OLED Display Fundamentals and Applications E-Book

Takatoshi Tsujimura

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley Series in Display Technology
• Sprache: Englisch

Seitenzahl: 334

Veröffentlichungsjahr: 2017

Beschreibung

This new edition specifically addresses the most recent and relevant developments in the design and manufacture of OLED displays * Provides knowledge of OLED fundamentals and related technologies for applications such as displays and solid state lighting along with processing and manufacturing technologies * Serves as a reference for people engaged in OLED research, manufacturing, applications and marketing * Includes coverage of white + color filter technology, which has become industry standard technology for large televisions

Leseprobe

Table of Contents

Title Page

Copyright

About the Author

Preface

Series Editor's Foreword to the Second Edition

Chapter 1: Introduction

References

Chapter 2: OLED Devices

2.1 OLED Definition

2.2 Basic Device Structure

2.3 Basic Light Emission Mechanism

2.4 Emission Efficiency

2.5 Lifetime and Image Burning

2.6 Technologies to Enhance the Device Performance

References

Chapter 3: OLED Manufacturing Process

3.1 Material Preparation

3.2 Evaporation Process

3.3 Encapsulation

3.4 Problem Analysis

References

Chapter 4: OLED Display Module

4.1 Comparison Between OLED and LCD Modules

4.2 Basic Display Design and Related Characteristics

4.3 Passive-Matrix OLED Display

4.4 Active-Matrix OLED Display

References

Chapter 5: OLED Color Patterning Technologies

5.1 Color-Patterning Technologies

5.2 Solution-Processed Materials and Technologies

5.3 Next-Generation OLED Manufacturing Tools

References

Chapter 6: TFT and Driving for Active-Matrix Display

6.1 TFT STRUCTURE

6.2 TFT PROCESS

6.3 MOSFET BASICS

6.4 LTPS-TFT-DRIVEN OLED DISPLAY DESIGN

6.5 TFT TECHNOLOGIES FOR OLED DISPLAYS

References

Chapter 7: OLED Television Applications

7.1 Performance Target

7.2 Scalability Concept

7.3 Murdoch's Algorithm to Achieve Low Power and Wide Color Gamut

7.4 An Approach to Achieve 100 NTSC Color Gamut With Low Power Consumption Using White + Color Filter

References

Chapter 8: New OLED Applications

8.1 Flexible Display/Wearable Displays

8.2 Transparent Displays

8.3 Tiled Display

References

Chapter 9: OLED Lighting

9.1 Performance Improvement of OLED Lighting

9.2 Color Rendering Index

9.3 OLED Lighting Requirement

9.4 Light Extraction Enhancement of OLED Lighting

9.5 Color Tunable OLED Lighting

9.6 OLED Lighting Design

9.7 Roll-to-Roll OLED Lighting Manufacturing

References

Appendix

Index

Wiley-SID Series in Display Technology

End User License Agreement

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Guide

Table of Contents

Begin Reading

List of Illustrations

Chapter 1: Introduction

Figure 1.1 The first active-matrix OLED display product on the market

Figure 1.2 Example of a cellular phone using active-matrix OLED (AMOLED)

Figure 1.3 Example of a smart watch using active-matrix OLED (AMOLED)

Figure 1.4 Example of an audio player using active-matrix OLED (AMOLED)

Figure 1.5 Example of a large television using active-matrix OLED (AMOLED)

Figure 1.6 111-in. dual-sided flexible OLED television prototype

Chapter 2: OLED Devices

Figure 2.1 Diagram of the OLED emission mechanism.

Figure 2.2 OLED device reported by Tang and Van Slyke in 1987 [5].

Figure 2.3 Example of a polymer OLED with polyvinylcarbazole molecular structure.

Figure 2.4 Potential curve of ground state and excited state in the case of a two-atom molecule.

Figure 2.5 An example of absorption spectrum and fluorescent emission spectrum.

Figure 2.6 Electron configuration of double bond molecular orbital in molecular orbital.

Figure 2.7 Electron configuration in molecular orbital.

Figure 2.8 Electron configuration in ground state and excited states.

Figure 2.9 Electron configuration of ethylene molecule in

S

0

ground state and in

S

1

excited state.

Figure 2.10 Energy state of each exciton (Jablonski energy diagram) (a) with and (b) without vibration states.

Figure 2.11 Emission mechanisms of (a) fluorescence (singlet) and (b) phosphorescence (triplet) (Jablonski energy diagram).

Figure 2.12 Electron injection from cathode to LUMO level of EIL(ETL) material.

Figure 2.13 Hole injection from anode to HOMO level of HIL material.

Figure 2.14 Barrier lowering due to image potential.

