• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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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.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.399-399
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• 2012

II-V 족 화합물 반도체인 황화카드뮴(CdS)은 상온에서 2.42 eV의 밴드갭을 갖는 직접 천이형 물질로서 CdTe 또는 $CuInSe_2$와 같은 박막형 태양전지의 투과층(window layer)으로 널리 사용되고 있다. CdS 박막은 전자빔 증착법(e-beam evaporation), 화학용액증착법(chemical bath deposition), 열분해법(spray pyrolysis), 스퍼터링법(sputtering) 등으로 제작되고 있다. 이 중 스퍼터링법의 경우, 다른 증착법에 비해 조작이 간단하고 넓은 면적에서 균일한 박막을 증착할 수 있을 뿐만 아니라, 박막두께 조절이 용이하다. 따라서 본 실험에서는 RF 마그네트론 스퍼터링법으로 증착된 CdS 박막의 기판온도 및 열처리 온도변화에 따른 구조적 및 광학적 특성을 조사하였다. 기판은 RCA 기법으로 세정된 Corning Eagle 2000 유리 기판을 사용하였다. 박막 공정은 초기 진공 $1{\times}10^{-6}Torr$ 상태에서 20 sccm의 Ar 가스를 주입하고 100 W의 RF 파워, 7 mTorr의 공정 압력에서 기판 온도를 $200^{\circ}C$부터 $500^{\circ}C$까지 변화시키면서 수행하였다. 증착된 CdS 박막은 질소 분위기의 가열로(furnace)를 이용해 $300-500^{\circ}C$ 온도에서 30분간 열처리되었다. 시료들의 표면 형상은 scanning electron microscope를 사용하여 관찰하였으며, UV-vis-NIR spectrophotometer를 사용하여 400-1,000 nm 파장영역에서의 투과율을 측정하였다. 그리고 X-선 회절분석(X-Ray Diffraction)으로 결정구조를 조사하고 결정립 크기를 산출하였다.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.377-382
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• 2012

CdS thin films have been widely used as a buffer layer of CIGS semiconductor solar cells to reduce the lattice mismatch between transparent electrode and absorber layer. In order to prepare the CdS films with high transparency and low resistivity, they were deposited by varying Cd concentration with the constant S concentration in the solution using chemical bath deposition method. They were analyzed in terms of structural, optical and electrical properties of CdS films according to the $[S^{2-}]/[Cd^{2+}]$ ratio. In the case of Cd concentration higher than S concectration, CdS thin films were formed mainly by cluster- by-cluster formation due to the homogeneous reaction between Cd and S in the solution. Therefore the grain size increased and the transmittance decreased. On the other hand, in the case of Cd concentration lower than S concentration, CdS films were formed by heterogeneous reaction on the substrate rather than in the solution. The CdS films have the grains with the uniform circular shape of a few hundreds ${\AA}$. As the Cd concentration increased in the solution, the $[S^{2-}]/[Cd^{2+}]$ ratio decreased and the resistivity decreased by the increase in the carrier concentration due to the formation S vacancy by the excess Cd.

• Journal of the Korean Chemical Society
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• v.43 no.1
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• pp.1-7
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• 1999

Metal colloidal particles have been prepared by a photo-chemical process in an aqueous solution containing semiconductor nanocrystallites. Metal colloidal particles produced in CdS and AgBr exhibit different absorption spectra. Au particles produced in solution with CdS show typical Au plasmon resonance absorption spectra. On the other hand Ag particles in solution with AgBr shows surface plasmon resonance absorption spectra which are red-shifted, as compared to that of a dispersion of homogeneous Ag colloidal particles in the same host. The extent of red-shift depends on the UV illumination time. This phenomenon is interpreted within the context of effective medium theory for small volume fractions. From the theory, a metal coated particle predicts Ag plasmon resonance, red shifted with respect to 400 nm that would be associated with a silver particle in solution. The absorption peak position is very sensitive to the coating thickness.

• Clean Technology
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• v.26 no.4
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• pp.311-320
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• 2020

In this study, the photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) was carried out under visible light irradiation using CdS and CdZnS/ZnO photocatalysts prepared by a simple precipitation method. This study focused on examining the effect of physicochemical properties of dye and photocatalyst on the reaction pathway of photocatalytic degradation. The prepared photocatalysts were characterized by XRD, UV-vis DRS and XPS. Both the CdS and CdZnS/ZnO photocatalysts exhibit an excellent absorption in the visible light and the UV light regions. It was observed that the photocatalytic degradation of MO proceeds via the same reaction mechanism on both the CdS and CdZnS/ZnO photocatalysts. However, the photocatalytic degradation of RhB and MB was found to proceed through a different reaction pathway on the CdS and CdZnS/ZnO catalysts. It is interesting to note that MB dimer was formed on the CdS catalyst at the beginning of the photocatalytic reaction, while the MB monomer was degraded during the overall photocatalytic reaction on CdZnS/ZnO. The above results may be mainly ascribed to the difference of band edge potential of the conduction band in the CdS and CdZnS/ZnO semiconductors and the adsorption property of dye on the catalysts.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.111-111
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• 2003

