• 인포메이션 디스플레이
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• 제18권1호
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• pp.20-26
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• 2017

앞서 살펴본 것처럼, QLED의 풀컬러 디스플레이 적용을 위해서는 QD의 RGB 패터닝이 핵심 기술이고, 이를 위해 최근 프린팅 기반의 다양한 패터닝 기술이 연구개발 되고 있다. 아직까지 QLED 소자 기술도 완전히 성숙하지는 않은 상황이므로 풀컬러 디스플레이 실현 시기를 논하기는 조금 이를지도 모르겠다. 하지만 OLED 등의 유사 기술에 비해 발전 속도가 훨씬 빠르기에 긍정적인 시각에서 바라볼 수 있다. LCD 이후 OLED에 이르기까지 국내 디스플레이 산업은 세계 시장에서 주도권을 잃지 않고 있다. OLED의 뒤를 이을 차세대 디스플레이 기술로 QLED가 가장 유망하고, QLED에 대한 정부 및 기업도 큰 관심을 갖는 만큼, 국내 디스플레이 산업의 발전과 세계시장 주도권 유지를 위해 보다 적극적인 R&D 투자, 연구 확대 등이 필요한 상황이다. 이를 바탕으로 머지않은 미래에 QLED가 디스플레이로 활용되기를 기대해 본다.

• 인포메이션 디스플레이
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• 제22권2호
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• pp.22-29
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• 2021

• 한국세라믹학회지
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• 제54권6호
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• pp.449-469
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• 2017

The development of quantum dots (QDs) has had a significant impact on various applications, such as solar cells, field-effect transistors, and light-emitting diodes (LEDs). Through successful engineering of the core/shell heterostructure of QDs, their photoluminescence (PL) quantum yield (QY) and stability have been dramatically enhanced. Such high-quality QDs have been regarded as key fluorescent materials in realizing next-generation display devices. Particularly, electrically driven (or electroluminescent, EL) QD light-emitting diodes (QLED) have been highlighted as an alternative to organic light-emitting diodes (OLED), mostly owing to their unbeatably high color purity. Structural optimizations in QD material as well as QLED architecture have led to substantial improvements of device performance, especially during the past decade. In this review article, we discuss QDs with various semiconductor compositions and describe the mechanisms behind the operation of QDs and QLEDs and the primary strategies for improving their PL and EL performances.

• 센서학회지
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• 제32권6호
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• pp.455-461
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• 2023

We investigated the electrical characteristics of ZnO nanoparticles (NPs) with air exposure that is a widely used electron transport layer for quantum dot light-emitting diodes (QLEDs). Upon air exposure, we observed changes in the density of states (DOS) of the trap levels of ZnO NPs. In particular, with air exposure, the concentration of deep trap energy levels in ZnO NPs decreased and electron mobility significantly improved. Consequently, the air-exposed ZnO reduced leakage current by approximately one order of magnitude and enhanced the external quantum efficiency at the low driving voltage region of the QLED. In addition, based on the excellent conductivity properties, high-brightness QLEDs could be achieved.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.69-72
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• 2020

본 연구에서는 SnO₂ nanoparticles (NPs) 위에 TiO₂ NPs를 코팅하여 Quantum Dots Light Emitting Diodes (QLEDs)를 제작하였다. TiO₂ NPs는 SnO₂ NPs보다 conduction band minimum (CBM) 준위가 낮다. 따라서 SnO₂ 층과 발광층의 CBM 준위 사이에 위치해 에너지 장벽을 감소시키고, 전자의 이동을 원활하게 할 것으로 예상하였다. QLEDs는 inverted 구조로 제작되었으며, SnO₂ 단일층을 사용한 경우보다 발광 특성이 향상된 것을 확인하였다. 이중 전자수송층을 적용한 이번 연구를 통해 SnO₂를 QLEDs에 전자수송층으로 적용할 수 있을 것으로 기대한다.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.393-398
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• 2019

A poly[bis(4-butypheny)-bis(phenyl)benzidine] (poly-TPD) and poly(9-vinylcarbazole) (PVK) bilayer was employed as a hole transport layer (HTL) in solution-processed CdSe/ZnS quantum dot light-emitting diodes (QLEDs). The thickness of the PVK layer spin-coated onto the poly-TPD layer, whose thickness was fixed to 40 nm, was varied, with PVK layer thicknesses of 0 nm, 35 nm, 45 nm, and 55 nm. Because the thickness of the PVK can determine the hole transport properties of the HTL, a PVK thickness that maximizes the performance of the HTL for the QLEDs was investigated. By employing the optimized PVK thickness of 45 nm, the current efficiency of the QLED exhibited a 1.74 times improvement when compared with that of the QLED with poly-TPD based HTL without PVK. This was mainly attributed to the decrease in the energy barrier between the HTL and the quantum dot (QD) emitting layer (EML).