Figure 2.15 Band diagram with and without vacuum-level shift.

Figure 2.16 Electron transfer in EIL/ETL/EML.

Figure 2.17 Hole transfer in HIL/HTL/EML.

Figure 2.18 OLED band diagram for a single organic layer.

Figure 2.19 Enhancement of electron–hole recombination efficiency by multilayer structural configuration.

Figure 2.20 Example layout of an OLED device using role sharing by multiple layers.

Figure 2.21 Explanation of internal conversion by potential curve.

Figure 2.22 Explanation of radiationless deactivation by potential curve.

Figure 2.23 Doping emission by fluorescence mechanism.

Figure 2.24 Doping emission by phosphorescence mechanism.

Figure 2.25 Schematic representation of Snell's law.

Figure 2.26 Schematic representation of light extraction loss.

Figure 2.27 Image sticking on a display caused by the differential aging.

Figure 2.28 Luminance decay curve.

Figure 2.29 Pixel arrangement without aperture adjustment.

Figure 2.30 Individual degradation curves for three colors.

Figure 2.31 Pixel arrangement with aperture adjustment.

Figure 2.32 OLED pixel display curve for a display with aperture adjustment.

Figure 2.33 Energy diagram of TADF system.

Figure 2.34 Ground state and excited state of CT complex.

Figure 2.35 Schematic representation of a conventional OLED device.

Figure 2.36 Schematic examples of a tandem OLED device with (a) two-layer and (b) five-layer serial connections.

Chapter 3: OLED Manufacturing Process

Figure 3.1 Example of energy diagram using HIL layer with stepwise energy location mechanism.

Figure 3.2 Example structures of hole injection material.

Figure 3.3 Structure of HAT(CN)

6

. hole injection material.

Figure 3.4 Example of energy diagram using HIL layer with charge-transfer complex mechanism.

Figure 3.5 Example structures of hole transportation material.

Figure 3.6 Example structures of fluorescent light-emitting materials.

Figure 3.7 Example structures of phosphorescent dopant materials.

Figure 3.8 Example structure of a phosphorescent host material.

Figure 3.9 Example structures of electron transportation material.

Figure 3.10 Schematic representation of energy diagram using two-layer OLED device without hole blocking layer.

Figure 3.11 Schematic representation of energy diagram using two-layer OLED device with hole blocking layer.

Figure 3.12 Schematic representation of sublimation purification equipment.

Figure 3.13 Basic structure of an evaporation source.

Figure 3.14 Schematic representation of a Knudsen cell (where

D

= diameter,

L

= length).

Figure 3.15 Incident evaporation molecule to substrate at point

A

from point source.

Figure 3.16 Incident evaporation molecule to substrate at point

A

from area source.

Figure 3.17 Thickness distribution in the case of motionless evaporation.

Figure 3.18 Schematic example of evaporation with offset and substrate rotation.

Figure 3.19 Evaporation equipment using a revolver apparatus.

Figure 3.20 Schematic representation of material in an evaporation source.

Figure 3.21 A thermoball.

Figure 3.22 Thin-film evaporation by linear source.

Figure 3.23 Linear source evaporation equipment.

Figure 3.24 Schematic representation of a thickness monitoring apparatus using a quartz crystal oscillator.

Figure 3.25 Dark spot formation.

Figure 3.26 Schematic representation of dark spot formation mechanism.

Figure 3.27 Edge growth (a) before and (b) after high-temperature/high-humidity testing (sample with encapsulation).

Figure 3.28 Light emission from (a) bottom and (b) top of the OLED structure.

Figure 3.29 Schematic example of bottom emission sealing.

Figure 3.30 Schematic representation of seal dispensing.

Figure 3.31 An example of perimeter-sealing process (bird's-eye view).

Figure 3.32 Schematic example of top emission encapsulation.

Figure 3.33 Schematic representation of film encapsulation by inorganic–organic repetition.

Figure 3.34 SiO

2

film deposited by CVD on tapered aluminum [20].

Figure 3.35 SiO

2

film deposited by CVD on nontapered aluminum [20].

Figure 3.36 Schematic depiction of the reaction mechanism of the atomic layer deposition (ALD) method.

Figure 3.37 Schematic depiction of spatial ALD system.

Figure 3.38 An example of face sealing encapsulation structure (cross-sectional view).

Figure 3.39 An example of face-frit encapsulation structure (cross-sectional view).

Figure 3.40 Examples of frit sealing encapsulation structure (bird's-eye view).

Figure 3.41 An example of sample structure for the calcium test.

Figure 3.42 Equipment for the Mocon method of humidity permeation measurement [25].

