Effects of the Cu/(Ga+In) ratio on the bulk and interface properties of Cu(InGa)(SSe)₂ solar cells

Lee, Dongho,Yang, JungYup,Kim, Young-Su,Mo, Chan B.,Park, Sungchan,Kim, ByoungJune,Kim, Dongseop,Nam, Junggyu,Kang, Yoonmook Elsevier 2016 Solar energy materials and solar cells Vol.149 No.-

<P><B>Abstract</B></P> <P>In this study, we systematically investigated the performance loss factors in Cu(InGa)(SSe)<SUB>2</SUB> (CIGSSe) solar cells with various Cu/(Ga+In) (CGI) ratios, which were fabricated with sputtering and sequential selenization/sulfurization processes. The effects of the CGI ratio on the CIGSSe solar cells were determined by measuring the current–voltage (IV) curves and junction capacitance of the solar cells, as well as by performing X-ray analysis techniques on the cells. An increase in the defect density and decrease in the free carrier density were observed in samples with high Cu concentrations (CGI ratio >0.89), which resulted in a drastic decrease in the open-circuit voltage (<I>V</I> <SUB>OC</SUB>) and fill factor (FF). The temperature-dependent IV (IVT) and X-ray diffraction (XRD) results of the bulk characterization corresponded well with the capacitance measurements for all CGI ratios. The low crystal quality and short minority-carrier diffusion length at high CGI ratios resulted in a significant bulk recombination rate. A qualitative analysis of the interface characteristics was performed with IVT measurements, and the results showed that the recombination activation energy in the samples with high CGI ratios was lower than the bandgap (<I>E</I> <SUB>g</SUB>), decreasing the <I>V</I> <SUB>OC</SUB> of these devices. For the samples with high CGI ratios, their inferior bulk and interface characteristics caused recombination to occur at the interface as well as in the bulk. However, the interface recombination rate was negligible for the samples with low CGI ratios (CGI ratio <0.89). In addition, a CIGSSe solar module was fabricated on a mass production assembly line, with the size of the CIGSSe solar module the same as that of commercially available crystalline-Si-based solar modules. The record efficiency of a solar module with a total area of is 16.0%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Explain the effect of CGI ratio in CIGSSe fabricated by heat treatment of precursor. </LI> <LI> The characterization of junction properties <I>via</I> electrical measurement. </LI> <LI> Short carrier diffusion length at high CGI samples due to the poor crystal quality. </LI> <LI> Fabrication of 16% high efficiency CIGSSe module based on the optimum CGI ratio. </LI> </UL> </P>

Fabrication of carbon nanotube reinforced alumina matrix nanocomposite by sol–gel process

Mo, Chan B.,Cha, Seung I.,Kim, Kyung T.,Lee, Kyung H.,Hong, Soon H. Elsevier 2005 Materials science & engineering. properties, micro Vol.395 No.1

<P><B>Abstract</B></P><P>Carbon nanotube reinforced alumina matrix nanocomposite was fabricated by sol–gel process and followed by spark plasma sintering process. Homogeneous distribution of carbon nanotubes within alumina matrix can be obtained by mixing the carbon nanotubes with alumina sol and followed by condensation into gel. The mixed gel, consisting of alumina and carbon nanotubes, was dried and calcinated into carbon nanotube/alumina composite powders. The composite powders were spark plasma sintered into carbon nanotube reinforced alumina matrix nanocomposite. The hardness of carbon nanotube reinforced alumina matrix nanocomposite was enhanced due to an enhanced load sharing of homogeneously distributed carbon nanotubes. At the same time, the fracture toughness of carbon nanotube reinforced alumina matrix nanocomposite was enhanced due to a bridging effect of carbon nanotubes during crack propagation.</P>

Synergistic Strengthening Effect of Ultrafine-Grained Metals Reinforced with Carbon Nanotubes

Jeong, Yong ,J.,Cha, Seung ,I.,Kim, Kyung ,T.,Lee, Kyong ,H.,Mo, Chan ,B.,Hong, Soon ,H. WILEY-VCH Verlag 2007 Small Vol.3 No.5

