Studies on chemical bath deposited SnS₂ films for Cd-free thin film solar cells

Gedi, Sreedevi,Minnam Reddy, Vasudeva Reddy,Pejjai, Babu,Park, Chinho,Jeon, Chan-Wook,Kotte, Tulasi Ramakrishna Reddy Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.4

<P><B>Abstract</B></P> <P>Tin disulfide (SnS<SUB>2</SUB>) is a simple binary metal chalcogenide and it has been proposed as a promising buffer material for Cd-free thin film solar cells. The present work explores the deposition of SnS<SUB>2</SUB> films by a facile chemical bath deposition at different deposition times in the range of 30–120min. The effect of deposition time on the structural, optical and electrical properties was investigated. The as-grown SnS<SUB>2</SUB> films showed a hexagonal crystal structure with a high intensity (001) peak at 15.03°. The films showed shuttle shaped grains that were uniformly distributed across the surface of the substrate. The films showed an optical energy band gap in the range of 2.95–2.80eV. PL spectra showed a strong emission peak in the wavelength range, 410–460nm with the variation of deposition time. The SnS<SUB>2</SUB> films prepared at a deposition time of 90min showed good crystallinity and morphology with low resistivity of 11.2Ω-cm. A solar cell with device structure of Mo/SnS/SnS<SUB>2</SUB>/i-ZnO/Al: ZnO/Ni/Ag was fabricated. The fabricated solar cell showed an efficiency of 0.91%, which validate the photovoltaic performance of SnS<SUB>2</SUB> films.</P>

Effect of C₄H₆O₆ concentration on the properties of SnS thin films for solar cell applications

Gedi, Sreedevi,Minnam Reddy, Vasudeva Reddy,Kotte, Tulasi Ramakrishna Reddy,Park, Youngsang,Kim, Woo Kyoung Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.465 No.-

<P><B>Abstract</B></P> <P>SnS thin films were prepared by chemical bath deposition using an environmentally friendly and economic complexing agent, tartaric acid (C<SUB>4</SUB>H<SUB>6</SUB>O<SUB>6</SUB>) with different concentrations. X-ray diffraction analysis confirmed that all the deposited films exhibited polycrystalline nature with a predominant plane of (1 1 1) related to an orthorhombic structure. The intensity of the (1 1 1) plane increased with increasing concentration of the complexing agent. Raman spectra of the films showed the characteristic vibrational modes at 94, 160, 191, and 217 cm<SUP>−1</SUP>, corresponding to orthorhombic SnS. SEM micrographs showed homogeneous surfaces with the presence of nut-shaped grains. The optical absorption coefficient for the prepared films was >10<SUP>4</SUP> cm<SUP>−1</SUP>, representing that the deposited films showed high absorption. Electrical studies revealed the p-type conducting nature of the deposited films. The SnS solar cell fabricated with a tartaric acid concentration of 1.2 M showed the highest efficiency of 1.62% with an open-circuit voltage of 0.283 V, a short-circuit current density of 13.9 mA cm<SUP>−2</SUP>, and a fill factor of 41.1%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A low-cost SnS-based solar cell is developed using chemical bath deposition. </LI> <LI> Eco-friendly tartaric acid is used as complexing agent. </LI> <LI> Single phase and good crystalline SnS absorber was prepared. </LI> <LI> SnS-based thin film solar cell showed a conversion efficiency of 1.62%. </LI> <LI> The obtained efficiency is higher than reported chemical bath deposited SnS devices. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Current density-voltage (J–V) characteristics of SnS (0.6–1.6 M)-based thin film solar cell.</P> <P>[DISPLAY OMISSION]</P>

Sensitive on-chip detection of cancer antigen 125 using a DNA aptamer/carbon nanotube network platform

Gedi, Vinayakumar,Song, Chung Kil,Kim, Gae Baik,Lee, Jin Oh,Oh, Eunkyul,Shin, Bum Seok,Jung, Mingi,Shim, Jinhee,Lee, Haiwon,Kim, Young-Pil Elsevier 2018 Sensors and actuators. B Chemical Vol.256 No.-

