Highly efficient epitaxial Ge solar cells grown on GaAs (001) substrates by MOCVD using isobutylgermane

Kim, Youngjo,Kim, Kangho,Kim, Chang Zoo,Jung, Sang Hyun,Kang, Ho Kwan,Park, Won-Kyu,Lee, Jaejin North-Holland 2017 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>Single-junction Ge solar cells have been epitaxially grown on GaAs (001) substrates by a low pressure metalorganic chemical vapor deposition using isobutylgermane. Various growth conditions have been studied to reduce the high doping level of over 1×10<SUP>19</SUP> cm<SUP>−3</SUP> of the p-type Ge epitaxial layer, which is detrimental to the minority carrier collection efficiency. By increasing the growth rate and employing a discontinuous doping technique, the p-type doping level of the epitaxial Ge layer has been lowered to 2×10<SUP>18</SUP> cm<SUP>−3</SUP>, and the hole mobility increased from 44 to 162cm<SUP>2</SUP>/Vs. A high power conversion efficiency of 6.72% can be achieved under AM1.5G illumination by the epitaxial Ge solar cell with the lowered doping level in the p-type Ge base region. The spectral response of the epitaxial Ge solar cell with a 5µm thick base layer is good enough to use for InGaP/GaAs/Ge triple-junction solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single-junction Ge solar cells are epitaxially grown on GaAs (001) substrates. </LI> <LI> Epitaxial Ge p-n junction is realized by MOCVD growth using isobutylgermane. </LI> <LI> Discontinuous doping technique is introduced to minimize the p-type Ge doping level. </LI> <LI> High efficiencies over 6.5% can be achieved by the epitaxial Ge solar cells. </LI> <LI> Ge epitaxy using MOCVD can be employed for III-V multi-junction solar cells. </LI> </UL> </P>

Novel Anti-Reflection Technology for GaAs Single-Junction Solar Cells Using Surface Patterning and Au Nanoparticles

Kim, Youngjo,Lam, Nguyen Dinh,Kim, Kangho,Kim, Sangin,Rotermund, Fabian,Lim, Hanjo,Lee, Jaejin American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7

<P>Single-junction GaAs solar cell structures were grown by low-pressure MOCVD on GaAs (100) substrates. Micro-rod arrays with diameters of 2 microm, 5 microm, and 10 microm were fabricated on the surfaces of the GaAs solar cells via photolithography and wet chemical etching. The patterned surfaces were coated with Au nanoparticles using an Au colloidal solution. Characteristics of the GaAs solar cells with and without the micro-rod arrays and Au nanoparticles were investigated. The short-circuit current density of the GaAs solar cell with 2 microm rod arrays and Au nanoparticles increased up to 34.9% compared to that of the reference cell without micro-rod arrays and Au nanoparticles. The conversion efficiency of the GaAs solar cell that was coated with Au nanoparticles on the patterned surface with micro-rod arrays can be improved from 14.1% to 19.9% under 1 sun AM 1.5G illumination. These results show that micro-rod arrays and Au nanoparticle coating can be applied together in surface patterning to achieve a novel cost-effective anti-reflection technology.</P>

Epitaxial Ge Solar Cells Directly Grown on Si (001) by MOCVD Using Isobutylgermane

Kim, Youngjo,Kim, Kangho,Lee, Jaejin,Kim, Chang Zoo,Kang, Ho Kwan,Park, Won-Kyu Korean Physical Society 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.5

<P>Epitaxial Ge layers have been grown on Si (001) substrates by metalorganic chemical vapor deposition (MOCVD) using an isobutylgermane (IBuGe) metalorganic source. Low and high temperature two-step growth and post annealing techniques are employed to overcome the lattice mismatch problem between Ge and Si. It is demonstrated that high quality Ge epitaxial layers can be grown on Si (001) by using IBuGe with surface RMS roughness of 2 nm and an estimated threading dislocation density of 4.9 x 10(7) cm (-2). Furthermore, single-junction Ge solar cells have been directly grown on Si substrates with an in situ MOCVD growth. The epitaxial Ge p-n junction structures are investigated with transmission electron microscopy and electrochemical C-V measurements. As a result, a power conversion efficiency of 1.69% was achieved for the Ge solar cell directly grown on Si substrate under AM1.5G condition.</P>

Genetic activation of parkin rescues TAF15-induced neurotoxicity in a <i>Drosophila</i> model of amyotrophic lateral sclerosis

Kim, Youngjo,Kim, Hyung-Jun,Cha, Sun Joo,Choi, Hyun-Jun,Kim, Hayoung,Lee, Sanghyun,Jeon, Yu-Mi,Lee, Mihye,Lee, Seongsoo,Kim, Kiyoung Elsevier 2019 NEUROBIOLOGY OF AGING Vol.73 No.-

