Isolation of Polypeptide Fractions from Different Parts of Red Ginseng

Liudmila Larina,T. Muranova,B. G. Cho,H. Park 고려인삼학회 1998 International Symposium on Ginseng Vol.- No.-

Charge Transfer across a ZnO/Electrolyte Interface Induced by Sub-Bandgap Illumination

Larina, Liudmila,Ahn, Byung-Tae 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11

Development of a New Double Buffer Layer for Cu(In, Ga) Se₂ Solar Cells

Larina, Liudmila,Kim, Ki-Hwan,Yoon, Kyung-Hoon,Ahn, Byung-Tae 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06

The new approach to buffer layer design for CIGS solar cells that permitted to reduce the buffer absorption losses in the short wavelength range and to overcome the disadvantages inherent to Cd-free CIGS solar cells was proposed. A chemical bath deposition method has been used to produce a high duality buffer layer that comprises thin film of CdS and Zn-based film. The double layer was grown on either ITO or CIGS substrates and its morphological, structural and optical properties were characterized. The Zn-based film was described as the ternary compound ZnS_x(OH)_y. The composition of the ZnS_x(OH)_y layer was not uniform throughout its thickness. ZnS_x(OH)_y/CdS/substrate region was a highly intermixed region with gradually changing composition. The short wavelength cut-off of double layer was shifted to shorter wavelength (400nm) compared to that (520 nm) for the standard CdS by optimization of the double buffer design. The results show the way to improve the light energy collection efficiency of the nearly cadmium-free CIGS-based solar cells.

Growth of Ultrathin Zn Compound Buffer Layer by a Chemical Bath Deposition for Cu(In,Ga)Se[sub 2] Solar Cells

Larina, Liudmila,Shin, Dong Hyeop,Tsvetkov, Nikolay,Ahn, Byung Tae The Electrochemical Society 2009 Journal of the Electrochemical Society Vol.156 No.11

Alignment of energy levels at the ZnS/Cu(In,Ga)Se₂ interface

Larina, Liudmila,Shin, Donghyeop,Kim, Ji Hye,Ahn, Byung Tae Royal Society of Chemistry 2011 ENERGY AND ENVIRONMENTAL SCIENCE Vol.4 No.9

<P>Further understanding of the electronic structure at the ZnS/Cu(In,Ga)Se<SUB>2</SUB> interface is necessary to enhance the electron injection across the interface in Cu(In,Ga)Se<SUB>2</SUB> solar cells. The valence band structure and shallow core levels were investigated by ultraviolet photoelectron spectroscopy depth profile analysis with He II line excitation. ZnS film was grown by a chemical bath deposition on a Cu(In,Ga)Se<SUB>2</SUB> absorber deposited by the co-evaporation of Cu, In, Ga, and Se elemental sources. The discontinuity of 2.0 eV in the valence band edge at the ZnS/Cu(In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>)Se<SUB>2</SUB> interface was directly determined. This type of valence band offset yields a spike conduction band alignment of 0.25 eV. The positions of the VBM and the Zn 3d core-level emission of the buffer underwent the substantial shifts of 0.36 eV and 0.64 eV to a lower binding energy levels during the etching process. The shifts are ascribed to the contribution of the band bending in the ZnS buffer layer and its graded chemical composition. This study is the first to determine the small conduction band offset at the interface formed by the chemical bath deposited ZnS layer and the Cu(In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>)Se<SUB>2</SUB> absorber. Our results also provide information toward the design optimization of the optoelectronic properties of the ZnS/Cu(In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>)Se<SUB>2</SUB> interface. To enhance the electron injection from Cu(In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>)Se<SUB>2</SUB> absorber to ZnS layer further lowering of the energy barrier is required. For this purpose, the bandgap of ZnS should be reduced by controlling the crystal structure and composition or its Fermi level should be upward shifted by appropriate doping.</P> <P>Graphic Abstract</P><P>For the first time a small conduction band offset at the ZnS/Cu(In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>)Se<SUB>2</SUB> interface was found. The spike conduction band alignment of 0.25 eV is consistent with the efficiency of CIGS cell based on CBD ZnS buffer. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1ee01292d'> </P>

Optimum engineering of a PtSn alloys/reduced graphene oxide nanohybrid for a highly efficient counter electrode in dye-sensitized solar cells