Figure 3.43 An example of HTO humidity measurement [26].

Figure 3.44 Schematic representation of workfunction and ionization potential.

Figure 3.45 Schematic representation of operating principle of an ionization potential analyzer.

Figure 3.46 Graphical example of ionization potential analyzer measurement.

Figure 3.47 Flowchart of HPLC analysis equipment.

Figure 3.48 Schematic example of a cyclic voltammogram.

Chapter 4: OLED Display Module

Figure 4.1 Examples of display components used in LCD (a) and OLED (b) television sets.

Figure 4.2 Relationship between luminous flux and luminous intensity.

Figure 4.3 Relationship between luminous flux and luminance of an area light source.

Figure 4.4 Relationship between luminous flux and illuminance of point light.

Figure 4.5 Relationship between luminous flux and illuminance of area light.

Figure 4.6 (a) Perfect diffusion surface; (b) incident light from a perfect diffusion surface. (Lambertian distribution.)

Figure 4.7 Example of a current–voltage curve of an OLED device.

Figure 4.8 Example of a luminance–voltage curve of an OLED device.

Figure 4.9 Example plot of luminance versus current.

Figure 4.10 Graph showing dependence of voltage on current efficiency.

Figure 4.11 Example of emission spectrum of RGB (red+green+blue) subpixels.

Figure 4.12 Plot of the area reproducible by RGB color mixture.

Figure 4.13 Graphical representation of the three color standards applied in television manufacture.

Figure 4.14 Graphical representation of the three color standards applied in digital camera manufacture.

Figure 4.15 Graphical representation of McAdam ellipse, showing the human eye's perception limit (at 10° magnification).

Figure 4.16 CIE-LAB uniform color space.

Figure 4.17 Blackbody emission spectrum for each color temperature.

Figure 4.18 Graphical representation of blackbody versus color temperatures.

Figure 4.19 Optimum and limit of color boosting (Courtesy by Y. Hisatake).

Figure 4.20 Matrix driving of a passive-type OLED display.

Figure 4.21 Structure of a passive-matrix OLED display.

Figure 4.22 Microscopic view of a passive-matrix OLED display.

Figure 4.23 A passive-matrix display employing the cathode separator patterning method.

Figure 4.24 Pixel circuit of a passive-matrix OLED display.

Figure 4.25 A passive-matrix OLED display prototype employing a multiline scanning method (2.2-in.-scale demonstration by TDK at CEATEC 2009).

Figure 4.26 A passive-matrix OLED display product (FOMA N2001).

Figure 4.27 A white monochrome passive-matrix OLED display product (EDIROL R09 digital audiorecorder).

Figure 4.28 A smart phone with round-shape bezel by flexible OLED display (in SID Display Week 2015 exhibition by LG display).

Figure 4.29 An example of an OLED pixel used in an actual product.

Figure 4.30 Two ways of OLED-TFT connection.

Figure 4.31 Expression of NMOS FET and PMOS FET.

Figure 4.32 Active-matrix driving by one TFT per pixel approach.

Figure 4.33 Active-matrix driving by two TFT and one capacitor (2T1C) per pixel approach.

Figure 4.34 Common-cathode and common-anode connection.

Figure 4.35 Two ways of pixel configuration using NMOS driver TFT (omitting capacitor to avoid complexity).

Figure 4.36 Two ways of pixel configuration using PMOS driver TFT (omitting capacitor to avoid complexity).

Figure 4.37 An example of common-cathode tandem white OLED pixel configuration by NMOS TFT [32].

Figure 4.38 An example of common-anode pixel configuration by NMOS TFT [33].

Figure 4.39 OLED current change due to OLED performance change in source-follower type.

Figure 4.40 OLED current change due to TFT performance change in source-follower type.

Figure 4.41 An active-matrix OLED display.

Figure 4.42 Plot of contrast ratio versus surface reflection in a living room.

Figure 4.43 An example of an RGBW (RGB+white) pixel layout.

Chapter 5: OLED Color Patterning Technologies

Figure 5.1 Patterning using a shadow mask.

Figure 5.2 Microscopic view of a shadow mask.

Figure 5.3 Color variation due to shadow mask deformation.

Figure 5.4 Cross-sectional view of a shadow mask.

Figure 5.5 Blue Common Layer structure.

Figure 5.6 Energy diagram of red device in Blue Common Layer Structure.

Figure 5.7 Energy diagram of blue device in Blue Common Layer Structure.

Figure 5.8 Conventional pixel arrangement (a) and polychromatic pixel arrangement (b).

Figure 5.9 Schematic depiction of the RGB pixelation method.

