• 한국콘텐츠학회논문지
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• 제8권11호
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• pp.18-24
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• 2008

유기 발광 다이오드(Organic light-emitting diode, OLED)는 저전력 구동, 자체발광, 넓은 시야각, 우수한 고해상도, 풀 칼라, 높은 재현성, 빠른 응답속도, 간편한 제조 공정 등의 장점을 가지고 있으나, 고성능 디스플레이로서 실용화하기 위해서는 아직도 해결되어야 할 과제가 많다. 소자의 저소비전력, 제조공정의 안정성, 대형 기판기술, 봉지 기술, 소자의 수명, 풀 컬러화를 위한 적색, 청색, 발광 소자의 고휘도등이 시급하다. 무엇보다 중요한 것은 유기 발광 소자의 효율을 향상시키는 것이 상용화를 위한 키(key)이다. 이를 위해서 유기 발광 소자의 구조 개선과 새로운 유기 물질 적용을 통해 구동전압을 낮춤으로써 효율을 향상시킬 수 있다. 따라서 본 연구에서는 유기 발광 소자의 효율을 향상시킬 목적으로 ITO/TPD/Znq2+DCJTB/Znq2/Al의 구조와 ITO/CuPc/NPB/Alq3+DCJTB/Alq3/Al의 구조를 가지는소자의 발광 층에 형광염료를 도포한 적색 발광 소자를 제작하고, 그 전기적 및 광학적인 특성을 평가하였다.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.301-305
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• 2008

유기 발광 다이오드(Organic light-emitting diode, OLED)는 저전력 구동, 자체발광, 넓은 시야각, 우수한 고해상도, 풀 칼라, 높은 재현성, 빠른 응답속도, 간편한 제조 공정 등의 장점을 가지고 있으나, 고성능 디스플레이로서 실용화하기 위해서는 아직도 해결되어야 할 과제가 많다. 소자의 저소비전력, 제조공정의 안정성, 대형 기판기술, 봉지 기술, 소자의 수명, 풀 컬러화를 위한 적색, 청색, 발광소자의 고휘도 등이 시급하다. 무엇보다 중요한 것은 유기 발광 소자의 효율을 향상시키는 것이 상용화를 위한 키(key) 이다. 이를 위해서 유기 발광 소자의 구조 개선과 새로운 유기 물질 적용을 통해 구동전압을 낮춤으로써 효율을 향상시킬 수 있다. 따라서 본 연구에서는 유기 발광 소자의 효율을 향상시킬 목적으로 ITO/TPD/Znq2+DCJTB/Znq2/Al의 구조와 ITO/CuPc/N PB/Alq3+DCJTB/Alq3/Al의 구조를 가지는 소자의 발광층에 형광염료를 도포한 적색 발광 소자를 제작하고, 그 전기적 및 광학적인 특성을 평가하였다.

• 한국재료학회지
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• 제26권2호
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• pp.84-89
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• 2016

We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to $200^{\circ}C$. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as $100^{\circ}C$ and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.

• 한국진공학회지
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• 제17권6호
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• pp.566-575
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• 2008

촉매 화학기상증착법을 이용하여 합성된 이중층 탄소나노튜브를 가지고 전계전자 방출원을 제작하여 이들의 신뢰성 있는 전계전자 방출특성을 조사하였다. 합성된 탄소 필라멘트들은 TEM, TGA, 그리고 Raman 분석을 통하여 결함이 없고 순도가 높은 이중층 탄소나노튜브가 합성이 되었음을 확인하였다. 이들 이중층 탄소나노튜브 전계전자 방출원은 이전극 구조에서 낮은 턴-온 전계와 높은 전류밀도의 전계전자 방출 특성을 보여주었고, 균질한 전계방출 패턴과 좋은 전계방출 안정성을 나타내었다.

• 조명전기설비학회논문지
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• 제19권5호
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• pp.54-59
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• 2005

브러시리스 직류 전동기(Brushless U Motor : BLDCM)는 기존의 직류 전동기의 단점인 브러시를 제거한 것으로 제어가 간단하면서도 넓은 범위에서 속도 제어가 가능하고 효율이 높으며 경제적으로 제어기 제작이 가능하여 산업용 뿐 아니라 가전에까지 널리 사용된다. 그러나 BLDCM을 구동하는데 필수적인 센서는 제품 가격을 증가시킬 뿐만 아니라 운전 환경이 열악한 곳에서는 동작 오류를 발생하는 원인이 되고 있다. 본 논문에서는 BLDCM의 센서리스 구동에서 정상상태 운전뿐만 아니라 안정된 초기 구동에 관한 연구를 수행한다. 정상상태 운전은 측정된 역기전력을 이용하여 회전자의 위치를 결정함으로써 이루어지며, 초기 구동을 개선하기 위해 환류 다이오드로부터 측정된 전류 신호를 이용하여 초기 구동을 하게 된다. 이것은 실험을 통해 타당성을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.559-562
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• 2003