진익규,DAOVANDUONG,Liudmila L. Larina,최호석 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.36 No.-

Well-dispersed Pt1–xSnx alloy nanoparticles (NPs) were stabilized with RGO after a co-reduction of metalprecursor ions and graphene oxide via a dry plasma reduction under an atmospheric pressure and closeto room temperature. The highest electrocatalytic performance, which corresponds to the lowest chargetransfer resistance of 1.12 V, is achieved with the Pt0.9Sn0.1 NPs/RGO nanohybrid. The application ofthe optimized Pt0.9Sn0.1 NPs/RGO nanohybrid as an alternative CE for DSCs results in an increase of theefficiency by 14.67% over that of a Pt/RGO-based DSC and an increase of 48.96% over the efficiency of aPt-free device.

Atomistic consideration of earth-abundant chalcogenide materials for photovoltaics: Kesterite and beyond

Kim, Jekyung,Larina, Liudmila,Chung, Sung-Yoon,Shin, Donghyeop,Shin, Byungha Published for the Materials Research Society by th 2018 Journal of materials research Vol.33 No.23

<▼1><B>Abstract</B><P/></▼1><▼2><P>Despite the potential as a promising alternative to CdTe and Cu(In,Ga)Se2, the kesterite compound Cu2ZnSn(S,Se)4 (CZTSSe) presents a critical challenge mainly from its high open-circuit voltage (<I>V</I>oc) deficit. Indeed, the <I>V</I>oc of the record CZTSSe solar cell to date has accounted for only 61% of that calculated by the Shockley-Queisser limit, whose origin can be ascribed to nonradiative recombination from a high density of defects and secondary phases. Therefore, an atomistic understanding and characterization of CZTSSe is highly essential to overcoming the current shortcomings in kesterite. This review discusses the advanced characterization techniques for studying the intrinsic properties of kesterite at a nanometer scale. Moreover, a cation substitution with an ionic mismatch around constituents is recognized as an effective route to address the fundamental limit (i.e., the cationic disorder) in CZTSSe. Here, we review recent studies on a novel chalcogenide Cu2BaSn(S,Se)4 that substitutes Zn with Ba and results in less cationic disordering.</P></▼2>

Characterization of surface chemistry of PtFe bimetallic nanoparticles

Omelianovych, Oleksii,Larina, Liudmila L.,Dao, Van-Duong,Choi, Ho-Suk Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.457 No.-

<P><B>Abstract</B></P> <P>The aim of this study is to find optimal Ar plasma etching conditions without significantly altering the surface of PtFe bimetallic nanoparticles (BNPs). Various treatment parameters such as acceleration voltage, ion beam current, and etching time are considered in this study. Studies have shown that severe alteration of surface chemical composition is closely related to the energy of Ar ions. High energy (3 keV) Ar cleaning, leads to partial reduction of alloy particles along with decontamination. However, the use of ion energies of 1 keV or lower leads to preferential cleaning with minor alteration of surface chemistry and subsequently allows us to acquire reliable XPS data of PtFe BNPs. Profiling of the NPs revealed that both metal oxides and elemental metals are simultaneously synthesized during dry plasma reduction. PtO is formed at the level of 30 atomic percent in the synthesis procedure, which is due to the influence of oxygen radicals in atmospheric plasma.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High energy (3 keV) Ar<SUP>+</SUP> cleaning leads to serious alteration of surface chemistry of PtFe nanoparticles. </LI> <LI> For PtFe NPs Ar<SUP>+</SUP> cleaning should be conducted using ion energies of 1 keV or less. </LI> <LI> Reasonable amount of metal nanoparticles can be oxidized due to synthesis operation conditions. </LI> <LI> Significant amount of metallic iron is present in a bulk of PtFe nanoparticles synthesized via dry plasma reduction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Wet Pretreatment-Induced Modification of Cu(In,Ga)Se₂/Cd-Free ZnTiO Buffer Interface

Hwang, Suhwan,Larina, Liudmila,Lee, Hojin,Kim, Suncheul,Choi, Kyoung Soon,Jeon, Cheolho,Ahn, Byung Tae,Shin, Byungha American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.24

