• 센서학회지
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• 제31권4호
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• pp.249-254
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• 2022

To achieve high-performance colloidal quantum dot light-emitting diodes (QD-LEDs), the use of a densely packed QD film is crucial to prevent the formation of leakage current pathways and increase in interface resistance. Spin coating is the most common method to deposit QDs; however, this method often produces pinholes that can act as short-circuit paths within devices. Since state-of-the-art QD-LEDs typically employ mono- or bi-layer QDs as an emissive layer because of their low conductivities, the use of a densely packed and pinhole-free QD film is essential. Herein, we introduce the Langmuir-Blodgett (LB) technique as a deposition method for the fabricate densely packed QD films in QD-LEDs. The LB technique successfully transfers a highly dense monolayer of QDs onto the substrate, and multilayer deposition is performed by repeating the transfer process. To validate the comparability of the LB technique with the standard QD-LED fabrication process, we fabricate and compare the performance of LB-based QD-LEDs to that of the spin-coating-based device. Owing to the non-destructiveness of the LB technique, the electroluminescence efficiency of the LB-based QD-LEDs is similar to that of the standard spin coating-based device. Thus, the LB technique is promising for use in optoelectronic applications.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.246.1-246.1
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• 2014

Over the past several years, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED). In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[1] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 8 V, the QDLED device emitted spectrally orange color lights with high luminance up to 2450 cd/m2, and showed current efficacy of 0.6 cd/A, respectively.

• Current Optics and Photonics
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• 제3권6호
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• pp.590-596
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• 2019

To improve the color gamut of a liquid-crystal display (LCD), we propose a bandpass filter that is added to the backlight unit to optimize the backlight spectrum. The bandpass filter can only transmit red, green and blue light in the visible range, while reflecting the unwanted light. We study the optical properties of the bandpass filter using the transfer-matrix method, and the effect of the bandpass filter on the color gamuts of LCDs is also investigated. When a bandpass filter based on a 5-layer configuration comprising low and high refractive indices ((HL)²H) is used in phosphor-converted white-light-emitting diode (pc-WLED), K₂SiF₆:Mn⁴⁺ (KSF-LED), and quantum-dot (QD) backlights, the color gamuts of the LCDs improve from 72% to 95.3% of NTSC, from 92% to 106.7% of NTSC, and from 104.3% to 112.2% of NTSC respectively. When the incident angle of light increases to 30°, the color gamuts of LCDs with pc-WLED and KSF-LED backlights decrease by 2.9% and 1% respectively. For the QD backlight, the color gamut almost does not change. When the (HL)²H structure is coated on the diffusion film, the color gamut can be improved to 92.6% of NTSC (pc-WLED), 105.6% of NTSC (KSF-LED), and 111.9% of NTSC (QD). The diffusion film has no obvious effect on the color gamut. The results have an important potential application in wide-color-gamut LCDs.

• 한국콘텐츠학회논문지
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• 제19권6호
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• pp.663-675
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• 2019

최근 10여 년간 디스플레이 시장에서의 지배적 디자인은 LCD로 한국 업체들이 이를 주도해 왔다. 그러나 최근 중국 기업들로부터의 위협이 증가되고 있어, 국내 업체들은 차세대 디스플레이 분야로 진출하기 위한 노력을 기울이고 있다. 한국 디스플레이 업체들은 최근 양자점 디스플레이 및 유기발광디스플레이 등의 신기술을 출시하여, 특히 TV용 차세대 디스플레이 시장에서 지배적 디자인을 차지하기 위한 표준 경쟁에 돌입하였다. 지배적 디자인을 결정하는 요소는 다양한 가운데, 디스플레이 제품은 특히 제품 자체의 기술적 속성이 가장 중요할 것으로 예상된다. 따라서 본 연구에서는 TV용 차세대 디스플레이에 대한 소비자의 선호 속성을 파악함으로써, 이 분야 표준 경쟁을 위한 시사점을 제공하고자 한다. 이를 위해 본 연구에서는 잠재적 소비자들을 대상으로 한 컨조인트 분석을 실시하였다. 분석 결과, 초고해상도 화면에 자연스런 색상을 표현할 수 있는 내구성 높은 제품에 대한 선호도가 높은 가운데, 제품의 가격이 중요한 요소로 작용하는 것으로 나타났다.