• Journal of Fashion Business
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• v.25 no.4
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• pp.125-140
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• 2021

Recently, flexible displays have been used as part of fashion beyond the concept of parts for electronic products. The flexible display applied to wearable fashion products flexibly bends according to the wearing position of the human body and, at the same time, decorates the fashion product more splendidly through the screen on which images or videos are displayed. Flexible displays, which are used for clothes and accessories, combine analogue fashion sensibility with digital screens to create a new level of convergence product design and expand the range of fashion design and fashion materials. This study aims to analyze the trends of the development and commercialization of fashion products that use flexible displays. As a research method, theoretical research and empirical research through case analysis were conducted in parallel. First, as a theoretical study, the morphological and technical characteristics of flexible displays were examined. Through theoretical studies, the effect of the characteristics of flexible displays on the development of wearable fashion products was investigated. Second, as an empirical case study, the design of wearable fashion products using flexible displays over the past 10 years and the characteristics of the displays used in the products were analyzed. Based on the characteristics analyzed, the product design, display and product integration methods and the commercialization stages of wearable fashion products using flexible displays were analyzed.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.71-75
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• 2018

In this study, we prepared OLED cell with ITO (Indium Tin Oxide) films grown on the glass substrate by facing targets sputtering. Before fabrication of OLED cells, we investigated properties of ITO films deposited at various sputtering conditions. To investigate properties of as-prepared films, we employed four-point probe, UV-VIS spectrometer, X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), hall-effect measurement. As a results, as-prepared ITO films have high transmittance of over 85 % in the visible range (300-800 nm) and a resistivity of under $10^{-4}$ (${\Omega}-cm$). Their resistivity increased as a function of oxygen gas flow and substrate temperature. OLED cell with ITO films were fabricated by thermal evpoeartor. Properties of OLEDs cell referring to properties of ITO films.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1295-1296
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• 2006

수소화된 비정질 실리콘 박막 트랜지스터(a-Si:H TFT)의 이력 현상이 능동형 유기 발광 다이오드(Active-Matrix Organic Light Emitting Diode) 디스플레이 패널을 구동할 경우에, 발생할 수 있는 잔상(Residual Image) 문제를 단위 소자 및 회로에서 실험을 통하여 규명하였다. 게이트 시작 전압을 바꾸어 VGS-ID 특성을 측정할 경우, 게이트 시작 전압이 5V에서 시작한 VGS-ID 곡선이 10V에서 시작한 VGS-ID 곡선에 비해 왼쪽으로 0.15V 이동하였다. 이러한 결과는 게이트 시작 전압의 차이에 의해 발생한 트랩된 전하량(Trapped Charge) 변화로 설명할 수 있다. 또한, 인가하는 게이트 전압 간격을 0.5V에서 0.05V로 감소시켰을 때 전하 디트래핑 비율의 변화(Charge De-trapping Rate)로 인하여, 이력 현상(Hysteresis Phenomenon)으로 인한 단위 소자에서의 문턱전압의 변화가 0.78V에서 0.39V로 감소함을 관찰하였다. 제작된 2-TFT 1-Capacitor의 ANGLED 화소에서 (n-1)번째 프레임에서의 OLED 전류가 (n)번째 프레임에서의 OLED 전류에 35%의 전류오차를 발생시키는 것을 측정 및 분석하였다.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.119-124
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• 2022

Top emission organic light-emitting diode (TEOLED) is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device (BEOLED). Unlike BEOLED, TEOLED contain semitransparent metal cathode and capping layer. Because there are many characteristics to consider just simple thickness change, optimizing organic thickness of TEOLED for microcavity is difficult. So, in this study, we optimized Device capping layer at unoptimized micro-cavity structure TEOLED device. And we compare only capping layer with unoptimized microcavity structure can overcome optimized micro-cavity structure device. We used previous our optimized micro-cavity structure to compare each other. As a result, it has been found that the efficiency can be obtained almost the same or higher only capping layer, which is stacked on top of the device and controls only the thickness and refractive index, without complicated structural calculations. This means that higher efficiencies can be obtained more easily in laboratories with limited organic materials or when optimizing new structures etc.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.71-74
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• 2022