<B>Graphic Abstract</B> <P>From strength to strength: Two strengthening mechanisms, grain-size refinement of a metal matrix and reinforcement with homogeneously dispersed CNTs, are combined to fabricate strong CNT/Co nanocomposites (see image). The CNT/Co nanocomposites with an ultrafine-grained Co matrix and homogeneously dispersed CNTs show synergetic strengthening effects with improved mechanical performance. <img src='wiley_img/16136810-2007-3-5-SMLL200600523-content.gif' alt='wiley_img/16136810-2007-3-5-SMLL200600523-content'> </P>

Electrical and mechanical properties of carbon nanotube reinforced copper nanocomposites fabricated by electroless deposition process

Daoush, Walid M.,Lim, Byung K.,Mo, Chan B.,Nam, Dong H.,Hong, Soon H. Elsevier 2009 Materials science & engineering. properties, micro Vol.513 No.-

<P><B>Abstract</B></P><P>Multiwalled carbon nanotube/copper (CNT/Cu) nanocomposite powders with different CNTs volume fractions were prepared by electroless Cu deposition on the CNTs. The CNTs underwent acid treatment, sensitization and electroless copper deposition on their surface respectively. The microstructure of the prepared CNT/Cu nanocomposites was investigated by SEM and HRTEM as well as by XRD analysis. Copper was deposited in a form of a layer on the CNTs surface. The CNT/Cu nanocomposite powders were sintered by spark plasma sintering. The microstructure of the sintered materials were investigated by SEM indicating that the CNTs were homogenous distributed in the copper matrix with good sinterability and porosity content lower than unity in case of 5 and 10vol.% of CNT/Cu nanocomposites and 2.9 and 3.5% respectively for 15 and 20vol.% CNT/Cu nanocomposites. The electrical conductivity, hardness and the tensile properties were measured for evaluating the sintered CNT/Cu nanocomposites. The electrical conductivity decreased by increasing CNTs volume fraction in copper matrix, but the hardness was increased by increasing CNTs volume fraction. The Young's modulus was increased and the elongation was decreased by increasing the volume fraction of CNTs in copper matrix. In addition, the yield strength of the sintered materials was increased by increasing CNTs volume fraction except in case of 20vol.% CNT/Cu composite the material was fractured before yielding.</P>

우리나라 화주기업의 입지선택 특성분석

김찬성(Kim, Chan-Seong),안승범(Seung B . Ahn),성홍모(Seong, Hong-Mo),예충렬 대한교통학회 2006 대한교통학회 학술대회지 Vol.53 No.-

우리나라에서는 국가물류 개선대책의 일환으로 1996년 이래로 매 5년마다 전국 단위의 물류조사가 시행되고 있다. 가장 최근 년도인 2005년에는 제3차의 물류조사가 시행되었고, 현재 데이터베이스화 되어 있다. 본 연구는 최근 조사된 물류조사 자료와 사회경제지표 자료를 이용하여 우리나라 화주기업의 입지선택 특성을 분석한다. 분석에 사용되어진 자료는 첫째, 최근에 수행된 사업체 물류조사 중 개별 입하 및 출하에 대하여 입출하 지역, 입출하 품목, 교통수단, 통행시간 그리고 통행비용이 조사된 자료를 이용하였다. 둘째, 통계조사를 통하여 화주기업이 입지하고 있는 지역의 사회경제지표를 이용한다. 기업의 입지 선택 효용을 구하기 위하여 location choice 모형을 채택 하였으며, 입하지역과 출하지역의 수송비용 특성 그리고 입하지역과 출하지역의 시장크기 등 입지 결정에 미치는 요인이 분석된다. 최근 수년동안 급속히 변화하고 있는 국내외 물류환경변화에 기업이 중요하게 판단하고 있는 입지선택요인을 파악하고 향후 적부의 기업입지정책에 필요한 향후 연구 방향을 제시한다.

Highly stable trypsin-aggregate coatings on polymer nanofibers for repeated protein digestion

Kim, Byoung Chan,Lopez-Ferrer, Daniel,Lee, Sang-Mok,Ahn, Hye-Kyung,Nair, Sujith,Kim, Seong H.,Kim, Beom Soo,Petritis, Konstantinos,Camp, David G.,Grate, Jay W.,Smith, Richard D.,Koo, Yoon-Mo,Gu, Man B WILEY-VCH Verlag 2009 Proteomics Vol.9 No.7