<P>We report a novel Cd-free ZnTiO buffer layer deposited by atomic layer deposition for Cu(In,Ga)Se<SUB>2</SUB> (CIGS) solar cells. Wet pretreatments of the CIGS absorbers with NH<SUB>4</SUB>OH, H<SUB>2</SUB>O, and/or aqueous solution of Cd<SUP>2+</SUP> ions were explored to improve the quality of the CIGS/ZnTiO interface, and their effects on the chemical state of the absorber and the final performance of Cd-free CIGS devices were investigated. X-ray photoelectron spectroscopy (XPS) analysis revealed that the aqueous solution etched away sodium compounds accumulated on the CIGS surface, which was found to be detrimental for solar cell operation. Wet treatment with NH<SUB>4</SUB>OH solution led to a reduced photocurrent, which was attributed to the thinning (or removal) of an ordered vacancy compound (OVC) layer on the CIGS surface as evidenced by an increased Cu XPS peak intensity after the NH<SUB>4</SUB>OH treatment. However, the addition of Cd<SUP>2+</SUP> ions to the NH<SUB>4</SUB>OH aqueous solution suppressed the etching of the OVC by NH<SUB>4</SUB>OH, explaining why such a negative effect of NH<SUB>4</SUB>OH is not present in the conventional chemical bath deposition of CdS. The band alignment at the CIGS/ZnTiO interface was quantified using XPS depth profile measurements. A small cliff-like conduction band offset of −0.11 eV was identified at the interface, which indicates room for further improvement of efficiency of the CIGS/ZnTiO solar cells once the band alignment is altered to a slight spike by inserting a passivation layer with a higher conduction band edge than ZnTiO. Combination of the small cliff conduction band offset at the interface, removal of the Na compound via water, and surface doping by Cd ions allowed the application of ZnTiO buffer to CIGS treated with Cd solutions, exhibiting an efficiency of 80% compared to that of a reference CIGS solar cell treated with the CdS.</P> [FIG OMISSION]</BR>

Electronic structure study of lightly Nb-doped TiO₂ electrode for dye-sensitized solar cells

Nikolay, Tsvetkov,Larina, Liudmila,Shevaleevskiy, Oleg,Ahn, Byung Tae Royal Society of Chemistry 2011 ENERGY AND ENVIRONMENTAL SCIENCE Vol.4 No.4

<P>To improve the conversion efficiency of dye-sensitized solar cells (DSSCs) it is necessary to understand the electronic structure of the TiO<SUB>2</SUB>–dye–electrolyte interface in detail. A sturdy junction at the interface can be provided by modifying the electronic structure of the TiO<SUB>2</SUB> electrode with Nb doping. The Nb-doped TiO<SUB>2</SUB> was prepared by a sol–gel method followed by a hydrothermal treatment; the Nb content was varied from 0.5 to 3.0 mol%. The X-ray photoelectron spectroscopy showed that the Fermi level of TiO<SUB>2</SUB> electrode shifted away from the conduction band minimum (CBM) when the Nb content is low (≤1.5 mol%) and shifted toward the CBM when the Nb content is high (≥2.5 mol%). The shift of Fermi level with low Nb doping was due to the passivation of the oxygen vacancies at the TiO<SUB>2</SUB> nanoparticle surface. Intraband states were formed when dopant content was 1.5 and 2.5 mol%. We have found that the photovoltaic parameters of DSSCs based on doped TiO<SUB>2</SUB> sensitized with a <I>cis</I>-[Ru(dcbpyH)<SUB>2</SUB>(NCS)<SUB>2</SUB>](NBu<SUB>4</SUB>)<SUB>2</SUB>, N719 dye, are closely related to the electronic structure of the Nb-doped TiO<SUB>2</SUB> electrode. The changes of short circuit current and open circuit voltage of DSSCs were explained in relation to the electronic structure of the TiO<SUB>2</SUB> electrode. The best efficiency of 8.0% was demonstrated by DSSCs with 2.5 mol% Nb-doped TiO<SUB>2</SUB>.</P> <P>Graphic Abstract</P><P>Lightly Nb-doped TiO<SUB>2</SUB> electrodes with improved electronic structure were fabricated and used as photoanodes for dye sensitized solar cells with increased performance. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0ee00678e'> </P>