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>

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>

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>

Photoluminescence Study of Chemical Bath Deposited ZnIn2Se4 Thin Films

Pejjai Babu,MINNAM REDDY VASUDEVA REDDY,Kotte Tulasi Ramakrishna Reddy 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4

Thin films of ZnIn2Se4 (ZIS) have been prepared by chemical bath deposition (CBD) using a novel and water soluble Na2SeO3 as a source of selenium ion for the first time. The deposition of the films was carried out at various pH values in the range of 6 - 11, keeping all other bath parameters at optimised values. EDAX analysis revealed that all the grown layers were selenium deficient with trace amounts of oxygen and chlorine incorporation. FTIR spectral measurements revealed the associated symmetric and asymmetric stretching modes of bridged oxygen atoms on the surface of the films. The room temperature photoluminescence properties of these samples at different pH values are studied in detail. Further, Gaussian curve fitting was employed to deconvolute the PL spectra and the change in intensities of these peaks with respective to pH values was addressed and correlated to the role of native defects that were incorporated while deposition. The results indicate that the variation of solution pH had a noticeable effect on the photoluminescence ZIS films.

Synthesis of binary Cu-Se and In-Se nanoparticle inks using cherry blossom gum for CuInSe2 thin film solar cell applications

Babu Pejjai,Vasudeva Reddy Minnam Reddy,Kondaiah Seku,조해윤,Mohan Reddy Pallavolu,Trang Thi Thuy Le,정동섭,Tulasi Ramakrishna Reddy Kotte,박진호 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.12

Selenium (Se)-rich binary Cu-Se and In-Se nanoparticles (NPs) were synthesized by a modified heat-up method at low temperature (110 oC) using the gum exudates from a cherry blossom tree. Coating of CISe absorber layer was carried out using Se-rich binary Cu-Se and In-Se NPs ink without the use of any external binder. Our results indicated that the gum used in the synthesis played beneficial roles such as reducing and capping agent. In addition, the gum also served as a natural binder in the coating of CISe absorber layer. The CISe absorber layer was integrated into the solar cell, which showed a power conversion efficiency (PCE) of 0.37%. The possible reasons for low PCE of the present solar cells and the steps needed for further improvement of PCE were discussed. Although the obtained PCE is low, the present strategy opens a new path for the fabrication of eco-friendly CISe NPs solar cell by a relatively chief non-vacuum method.