Figure 5.10 Schematic representation of the white + color filter method.

Figure 5.11 Schematic representation of organic material patterning using the laser-induced thermal imaging (LITI) method.

Figure 5.12 An active-matrix OLED display obtained using the LITI method

Figure 5.13 Schematic representation of organic material patterning using the radiation-induced sublimation transfer (RIST) method.

Figure 5.14 An active-matrix OLED display obtained using the RIST method

Figure 5.15 Schematic representation of a display structure obtained using the dual-plate OLED display (DOD) method.

Figure 5.16 Flowchart of the DOD process.

Figure 5.17 An example of an active-matrix OLED display obtained using the DOD method

Figure 5.18 An example of a photopatternable polymer OLED (PLED) material

Figure 5.19 Active-matrix OLED display cost simulation.

Figure 5.20 Setup for thin-film formation using the inkjet method.

Figure 5.21 Schematic representation of a hydrophilic/hydrophobic structure designed for inkjet patterning.

Figure 5.22 Schematic depiction of contact angle measurement.

Figure 5.23 An OLED display obtained using the PLED inkjet method

Figure 5.24 Structure of a dendrimer material (IrppyD)

Figure 5.25 Illustration of the concept of vapor injection source technology (VIST), an application of flash evaporation.

Figure 5.26 Comparison of device performance for point and VIST sources.

Figure 5.27 Comparison of doping performance for materials with widely different evaporation pressures.

Figure 5.28 A dopant-monitoring apparatus in which multiple injectors are connected to a single manifold.

Figure 5.29 Examples of multilayer fabrication using a VIST source.

Figure 5.30 A pressure-monitoring apparatus in which a Pirani gauge is attached to a manifold.

Figure 5.31 Graph illustrating correlation between crystal thickness monitoring and pressure sensing.

Figure 5.32 Schematic representations of OLED material deposition mechanism using (a) conventional evaporation and (b) hot-wall methods.

Figure 5.33 Schematic depiction of the behavior of an incident evaporation molecule on collision with a wall.

Figure 5.34 Flowchart showing thin-film deposition using the organic vapor-phase deposition (OVPD®; a trademark of Universal Display Corp.) method.

Figure 5.35 Schematic representation of the OVPD apparatus.

Chapter 6: TFT and Driving for Active-Matrix Display

Figure 6.1 Differences between (a) polysilicon (inside grain) and (b) (hydrogenated) amorphous silicon.

Figure 6.2 An example of a polysilicon-driven OLED display panel.

Figure 6.3 (a) Top-gate and (b) bottom-gate TFTs.

Figure 6.5 Cross section of typical amorphous silicon TFT.

Figure 6.4 Cross section of CMOS polysilicon TFT.

Figure 6.6 Flowchart of polysilicon TFT process.

Figure 6.7 Schematic representation of equipments used to form TFT by thin-film deposition: (a) chemical vapor deposition (CVD) method; (b) sputtering method.

Figure 6.8 Flowchart of patterning process (photoengraving process [PEP]) for TFT fabrication.

Figure 6.9 Reaction mechanism of positive resist.

Figure 6.10 Photoexposure tools for resist patterning: (a) stepper exposure; (b) integrated exposure.

Figure 6.11 Flowchart of resist pattern formation process: (a) resist coating; (b) photoexposure; (c) development.

Figure 6.12 Schematic representation of film etching methods.

Figure 6.13 An example of a planarization layer for active-matrix OLED display pixels.

Figure 6.14 Schematic representation of polysilicon formation by the solid-phase crystallization (SPC) method.

Figure 6.15 Schematic illustration of the principle of laser annealing crystallization.

Figure 6.16 Schematic representation of apparatus used for excimer laser annealing crystallization.

Figure 6.17 Graphical depiction of dependence of laser irradiation energy on crystal grain size.

Figure 6.18 Plots showing correlation between crystal grain size and TFT characteristics.

Figure 6.19 Graphical representation of correlation between laser shot number and crystal grain size.

Figure 6.20 A schematic diagram of N-channel transistor operation in the linear region.

Figure 6.21 Photographic image of a double-gate TFT structure.

Figure 6.22 Graph depicting correlation between lightly doped drain (LDD) length and TFT characteristics.

Figure 6.23 Images of displays (a) without voltage drop and (b) with severe voltage drop.

Figure 6.24 Voltage drop simulation results, assuming wiring with same parameters as those in LCDs.

Figure 6.25 Plot showing voltage drop reduction with increase in wire thickness.

Figure 6.26 Plot showing voltage drop reduction with increase in wire thickness in a low-resistivity wiring material.

Figure 6.27 Schematic example of an active-matrix-driven tandem OLED structure.

