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Principles and Applications of Organic Light Emitting Diodes (OLEDs)

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Contents

1 Luminescence: Basic Principles and Applications

1.1 Introduction

1.2 Light

1.3 Mechanism of Light Emission

1.3.1 Incandescence

1.3.1.1 Incandescence Sources

1.3.2 Luminescence

1.3.2.1 Luminescence in Transition Metal Ions

1.3.2.2 Luminescence in Rare Earth Metal Complexes

Origin of Luminescence in Lanthanides: Screening Effect

The Antenna Effect: Sensitized Emission

Ligand and Lanthanide Ion Excitation: Jablonski Diagram

1.3.2.3 Luminescence in Actinides

1.3.2.4 Luminescence in Heavy Metals

1.3.2.5 Luminescence in Electron–Hole Centers

1.3.2.6 Luminescence in Extended Defects

1.3.3 Classification of Luminescence Based on Time Lag

1.3.3.1 Fluorescence

1.3.3.2 Phosphorescence

1.3.4 Classification of Luminescence Based on the Source of Excitation

1.3.5 Luminescent Sources

1.4 Terminology Associated with Luminescence

1.5 Realm of Luminescent Materials

1.5.1 Lamp Phosphor

1.5.2 Lasers

1.5.3 Nanophosphors

1.5.4 Super Luminescent Diodes

1.5.5 Light-Emitting Devices

1.5.6 Organic Light-Emitting Diodes

1.5.7 Solid-State Lighting

1.5.8 Displays

1.5.8.1 LED Displays

1.5.8.2 Organic Light-Emitting Diode Displays

1.6 Conclusion

References

2 Luminescence in Organic Semiconductors

2.1 Introduction

2.2 Organic Compounds

2.2.1 Classification of Organic Compounds

2.2.1.1 Based on the Presence of Heteroatoms

2.2.1.2 Based on Size

Small Molecules

Polymers

2.2.1.3 Based on Functional Group

2.2.2 Characterization

2.2.3 Properties

2.3 Organic Semiconductors

2.3.1 Charge Transport in Organic Semiconductors

2.4 HOMO and LUMO in Organic Semiconductors

2.5 Charge Transport in Organic Materials and Devices

2.5.1 Band-Transport Mechanism

2.5.2 Hopping-Transport Mechanism

2.5.3 Tunneling-Transport Mechanism

2.6 Luminescent Organic Materials: An Overview

2.6.1 Fluorescent Materials

2.6.2 Phosphorescent Materials

2.7 Organic verses Inorganic Luminescent Materials

2.8 Conclusions

References

3 Evolution of Luminescent Materials for Organic Light-Emitting Diodes

3.1 Introduction

3.2 Red-Light-Emitting Materials for OLEDs

3.3 Green-Light Emitting Materials for OLEDs

3.4 Blue-Light-Emitting Materials and OLEDs

3.5 White-Light-Emitting Materials and OLEDs

3.6 Conclusions

References

4 Artificial Lighting: Origin—Impact and Future Perspectives

4.1 Introduction

4.2 Light

4.3 Lighting

4.4 Classification of Lighting

4.4.1 Ambient Lighting

4.4.2 Task Lighting

4.4.3 Accent Lighting

4.5 Artificial Lighting: Origin and Impact

4.6 Lighting Terminology

4.7 Light Sources

4.7.1 Natural Light Sources

4.7.2 Artificial Light Sources

4.8 Evaluating Quality of White Light

4.8.1 CIE Coordinates

4.8.2 Color Rendering Index

4.8.3 Color Correlated Temperature

4.9 Spectral Distribution of Different Light Sources

4.10 Electrically Powered Incandescent Lamps

4.10.1 Incandescent Lamps

4.10.2 Halogen Lamps

4.11 Electrically Powered Luminescent Lamps

4.11.1 Electron-Stimulated Luminescence Lamps

4.11.2 Discharge Lamps

4.11.2.1 High-Intensity Discharge Lamps

4.11.2.2 Metal-Halide Lamps

4.11.2.3 Mercury Vapor Lamps

4.11.2.4 Sodium Lamps

