• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.221-226
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• 2013

The water soluble quantum dots (QDs) are synthesized by the phase transfer and silica coating reaction. The photoluminescence intensity of silica-coated QDs are mainly affected by the amount of phase transfer agent, SDS (sodium dodecyl sulfate), and the maximum value is obtained at the cmc (critical micell concentration) concentration of SDS in the phase transfer reaction. Based on fluorescence spectra and field emission transmission electron microscope (FETEM), the energy transfer rate by forster resonance energy transfer (FRET) is increasing with the thickness of the silica shell coated on CdSe/ZnS QDs.

• 한국재료학회지
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• 제19권1호
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• pp.44-49
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• 2009

Conjugated nanocrystals using CdSe/ZnS core/shell nanocrystal quantum dots modified by organic linkers and glucose oxidase (GOx) were prepared for use as biosensors. The trioctylphophine oxide (TOPO)-capped QDs were first modified to give them water-solubility by terminal carboxyl groups that were bonded to the amino groups of GOx through an EDC/NHS coupling reaction. As the glucose concentration increased, the photoluminescence intensity was enhanced linearly due to the electron transfer during the enzymatic reaction. The UV-visible spectra of the as-prepared QDs are identical to that of QDs-MAA. This shows that these QDs do not become agglomerated during ligand exchanges. A photoluminescence (PL) spectroscopic study showed that the PL intensity of the QDs-GOx bioconjugates was increased in the presence of glucose. These glucose sensors showed linearity up to approximately 15 mM and became gradually saturated above 15 mM because the excess glucose did not affect the enzymatic oxidation reaction past that amount. These biosensors show highly sensitive variation in terms of their photoluminescence depending on the glucose concentration.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.148-148
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• 2015

Over the past several years, Colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been developed for the future of optoelectronic applications. An inverted-type quantum-dot light-emitting-diode (QDLED), employing low work function organic material polyethylenimine ethoxylated(PEIE) (<10 nm)[1] modified ZnO nanoparticles (NPs) as electron injection and transport layer, was fabricated by all solution processing method, instead of electrode in the device. The PEIE surface modifier incorporated on the top of the ZnO NPs film, facilitates the enhancement of both electorn injection into the CdSe-ZnS QD emissive layer by lowering the workfunction of ZnO from 3.58eV to 2.87eV and charge balance on the QD emitter. 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 7.5 V, the QDLED device emitted spectrally orange color lights with high luminance up to 11110 cd/m2, and showed current efficiency of 2.27 cd/A.[2]

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.35.1-35.1
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• 2010

The Cu(In,Ga)Se2(CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, many groups made hard efforts to overcome its disadvantages in terms of high absorption of short wavelength, Cd hazardous element. Among Cd-free candidate materials, the CIGS thin film solar cells with Zn compound buffer layer seem to be promising with 15.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, few groups were successful to report high-efficiency CIGS solar cells with Zn compound buffer layer, compared to be known how to fabricate these solar cells. Each group's chemical bah deposition (CBD) condition is seriously different. It may mean that it is not fully understood to grow high quality Zn compound thin film on the CIGS using CBD. In this study, we focused to clarify growth mechanism of chemically deposited Zn compound thin film on the CIGS, especially. Additionally, we tried to characterize junction properties with unfavorable issues, that is, slow growth rate, imperfect film coverage and minimize these issues. Early works reported that film deposition rate increased with reagent concentration and film covered whole rough CIGS surface. But they did not mention well how film growth of zinc compound evolves homogeneously or heterogeneously and what kinds of defects exist within film that can cause low solar performance. We observed sufficient correlation between growth quality and concentration of NH3 as complex agent. When NH3 concentration increased, thickness of zinc compound increased with dominant heterogeneous growth for high quality film. But the large amounts of NH3 in the solution made many particles of zinc hydroxide due to hydroxide ions. The zinc hydroxides bonded weakly to the CIGS surface have been removed at rinsing after CBD.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.729-732
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• 2012

본 논문에서 이온성액체를 이용한 초음파화학을 통해서 칼코젠 나노입자를 in-situ로 합성하여서 다중벽 탄소나노튜브(MWCNT) 위에 도포하였다. 1-Butyl-3-methylimidazolium tetrafluoroborate ($BMimBF_4$) 이온성액체를 이용해서 MWCNT의 표면을 기능화하였다. 합성된 MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe, MWCNT/$BMimBF_4$/ZnSe 나노복합체를 TEM과 EDS를 이용해서 분석하였다. 특히, MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe, and MWCNT/$BMimBF_4$/ZnSe 나노복합체는 각각 요철과 같거나, 거칠거나 부드러운 코어-쉘 형태와 같은 특이한 구조를 보여주었다. 본 연구는 반응속도가 다른 전구체로부터 얻어진 이성분 반도체 나노입자를 합성과 동시에 탄소나노튜브에 도포할 수 있는 새로운 합성법을 제시한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.672-672
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• 2013

