structure 2689.4.5 Reduction of Plasmon Absorption 2689.4.5.1 Plasmonic Loss Mechanism 2689.5 Color Tunable OLED Lighting 2699.6 OLED Lighting Design 2729.6.1 Resistance Reduction 2729.6.2 Current Reduction 2729.7 Roll-to-Roll OLED Lighting Manufacturing 273References 275Appendix 277Index 281