<P><B>Abstract</B></P> <P>Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that is characterized pathologically by the loss of motor neurons. Mutations in the <I>TAF15</I> gene have been implicated in the pathogenesis of ALS. TATA-binding protein associated factor 15 (TAF15) accumulates as cytoplasmic aggregates in neuronal cells, the clearance of which may be a therapeutic strategy for ALS. However, the identification of a novel regulator for protection against a TAF15-induced proteinopathy and the exact pathogenic mechanism of TAF15-induced neurodegeneration remain to be elucidated. Here, we show that parkin directly binds to TAF15 and that parkin overexpression can suppress the defective phenotypes, including the life span and locomotive activity of a TAF15-induced proteinopathy. We also found that overexpression of parkin in neuronal cells leads to a reduction in TAF15 levels, because of the E3 ubiquitin ligase activity of parkin. Our study provides in vivo evidence supporting the use of parkin for neuroprotection in a TAF15-induced proteinopathy and offers new insights into the pathogenic mechanisms underlying TAF15-induced ALS.</P>

Copper-Catalyzed Selective Arylations of Benzoxazoles with Aryl Iodides

Kim, Donghae,Yoo, Kwangho,Kim, Se Eun,Cho, Hee Jin,Lee, Junseong,Kim, Youngjo,Kim, Min American Chemical Society 2015 Journal of organic chemistry Vol.80 No.7

<P>A copper-catalyzed direct ring-opening double N-arylation of benzoxazoles with aryl iodides has been developed. The present system exhibits high selectivity despite competition from C-arylation. The selectivity between ring-opening N-arylation and C-arylation was controlled by the choice of reaction vessel. The nitrile bound bis(triphenylphosphine)copper cyanide was identified as the active catalytic species for both reactions, and when combined with a nitrile-containing solvent, enhanced the reaction efficiency.</P>

Boratranes with all six-membered rings or with two different ring sizes: Synthesis, characterization, and X-ray crystal structures

Kim, Da Jung,Hong, Younjin,Kim, So Han,Lee, Kang Mun,Mun, Sang-deok,Yoon, Sungwoo,Lee, Junseong,Do, Youngkyu,Kim, Youngjo Elsevier 2011 Inorganica chimica acta Vol.378 No.1

<P><B>Graphical abstract</B></P><P>A novel series of three boratrane derivatives featuring a stepwise change in ring size from three six-membered rings to one six-membered and two five-membered rings were prepared. X-ray analysis revealed that the coordination around boron and nitrogen was a slightly distorted tetrahedral geometry and the tricyclic cage moiety resembled a three-bladed turbine of <I>C</I><SUB>3</SUB> or <I>C<SUB>s</SUB></I> symmetry.<ce:figure id='f0005'></ce:figure></P><P><B>Highlights</B></P><P>► (HO-<I>o</I>-ArCH<SUB>2</SUB>)<SUB>3−</SUB><I><SUB>n</SUB></I>N(CH<SUB>2</SUB>CH<SUB>2</SUB>OH)<I><SUB>n</SUB></I> (<I>n</I>=0–2) were used as ligands. ► B(OMe)<SUB>3</SUB> was used as a boron precursor. ► Boratrane derivatives with (HO-<I>o</I>-ArCH<SUB>2</SUB>)<SUB>3−</SUB><I><SUB>n</SUB></I>N(CH<SUB>2</SUB>CH<SUB>2</SUB>OH)<I><SUB>n</SUB></I> (<I>n</I>=0–2) were prepared. ► The tricyclic cage moiety resembled a three-bladed turbine of <I>C</I><SUB>3</SUB> or <I>C<SUB>s</SUB></I> symmetry. ► The N–B bond length of 1.6322(19)Å is the shortest among reported boratranes.</P> <P><B>Abstract</B></P><P>New types of boratranes B[(O-<I>o</I>-ArCH<SUB>2</SUB>)<SUB>3−</SUB><I><SUB>n</SUB></I>N(CH<SUB>2</SUB>CH<SUB>2</SUB>O)<I><SUB>n</SUB></I>] (Ar=2,4-di-MeC<SUB>6</SUB>H<SUB>2</SUB>; <I>n</I>=0, <B>1</B>; <I>n</I>=1, <B>2</B>; <I>n</I>=2, <B>3</B>) featuring three six-membered chelating ring (<B>1</B>) to two five-membered chelating rings (<B>3</B>) in a stepwise fashion through <B>2</B> have been synthesized by the reaction of B(OMe)<SUB>3</SUB> with a series of tetradentate ligands such as (HO-<I>o</I>-ArCH<SUB>2</SUB>)<SUB>3−</SUB><I><SUB>n</SUB></I>N(CH<SUB>2</SUB>CHOH)<I><SUB>n</SUB></I> (Ar=2,4-di-MeC<SUB>6</SUB>H<SUB>2</SUB>; <I>n</I>=0, <B>L1H<SUB>3</SUB></B>; <I>n</I>=1, <B>L2H<SUB>3</SUB></B>; <I>n</I>=2, <B>L3H<SUB>3</SUB></B>). Compounds <B>1</B>–<B>3</B> have been characterized by solution <SUP>1</SUP>H, <SUP>13</SUP>C{<SUP>1</SUP>H} and, <SUP>11</SUP>B NMR and the crystal structures of <B>1</B> and <B>3</B> have been determined by single crystal X-ray diffraction. Compounds <B>1</B> and <B>3</B> are the first structurally characterized boratrane derivatives bearing all six-membered rings and mixed ring systems in the atrane cage, respectively. Especially, the molecular structures of <B>1</B> revealed that its transannular N–B bond length of 1.6322(19)Å is the shortest among the previously reported boratrane and its derivatives.</P>