Figure 6.28 Image of luminance mura (nonuniformity) due to variation in threshold voltage.

Figure 6.29 Schematic representation of threshold voltage detection via gate–drain node connection.

Figure 6.30 Voltage programming circuit drawn by Dawson et al. [9].

Figure 6.31 Current mirror-type compensation circuit proposed by Sasaoka et al. [16].

Figure 6.32 A portable television set using the external global mura compensation method (GMC)

Figure 6.33 Images of luminance variation before (b) and after (a) compensation.

Figure 6.34 Flowchart showing operation of external GMC method.

Figure 6.35 GMC offset measurement equipment used in production.

Figure 6.36 Schematic representation of the pseudocontour mechanism.

Figure 6.37 Schematic representation of circuit integration using low-temperature polycrystalline silicon (LTPS) TFTs.

Figure 6.38 Schematic representation of a CMOS-type static shift register.

Figure 6.39 Schematic representation of an NMOS-type dynamic shift register.

Figure 6.40 Schematic representation of an NMOS-type static shift register.

Figure 6.41 Schematic example of a display obtained using the two-shot sequential lateral solidification (SLS) method.

Figure 6.42 Schematic example of the selective annealing process by micro lens array.

Figure 6.43 A large OLED display prototype obtained using a non-LTPS substrate

Figure 6.44 Graphical depiction of crystalline condition monitoring using the plasma-enhanced chemical vapor deposition (PECVD) method.

Figure 6.45 Schematic illustration of a high-density plasma CVD apparatus.

Figure 6.46 Diagram illustrating formation of microcrystalline silicon induced by diode laser annealing.

Figure 6.47 Schematic illustration of the principle of solid-phase crystallization using the metal-induced lateral crystallization (MILC) method.

Figure 6.48 Diagram of crystallization apparatus employing the alternating magnetic field crystallization (AMFC) method.

Figure 6.49 sp

3

hybrid orbital conduction mechanism by silicon-based semiconductors.

Figure 6.50 s-orbital-based conduction mechanism by oxide semiconductors.

Figure 6.51 First active-matrix OLED driven by oxide semiconductor

Figure 6.52 OLED television product using oxide semiconductor TFT.

Chapter 7: OLED Television Applications

Figure 7.1 Impact of defect to the display production yield.

Figure 7.2 Graph illustrating defective pixel number simulation.

Figure 7.3 Schematic representation of a color-coordinated histogram constructed from analyses of 13,000 photographic images.

Figure 7.4 Schematic representation of a color-coordinated histogram constructed from analysis of a television signal.

Figure 7.5 Graph illustrating color reproduction using the normal RGB method.

Figure 7.6 Plot showing color expression by GBW (green + blue + white) subpixels.

Figure 7.7 Plot showing color expression by RGW (red + green + white) subpixels.

Figure 7.8 Plot showing color expression by RBW (red + blue + white) subpixels.

Figure 7.9 Graph comparing power consumption levels of W-RGB and W-RGBW methods for various images.

Figure 7.10 14-in. active-matrix OLED display by white + color filter method.

Figure 7.11 Histogram of pixel colors in 19,419 images (log scale).

Figure 7.12 Total (W + R + G + B) driving current for W-RGBW method.

Figure 7.13 Current density of color coordinate (

x, y

) for actual display showing picture image.

Figure 7.14 Driving current dependence of RGB subpixel efficiency in W-RGBW system.

Figure 7.15 Conventional white + color filter approach.

Figure 7.16 Relative luminosity curve.

Figure 7.17 Wide spectrum white formulation for high white subpixel efficiency.

Figure 7.18 High color gamut color filter design for wide spectrum white emission.

Figure 7.19 New formulation with new color filter.

Figure 7.20 Emission output of W-RGBW display using new formulation, color filter set.

Figure 7.21 An OLED display prototype with a product-level specification using white + color filter technology (8.1-in. demonstration at SID 2008 by Eastman Kodak; this model has a 100% NTSC color gamut) [4].

Chapter 8: New OLED Applications

Figure 8.1 An example of a flexible display (demonstration at FPD International 2007 by Samsung SDI).

Figure 8.2 Demonstration of rollability of a flexible display: rolled (upper) and unrolled (lower) display (demonstration at SID2010 by Sony).

Figure 8.3 An example of rollable OLED display demonstrated in SID Display Week 2015 by LG display.

Figure 8.4 An example of a foldable display (demonstration at SID2008 by Samsung Mobile Display).

Figure 8.5 Laser liftoff process to make flexible device.

Figure 8.6 Examples of organic polymer conductors.

Figure 8.7 Examples of small-molecule organic semiconductors.