<P><B>Abstract</B></P> <P>Despite the major role of cancer antigen 125 (CA125) in cancer progression, its structural diversity makes antibody-based immunoassay of this protein difficult. Here we report the selection of an anti-CA125 ssDNA aptamer and its application to sensitive detection of CA125 when used together with a CA125-specific antibody immobilized on a three-dimensional network of carbon nanotubes (3DN-CNTs). With exceptional stability and easy modifications over antibodies, the selected ssDNA aptamer (rCAA-8) showed high binding affinity (166nM) for recombinant CA125, which enabled CA125-specific imaging in ovarian cancer cells (OVCAR-3). Furthermore, when compared to other fluorescent assays based on graphene oxide or flat surface and traditional enzyme-linked immunosorbent assay, a chip-based assay using a 3DN-CNT surface and anti-CA125 antibody-aptamer pair resulted in higher sensitivity and broader dynamic range as a function of CA125 concentration, due to high target specificity and high surface loading density. Our on-chip aptamer-based assay will facilitate sensitive and specific monitoring of CA125 in the biological and clinical fields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The ssDNA aptamer for cancer antigen 125 (CA125) was selected through SELEX. </LI> <LI> Specificity of aptamer to CA125 was validated using cell imaging and 3DN-CNT. </LI> <LI> Biochip platform showed much improved sensitivity than that of 2D or ELISA. </LI> </UL> </P>

Impact of high temperature and short period annealing on SnS films deposited by E-beam evaporation

Gedi, Sreedevi,Reddy, Vasudeva Reddy Minnam,Kang, Jeong-yoon,Jeon, Chan-Wook Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.402 No.-

<P><B>Abstract</B></P> <P>Thin films of SnS were deposited on Mo-substrate using electron beam evaporation at room temperature. As-deposited SnS films were annealed at a constant high temperaure of 860K for different short period of times, 1min, 3min, and 5min. The impact of heat treatment period on the physical properties of SnS films was investigated using appropriate characterization tools. XRD analysis revealed that the films were highly oriented along (111) plane with orthorhombic crystal structure. Surface morphology of as-deposited SnS films showed an identical leaf texture where as the annealed films showed large orthorombic slab shape grains in adidition to the leaf shape grains, which indicates the significance of short period annealing at high temperature. The transmission electron microscopy confirmed that those large orthorombic slabs had single-crystalline nature. The results emphasized that the short period annealing treatment at high temperature stimulated the growth of film towards the single crystallinity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Preparation SnS films using electron beam evaporation at room temperature. </LI> <LI> SnS films were annealed at a high temperaure for different short period of times. </LI> <LI> The films showed highly oriented (111) planes with orthorhombic crystal structure. </LI> <LI> Surface morphology showed bigger and faceted grains embedded in orthorombic. </LI> <LI> The TEM confirmed that big orthorombic slabs had single-crystalline nature. </LI> </UL> </P>

Influence of deposition temperature on the efficiency of SnS solar cells

Gedi, Sreedevi,Minnam Reddy, Vasudeva Reddy,Alhammadi, Salh,Reddy Guddeti, Phaneendra,Kotte, Tulasi Ramakrishna Reddy,Park, Chinho,Kim, Woo Kyoung Elsevier Science B.V., Amsterdam. 2019 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.184 No.-

<P><B>Abstract</B></P> <P>In this paper, studies on the photovoltaic performance of the orthorhombic SnS device with respect to bath temperature are reported. Firstly, the effect of bath temperature on the physical properties of SnS layers was analyzed using appropriate characterization techniques. The deposited films exhibited an orthorhombic crystal structure with an intense (1 1 1) reflection of SnS. The band gap of 1.3 eV for good solar radiation absorption and a minimum value of electrical resistivity of 38 Ω-cm for easy carrier transport were obtained at 70 °C. In addition, the films had compact morphology with uniformly distributed large grains of approximately 220 nm. Finally, the optimal SnS absorber exhibited a high efficiency of 0.94%. This work gives a new insight into the efficient deposition of SnS solar absorbers with low material wastage and low environmental pollution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SnS films prepared by cost effective technique CBD. </LI> <LI> Bath temperature was optimized for PV absorber. </LI> <LI> Single phase orthorhombic SnS films with good morphology were prepared. </LI> <LI> SnS solar cell showed a conversion efficiency of 0.94%. </LI> <LI> The efficiency of present device is higher than reported CBD SnS (Orthorhombic)-devices. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Chemically synthesized Ag-doped SnS films for PV applications

