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Study of degradation in bulk lifetime of n-type silicon wafer due to oxidation of boron-rich layer
Kyungsun Ryu,Chel-Jong Choi,Ajeet Rohatgi,Young-Woo Ok 한국물리학회 2016 Current Applied Physics Vol.16 No.5
Various boron (B) diffusion techniques are being investigated to fabricate n-type Si solar cells. Thermal oxidation is often used to remove boron-rich layer (BRL) formed as a byproduct of B diffusion because BRL interferes with surface passivation of boron emitter. However, oxidizing the BRL can cause significant degradation in bulk lifetime. In this paper, high resolution electron microscopy (HREM) was performed to detect the presence of BRL after B diffusion and its removal after subsequent oxidation. In addition, bulk lifetime of n-type Si with BRL was measured after various oxidation conditions to systematically investigate the mechanism of oxidation-induced lifetime degradation in n-type Si. Detailed analysis of the oxidized samples revealed that iron (Fe) is primary metal impurity responsible for the bulk lifetime degradation after oxidation. This happens because Fe is gettered in BRL after B diffusion and during the oxidation, when the BRL is consumed, Fe is released into the bulk to degrade lifetime.
Kyungsun Ryu,Keeya Madani,Ajeet Rohatgi,Young-Woo Ok 한국물리학회 2018 Current Applied Physics Vol.18 No.2
We present the fabrication and analysis of Passivated Emitter and Rear Totally Diffused (PERT) solar cells on n-type silicon using a co-diffusion process. In a single high temperature step, a BSG/SiOx stack deposited by APCVD and a POCl3 back surface field diffuse into the wafer to form the boron doped emitter and phosphorus doped back surface field. The SiOx layer on top of BSG acts as a masking layer to prevent cross-doping of phosphorus as well as a blocking layer for boron out-diffusion. This resulted in an initial sheet resistance of 76 Ω/□ with good uniformity and a final p+ emitter sheet resistance of 97 Ω/□ after boron rich layer removal. Additionally, bulk lifetime was investigated before and after the high temperature step that resulted in an increase from 1.2 ms to 1.5 ms due to a POCl3 gettering effect. A peak cell efficiency of 20.3% was achieved and each recombination component in terms of saturation current density was calculated and analyzed to understand the cell for further efficiency enhancement.
Song, Kyungsun,Kim, Wonbaek,Ryu, Taegong,Ryu, Kyung-Won,Bang, Jun-Hwan,Jang, Young-Nam The Japan Institute of Metals 2011 MATERIALS TRANSACTIONS Vol.52 No.2
<P>The waste calcite, by-product of the carbonation reaction of flue gas desulfurization (FGD) gypsum, was evaluated as low-cost adsorbent for Cd(II) removal from wastewater. Batch experiments were performed in aqueous solution varying contact time, initial pH of Cd(II) solution, adsorbent dose, and Cd(II) concentration. The sorption rate of Cd(II) on the adsorbent was high during initial 1 h and decreased slowly reaching a plateau after about 12 h. The adsorption kinetics of Cd(II) could be best described by the pseudo-second order model while its isotherm was found to fit with the Langmuir model. The maximum adsorption capacity was 7.99 mg g<SUP>−1</SUP>. It is believed that waste calcite would be an addition to the list of low-cost adsorbents for Cd(II) removal in wastewater treatment.</P>
Ryu, Seung-Wook,Choi, Kyungsun,Park, Jong-Hwan,Park, Yeong-Min,Kim, Sunchang,Choi, Chulhee Elsevier 2012 Cancer letters Vol.323 No.1
<P><B>Abstract</B></P> <P>Mitochondrial fusion and fission are dynamically regulated during apoptotic cell death, and mitofusin (Mfn) and related proteins have been shown to be involved in apoptosis-associated changes in mitochondrial morphology and function. Here, we investigated the involvement of Mfn proteins in the conformational activation and mitochondrial translocation of Bax, a key molecule responsible for apoptosis-associated mitochondrial changes. When ectopically expressed, Mfn1 inhibited the amino-terminal activation, but not the mitochondrial translocation, of Bax during staurosporine-induced apoptosis; overexpression of Mfn2 had no effect. Overexpression of Mfn1 mutants carrying point mutations in the GTPase domain (Mfn1-K88T and Mfn1-T109A) did not inhibit the amino-terminal activation of Bax. Furthermore, staurosporine-induced amino-terminal activation of Bax was significantly delayed in Mfn1-shRNA transfected (Mfn1-depleted) HeLa cells compared to cells transfected with control shRNA. These results collectively suggest a role for Mfn1 in regulating the activation of Bax on the outer mitochondrial membrane in a GTPase-dependent manner.</P>
Choi, Kyungsun,Lee, Kihwang,Ryu, Seung-Wook,Im, Minju,Kook, Koung Hoon,Choi, Chulhee Molecular Vision 2012 Molecular vision Vol.18 No.-
<P><B>Purpose</B></P><P>Transforming growth factor-β (TGF-β) plays a key role in transforming retinal pigment epithelial (RPE) cells into mesenchymal fibroblastic cells, which are implicated in proliferative vitreoretinopathy. Herein, we tested the effect of pirfenidone, a novel antifibrotic agent, on TGF-β1-mediated fibrogenesis in the human RPE cell line ARPE-19.</P><P><B>Methods</B></P><P>The effect of pirfenidone on the TGF-β1-induced phenotype in ARPE-19 cells was measured with immunocytochemistry as the change in F-actin. Fibronectin and collagen production was measured with enzyme-linked immunosorbent assay, and cell migration activity was investigated using a scratch assay. Immunoblot analyses of cofilin, sma and mad protein (smad) 2/3, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and extracellular signal-related kinase expression were conducted to elucidate the cell signaling networks that contribute to the antifibrotic effect of pirfenidone.</P><P><B>Results</B></P><P>Treatment with TGF-β1 induced typical phenotypic changes such as formation of stress fiber running parallel to the long axis of cells and enhanced migration and production of extracellular matrix components such as collagen type I and fibronectin. This fibroblast-like phenotype induced by TGF-β1 was significantly inhibited by pretreatment with pirfenidone in a dose-dependent manner. We also elucidated the TGF-β signaling pathways as the target of the inhibitory effect of pirfenidone. Pirfenidone inhibited TGF-β signaling by preventing nuclear accumulation of active Smad2/3 complexes rather than phosphorylation of Smad2/3.</P><P><B>Conclusions</B></P><P>These results collectively provide a rational background for future evaluation of pirfenidone as a potential antifibrotic agent for treating proliferative vitreoretinopathy and other fibrotic retinal disorders.</P>