반도체 나노결정은 양자구속효과(quantum confinement effect)에 의한 광학적인 특성을 갖기 때문에 광전자공학(optoelectronic), 광전지(photovoltaic)분야에 응용하려는 연구가 활발히 진행되고 있다. 본 연구에서는 고순도의 CdTe 나노결정을 1-thioglycerol 표면 완화제(surface stabilizer)로 사용하여 수용액 상태로 합성하였다. 모든 실험은 $N_2$ 분위기의 삼각플라스크에서 실험하였다. Cadmium 소오스로는 Cd(CIO$_4$)$_2$.6$H_2O$(Cadmium perchlorate hydrate-Aldrich)를 사용하였고 Tellurium 소오스로는 A1$_2$Te$_3$(Aluminum telluride-CERAC)와 H$_2$SO$_4$가 반응하여 H$_2$Te gas가 주입되도록 하였다. 합성된 CdTe 나노결정은 core-shell 형태로 존재하며 결정크기에 따른 특성분석을 위해서 High Resolution Transmission Electron Microscope (HRTEM), Photoluminescence spectroscopy, X-ray diffraction(XRD), UV-vis absorption spectra 분석을 하였다 또한 CdTe 나노결정을 나노와이어로 제작하여 CdTe 나노결정을 이용한 태양전지 제작에 응용하고자 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.76-77
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• 2009

CdS 박막은 에너지 밴드갭이 상온에서 2.42 eV인 직접 천이헝 반도체로써 태양전지 및 광전도 셀과 광센서 등에 널리 사용되고 있다. 본 논문에서는 유연성을 가지고 있는 PC, PET, PEN등 폴리머 기판을 $O_2$ 플라즈마를 사용하고 RF Power 100W, 공정시간 60~1200s의 조건에서 전처리하고, 이 기판을 CBD법을 이용하여 CdS 박막을 증착시켰다. 폴리머 기판의 결정립크기는 180s의 처리시간 부터 증가를 보였으며, 전기적 특성은 60s 와 180s에서 이동도와 비저항이 반비례하는 경향성을 나타내었고 광투과율은 처리시간에 따른 뚜렷한 변화를 보이지 않았다.

• Analytical Science and Technology
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• v.14 no.3
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• pp.259-265
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• 2001

Photocatalytic degradation of Congo red was performed using various semiconductors as ZnO, CdS, rutile-$TiO_2$ or mixed rutile-$TiO_2$/ZnO. The change of degradation of the dye was investigated by UV-visible spectrophotometric method. The photocatalytic action of CdS was greater than ZnO and rutile-$TiO_2$ in account of low band gap energy of CdS. The rate of photocatalytic degradation reaction increased drastically in according to increasing ratio of ZnO on mixed rutile-$TiO_2$/ZnO. These photocatalytic effect of rutile-$TiO_2$ was suppressed by more stable rutile-$TiO_2$, doping the hydrolysis product with $Zn^{2+}$ prior to calcination onto the rutile-$TiO_2$ surface.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.450-454
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• 2021

Currently, gamma nuclide analysis is mainly used using inorganic scintillators or semiconductor detectors. These detectors have high resolution but there are less economical, limited in size, and low process ability than plastic scintillators. Therefore, quantum dot-based plastic scintillator was developed using the advantages of the quantum dot nanomaterial and the conventional plastic scintillator. In this study, efficient plastic scintillator was fabricated by adding CdS/ZnS based on the most widely used Cd-based nanomaterial in a polystyrene matrix. In addition, the performance of the commercial plastic scintillator was compared and it was analyzed through radiological measurement experiments. The detection efficiency of fabricated plastic scintillator was higher than commercial plastic scintillator, EJ-200. It is believed that this fabricated plastic scintillator can be used as a radioactivity analyzer in the medical and nuclear facility fields.

• Solar Energy
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• v.17 no.2
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• pp.55-66
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• 1997

The structural and optoelectronic properties of polycrystalline CdS films up to several microns in thickness, fabricated by three different methods, are compared to one another for the purpose of preparing CdTe/CdS solar cells. All films were deposited on an indium tin oxide on glass substrate. The three methods are: 1) alternated spraying of cation and anion solution at room temperature; 2) spray pyrolysis with substrate temperature up to $500^{\circ}C$; 3) chemical bath deposition (CBD). Deposited films were thermally treated in various ways. All films showed a well-developed wurtzite structure. Films grown by the alternated-spray method and the chemical bath method consist of randomly-oriented crystallites with dimensions <0.5 microns. Annealing at $400^{\circ}C$ increases the crystallite size slightly. Films which were grown by pyrolysis at substrate temperatures from $400^{\circ}C\;to\;500^{\cir\c}C$ were oriented in the <002> direction. For growth by pyrolysis at $500^{\circ}C$, the surface is rough on a lateral scale of 0.1 to 0.3 microns. The optical band gap and defect states are investigated by optical absorption, photoluminescene, Raman, and photothermal deflection spectroscopies.