Figure 8.8 An example of a charge transfer complex.

Figure 8.9 Various organic TFT structures. (a) Top-contact bottom gate TFT. (b) Bottom-contact bottom gate TFT. (c) Top gate TFT.

Figure 8.10 An example of a transparent OLED display (demonstration at FPD International 2009 by LG Display).

Figure 8.11 A schematic explanation of facing-target sputtering system.

Figure 8.12 An example of a tiled passive-matrix display (demonstration at FPD International 2011 “Geo-cosmos” spherical display in Miraikan museum, Japan by Mitsubishi Electric).

Figure 8.13 An example of a passive-matrix tiling pixel arrangement.

Figure 8.14 Seamless tiling using image guide arrays [25].

Figure 8.15 Tiling display using four OLED panels with blanket film encapsulation.

Figure 8.16 An example of active-matrix display tiling [27].

Chapter 9: OLED Lighting

Figure 9.1 An example of table lighting using OLED

Figure 9.2 An example of an OLED ceiling lamp

Figure 9.3 Efficacy of commercial LED packages.

Figure 9.4 White OLED efficacy trend

Figure 9.5 Graph showing eight nominal correlated color temperature (CCT) quadrangles on a CIE1931 chromaticity diagram.

Figure 9.6 Schematic representations of (a) a microlens array and (b) a micropyramidal structure.

Figure 9.7 Diagrams of an internal extraction structure (IES) and an external extraction structure (EES).

Figure 9.8 Image showing actual emission using IES and EES techniques.

Figure 9.9 Schematic representation of light extraction enhancement employing diffraction structure.

Figure 9.10 Surface-plasmon polariton wave.

Figure 9.11 Two types of color tunable OLED device structures.

Figure 9.12 Structure of vertically stacked color tunable OLED.

Figure 9.13 Transparent OLEDlighting device [12].

Figure 9.14 Lighting instrument using vertically stacked color tunable OLED lighting [12].

Figure 9.15 Schematic representation of a serial connection structure.

Figure 9.16 OLED Tulip illumination demonstrated in Japanese theme park with shining flexible-OLED petals.

List of Tables

Chapter 2: OLED Devices

Table 2.1 Differences between Liquid Crystal and OLED Displays

Table 2.2 Timeline for OLED Technology Development

Chapter 4: OLED Display Module

Table 4.1 Summary of Photometric Parameters

Table 4.2 (

x

,

y

) Coordinate of Color Primaries for Each Standard

Table 4.3 Illuminance in Various Environments

Chapter 6: TFT and Driving for Active-Matrix Display

Table 6.1 Typical Steps in the CMOS Polysilicon TFT Process

Chapter 7: OLED Television Applications

Table 7.1 Specification of Commercially-Available OLED Television (As of September 2016)

Table 7.2 Examples of Scalable Technology

Table 7.3 Scalable TFT Technologies

Chapter 8: New OLED Applications

Table 8.1 Various Substrate for Flexible OLED Device

Table 8.2 Viewing Distance Required for Signage Display

Chapter 9: OLED Lighting

Table 9.1 CIE Coordinates of Nominal CCTs

Table 9.2 General ENERGY STAR Program Requirements

Table 9.3 Near-Term ENERGY STAR Application Requirements

Table 9.4 Light Extraction Experimental Data

Appendix

Table A.1 Color Matching Function

λ

Values

The Development of Catalysis

Second Edition

Takatoshi Tsujimura

This edition first published 2017

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Library of Congress Cataloguing-in-Publication Data

Names: Tsujimura, Takatoshi.

Title: OLED display fundamentals and applications / Takatoshi Tsujimura.

Description: Second edition. | Hoboken, New Jersey : John Wiley & Sons Inc.,

2017. | Series: Wiley series in display technology | Includes

bibliographical references and index.

Identifiers: LCCN 2016042831| ISBN 9781119187318 (hardback) | ISBN

9781119187486 (epub) | ISBN 9781119187325 (epdf)

Subjects: LCSH: Flat panel displays. | Electrtoluminescent devices. | Organic

semiconductors. | Light emitting diodes. | BISAC: TECHNOLOGY & ENGINEERING

/ Electronics / General.

