• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.108-113
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• 2013

Chalcopyrite material $CuInSe_2$ (CIS) is known to be a very prominent absorber layer for high efficiency thin film solar cells. Current interest in the photovoltaic industry is to identify and develop more suitable materials and processes for the fabrication of efficient and cost-effective solar cells. Various processes have been being tried for making a low cost CIS absorber layer, this study obtained the CIS nanoparticles using commercial powder of 6 mm pieces for low cost CIS absorber layer by high frequency ball milling and cryogenic milling. And the CIS absorber layer was prepared by paste coating using milled-CIS nanoparticles in glove box under inert atmosphere. The chalcopyrite $CuInSe_2$ thin films were successfully made after selenization at the substrate temperature of $550^{\circ}C$ in 30 min, CIS solar cell of Al/ZnO/CdS/CIS/Mo structure prepared under various deposition process such as evaporation, sputtering and chemical vapor deposition respectively. Finally, we achieved CIS nanoparticles solar cell of electric efficient 1.74 % of Voc 29 mV, Jsc 35 $mA/cm^2$ FF 17.2 %. The CIS nanoparticles-based absorber layers were characterized by using EDS, XRD and HRSEM.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.355-355
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• 2016

There has been an explosive development of nanocrystal (NC) synthesis and application due to their composition-dependent specific properties. Despite the composition, shape, and size of NCs foremost determine their physicochemical properties, the surface state and molecule conjugation also drastically change their characteristics. To make practical use of NCs, it is a prerequisite to understand the NC surface state and the degree to which they have been modified because the reaction occurs on the interface between the NCs and the surrounding medium. We report in here an analysis method to identify conjugated ligands and their binding states on semiconductor nanocrystals based on their molecular information. Surface science techniques, such as time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and FT-IR spectroscopy, are adopted based on the micro-aggregated sampling method. Typical trioctylphosphine oxide-based synthesis methods of CdSe/ZnS quantum dots (QDs) have been criticized because of the peculiar effects of impurities on the synthesis processes. Since the ToF-SIMS technique provides molecular composition evidence on the existence of certain ligands, we were able to clearly identify the n-octylphosphonic acid (OPA) as a surface ligand on CdSe/ZnS QDs. Furthermore, the complementary use of the ToF-SIMS technique with the FT-IR technique could reveals the OPA ligands' binding state as bidentate complexes.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.97-97
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• 2010

We demonstrate the hybrid polymer-quantum dot based multi-functional device (Organic bistable devices, Light-emitting diode, and Photovoltaic cell) with a single active-layer structure consisting of CdSe/ZnS semiconductor quantum-dots (QDs) dispersed in a poly N-vinylcarbazole (PVK) and 1,3,5-tirs- (N-phenylbenzimidazol-2-yl) benzene (TPBi) fabricated on indium-tin-oxide (ITO)/glass substrate by using a simple spin coating technique. The multi-functionality of the device as Organic bistable device (OBD), Light Emitting Diode (LED), and Photovoltaic cell can be successfully achieved by adding an electron transport layer (ETL) TPBi to OBD for attaining the functions of LED and Photovoltaic cell in which the lowest unoccupied molecular orbital (LUMO) level of TPBi is positioned at the energy level between the conduction band of CdSe/ZnS and LiF/Al electrode (band-gap engineering). Through transmission electron microscopy (TEM) study, the active layer of the device has a p-i-n structure of a consolidated core-shell structure in which semiconductor QDs are uniformly and isotropically adsorbed on the surface of a p-type polymer core and the n-type small molecular organic materials surround the semiconductor QDs.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.16-22
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• 2021