• 마이크로전자및패키징학회지
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• 제28권4호
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• pp.69-72
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• 2021

Quantum Dot Light-Emitting Diodes (QLEDs)는 제조 공정이 용액 공정을 기반으로 하기 때문에 잉크젯 공정에 쉽게 적용할 수 있다. 하지만 QLED의 적층은 서로 다른 용매를 사용하는 직교 공정이 필요하기 때문에 잉크젯 인쇄 공정이 더 복잡하며 비용이 상승한다. 따라서 한 번의 공정으로 두 개의 층을 증착하면 제조 단계를 줄일 수 있어 공정 시간이 절감된다. 이 연구에서 우리는 QD와 정공 수송 재료의 혼합물을 사용하여 standard 구조의 QLED를 제작하였다. TFB와 QD를 클로로벤젠에 분산시켜 혼합층에 사용하였고, 소자는 45,850 cd/m²의 최고 휘도를 나타내었다. 이 연구는 잉크젯 프린팅 공정을 적용하여 전계발광 장치를 제작할 수 있는 가능성을 확인하였다.

• Journal of Information Display
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• 제13권2호
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• pp.91-95
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• 2012

Indium phosphide (InP) quantum dots (QDs) are considered alternatives to Cd-containing QDs for application in light-emitting devices. The multishell coating with ZnSe/ZnS was shown to improve the photoluminescence quantum yield (QY) of InP QDs more strongly than the conventional ZnS shell coating. Structural proof for this system was provided by X-ray diffraction and transmission electron microscopy. QY values in the range of 50-70% along with peak widths of 45-50 nm can be routinely achieved, making the optical performance of InP/ZnSe/ZnS QDs comparable to that of Cd-based QDs. The fabrication of a working electroluminescent light-emitting device employing the reported material demonstrated the feasibility of the desired application.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.466-466
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• 2013

Quantum-dot materials have introduced novel applications in organic light-emitting diodes and solar cells. The size controllability and structure modifications have continuously been upgrading the applicability to optoelectronic and flat-panel displays. In particular, quantum-dot organic light-emitting diodes (QLEDs) are a device driven through the electrical field applied to the electrical diodes. The QLEDs are affected by the constituent materials and the corresponding device structures. Conventionally, the electrical properties are characterized only in terms of dc-based current-voltage characteristics. The dynamic change in light-emitting diodes should be characterized in emitted and non-emitted states. Therefore, the frequency-dependent impedance can offer different information on the electrical performance in QLED. The current work reports an auxiliary information on the electrical and optical features originating from quantum-dot organic light-emitting diodes. The empirical characterizations are discussed towards an experimental tool in optimizing the light-emitting diodes.

• Current Optics and Photonics
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• 제4권3호
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• pp.161-173
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• 2020

Colloidal quantum dots (QDs) have gained tremendous attention as a key material for highly advanced display technologies. The performance of QD light-emitting diodes (QLEDs) has improved significantly over the past two decades, owing to notable progress in both material development and device engineering. The brightness of QLEDs has improved by more than three orders of magnitude from that of early-stage devices, and has attained a value in the range of traditional inorganic LEDs. The emergence of high-luminance (HL) QLEDs has induced fresh demands to incorporate the unique features of QDs into a wide range of display applications, beyond indoor and mobile displays. Therefore it is necessary to assess the present status and prospects of HL-QLEDs, to expand the application domain of QD-based light sources. As part of this study, we review recent advances in HL-QLEDs. In particular, based on reports of brightness exceeding 10⁵ cd/㎡, we have summarized the major approaches toward achieving high brightness in QLEDs, in terms of material development and device engineering. Furthermore, we briefly introduce the recent progress achieved toward QD laser diodes, being the next step in the development of HL-QLEDs. This review provides general guidelines for achieving HL-QLEDs, and reveals the high potential of QDs as a universal material solution that can enable realization of a wide range of display applications.