Mathematical Models to Predict Staphylococcus aureus Growth on Processed Cheeses

Kim, Kyungmi,Lee, Heeyoung,Moon, Jinsan,Kim, Youngjo,Heo, Eunjeong,Park, Hyunjung,Yoon, Yohan The Korean Society of Food Hygiene and Safety 2013 한국식품위생안전성학회지 Vol.28 No.3

본 연구는 가공치즈에서 Staphylococcus aureus의 생장을 예측하기 위한 수학적 모델을 개발하였다. 모짜렐라 슬라이스 치즈와 체다 슬라이스 치즈에 S. aureus 혼합균액(ATCC13565, ATCC14458, ATCC23235, ATCC27664, NCCP10826) 0.1 ml (log CFU/g)을 접종한 후 $4^{\circ}C$ (1440 h), $15^{\circ}C$ (288 h), $25^{\circ}C$ (72 h), and $30^{\circ}C$ (48 h)에 저장하면서 총 세균수와 S. aureus 세균수를 tryptic soy agar와 mannitol salt agar를 이용해 각각 확인하였다. S. aureus의 세균 수를 Baranyi model로 분석하여 생장률(${\mu}_{max}$; ${\log}CFU{\cdot}g^{-1}{\cdot}h^{-1}$), 유도기(LPD; h), 초기 세균 수(log CFU/g), 최대 생장 세균수(log CFU/g)를 계산함으로써 1차 모델을 개발하였다. 또한 저장온도와 S. aureus의 ${\mu}_{max}$, LPD의 관계를 분석하기 위해 square root model과 exponential decay model을 이용하였고 이를 통해 2차모델을 개발하였으며 개발된 모델의 평균제곱근 편차(RMSE)를 계산하여 적합성을 검증하였다. $4^{\circ}C$에서는 모든 가공치즈에서 황색포도상구균의 생장이 관찰되지 않았으나 $15^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$에서는 모짜렐라 슬라이스와 체다 슬라이스 치즈에서 황색포도상구균이 생장하였으며($R^2=0.785-0.996$) 저장온도가 높아짐에 따라 생장률은 증가한 반면 유도기는 감소하였다($R^2=0.879-0.999$). 또한 개발된 모델의 RMSE 값은 0.3500-0.5344로 적합하였다. 따라서 본 연구결과는 가공치즈에서 황색포도상구균의 생장 예측에 유용하게 사용될 것이다. This study developed predictive models for the kinetic behavior of Staphylococcus aureus on processed cheeses. Mozzarella slice cheese and cheddar slice cheese were inoculated with 0.1 ml of a S. aureus strain mixture (ATCC13565, ATCC14458, ATCC23235, ATCC27664, and NCCP10826). The inoculated samples were then stored at $4^{\circ}C$ (1440 h), $15^{\circ}C$ (288 h), $25^{\circ}C$ (72 h), and $30^{\circ}C$ (48 h), and the growth of all bacteria and of S. aureus were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data of S. aureus to calculate growth rate (${\mu}_{max}$; ${\log}CFU{\cdot}g^{-1}{\cdot}h^{-1}$), lag phase duration (LPD; h), lower asymptote (log CFU/g), and upper asymptote (log CFU/g). The growth parameters were further analyzed using the square root model as a function of temperature. The model performance was validated with observed data, and the root mean square error (RMSE) was calculated. At $4^{\circ}C$, S. aureus cell growth was not observed on either processed cheese, but S. aureus growth on the mozzarella and cheddar cheeses was observed at $15^{\circ}C$, $25^{\circ}C$, and $30^{\circ}C$. The ${\mu}_{max}$ values increased, but LPD values decreased as storage temperature increased. In addition, the developed models showed acceptable performance (RMSE = 0.3500-0.5344). This result indicates that the developed kinetic model should be useful in describing the growth pattern of S. aureus in processed cheeses.

