• 한국결정성장학회지
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• 제12권1호
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• pp.11-20
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• 2002

The world at the end of the $20^{th}$ Century has become "blue" Indeed, this past decade has witnessed a "blue rush" towards the development of violet-blue-green light emitting diodes (LEDs) and laser diodes (LDs) based on wide bandgap III-Nitride semiconductors. And the hard work has culminated with, first, the demonstration of commercial high brightness blue and green LEDs and of commercial violet LDs, at the very end of this decade. Thanks to their extraordinary properties, these semiconductor materials have generated a plethora of activity in semiconductor science and technology. Novel approaches are explored daily to improve the current optoelectronics state-of-the-art. Such improvements will extend the usage and the efficiency of new light sources (e.g. white LEDs), support the rising information technology age (e.g. high density optical data storage), and enhance the environmental awareness capabilities of humans (ultraviolet and visible photon detectors and sensors). Such opportunities and many others will be reviewed in this presentation.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.453-459
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• 2013

In phtosynthetic light harvesting complexes, the electronic transition energies of chlorophylls are influenced by the Coulombic interaction with nearby molecules. Variation of the interactions caused by structural inhomogeneity in biological environment results in a distribution of disordered electronic transition energies of chlorophylls. In order to provide a practical guide to predict qualitative tendency of such distribution, we model four porphyrin derivatives including chlorophyll a molecule interacting with an external positive charge and calculate their transition energies using the time dependent density functional method. It is found that ${\pi}-{\pi}^*$ transition energies of the molecules are generally blue-shifted by the charge because this stabilizes occupied molecular orbitals to a greater extent than unoccupied ones. Furthermore, new transitions in the visible region emerge as a result of the red-shift in energy of an unoccupied Mg orbital and it is suggested that light-induced electron transfer may occur from the tetrapyrrole ring to the central magnesium when the molecules are interacting with a positive charge.

• Transactions on Electrical and Electronic Materials
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• 제17권1호
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• pp.41-45
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• 2016

The Cs₃Sb photocathode was formed by non-vacuum process technology and successive in-situ photocathode vacuum device fabrication carried out in a process chamber. Performance testing of the device was followed. Light emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The luminescent characteristics of the devices were investigated by measuring the optical parameters as functions of the applied anode voltages. The results showed that this approach could produce a more easily directed and controlled stream of light. These features make these devices suitable for a variety of planar lighting applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.444-445
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• 2007

Aluminum-doped zinc oxide (AZO) films are attractive materials as transparent conductive electrode because they are inexpensive, nontoxic and abundant element compared with indium tin oxide (ITO). AZO films have been deposited on glass (coming 1737) substrates by RF magnetron sputtering system. An ultrathin layer of nickel oxide (NiO) was deposited on the AZO anode to enhance the hole injections in organic light-emitting diodes (OLED). The current density-voltage and luminescence-voltage properties of devices were studied and compared with ITO device.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.535-536
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• 2005

Organic photovoltaic effects were studied in a device structure of ITO/CuPc/Al and ITO/CuPc/$C_{60}$/BCP/Al. A thickness of CuPc layer was varied from 10 nm to 50 nm, we have obtained that the optimum CuPc layer thickness is around 40 nm from the analysis of the current density-voltage characteristics in CuPc single layer photovoltaic cell. From the thickness-dependent photovoltaic effects in CuPc/$C_{60}$ heterojunction devices, higher power conversion efficiency was obtained in ITO/20nm CuPc/40nm $C_{60}$/Al, which has a thickness ratio (CuPc:$C_{60}$) of 1:2 rather than 1:1 or 1:3. Light intensity on the device was measured by calibrated Si-photodiode and radiometer/photometer of International Light Inc(IL14004).

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.120-130
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• 2023

PEMFC has high potential for future development due to its high energy density, eco-friendliness, and high energy efficiency. When it becomes small, light and flexible, it can be competitive as an energy source for portable devices or flexible electronic devices. However, the use of hard and heavy materials for structural rigidity and uniform contact pressure transmission has become an obstacle to reducing the weight and flexibility of PEMFCs. This review intends to provide an example of the application of a new structure and material for lightweight and flexibility. As a lightweight PEMFC, a tubular design is presented and structural advantages through numerical modeling are explained. Manufacturing methods to realize the structural advantages and possibilities of tubular PEMFCs are discussed. In addition, the materials and manufacturing processes used to fabricate lightweight and flexible PEMFCs are described and factors affecting performance are analyzed. Strategies and structural improvements of light and flexible movements are discussed according to the component parts.

• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.397-402
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• 2023

We have developed inverted green phosphorescent organic light emitting diodes (OLEDs) using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and bis(carbazole-9-yl)biphenyl (CBP) hole transport layers. The driving voltage, current efficiency, power efficiency, and emission characteristics of devices were investigated. While the driving voltage for the same current density was about 1~2 V lower in the devices with the TAPC layer, the maximum luminance was higher in the device with the CBP layer. The maximum current efficiency and power efficiency were 3.2 and 2.7 times higher in the device with the CBP layer, respectively. The higher efficiency in the CBP device resulted from the enhanced hole-electron balance although weak parasitic recombination takes place in the CBP hole transport layer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.59.2-59.2
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• 2010

Throughout history, daylight has been a primary source of lighting in buildings, supplemented originally with burned fuels and more recently with electrical energy. Before daylight was supplemented or replaced with electric light in the late 19th-century, consideration of good daylight strategies was essential. As we entered the mid-20th-century, electric light supplanted daylight in buildings in many cases. Fortunately, during the last quarter of the 20th-century and early years of this century, architects and designers have recognized the importance and value of introducing natural light into buildings. There are many simple strategies that can enhance daylighting and reduce the need for electric lights. Good quality daylight is always welcome, but remember that the electric lights must be dimmed or shut off in order for daylighting to save energy. We designed and built mirror systems and vertical daylighting devices to improve daylight condition of office buildings in bad condition because urban density is getting higher. This case study aims to analysis the principles and characteristics of mirror systems and vertical daylighting devices and selected the method that can improve constructability. The results of this study are going to use the back data to set-up the design standards. Hereafter we're going to progress the performance test and product the design manual to improve applicability of daylighting systems at design phase.

• 중소기업융합학회논문지
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• 제6권4호
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• pp.99-106
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• 2016

본 논문에서는 White 색상을 달성하기 위한 R, G, B 혼합비율 Type을 기반으로 상대적으로 열화된 BER성능을 달성하는 파장 대역에 Forward Error Correction (FEC) 기법을 적용하여, 전체 시스템의 BER성능을 향상 시킬 수 있는 가시광 통신 시스템을 제안한다. FEC기법으로 Low Density Parity Check (LDPC) 코드를 적용하였으며, LDPC 부호는 Shannon의 한계치에 가장 근접하는 오류정정 부호로 평가되고 있으며, 오류마루(error floor) 현상이 나타나지 않고, 완전 병렬처리가 가능하여 고속 복호가 가능한 장점을 가지고 있다. 이와 같은 시스템에서 LDPC채널 코딩을 각 파장 대역에 부분적으로 적용함으로써, 주파수 효율 감소 및 데이터 전송률 감소를 완화 할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.90-93
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• 2002

In the surface pressure-area isotherms of mixed monolayers, mixtures containing as much as 30 mol% of AA form stable condensed monolayer while the monolayer without AA is in the expanded state because PVK take on 3D collapsed. All of the mixed monolayers with 0, 10, 20 and 30 mol% of AA could be readily transferred onto ITO substrate at 16, 17, 24 and 26 mN/m, respectively. The monolayer containing 30 mol% of AA, however, showed a roughness value of 28A and became homogeneous decreasing with the phase separation. We fabricated organic EL device of ITO/CuPc/MEL/BBOT/iLiF/Al using mixed monolayer of 13, 19 and 25 layer deposited by LB method as a emitting layer. In the voltage-current characteristics of EL device, current density was much smaller than that of the spin-coated devices. It may due to the large contact resistance existed at the interface of LB layer/organic layer inhibit carrier injection to the emitting layer. EL spectra of device showed peaks at 450. 470, 505, 555 and 650 nm and the white light emission indicate the CIE coordinate x=0.306, y=0.353.