For the process simplification in the fabrication of organic light emitting diode(OLED), top emission OLED (TEOLED) was fabricated without lithium fluoride(LiF) used as an electron injection layer (EIL). After co-deposition of Mg and Ag with a different process conditions, a cathode material adjacent to EIL was optimized when Mg and Ag have a ratio of 1:9 considering sheet resistance and transmittance. From the energy band diagram of TEOLED, band gap difference between Trisaluminium (Alq3) and Mg:Ag cathode show the difference of 0.4 eV according to the usage of LiF The fabricated TEOLED without LiF showed the improvement of 5.2 % and 2.7 % in the luminance and the current density comparing that with LiF. The results show there is no significant difference in OLED characteristics regardless of LIF layer in the TEOLED structures.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.91-94
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• 2022

Top emission organic light-emitting diode is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device. Unlike BEOLED, TEOLED contain semi-transparent metal cathode. Because of semi-transparent cathode, micro cavity effect occurs in TEOLED. We optimized this effect by changing the thickness of hole injection layer. Device consists of is indium-tin-oxide / N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (x nm) / tris-(8-hydroxyquinoline) aluminum (50nm) / LiF(0.5nm) / Mg:Ag (1:9), and we changed NPB thickness which is used as HTL in our device in order to study how micro cavity effects are changed by optical path. As the results, NPB thickness at 35nm showed the current efficiency of 8.55Cd/A.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.725-729
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• 2015

Organic light emitting diodes (OLEDs) are regarded as the next generation display and solid-state lighting due to their superb achievements from extensive research efforts on improving the efficiency and stability of OLEDs in addition to developing new materials. Herein, efficient green phosphorescent OLEDs were obtained by using hexaazatrinaphthylene (HAT) derivatives as a hole injection layer. External quantum and current efficiencies of OLEDs were enhanced from 8.8% and 30.8 cd/A to 13.6% and 47.7 cd/A, respectively by inserting a thin layer of HAT derivatives between the ITO and hole transporting layer. The enhancement of OLEDs was found to be originated from the inserted HAT derivatives, which resulted in the optimized hole-electron balance inside the emission layer.

• Fashion & Textile Research Journal
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• v.23 no.6
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• pp.860-868
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• 2021

Clothing has a very important role in human life, and it is the most human-friendly platform because humans wear it in almost all the time. In the recent years, smart clothing integrated with various functions is solidifying its position as the core of next-generation Information and Communications Technology(ICT). With this global trend, the smart textiles, textiles embedded with electronic devices that are capable of performing various functions, have been attracting a lot of attention. Therefore, various research activities on the smart textiles are in progress, and the global market outlook for the smart textiles is also showing rapid growth. Among the various smart textile technologies, the textile/fiber-based wearable display has been attracting more attention because it is an essential element for wearers to intuitively control the functions integrated in the smart textiles. This paper provides insightful information and the technological elements of organic light emitting diodes(OLEDs) display, which have been evaluated as the most ideal device for luminescent clothing. Since, OLEDs have many advantages such as light weight, extremely thin thickness and great flexibility, the textile/fiber-based wearable OLEDs can be worn without any inconvenience. In addition, by introducing previous studies on the textile/fiber-based OLED displays, we intend to consider the commercial potential of the textile/fiber-based smart luminescent clothing using the OLED technologies.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.311-311
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• 2014