<P>A stable and robust trypsin-based biocatalytic system was developed and demonstrated for proteomic applications. The system utilizes polymer nanofibers coated with trypsin aggregates for immobilized protease digestions. After covalently attaching an initial layer of trypsin to the polymer nanofibers, highly concentrated trypsin molecules are crosslinked to the layered trypsin by way of a glutaraldehyde treatment. This process produced a 300-fold increase in trypsin activity compared with a conventional method for covalent trypsin immobilization, and proved to be robust in that it still maintained a high level of activity after a year of repeated recycling. This highly stable form of immobilized trypsin was resistant to autolysis, enabling repeated digestions of BSA over 40 days and successful peptide identification by LC-MS/MS. This active and stable form of immobilized trypsin was successfully employed in the digestion of yeast proteome extract with high reproducibility and within shorter time than conventional protein digestion using solution phase trypsin. Finally, the immobilized trypsin was resistant to proteolysis when exposed to other enzymes (i.e., chymotrypsin), which makes it suitable for use in “real-world” proteomic applications. Overall, the biocatalytic nanofibers with trypsin aggregate coatings proved to be an effective approach for repeated and automated protein digestion in proteomic analyses.</P>

Synthesis and Magnetic Properties of Co Nanoparticles by Polyol Process

Cha Seung-I.,Mo Chan-B.,Kim Kyung-T.,Hong Soon-H. 한국분말야금학회 2004 한국분말야금학회 학술대회논문집 Vol.2004 No.1

Mechanical and electrical properties of carbon nanotube/Cu nanocomposites by molecular-level mixing and controlled oxidation process.

Lim, Byung K,Mo, Chan B,Nam, Dong H,Hong, Soon H American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.1

<P>A molecular-level mixing and controlled oxidation process is proposed as a novel fabrication technique for the production of CNT/Cu nanocomposite powders. The fabricated CNT/Cu2O nanocomposite powders showed microstructures with homogeneous dispersion of implanted CNTs in a Cu2O matrix. The CNT/Cu2O nanocomposite powders were reduced to CNT/Cu nanocomposite powders with H2 gas and then the as-prepared CNT/Cu nanocomposite powders were spark plasma sintered to fabricate CNT/Cu nanocomposites. The mechanical properties of the Cu and the CNT/Cu nanocomposites were characterized by tensile testing before and after hot compression. Before hot compression, the CNT/Cu nanocomposites were brittle, but after hot compression both yield strength and elongation were increased, while the yield strength of the Cu was decreased after hot compression. Hot compression enhanced the ductility and strength of the CNT/Cu nanocomposites due to alignment of Cu grains and CNTs. Electrical conductivity was also enhanced due to a reduced scattering of electrons because of the alignment of the CNTs and Cu grains as well as the annealing effects of the Cu matrix.</P>

Fabrication Process and Properties of Carbon Nanotube/Cu Nanocomposites

Cha Seung-I.,Kim Kyung-T.,Mo Chan-B.,Hong Soon-H. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

Carbon nanotubes (CNTs) have attracted remarkable attention as reinforcement for composites owing to their outstanding mechanical properties. The CNT/Cu nanocomposite is fabricated by a novel fabrication process named molecular level process. The novel process for fabricating CNT/Cu composite powders involves suspending CNTs in a solvent by surface functionalization, mixing Cu ions with CNT suspension, drying, calcination and reduction. The molecular level process produces CNT/Cu composite powders whereby the CNTs are homogeneously implanted within Cu powders. The mechanical properties of CNT/Cu nanocomposite, consolidated by spark plasma sintering of CNT/Cu composite powders, shows about 3 times higher strength and 2 times higher Young's modulus than those of Cu matrix.

Mechanism for Shape Control of Cu Nanocrystals Prepared by Polyol Process

Cha Seung-I.,Kim Kyung-T.,Mo Chan-B.,Jeong Yong-J.,Hong Soon-H. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

This study investigated a mechanism for controlling the shape of Cu nanocrystals fabricated using the polyol process, which considers the thermodynamic transition from a facetted surface to a rough surface and the growth mechanisms of nanocrystals with facetted or rough surfaces. The facetted surfaces were stable at relatively low temperatures due to the low entropy of perfectly facetted surfaces. Nanocrystals fabricated using a coordinative surfactant stabilized the facetted surface at a higher temperature than those fabricated using a non-coordinative surfactant. The growth rate of the surface under a given driving force was dependent on the surface structure, i.e., facetted or rough, and the growth of a facetted surface was a thermally activated process. Surface twins decreased the activation energy for growth of the facetted surface and resulted in rod- or wire-shaped nanocrystals