• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.134.2-134.2
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• 2014

Photonic crystal solar cells have the potential for addressing the disparate length scales in polymer photovoltaic materials, thereby confronting the major challenge in solar cell technology: efficiency. One must achieve simultaneously an efficient absorption of photons with effective carrier extraction. Unfortunately the two processes have opposing requirements. Efficient absorption of light calls for thicker PV active layers whereas carrier transport always benefits from thinner ones, and this dichotomy is at the heart of an efficiency/cost conundrum that has kept solar energy expensive relative to fossil fuels. This dichotomy persists over the entire solar spectrum but increasingly so near a semiconductor's band edge where absorption is weak. We report a 2-D, photonic crystal morphology that enhances the efficiency of organic photovoltaic cells relative to conventional planar cells. The morphology is developed by patterning an organic photoactive bulk heterojunction blend of Poly(3-(2-methyl-2-hexylcarboxylate) thiophene-co-thiophene) and PCBM via PRINT, a nano-embossing method that lends itself to large area fabrication of nanostructures. The photonic crystal cell morphology increases photocurrents generally, and particularly through the excitation of resonant modes near the band edge of the organic PV material. The device performance of the photonic crystal cell showed a nearly doubled increase in efficiency relative to conventional planar cell designs. Photonic crystals can also enhance performance of other optoelectronic devices including organic laser.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.633-641
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• 2020

Microbial rhodopsins are a superfamily of photoactive membrane proteins with the covalently bound retinal cofactor. Isomerization of the retinal chromophore upon absorption of a photon triggers conformational changes of the protein to function as ion pumps or sensors. After the discovery of proteorhodopsin in an uncultivated γ-proteobacterium, light-activated proton pumps have been widely detected among marine bacteria and, together with chlorophyll-based photosynthesis, are considered as an important axis responsible for primary production in the biosphere. Rhodopsins and related proteins show a high level of phylogenetic diversity; we focus on a specific class of bacterial rhodopsins containing the '3 omega motif.' This motif forms a stack of three non-consecutive aromatic amino acids that correlates with the B-C loop orientation and is shared among the phylogenetically close ion pumps such as the NDQ motif-containing sodium-pumping rhodopsin, the NTQ motif-containing chloride-pumping rhodopsin, and some proton-pumping rhodopsins including xanthorhodopsin. Here, we reviewed the recent research progress on these 'omega rhodopsins,' and speculated on their evolutionary origin of functional diversity.

• 한국수소및신에너지학회논문집
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• 제18권1호
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• pp.40-45
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• 2007

Methylene blue(MB) was photocatalytically degraded with one-body photoanode and solar simulator to investigate the possible application to both environmental purification and photoelectrochemical cell for hydrogen production. Photoactive titanium dioxide was formed on both sides of Ti plate following steps such as rinsing-annealing-calcination or anodizing(20 V, 30 V)-annealing($350^{\circ}C$, $450^{\circ}C)$ after etching. The prepared titania plate($2cm{\times}2\;cm$, ca 1.6 mg $TiO_2$ on the basis of $1\;{\mu}m$ thickness) was used to degrade MB(10 ppm in 200 mL solution). The reaction tended to follow the Langmuir-Hinshelwood kinetics with zero order. Comparative experiments with Degussa P25 showed the same zero order kinetics when 2 mg of P25 had been used, while the first order kinetics when 200 mg used. This concludes the feasibility of the prepared titania plate as a material for the purification of low-level harmful organics and an electrode or a membrane for photoelectrochemical system for hydrogen production.

• ETRI Journal
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• 제35권4호
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• pp.587-593
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• 2013

We demonstrate semitransparent organic photovoltaics (OPVs) based on thin metal electrodes and polymer photoactive layers consisting of poly(3-hexylthiophene) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester. The power conversion efficiency of a semitransparent OPV device comprising a 15-nm silver (Ag) rear electrode is 1.98% under AM 1.5-G illumination through the indium-tin-oxide side of the front anode at 100 $mW/cm^2$ with 15.6% average transmittance of the entire cell in the visible wavelength range. As its thickness increases, a thin Ag electrode mainly influences the enhancement of the short circuit current density and fill factor. Its relatively low absorption intensity makes a Ag thin film a viable option for semitransparent electrodes compatible with organic layers.

• 한국재료학회지
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• 제30권11호
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• pp.595-600
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• 2020

The photovoltaic properties of perovskite solar cells (PSCs) with a carbon electrode fabricated using different annealing processes are investigated. Perovskite formation (50 ℃, 60 min) using a hot-plate and an oven is carried out on cells with a glass/fluorine doped TiO₂/TiO₂/ZrO₂/carbon structure, and the photovoltaic properties of the PSCs are analyzed using a solar simulator. The microstructures of the PSCs are characterized using an optical microscope, a field emission scanning electron microscope, and an electron probe micro-analyzer (EPMA). Photovoltaic analysis shows that the energy conversion efficiency of the samples fabricated using the hot-plate and the oven processes are 2.08% and 6.90%, respectively. Based on the microstructure of the samples and the results of the EPMA, perovskite is formed locally on the carbon electrode surface as the γ-butyrolactone (GBL) solvent evaporates and moves to the top of the carbon electrode due to heat from the bottom of the sample during the hot plate process. When the oven process is used, perovskite forms evenly inside the carbon electrode, as the GBL solvent evaporates extremely slowly because heat is supplied from all directions. The importance of the even formation of perovskite inside the carbon electrode is emphasized, and the feasibility of oven annealing is confirmed for PSCs with carbon electrodes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.291-291
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• 2010