4.11.2.5 Linear Fluorescent Lamps

4.11.2.6 Compact Fluorescent Lamps

4.12 Solid-State Lighting

4.12.1 LED Lamps

4.12.1.1 Various Approaches to Obtaining White Light from LEDs

4.12.1.2 LED Filament Bulb

4.12.2 Organic Light-Emitting Diode Lamps

4.13 Future Perspectives

References

5 Solid-State Lighting

5.1 Introduction

5.2 Solid-State Lighting: A Brief History

5.3 Requisite of Solid-State Lighting

5.4 Solid-State Lighting With LEDs

5.4.1 Strategies for Solid-State Lighting With LEDs

5.4.2 Overview of LED Types

5.4.2.1 Discrete LEDs

5.4.2.2 Single-Color LEDs

5.4.2.3 Bicolor LEDs

5.4.2.4 Tricolor LEDs

5.4.2.5 LED Clusters and Lights

5.4.2.6 Alphanumeric Displays

5.4.3 Physical Function

5.4.4 LED Configurations and Manufacturing

5.4.5 LED Materials

5.4.6 Advantages

5.4.7 Key Challenges

5.4.8 Applications

5.5 CSL With OLEDs: Future Lighting Sources

5.5.1 Anatomy of OLEDs

5.5.2 Light-Emitting Mechanism

5.5.3 White-Light Generation

5.5.4 Advantages

5.5.5 Challenges

5.6 Advantages of Organic over Inorganic

5.7 LEDs Versus OLEDs

5.8 Conclusions

References

6 Organic Light-Emitting Diodes: The Future of Lighting Sources

6.1 Introduction

6.2 Organic Light-Emitting Diodes

6.3 Structure of OLEDs

6.4 Light-Emitting Mechanism of OLEDs

6.5 Materials for OLEDs

6.5.1 Substrate Materials

6.5.2 Anode

6.5.2.1 Fluorine-Doped Tin Oxide

6.5.2.2 Al-Doped Zinc Oxide

6.5.2.3 Transparent Conductive Oxides

6.5.3 Hole-Transport Materials

6.5.4 Hole-Injection Materials

6.5.5 Emissive Materials

6.5.5.1 Small Molecules

6.5.5.2 Polymers

6.5.5.3 Conjugated Dendrimers

6.5.6 Electron-Transport Materials

6.5.7 Electron-Injection Materials

6.5.8 Cathode Materials

6.6 Efficiency of OLEDs

6.6.1 Light-Extraction Efficiency in OLEDs

6.6.2 Power Efficiency

6.6.3 Recombination Efficiency

6.6.4 Luminescence Quantum Yield

6.6.5 Quantum Efficiency

6.6.6 Techniques to Improve the Efficiency of OLED Devices

6.7 Device Architectures

6.7.1 Top-Emitting OLEDs

6.7.2 Bottom-Emitting OLEDs

6.7.3 Transparent OLEDs

6.7.4 Stacked OLEDs

6.8 Advantages of OLEDs

6.9 OLED Research Hurdles and Challenges

6.10 OLED Applications

6.10.1 OLEDs as Versatile Light Sources

6.10.2 OLED Small Displays

6.10.3 OLED Large Displays

6.11 Conclusions

References

7 Review of Literature on Organic Light-Emitting Diode Devices

7.1 Introduction

7.2 Device Architecture

7.3 Review of Literature on Red OLEDs

7.4 Review of Literature on Green OLEDs

7.5 Review of Literature on Blue OLEDs

7.6 Review of Literature on White OLEDs

7.7 Conclusions

References

8 History of Organic Light-Emitting Diode Displays

8.1 Introduction

8.2 Displays

8.3 Display Device

8.3.1 Active-Display Devices

8.3.2 Passive-Display Devices

8.4 Display Terminology

8.5 Display Categorization

8.6 History of Display Technology

8.6.1 Cathode Ray Tubes

8.6.2 Vacuum Fluorescent Displays

8.6.3 Incandescent Filament Displays

8.6.4 Field Emission Displays

8.6.5 Surface-Conduction Electron-Emitter Displays

8.6.6 Liquid Crystal Displays

8.6.6.1 LCD Display Categories

8.6.6.2 LCD Technologies

Passive-Matrix LCD Displays

Active-Matrix LCD Displays

8.7 Plasma Display Panels

8.8 Light-Emitting Diode Displays

8.9 Organic Light-Emitting Diode Displays

8.9.1 OLED Display Types

