- Chapter 1. Metal Oxide Thin-Film Transistor
Jae Kyeong Jeong (Professor at Hanyang University)
This review will give an overview of the recent progress in n-type oxide thin-film transistors (TFTs). The strategies toward high mobility will be addressed including the channel composition and structure, which is required to meet the demands of the ultra-high-resolution, large panel size and 3 dimensional visual effects as a megatrend of organic light emitting diodes and flexible displays. The device instability of oxide TFTs will be covered in details, which is critical for their implementation in the real product. The degradation mechanisms for the bias-thermal-stress and light illumination will be summarized including the carrier trapping/injection, defect creations such as oxygen vacancy, oxygen interstitial, hydrogen complex model. Finally, the self-aligned structure will be reviewed including the metallization process, copper interconnection for the AMOLED TV.
- Chapter 2. Pixel circuit of OLED display
Kee Chan Park (Professor at Konkuk University)
Each pixel of OLED display needs an analog current source for uniform brightness over a whole display panel. Otherwise, mura due to the deviation of OLED characteristics or image sticking due to the irregular degradation of OLED device might be observed. A thin-film transistor (TFT) biased as subthreshold or saturation mode is used as the analog current source for OLED driving in each pixel. However, the characteristics of TFTs are not uniform at all. Therefore, another mura occurs due to the non-uniform current-voltage characteristics of the TFTs. Various circuit techniques have been proposed and employed in the OLED display product according to the applications. The operating principles of these circuit techniques will be explained, and the pros and cons of several representative circuit structures will be dealt with in this chapter.
- Chapter
3
. Phosphorescent OLEDs for power efficient displays
Michael S. Weaver and Tyler Fleetham (UDC)
In this chapter we will discuss phosphorescent OLED (PHOLED) materials and technologies. PHOLEDs are now used in virtually all OLED display products. We will discuss here the history of this technology, the inherent advantages of these materials and their future. The spin-orbit coupling is therefore enhanced, resulting in a mixing between the MLCT triplet and the singlet. To ensure high efficiency, particularly at high luminance levels, it is essential to minimize the triplet excited state lifetime. To achieve this, the MLCT triplet energy should be lower than that of the ligand. PHOLEDs incorporating phosphorescent organometallic compounds today have potential to exceed 40% EQE. Later we will discuss where next this technology can be even further improved.
- Chapter
4
. TADF and
h
yperfluorescence
Junji Adachi, Hisashi Okada (Kyulux)
TADF (thermally activated delayed fluorescence) is recognized the third generation of OLED emitting technology, which provides highly efficient emission without using any rare metal, such as iridium. TADF, which is designed small the energy gap between the singlet and triplet excited state, enables efficient spin up-conversion from triplet to singlet. As a result, highly efficient emission from singlet as high as 100% internal quantum efficiency was achieved without using rare metal, such as iridium. HyperfluorescenceT (HF) combines TADF and fluorescence to provide the ultimate solution for OLED display. TADF acts as excitons generator and transfers excitons to Fluorescence by Förster resonance energy transfer (FRET). Fluorescence molecule receives excitons and emits light as high as 100% internal quantum efficiency.
- Chapter 5. Solution-processible OLED material based on conjugated polymer technology
Takeshi Yamada (Sumitomo)
The development history, technology and current status of conjugated-polymer based soluble OLED material are reviewed. In addition, the application to display fabrication, comparison with other display technologies are also summarized and discussed.
- Chapter 6. Soluble small molecules for ink jet printed OLEDs - history, status and prospects
Remi Anemian (Merck)
Solution processing via Ink Jet Printing (IJP) is thought to be the next generation production technology due to its flexible scalability, in particular for large size displays, its higher material utilization rate and potential low costs. The following chapter will review the performance history from monochrome emission layers based on soluble small molecules to true RGB side-by-side printed architecture. Besides material properties and performances, process related requirements such as wetting, film uniformity and flatness will be discussed including implications on stack design. An outlook is given about upcoming trends to be adopted from vapor, as well as specific requirements regarding top emission device architecture and high pixel resolutions beyond 250ppi.