본 연구에서는 수열합성법을 기반으로 한 3차원 ZnO 나노구조의 합성을 통해 효율적인 양자점 감응형 태양전지로의 응용을 하고 그 특성을 평가하였다. 기존의 1차원 ZnO 나노구조의 경우 높은 전자이동도와 구조적으로 얻을 수 있는 방향성 있는 전자의 효율적인 전달을 통해 효과적인 광전극으로 많은 관심을 받아왔다. 하지만 나노파티클 기반의 필름에 비해 표면적이 크게 떨어지기 때문에 효과적인 흡광이 어렵다는 단점이 존재하여 높은 효율특성을 내지는 못하였다. 본 연구에서는 이러한 단점을 극복하면서 기존 ZnO 나노선의 장점을 극대화 하기 위해 성장시킨 ZnO 나노선 위에 추가적으로 가지를 형성하여 표면적 향상과 효과적인 전자전달 특성을 얻고자 하였다. 3차원 ZnO 나노구조는citrate 계열의 capping agent의 첨가를 통한 수열 합성법을 통해 1차원의 ZnO 나노선 위에 nanosheet 형식의 가지를 형성하였고 이는 빛의 효과적인 산란특성 및 표면적 향상을 통한 CdS, CdSe의 양자점 증착량을 증가시키는 효과를 얻을 수 있었다. 이러한 태양전지의 소자 특성은 SEM, TEM을 통한 구조 특성평가 및 DRS, J-V curve 및 IPCE를 통한 광학적 특성평가를 통해 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.374-374
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• 2011

Cu(In,Ga)Se2 (CIGS) 박막 태양전지는 일반적으로 Soda lime glass/Mo/CIGS/CdS/ZnO/ITO/Al의 구조로 제작된다. 태양전지는 p형과 n형 반도체의 접합에 의해서 동작을 하게 되며, CIGS 박막 태양전지에서는 p형으로 CIGS 박막과 n형으로 CdS 박막이 사용된다. CIGS 박막태양전지에서는 p형과 n형이 서로 다른 물질로 이루어진 이종접합을 이루게 되고, 계면에서의 밴드가 어떻게 형성이 되느냐에 따라 태양전지 성능에 영향을 미치게 된다. p형의 CIGS 박막은 주로 다단계 증발법에 의해 형성되고 3단계 공정조건에 의해 계면의 특성에 많은 영향을 미치게 된다. n형의 CdS 박막은 주로 chemical bath deposition (CBD) 법에 의해 제작된다. 이렇게 제작되는 CBD-CdS는 시약의 농도, pH (수소이온농도), 박막 형성시의 온도 등의 조건에 따라 특성이 변하게 된다. 본 논문에서는 3단계 공정시간을 변화시켜 제작된 CIGS 박막 위에 CBD-CdS 증착 조건 중 thiourea 의 농도를 변화시켜 CIGS 태양전지를 제작하고 그에 따른 특성을 살펴보았다. CIGS 박막은 3단계 공정시간을 490초와 360초로 하여 제작하였고, CdS 박막은 thiourea 농도를 각각 0.025 M과 0.05 M, 0.074 M, 0.1 M로 변화시켜가며 제작하였다. 제작된 CIGS 박막 태양전지는 CIGS 3단계 공정시간과 thiourea의 조건에 따라 최고 15.81%, 최저 14.13%로 나타내었다. 또한, 외부양자효율을 측정하여 제작된 CIGS 박막 태양전지의 파장에 따른 특성을 비교하였다.

• 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.

• 한국환경과학회지
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• 제8권4호
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• pp.515-523
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• 1999

Nine trace metals (Zn, Fe, Al, Pb, Mn, Cu, Ni, Cr, and Cd) and Se concentrations were determined in organs and tissues(muscle, bone, kidney, liver and skin) of the striped field mice, Apodemus agrarius collected at Daejeo-dong, Pusan city and the Sorak Mt., Kangwon Province. All the trate elements were detected from all the mice examined. As for the metal concentrations in the mice from Daejeo-dong, Zn, Fe, Al, Mn, Ni and Cr were significantly higher than those in Sorak Mt.(p<0.05), suggesting that pesticides including Zn and factory wastes containing several metals might contaminated the environment of Daejeo-dong. As regards the element concentrations in each organ and tissue, Fe, Al, Pb, Mn, Cu, Cr and Cd concentrations were high in liver or kidney; Zn in skin and bone; Ni in bone, skin and kidney; and Se in muscle, liver and skin in all the mice examined. There were significant differences(p<0.05) between juveniles and adults in average concentration of metals(Zn, Fe, Pb, Mn, Ni, and Cd) in every organs and tissues of mice collected at Daejeo-dong. Much higher average levels of metals in juveniles indicate that considerable burdens fo metals might be transferred through the placenta. However, there were no significant differences between males and females, and between young and old adults in average metal concentrations, which suggests that the mice might accumulate the metals during their life time, although they might excrete the metals not only through reproductive activities, such as parturition, lactation and ejaculation of semen, but also through molting, judging from higher accumulating ratios of most metals in skin of adults than of juveniles.

• Applied Microscopy
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• 제27권3호
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• pp.257-263
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• 1997

Microstructural characterizations of II-VI blue laser diodes which consist of quaternary $Zn_{1-x}Mg_xS_ySe_{l-y}$ cladding layer, ternary $ZnS_ySe_{l-y}$ guiding layer and $Zn_{0.8}Cd_{0.2}Se$ quantum well as active layer were carried out using the transmission electron microscope working at 300 kV. Even though the entire structure is pseudomorphic to GaAs substrate, the structure had contained numerous extended stacking faults and dislocations which had created at ZnSe/GaAs interfaces and then further grown to the top of the epilayers. These faults might be expected to cause the degradation and shortening the lifetime of laser devices.