Synthesis, X-ray structures, and controlled ring opening polymerization behavior of <small>L</small>-lactide using titanium complexes chelated by tetradentate diamine–diethanolate ligand

Kim, So Han,Kim, Da Jung,Jeong Go, Min,Soo Ko, Young,Lee, Junseong,Kim, Youngjo The Royal Society of Chemistry 2012 Dalton transactions Vol.41 No.38

<P>The synthesis and characterization of LTi(O-i-Pr)<SUB>2</SUB> (<B>1</B>) and LTiCl<SUB>2</SUB> (<B>2</B>) complexes containing a new [ONNO]-type tetradentate diamine–diethanolate ligand such as (HOCMe<SUB>2</SUB>CH<SUB>2</SUB>NMeCH<SUB>2</SUB>CH<SUB>2</SUB>NMeCH<SUB>2</SUB>CMe<SUB>2</SUB>OH) (<B>LH<SUB>2</SUB></B>) was achieved. Single-crystal X-ray analyses revealed that monomeric complexes <B>1</B> and <B>2</B> had <I>pseudo-C</I><SUB>2</SUB> and <I>pseudo-C</I><SUB>1</SUB> symmetric distorted octahedral geometry, respectively. Interestingly, complex <B>1</B> has <I>fac</I>–<I>fac</I> geometry for tetradentate <B>L</B> around a Ti centre in both solid and solution, whereas complex <B>2</B> has different geometry in solid (<I>mer</I>–<I>fac</I>, <I>C</I><SUB>1</SUB>) and solution (<I>fac</I>–<I>fac</I>, <I>C</I><SUB>2</SUB>). They are effective catalysts for the controlled ring opening polymerization of <SMALL>L</SMALL>-lactide, as shown by the linearity of the number average of the molecular weight of polylactides <I>versus</I> conversion, as well as narrow PDI values.</P> <P>Graphic Abstract</P><P>Octahedral diisopropoxytitanium and dichlorotitanium complexes with tetradentate diamine–diethanolate ligands were prepared and characterized by X-ray crystallographic analysis. They proved to be useful catalysts for the controlled ring opening polymerization of <SMALL>L</SMALL>-lactide. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2dt31357j'> </P>

Monomeric or Dimeric Aluminum Complexes as Catalysts for Cycloaddition between CO₂ and Epoxides

Kim, So Han,Han, Sang Yeop,Kim, Jeong Hee,Kang, Yi Young,Lee, Junseong,Kim, Youngjo WILEY‐VCH Verlag 2015 European journal of inorganic chemistry Vol.2015 No.13

<P><B>Abstract</B></P><P>A monomeric aluminum complex containing aliphatic tetradentate ligand <B>L1 </B>(HOCMe<SUB>2</SUB>CH<SUB>2</SUB>NMeCH<SUB>2</SUB>CH<SUB>2</SUB>NMeCH<SUB>2</SUB>CMe<SUB>2</SUB>OH) was synthesized and used as a catalyst for cycloaddition between CO<SUB>2</SUB> and epoxides in the presence of PPNCl as a cocatalyst. To check the effect of ligand <B>L1</B>, coordinated to the aluminum center, on the activity of cycloaddition, the new ligand HOCMe<SUB>2</SUB>CH<SUB>2</SUB>NMe<SUB>2</SUB>, which corresponds to half of <B>L1</B>, was systematically designed to make monomeric or dimeric aluminum complexes. Comparison of the catalytic properties of the aluminum complex containing the tetradentate ligand with those of the two related aluminum complexes containing the bidentate ligand under the same conditions revealed that the first system showed higher activity than the other two for cycloaddition between CO<SUB>2</SUB> and epoxides in the presence of PPNCl, which was the best cocatalyst out of the six compounds <I>n</I>Bu<SUB>4</SUB>PBr, <I>n</I>Bu<SUB>4</SUB>NCl, <I>n</I>Bu<SUB>4</SUB>NBr, <I>n</I>Bu<SUB>4</SUB>NI, DMAP, and PPNCl.</P>

A Fast Intra Prediction Method Using the Distribution of Adjacent Pixels in HEVC

KIM, Youngjo,BYUN, Juwon,KIM, Jaeseok 'Institute of Electronics, Information and Communi 2014 IEICE transactions on fundamentals of electronics, Vol.ea97 No.1