In this paper, we introduce a new method detecting thyristor faults of the power converter module in Control Rod Control System. When we control the currents in each coil of Control Rod Drive Mechanism by using the current control method, the current value can follow the current reference despite the faults like the missing phase or the diode acting. Comparing the fault current values with the normal current values, the bad transient characteristics of the abnormal current can make the operations of control rods incorrect. In this case, the information from the current trends cannot be enough to detect the fault occurrence in thyristors. Instead of the coil currents, the state of thyristors can be watched by measuring the coil voltages. In the existing system of Westinghouse type, the ripple detector takes charge of this task. But this detector has some shortcomings in the point of time for fault detection, we come to devise a new fault detection method solving the problems which belong to the ripple detector.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1886-1900
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• 2018

This paper proposes a confronting feedback control structure and controllers for positive output elementary super lift Luo converters (POESLLCs) working in discontinuous conduction mode (DCM). The POESLLC offers the merits like high voltage transfer gain, good efficiency, and minimized coil current and capacitor voltage ripples. The POESLLC working in DCM holds the value of not having right half pole zero (RHPZ) in their control to output transfer function unlike continuous conduction mode (CCM). Also the DCM bestows superlative dynamic response, eliminates the reverse recovery troubles of diode and retains the stability. The proposed control structure involves two controllers respectively to control the voltage (outer) loop and the current (inner) loop to confront the time-varying ON/OFF characteristics of variable structured systems (VSSs) like POESLLC. This study involves two different combination of feedback controllers viz. the proportional integral controller (PIC) plus sliding mode controller (SMC) and the fuzzy logic controller (FLC) plus SMC. The state space averaging modeling of POESLLC in DCM is reviewed first, then design of PIC, FLC and SMC are detailed. The performance of developed controller combinations is studied at different working states of the POESLLC system by MATLAB-Simulink implementation. Further the experimental corroboration is done through implementation of the developed controllers in PIC 16F877A processor. The prototype uses IRF250 MOSFET, IR2110 driver and UF5408 diodes. The results reassured the proficiency of designed FLC plus SMC combination over its counterpart PIC plus SMC.

• Transactions on Electrical and Electronic Materials
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• 제6권4호
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• pp.154-158
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• 2005

Organic molecules have many properties that make them attractive for electronic applications. We have been examining the progress of memory cell by using molecular-scale switch to give an example of the application using both nano scale components and Si-technology. In this study, molecular electronic devices were fabricated with amino style derivatives as redox-active component. This molecule is amphiphilic to allow monolayer formation by the Langmuir-Blodgett (LB) method and then this LB monolayer is inserted between two metal electrodes. According to the current-voltage (I-V) characteristics, it was found that the devices show remarkable hysteresis behavior and can be used as memory devices at ambient conditions, when aluminum oxide layer was existed on bottom electrode. The diode-like characteristics were measured only, when Pt layer was existed as bottom electrode. It was also found that this metal layer interacts with organic molecules and acts as a protecting layer, when thin Ti layer was inserted between the organic molecular layer and Al top electrode. These electrical properties of the devices may be applicable to active components for the memory and/or logic gates in the future.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.141-141
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• 2010

The effect of thermal anneal on the characteristics of structural properties and the enhancement of luminescence and photovoltaic (PV) characteristics of silicon-rich silicon-nitride films were investigated. By using an ultra high vacuum ion beam sputtering deposition, B-doped silicon-rich silicon-nitride (SRSN) thin films, with excess silicon content of 15 at. %, on P-doped (n-type) Si substrate was fabricated, sputtering a highly B doped Si wafer with a BN chip by N plasma. In order to examine the influence of thermal anneal, films were then annealed at different temperature up to $1100^{\circ}C$ under $N_2$ environment. Raman, X-ray diffraction, and X-ray photoemission spectroscopy did not show any reliable evidence of amorphous or crystalline Si clusters allowing us concluding that nearly no Si nano-cluster could be formed through the precipitation of excess Si from SRSN matrix during thermal anneal. Instead, results of Fourier transform infrared and X-ray photoemission spectroscopy clearly indicated that defective, amorphous Si-N matrix of films was changed to be well-ordered thanks to high temperature anneal. The measurement of spectral ellipsometry in UV-visible range was carried out and we found that the optical absorption edge of film was shifted to higher energy as the anneal temperature increased as the results of thermal anneal induced formation of $Si_3N_4$-like matrix. These are consistent with the observation that higher visible photoluminescence, which is likely due to the presence of Si-N bonds, from anneals at higher temperature. Based on these films, PV cells were fabricated by the formation of front/back metal electrodes. For all cells, typical I-V characteristic of p-n diode junction was observed. We also tried to measure PV properties using a solar-simulator and confirmed successful operation of PV devices. Carrier transport mechanism depending on anneal temperature and the implication of PV cells based on SRSN films were also discussed.