- Chapter
7
. Chemical
m
echanisms of
i
ntrinsic
d
egradation of
e
mitting
l
ayers in OLED
d
evices
Youngmin You (Professor at Ewha Womans University)
Short operation lifetime of organic light-emitting devices (OLEDs) remains as a major hurdle. The poor device longevity results from accumulations of defects during normal operation. This chapter summarizes the current knowledge about the chemical defects in OLEDs. Focus is on chemical mechanisms of the generation of defects. Unimolecular degradation from excitons or polarons is disclosed with the key examples. Chemical degradation by bimolecular processes, including excitonexciton annihilation (EEA) and excitonpolaron annihilation (EPA), are summarized. Strategies toward minimizing the bimolecular degradation are introduced. Finally, a recently identified bimolecular degradation by exciton-mediated electron transfer is overviewed.
- Chapter
8
.
White OLED
d
evice
t
echnology and
large-sized a
pplications.
Chang Wook Han (LG Display)
Large-sized OLED TV has been commercialized as adopting tandem white OLED. Recently rollable and 8K OLED TV were also developed and open to the public. This chapter will cover key technologies including evaporation process, white OLED device and key technologies to realize OLED TV. Top emission white OLED for large-sized transparent display will also be reviewed. In the future, low power consumption is important due to environment problems. High-efficiency blue is most necessary to reduce power consumption. The latest research trends of high-efficiency blue OLED device such as phosphor-sensitized fluorescent (PSF) and hyper-fluorescent OLED.
- Chapter
9
. Encapsulation
t
echnology for
f
lexible OLEDs
Kyung Cheol Choi (Professor at KAIST)
Displays have evolved from rigid flat panels to flexible, rollable and foldable formats. Such changes in form-factor can provide improvements in consumer utility and convenience, including portability and ease of use. Developing a stable flexible display has attracted considerable attention for these reasons. But to realize the full potential of flexible OLEDs, they not only require enhanced characteristics to withstand rolling and folding, but a highly effective thin-film encapsulation barrier is also essential. This book chapter covers developments in encapsulation technologies, their structure designs, and materials for realizing flexible, rollable, and foldable OLEDs. Special focus is given to the existing hurdles to flexibility and how to overcome these limitations. Finally, further insights on the evolution of encapsulation technologies are discussed.
- Chapter 1
0
. Quantum
d
ot-
e
nabled
d
isplays
Charlie Hotz (Nanosys)
This chapter will describe the structure, benefits and development status of each type of QD display, including the challenges each one faces relative to competitive technologies. A comparison of the emitter properties of QDs and alternative display emitters will be will also be reviewed.
- Chapter 1
1
. Quantum
d
ot based
d
isplays
Wan Ki Bae (Professor at Sungkyunkwan University)
Colloidal quantum dots (QDs) are few nanometer sized semiconductor nanocrystals whose electronic states are subject to change depending on their dimension. QDs have been of great interest as light-emitting materials in future displays owing to their superb optical properties such as near-unity photoluminescence quantum yield and narrow emission spectra, as well as their solution processability. The present chapter focuses on the emerging display technologies based on quantum dots. Specifically, this chapter covers the history of quantum dots for light-emitting applications, photophysical properties of quantum dots relevant to light-emitting applications, the state-of-the-art of and the perspectives on QD based display technologies.
- Chapter 12. Micro LED
t
echnology for
d
isplay
a
pplications
Dong Seon Lee (Professor at GIST)
In general, micro LEDs are defined as LEDs with a size of 100 µm or less, which are manufactured based on inorganic materials. Researches for developing micro-LEDs have been underway around the world as the demand for micro-miniaturized light sources increases, especially for display applications, but various problems are emerging in many ways. We introduce current research trend, issues, and efforts to overcome various problems of micro-LEDs as full-color light sources for display applications. We also briefly review newly presented technologies by research institutes and companies including their patents and products to examine their R&D strategy for micro-LEDs.
- Chapter 13. Display techniques for augmented reality and virtual reality
Byoungho Lee (Professor at Seoul National University)
Augmented reality (AR) and virtual reality (VR) have become important topics with the rapid growth of display technology and advances in communication technology. In this chapter we will review display technologies for implementing AR and VR. AR/VR display technologies can be categorized into glasses-type such as head-mounted display and window-type such as head-up display. We will discuss key issues for them and explain various technologies for implementing them such as diffractive optical elements, holographic optical elements, and light field technology. Especially, resolving the accommodation-vergence conflict is an important issue for 3D AR/VR to minimize observer's eye fatigue. We will explain this issue as well.