Classification: LCC TK7882.I6 T84 2017 | DDC 621.3815/422–dc23 LC record available at https://lccn.loc.gov/2016042831

Cover image: © Blend Images - Colin Anderson/ Gettyimages

Cover design by Wiley

About the Author

Takatoshi Tsujimura joined IBM Japan for TFT-LCD development and was selected as one of the “10 best engineers/researchers in the 10 best Japanese companies” by Nikkei Electronics Magazine. He demonstrated OLED's capability to be applied to large television by the world's largest 20-in. demonstration and received SID Special Recognition Award in 2008. He moved to Kodak as a director and developed 100% NTSC white + color filter OLED display with less power consumption than LCDs, which has become industry-standard technology for OLED TV over 50 in. He is currently general manager of OLED business unit, Konica Minolta Inc. He received SID Fellow Award in 2013. He is an SID executive and is a former SID Japan chapter chair. He received PhD in materials science and engineering.

Dr. Tsujimura holds 144 worldwide registered patents and 7 publications including the following:

T. Tsujimura,

OLED Display Fundamentals and Application

, SID-Wiley Series in Display Science, ISBN: 978-1-118-14051-2 (2012)

T. Tsujimura,

OLED Overview (Japanese),

Sangyo Tosho, ISBN: 978–4782855560 (2010)

T. Tsujimura,

OLED display overview (Korean)

, Hantee Media, ISBN: 8964211766 (2013)

T. Tsujimura,

OLED display overview (Chinese)

, Publication House of Electronics Industry, ISBN: 9787121262814 (2015)

T. Tsujimura,

Technology and Material Development,

CMC Technical Library (2010)

T. Tsujimura,

OLED Material Technology,

CMC Publishing (2004)

T. Tsujimura,

OLED Handbook,

Realize Science and Engineering (2004).

Preface

In the 30 years that have passed since the release of the “first OLED paper,” there have been many publications promoting organic light-emitting diode (OLED) displays as a superior technology. Although many aspects of OLED performance are excellent, such as the ultimate high contrast provided by its self-emissive mechanism, it has not been an easy path to achieve wide acceptance in the industry. A decade ago, I was often told by my customers that they totally agree with the beauty of OLED screens, but they are not affordable for common display applications. It is always the case that emerging technology faces difficulty in the wide-scale adoption, in spite of its inherent advantages. The well-established liquid-crystal display (LCD) has been manufactured for a very long time, so it has already been progressively engineered to improve its shortcomings, such as viewing angle, response time, and cost. It was not easy for OLED to overcome such a situation.

What triggered OLED to become so popular was the rapid growth of smart phones. The touchscreen interface paired very well with the OLED screen, as OLED did not show any “touch mura,” a smear-like contrast reduction caused by flow-induced liquid crystal deformation. LCD, in a short time, improved the touch mura, but OLED makers utilized this momentary advantage to obtain a chance of growth. From this penetration of OLED display screens, end customers had a chance to recognize the superior display image quality of OLED, especially the beauty of its high contrast. This fortunate circumstance was a major benefit to OLED technology.

More recently, OLED has also penetrated the large television market, taking advantage of the high color gamut white + color filter method we developed, which promises high-yield manufacturing. OLED technology offers many important features for good television, so we expect it will gradually become more popular as the manufacturing cost goes down.

It is still a very important phase for OLED technology to become more widely used. The purpose of this book is to provide necessary information for everyone who is involved with this great technology, so that such knowledge can lead to further improvements. I also hope the contents will help readers to hit upon new great applications, taking advantage of the features of OLED devices.

Takatoshi Tsujimura

Series Editor's Foreword to the Second Edition

In the 4 years since the first edition of Dr Tsujimura's book was published, the status of OLED displays has undergone a transformation. Their development can be exemplified by two products; the introduction of OLED televisions with diagonal screen sizes and resolution fully matching those of LCD sets but with curved screens represented a striking innovation which at that time could not be provided by LCD panels. Many commentators were surprised by the speed with which LCD manufacturers responded to this challenge. On the other hand, OLED panels on flexible substrates provide thin, conformable displays offering excellent compatibility with touchscreen technologies, which many users regard as a benchmark for display performance on mobile electronic devices.

OLED devices are therefore showing their ability to drive customer expectations for display performance. OLED displays provide a performance lead in terms of thin profile, response speed, and black level dominated dark room contrast, which appear difficult to challenge, while brightness, stability, and manufacturing cost are relatively weaker points. Meanwhile, competition between OLED and LCD manufacturers has stimulated innovation in both technologies, driving improvement in key areas such as power efficiency, color gamut, and resolution. As self-emissive devices, OLEDs are also generating widespread interest for lighting applications where their ability to offer a large area source and to achieve high-quality color rendering and tunable color temperature promises an excellent quality of illumination.