In this study, quantum dot-sensitized solar cells (QDSSC) using CdSe/ZnS quantum dots (QD) of various sizes with green, yellow, and red colors are developed. Quantum dots, depending their different sizes, have advantages of absorbing light of various wavelengths. This absorption of light of various wavelengths increases the photocurrent production of solar cells. The absorption and emission peaks and excellent photochemical properties of the synthesized quantum dots are confirmed through UV-visible and photoluminescence (PL) analysis. In TEM analysis, the average sizes of individual green, yellow, and red quantum dots are shown to be 5 nm, 6 nm, and 8 nm. The J-V curves of QDSSC for one type of QD show a current density of 1.7 mA/㎠ and an open-circuit voltage of 0.49 V, while QDSSC using three type of QDs shows improved electrical characteristics of 5.52 mA/㎠ and 0.52 V. As a result, the photoelectric conversion efficiency of QDSSC using one type of QD is as low as 0.53 %, but QDSSC using three type of QDs has a measured efficiency of 1.4 %.

• Clinical and Experimental Reproductive Medicine
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• v.24 no.1
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• pp.67-81
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• 1997

To determine the concentration and the physiologic role of metal components in blood plasma and seminal plasma in relation to male infertility, the concentrations of twelve metal components in blood plasma and seminal plasma including Na, Mg, K, Ca, Cr, Mn, Fe, Cu, Zn, Se, Cd and Pb were measured by atomic absorbance spectrophotometery or ion selective electrode analysis. Semen and blood samples were obtained from a total of 110 men including 70 male infertility patients, 20 vasectomized persons and 20 fertility proven volunteers visited to the Male Infertility Clinic of Pusan National University Hospital. The concentrations of Ca, Zn, Mg, Cr and Cd in control group were higher in seminal plasma than in blood plasma, and additionally Pb were higher in infertility group. The concentrations of all metal components revealed no significant difference according to patients' age, resident, occupation, sperm density, motility and hormone level in blood plasma, but some metal components including Ca, Mg, Cu, Mn, Cd and Pb revealed a significant difference according to each these parameters except patient's age in seminal plasma. The concentrations of Mn, Cd and Pb in the vasectomy persons were higher than in the infertility group III including testicular and epididymal factors, but not in blood plasma. We conclude that the quantitative changes of metal components in the seminal plasma may have effects on not only spermatogenesis and sperm function, but also contribute to diagnostic parameter according to organ specificity of the metal in the male reproduction.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.339-342
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• 2007

$Cu(In_{1-x}Ga_{x})Se_2$(CIGS)는 매우 큰 광흡수계수를 가지고 있으므로 박막형 태양전지의 광흡수층 재료로서 많은 연구가 진행되고 있다. 박막이 태양전지의 광흡수층으로 이용되기 위해서는 큰 결정크기와 평탄한 표면, 적당한 전기적 특성을 가져야 한다. 이러한 특성들은 CIGS 박막의 조성에 큰 영향을 받고 있는 것으로 보고되고 있다. 본 연구에서는 동시증발법을 이용하여 Cu/(In+Ga) 비를 0.9로 고정한 후 Ga 조성(Ga/(In+Ga)의 비 : 0.32, 0.49, 0.69, 0.8, 1)을 변화시켜 Wide band gap CIGS 박막태양전지를 만들었다. 기판은 soda line glass를 사용하였고 뒷면 전극으로는 Mo를 스퍼터링법으로 증착하였다. 또한 버퍼층으로는 기존에 쓰이고 있는 CdS를 CBD(Chemical Bath Deposition)법으로 층착시켰으며, 윈도우층으로는 i-ZnO/n-ZnO를 스파터링 법으로 층착하였다. 그리고 앞면전극으로는 Al을 E-beam 으로 증착하였다. 분석은 XRD, SEM, QE로 분석하였다. 위 실험에서 얻은 결과로는 Ga/(In+Ga)비가 증가할수록 Cu(In,Ga)Se2 박막은 회절 peak들이 큰 회절각으로 이동하였고, 이것은 Ga 원자와 In 원자의 원자반경의 차이에서 기인된 것으로 사료된다. 또한 Ga 조성이 증가할수록 단파장 쪽으로 이동하는 것을 볼 수 있으며, Voc가 증가하다가 에너지 밴드캡이 1.62 eV 이상에서는 Voc가 감소하는 것을 볼 수 있는데 이것은 Ga 조성이 증가할수록 에너지 밴드캡이 커지면서 defect level 이 존재하기 때문인 것으로 사료된다. Ga/(In+Ga)비가 1일 때의 변환효율은 8.5 %이고， Voc : 0.74 (V), Jsc : 17.2 ($mA/cm^{2}$), F.F : 66.6(%) 이다.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1264-1267
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• 1998