Organic solar cells have attracted much interest due to the potential advantage of the lightness, simple solution processing and flexibility. Until recently, the focus of organic solar cells research has been on optimization of material processing to improve the power conversion efficiency. However, area scaling is an important position for alternative to the market dominating solar cells. Spray deposition technologies have advantage of less material wastage and possibility of large scale photoactive area coating when compared with spin coating process. We investigated the performance of organic solar cells as a function of active area using two types of deposition process. The commonly used process is spin coating which can be fabricated organic materials deposition for devices. Spray deposition process compare with spin coating for large-area organic solar cells. The spray deposition organic layer shows excellent performance up to the active area of $4\;cm^2$ with the PCE of ~3.0 % under AM.1.5 simulated illumination with an intensity of $100mW/cm^2$. This indicates that the spray deposition process can be used as a mass production process for evaluating large-area organic solar cells.

• 접착 및 계면
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• 제25권1호
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• pp.143-151
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• 2024

유기태양전지(Organic photovoltaics, OPV)는 기계적 유연성, 경량, 반투명성, 낮은 제조 비용 등 여러 가지 고유한 특성을 지니고 있어 차세대 신재생 에너지원으로 큰 잠재력을 보여 왔다. 최근 분자구조 및 소자 엔지니어링의 발전으로 19% 이상의 높은 효율을 달성했다. 그러나 이러한 높은 효율을 갖춘 광활성층 물질들은 복잡한 구조로 인해 합성 과정이 복잡하며 제조비용이 높아 상용화에 어려움이 있다. 이 문제를 해결 하기 위해 간단한 구조를 갖는 저비용 광활성층 물질들에 대한 연구가 활발히 이루어지고 있다. 본 논문에서는 이러한 낮은 비용의 광활성층 물질 및 이를 합성하기 위한 전략들에 대해 소개한다.

• Journal of Photoscience
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• 제9권2호
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• pp.122-125
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• 2002

Coherent oscillations in is fluorescence dynamics of W.-t. PYP and its site-directed mutants have been observed. Two oscillatory modes coupled with the ultrafast fluorescence due to the twisting of the excited chromophore were identified, a high ftequency mode (∼135 cm$\^$-1/) with ∼550 is damping time and a low frequency overdamped mode (-45 cm$\^$-1/) with ∼250 is damping time, respectively. Both modes disappear in the fluorescence dynamics of denatured PYP emphasizing the important role of the protein nanospace as the environment for photoreaction. The qualitative picture of fluorescence dynamics in site-directed mutants was rather similar to that in W.-t. PYP, i.e., similar oscillatory modes (∼130-140 cm$\^$-1/ and ∼40-70 cm$\^$-1/) have been observed. This indicates that the vibrational modes and electron-vibration couplings do not change dramatically due to the mutation though the damping time of low frequency mode a little decreases as the protein nanospace structure becomes looser and more disordered by mutation. On the other hand, in the case of some PYP analogues, the qualitative picture of fluorescence dynamics changes, showing the familiar picture of solvation effect whereas the oscillations are almost damped. Comparative analyses of these observations are presented.

• 공업화학
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• 제25권5호
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• pp.487-496
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• 2014

본 연구에서는 phenothiazine과 benzothiadiazole을 기반으로 하고, phenothiazine의 질소 위치에 다양한 side-chain을 치환한 고분자를 합성하였다. 합성된 고분자는 광학적, 전기화학적 분석 결과 300~700 nm에서 흡수를 보였고, -5.4 eV 정도의 이상적인 HOMO energy level를 갖는 특성을 확인하였다. 고분자와 $PC_{71}BM$을 광활성층으로 사용한 소자를 제작하였고, 측정결과 branched side-chain을 가지며 탄소수가 많은 P2HDPZ-bTP-OBT가 2.4%로 최대 광전변환효율을 갖는 것으로 확인되었다($V_{OC}$ : 0.74 V, $J_{SC}$ : $6.9mA/cm^2$, FF : 48.0%).

• Toxicological Research
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• 제21권2호
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• pp.99-105
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• 2005

Photo-mutagenic compounds have been known to alter skin cancer rates by acting as initiators or by affecting subsequent steps in carcinogenesis. The objectives of this study are to investigate the utility of photo-chromosomal aberration (photo-CA) assay for detecting photo-clastogens, and to evaluate its ability to predict rodent photocarcinogenicity. Photo-CA assay was performed with five test substances that demonstrated positive results in photo-carcinogenicity tests: 8-Methoxypsoralen (photoactive substance that forms DNA adducts in the presence of ultraviolet A irradiation), chlorpromazine (an aliphatic phenothiazine an alpha-adrenergic blocking agent), lomefloxacin (an antibiotic in a class of drugs called fluoroquinolones), anthracene (a tricyclic aromatic hydrocarbon a basic substance for production of anthraquinone, dyes, pigments, insecticides, wood preservatives and coating materials) and Retinoic acid (a retinoid compound closely related to vitamin A). For the best discrimination between the test substance-mediated genotoxicity and the undesirable genotoxicity caused by direct DNA absorption, a UV dose-response of the cells in the absence of the test substances was firstly analyzed. All 5 test substances showed a positive outcome in photo-CA assay, indicating that the photo-CA test is very sensitive to the photo-genotoxic effect of UV irradiation. With this limited data-set, an investigation into the predictive value of this photo-CA test for determining the photo-carcinogenicity showed that photo-CA assay has the high ability of a test to predict carcinogenicity. Therefore, the photo-CA test using mammalian cells seems to be a sensitive method to evaluate the photo-carcinogenic potential of new compounds.