This second edition of Dr Tsujimura's book recognizes all these advances through updating and revision of his earlier material, and the addition of extensive new sections covering advances in the technological exploitation of OLEDs. Some of the most prominent of these include approaches to improved power efficiency and color gamut for OLED television, and how to combine both of these key advances; materials and manufacturing methods for flexible OLED displays; roll-to-roll manufacture of OLED lighting panels; and structures of transparent OLED panels. The treatment of a number of the underlying scientific principles involved in device operation and efficiency is also expanded, with new material on luminescence mechanisms, light trapping and extraction, the behavior of various pixel driver circuits, and numerous other topics. It is our hope that these changes will both maintain the currency of the volume and increase its value to a broad range of users.

Dr Tsujimura brings to his subject, the experience and background knowledge gained through his long career researching and developing active matrix technologies, liquid crystal displays, and OLEDs. His knowledge and enthusiasm for his subject are clear in this book, which I believe will continue to provide a most valuable resource both for those working on OLED technologies and their applications, and for scientists and engineers who wish to increase their knowledge of this important field.

Malvern, UK

Ian Sage, Series Editor

Chapter 1Introduction

The basic structure of organic light-emitting diodes (OLEDs) was reported by Tang and Van Slyke at Eastman Kodak in 1987 [1]. This was a groundbreaking study and was later referred to as the “first OLED paper.” Now, almost 30 years later, there is a large market for OLED devices. The first OLED product was developed by Pioneer for car audio. Then the first mass production of AMOLED by SK display (a joint manufacturing venture by Eastman Kodak and Sanyo Electric) for Kodak's LS633 digital camera (Figure 1.1) accelerated the use of OLED for display applications.

Figure 1.1 The first active-matrix OLED display product on the market

(Kodak LS633 digital camera).

This was followed by the widescale development of many other OLED-based products, including cellular phones (Figure 1.2), smart watches (Figure 1.3), audio players (Figure 1.4), and portable global positioning satellite (GPS) devices, which now provide high-resolution displays in brilliant, multitone colors.

Figure 1.2 Example of a cellular phone using active-matrix OLED (AMOLED)

(Galaxy S7 smartphone by Samsung).

Figure 1.3 Example of a smart watch using active-matrix OLED (AMOLED)

(Apple Watch Series 2 by Apple).

Figure 1.4 Example of an audio player using active-matrix OLED (AMOLED)

(Sony Walkman NW-X-1050).

Larger-display products have also been introduced on the market, such as those shown in Figure 1.5. Much larger prototypes have also been developed (Figure 1.6). Because of their superior features such as slim flat-screen design and aesthetically pleasing screen image, and due to high-contrast image signal emission and very good response time, the current state of the art of OLED television technology that has debuted in the marketplace is indeed groundbreaking [2].

The main objective of this book is to explain the basics and application of this promising technology from various perspectives.

Figure 1.5 Example of a large television using active-matrix OLED (AMOLED)

(65-in. curved OLED TV demonstrated in SID2015 by LG display).

Figure 1.6 111-in. dual-sided flexible OLED television prototype

(LG Display at IMID2016).

References

1 C. W. Tang and S. A. Van Slyke, Organic electroluminescent diodes,

Appl. Phys. Lett.

51

(12):913–915 (1987).

2 T. Tsujimura, W. Zhu, S. Mizukoshi, N. Mori, M. Yamaguchi, K. Miwa, S. Ono, Y. Maekawa, K. Kawabe, M. Kohno, and K. Onomura, Advancements and outlook of high performance active-matrix OLED displays,

SID 2007 Digest

, 2007, p. 84.

Chapter 2OLED Devices

2.1 OLED Definition

2.1.1 History of OLED Research and Development

Before any in-depth discussion of OLED display structure, let us consider the initial origins of OLED technology, which are based on early observations of electroluminescence (EL). In the early 1950s, a group of investigators at Nancy University in France applied high-voltage alternating-polarity fields in air to thin films of cellulose or cellophane containing deposited or dissolved acridine orange and quinacrine, and observed light emission [1]. One mechanism identified in these reaction processes involved excitation of electrons. Then in 1960, a team of investigators at New York University (NYU) made ohmic (a nonrectifying charge injection, which shows linear current–voltage relationship) dark-injecting electrode contacts to organic crystals and described the necessary workfunctions (energy requirements) for hole and electron-injecting electrode contacts [2]. These contacts are the source of charge injection in all present-day OLED devices. The same NYU group also studied direct-current (DC) EL in vacuo on a single pure anthracene crystal and tetracene-doped anthracene crystals in the presence of a small-area silver electrode at 400 V [3]. The proposed mechanism for this reaction was termed field-accelerated electron excitation of molecular fluorescence. The NYU group later observed that in the absence of an external electric field, the EL in anthracene crystals results from recombination of electron and hole and that the conducting-level energy of anthracene is higher than the exciton energy level [4].