III-N계 물질로 이루어진 GaN 기반의 광 반도체는 직접 천이형 넓은 밴드갭 구조를 갖고 있기 때문에 적외선부터 가시광선 및 자외선까지를 포함한 폭 넓은 발광파장 조절이 가능하여 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있다. 하지만, GaN기반의 발광 다이오드는 많은 연구기관들의 오랜 연구에도 불구하고 고출력을 내는데 있어 여전히 많은 문제들이 존재한다. 그 중, 주입전류 증가에 따른 효율감소 현상은 출력을 저해하는 대표적인 요소로 알려져 있는데, 이전의 연구 결과에서 알려진 효율감소 현상의 원인으로 결정결함에 의한 누설전류, Auger 재결합, 이송자 넘침 현상 그리고 p-n접합부의 온도 상승 등의 현상이 알려져 있다 [1-2]. 하지만 여전히 주입 전류 증가에 따른 효율 감소 현상의 원인에 대해 명확한 해답은 없으며 아직도 많은 논의가 이루어 지고 있다. 따라서, 본 연구에서는 GaN기반의 청색 및 녹색 LD와 LED소자를 이용하여 주입전류 밀도의 변화에 따른 자발 발광 영역에서의 효율감소 현상의 원인을 규명하고 한다. 유기금속화학증착법(MOCVD)를 이용하여 c면 사파이어 위에 서로 다른 발광파장을 가지는 InGaN/GaN 다중양자우물구조의 질화물계 LED와 LD 박막을 제작하였으며 성장 구조에 의한 특성으로 인해 발생하는 효율 저하 현상을 방지하고자 InGaN/GaN으로 이루어진 다중양자우물층의 조성만 제어하여 청색과 녹색으로 발광하도록 하였다. 청색 및 녹색 LD 웨이퍼들을 이용하여 주입전류 증가에 따른 발광특성을 조사하기 위해 LD와 LED는 표준 팹 공정에 의해 제작되었다. 전계 발광 측정을 위해 상온에서 직류 전류를 주입하여 GaN계 청색 및 녹색 LED와 LD에 각 5 mA/cm2에서 50 mA/cm2까지 전류밀도를 증가시킴에 따라 LD 및 LED칩 형태에 상관없이 청색 LD와 LED의 파장은 약 465nm에서 약 458nm로 감소하였고 녹색 LD와 LED의 파장은 약 521nm에서 약 511~513 nm까지 단파장화가 발생했다. 이는 동일한 웨이퍼에 동일한 전류 밀도를 주입하였기 때문에 발생하는 것으로 판단된다. 그러나, 청색 LED의 효율은 50 mA/cm2에서 약 70%정도로 감소하고 반면 녹색 LED의 경우 동일한 전류밀도 하에 약 52%정도로 감소하였지만, 청색과 녹색 LD의 경우 동일한 전류 밀도의 범위 내에서 더욱 낮은 효율저하 현상을 나타내었다. 또한, 접합 온도를 측정한 바 청색소자가 녹색 소자에 비하여 낮은 접합 온도를 나타낼 뿐아니라, 청색 및 녹색 LD의 경우 LED 보다 낮은 접합 온도를 나타내고 있었다. 이는 InGaN 활성층의 In 조성이 증가할수록 비발광 센터에 의한 접합온도 상승 뿐 아니라, LD ridge 구조에서 더 많은 열이 방출되어 접합 온도가 감소될 수 있는 것으로 판단된다. 우리는 동일한 웨이퍼에 LED와 LD를 제작하였고, 동일한 전류 주입밀도를 인가하였기 때문에 LD와 LED의 효율 감소 현상의 차이는 이송자 넘침 현상, 결정 결함, 오제 재결합 등이 원인보다 활성층의 접합 온도 상승이 가장 큰 영향이 될 수 있을 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.525-532
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• 2017

The development of an inkjet-based manufacturing machine for the production of next-generation displays using organic and quantum-dot light emitting diodes at a low cost has been conducted. To employ inkjet printing in production lines of displays, the development of a high-speed inkjet-monitoring device to verify the reliable droplet jetting status from multiple nozzles is required. In this study, an inkjet monitoring device using a rotatable mirror with rotary and linear ultrasonic motors is developed in place of a conventional, linear reciprocating, motion-based inkjet monitoring device. Its performance is also demonstrated. The measurements of circular patterns with diameters of $10{\mu}m$, $30{\mu}m$, and $50{\mu}m$ are performed with the accuracies of $0.5{\pm}1.0{\mu}m$, $-1.2{\pm}0.3{\mu}m$, and $0.2{\pm}0.5{\mu}m$, respectively, within 17 sec. By optimizing the control program, the takt time can be reduced to as short as 8.6 sec.