$Cu(In_xGa_{1-x})Se_2$ thin films were prepared and characterized with various Ga contents. As the Ga content increased, the grain size of CIGS film became smaller. The 2 $\theta$ values in XRD patterns were shifted to larger values and the overlapped peaks were splitted. The energy bandgap increased from 1.04 to 1.67 eV and the resistivity decreased. The solar cell fabricated with ZnO/CdS/$Cu(In_{0.7}Ga_{0.3})Se_2/Mo$ structure yielded an efficeincy of 14.48% with an acitive area of 0.18 $cm^2$. The efficiency decreased with further increase of Ga content.

• Macromolecular Research
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• v.17 no.12
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• pp.995-1002
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• 2009

Luminescent polynorbornene (PNB)/quantum dot (CdSe@ZnS; QD) composite nanorods and nanotubes were successfully prepared using anodic aluminum oxide (AAO) membranes of various pore sizes as templates. To protect QDs with high quantum yield from quenching during the phosphoric acid treatment used to remove the AAO templates, chemically stable and optically clear norbornene-maleic anhydride copolymers (P(NB-r-MA)) were employed as a capping agent for QDs. The amine-terminated QDs reacted with maleic anhydride moieties in P(NB-r-MA) to form PNB-grafted QDs. The chemical- and photo-stability of QDs encapsulated with PNB copolymers were investigated by photoluminescence (PL) spectroscopy. By varying the pore size of the AAO templates from 40 to 380 urn, PNB/QD composite nanorods or nanotubes were obtained with a good dispersion of QDs in the PNB matrix.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.8.2-8.2
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• 2009

구리(Cu)-인듐(In)-갈륨(Ga)-셀레늄(Se)의 4 원소 화합물 반도체인 Cu(InGa)$Se_2$ (CIGS) 태양전지 세계 최고 셀효율은 2008년 현재 19.9% 로서 박막형 태양전지 중 가장 높은 효율을 보이고 있다. 이는 다결정(폴리) 실리콘 태양전지의 20.3%와 대등한 수준이다. 이 CIGS 태양전지는 제조단가를 표준 결정형 실리콘 태양전지 대비 50% 대로 획기적으로 낮출 수 있어 가장 경쟁력이 있는 차세대 재료로 꼽히고 있다. 본 연구에서는 CIGS태양전지를 고진공 물리 증작법으로 제작하였으며 표면과 박막의 순도를 외부오염을 방지하기 위하여 후면전극, 광흡수체 및 전면전극을 동일 진공에서 제작할 수 있는 멀티 챔버 클러스터 증착 시스템을 이용하였다. 기판으로 소다라 임유리, 후면전극으로 Mo, 전면전극으로 I-ZnO/Al:ZnO 및 ITO를 이용하였다. 버퍼층으로 CdS를 chemical bath deposition (CBD)를 이용하였다. 소자는 무반사막을 사용하지 않고 Al/Ni전극 그리드를 이용하였다. 이 소자로부터 0.22 $cm^2$에서 16%의 효율을 얻었다. 각 박막층 간 계면의 분석을 전기적인 특성, ellisometry에 의한 광특성, 표면과 결정성에 대한 SEM 및 XRD의 특성을 보고한다. 또한, 대표적 화합물 반도체 박막 태양전지인 CIGS 태양전지의 기술의 현황, 학문적인 과제 및 실용화의 문제점을 발표하기로 한다.