Gedi, Sreedevi,Minnam Reddy, Vasudeva Reddy,Reddy Kotte, Tulasi Ramakrishna,Kim, Soo-Hyun,Jeon, Chan-Wook Elsevier 2016 CERAMICS INTERNATIONAL Vol.42 No.16

<P><B>Abstract</B></P> <P>The present paper reports chemically synthesized silver (Ag)-doped SnS absorbers (0–15at%) with tunable opto-electrical properties. The deposide films exhibited a polycrystalline nature and the crystallinity was improved with Ag-doping concentration upto 9at%. The optical band gap of the films was varied in the range, 1.31–1.26eV. The electrical resistivity of the films decreased significantly and the carrier concentration was improved by the Ag-doping concentration. Therefore, the SnS films grown with a 9at% Ag-doping concentration exhibited a very low electrical resistivity of 6Ω-cm and a carrier concentration of 1.2×10<SUP>16</SUP> cm<SUP>−3</SUP> with an optical energy band gap of 1.26eV due to the interstitial inclusion of Ag-atoms, which are suitable for the fabrication of eco-friendly, low cost, reliable, and highly efficient thin film solar cells.</P>

Identification and characterization of inhibitors of Haemophilus influenzae acetohydroxyacid synthase

Gedi, V.,Moon, J.Y.,Lim, W.M.,Lee, M.Y.,Lee, S.C.,Koo, B.S.,Govindwar, S.,Yoon, M.Y. IPC Science and Technology Press ; Elsevier Scienc 2011 Enzyme and microbial technology Vol.49 No.1

Acetohydroxyacid synthase (AHAS), a potential target for antimicrobial agents, catalyzes the first common step in the biosynthesis of branched-chain amino acids. The gene coding for the AHAS catalytic subunit from Haemophilus influenzae (Hi) was cloned, overexpressed in Escherichia coli, and purified. To identify new inhibitory scaffolds, we used a high-throughput screen to test 221 small diverse chemical compounds against Hi-AHAS. Compounds were selected for their ability to inhibit AHAS in vitro. The screen identified 3 compounds, each representing a structural class, as Hi-AHAS inhibitors with an IC<SUB>50</SUB> in the low micromolar range (4.4-14.6μM). The chemical scaffolds of the three compounds were oxa-1-thia-4-aza-cyclopenta[b]naphthalene (KHG25229), phenyl-2,3-dihydro-isothiazole (KHG25386), and phenyl-pyrrolidine-3-carboxylic acid phenylamide (KHG25056). Further, molecular docking of the two most potent chemicals, KHG25229 and KHG25386, in Hi-AHAS yielded binding energies of -10.41 and -9.21kcal/mol, respectively. The binding modes were consistent with inhibition mechanisms, as both chemicals oriented outside the active site. As the need for novel antibiotic classes to combat drug resistant bacteria increases, screening compounds that act against Hi-AHAS may assist in the identification of potential new anti-Hi drugs.

Bacterial acetohydroxyacid synthase and its inhibitors – a summary of their structure, biological activity and current status

Gedi, Vinayakumar,Yoon, Moon‐,Young Blackwell Publishing Ltd 2012 FEBS JOURNAL Vol.279 No.6

<P>Acetohydroxyacid synthase (anabolic AHAS; EC 2.2.1.6) is a thiamin diphosphate‐dependent enzyme that catalyzes the first step in the branched‐chain amino acid (BCAA) biosynthesis pathway. BCAAs are synthesized by plants, algae, fungi and bacteria, although not by animals. Thus, the enzymes of the BCAA biosynthetic pathway are potential targets in the development of herbicides, fungicides and antimicrobial compounds. Plant AHASs are well studied in this regard because specific plant AHAS inhibitors are considered to comprise the most potent herbicides. These inhibitors are also effective against bacterial AHASs, inhibit the growth of several bacterial strains and have little to no toxicity in mammals. This review provides an overview of bacterial AHASs with an update of the current status of AHAS inhibitors.</P>

Characterization of Acetohydroxyacid Synthase Cofactors from Haemophilus influenza

Gedi, Vinayakumar,Koo, Bon-Sung,Kim, Dong-Eun,Yoon, Moon-Young Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.12

Studies on Cubic Tin Sulfide Thin Films for PV Application

Sreedevi Gedi,Ignatius Andre Setiawan,Ji Hyeon Noh,Woo Kyoung Kim 한국에너지학회 2021 한국에너지공학회 학술발표회 Vol.2021 No.4