8.10 Future Outlook

8.10.1 Ultrathin Displays

8.10.2 e-Paper

8.11 Conclusions

References

9 Organic Light-Emitting Diode Fabrication and Characterization Techniques

9.1 Introduction

9.2 OLED Fabrication

9.2.1 Doosan DND Fabrication System

9.2.1.1 General Specifications

9.2.1.2 OLED Fabrication Procedure

9.2.2 Fabrication on Prepatterned ITO Substrate

9.3 Fabrication Technologies

9.3.1 Vacuum Deposition Techniques

9.3.1.1 Vacuum Thermal Evaporation

Advantages of VTE

Disadvantages of VTE

9.3.1.2 Physical Vacuum Deposition

Advantages of PVD

Disadvantages of PVD

9.3.2 Solution Techniques

9.3.2.1 Spin-Coating

9.3.2.2 Ink-Jet Printing

9.3.2.3 Screenprinting

9.3.2.4 Laser-Induced Thermal Image

9.4 Characterization of OLEDs

9.4.1 V–I Characteristics

9.4.1.1 J–V–L Characteristics

9.4.2 EL Spectra

9.4.3 CIE Coordinates

9.4.4 Color Rendering Index

9.4.5 Correlated Color Temperature

9.4.6 Color Characteristics

9.4.7 Lifetime Measurements

9.5 Conclusions

References

10 Photo-Physical Properties of Some RGB Emissive Materials

10.1 Introduction

10.2 Experimental Details

10.2.1 Synthesis of RGB Phosphor

Synthesis Scheme of Eu Complexes

10.2.1.1 Synthesis Scheme of Organo Metallic Alq3 Complex

10.2.1.2 Synthesis Scheme of P-Acetyl biphenyl Cl-DPQ Organic Complex

10.2.2 R/G/B Phosphor in PMMA/PS Matrix

10.2.2.1 Preparation of Blended Films

10.2.3 Photo-Physical Properties of Red Light-Emitting Eu Complexes

10.2.3.1 Photo-Luminescence Spectra of Eu(TTA)3Phen

10.2.3.2 Photo-Luminescence Spectra of Eu(x) Y (1−x)(TTA)3Phen

10.2.3.3 Photo-Luminescence Spectra of Eu(x) Tb(1-x)(TTA)3Phen

10.2.3.4 Absorption Spectra of the Eu Complexes in PMMA Matrix

10.2.3.5 Energy Gap of Eu Complexes in PMMA Matrix

10.2.3.6 Photo-Luminescence Spectra of Eu (TTA)3 Phen in PMMA

10.2.3.7 Photo-Luminescence Spectra of Eu0.5Y0.5(TTA)3Phen in PMMA

10.2.3.8 Photo-Luminescence Spectra of Eu0.5Tb0.5 (TTA)3Phen in PMMA

10.2.3.9 Thermal Annealing Effect on Photo-Luminescence

10.2.3.10 Energy Gap of Solvated Eu Complexes

10.2.4 Photo-Physical Properties of Green Light-Emitting Alq3 Complex

10.2.4.1 Photo-Luminescence Spectra of Alq3

10.2.4.2 Absorption Spectra and Determination of Stokes Shift

10.2.4.3 Determination of Optical Energy-Band Gap in Chloroform

10.2.4.4 Photo-Luminescence Spectra of Alq3+PMMA

10.2.5 Photo-Physical Properties of BlueLight-Emitting P-Acetyl Biphenyl Cl-DPQ

10.2.5.1 UV-Visible Absorption Spectra

10.2.5.2 Determination of Band Gap in Various Solvents

10.2.5.3 Photo-Luminescence Spectra

10.2.5.4 Photo-Luminescence Spectra of P-Acetyl Biphenyl Cl-DPQ in PS Matrix

10.3 Conclusions

References

11 Future Prospects of Organic Light-Emitting Diodes

11.1 Introduction

11.2 Current Status of OLEDs

11.3 Future Prospects of OLEDs

11.3.1 Small Displays

11.3.2 Large Displays

11.3.3 Flexible Displays

11.4 OLEDs Research Trends in Past, Present, and Future

11.5 OLEDs: Future Perspectives

11.6 OLEDs in the Overall Lighting Sector

11.7 Industrial Challenges

11.7.1 Lifespan

11.7.2 Fabrication

11.7.3 Degradation Issues

11.7.4 Power-Conversion Efficiency

11.7.5 Improved Contrast Ratio

11.7.6 Scaling

11.7.7 Competition

11.8 Conclusions

References

Index

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