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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.
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.
Babu Pejjai,Vasudeva Reddy Minnam Reddy,Sreedevi Gedi,박진호 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.60 No.-
This article provides a status review on the chemical synthesis, structural transformation, morphological engineering, and band gap energy tuning of Cu–Sn–S(Se) nanoparticles (NPs). As the fabrication of Cu–Sn–S(Se) NPs based solar cells technology faces several problems, the photovoltaic behavior of Cu–Sn–S(Se) NPs is examined using photocurrent response. Further, the influence of nanoparticle ink properties on the deposition of NPs based absorber layer is discussed in detail. The challenges and prospects of nanoparticle based Cu–Sn–S(Se) solar cells are discussed. In addition, other photovoltaic applications such as photocatalytic, hydrogen production, and dye-degradation of Cu–Sn–S(Se) NPs are also outlined.
Studies on chemical bath deposited SnS<sub>2</sub> 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>
Hyungmin Lee,Dong-seob Jeong,Taehong Mun,Babu Pejjai,Vasudeva Reddy Minnam Reddy,Timothy James Anderson,박진호 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.8
CuInSe2 (CISe) thin films were grown on Mo-coated glass substrates by spray coating technique using nanocrystalline ink. The ink was prepared by dissolving binary CuSe and In2Se3 nanoparticles in iso-butanol. The grown films were subsequently annealed in vacuum and selenium atmosphere, and examined by various characterization techniques. The vacuum-annealed films showed the CuSe binary phase along with the CuInSe2 phase, whereas the selenized films showed a single phase CuInSe2. The elemental analysis of the selenized film exhibited near stoichiometry, and the photoluminescence peak was observed in the region of band-to-band transitions (0.97 eV), which indicated the good structural quality of the selenized films. The developed method opens a new prospect for the finetuning of CISe composition by pre-adjusting the composition of each element in the binary to best fit of CISe in the photovoltaic devices.
Green and low-cost preparation of CIGSe thin film by a nanocrystals ink based spin-coating method
Trang Thi Thuy Le,Nam Le,Mohan Reddy Pallavolu,전윤창,정동섭,Babu Pejjai,Vasudeva Reddy Minnam Reddy,Nguyen Tam Nguyen Truong,박진호 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.12
An “ink” solution based process, using spin-coating technique, followed by annealing in selenium environment with different temperature programs was utilized to prepare CIGSe thin films. Herein, the CuIn0.7Ga0.3Se2 nanocrystals were synthesized using ethanol - a “green” solvent. Three different solvents: 2-propanol, 2-methoxyethanol, and their 2:1 mixture (v/v ratio), were investigated as a dispersion medium for the as-synthesized CIGSe nanocrystals to form a stable ink solution. The last one- a mixture of 2-propanol:2-methoxyethanol=2:1 (v/v), was found to be the most suitable. Furthermore, the influences of various annealing modes on the CIGSe grain size and density in the resulting film were also studied. The as-prepared CIGSe thin film was around 1µm thick and possessed a tetragonal structure. A newly developed cheaper and “greener” non-vacuum process was applied successfully from the synthesis of nanocrystals to the formation of ink solution, and produced high quality thin films; this opens a new route to the cost-competitive commercialization of CIGSe thin film solar cells.
Review on Cu2SnS3, Cu3SnS4, and Cu4SnS4 thin films and their photovoltaic performance
Vasudeva Reddy Minnam Reddy,Mohan Reddy Pallavolu,Phaneendra Reddy Guddeti,Sreedevi Gedi,Kishore Kumar Yarragudi Bathal Reddy,Babu Pejjai,김우경,Thulasi Ramakrishna Reddy Kotte,박진호 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.76 No.-
The rapid progress on the Cu–Sn–S (Cu2SnS3, Cu3SnS4, and Cu4SnS4) solar cells has opened a new avenueto generate the electrical energy at ultra-low-cost. Therefore, the progress in the deposition of Cu2SnS3,Cu3SnS4, and Cu4SnS4 thinfilms by various chemical and physical methods is reviewed comprehensively. This article briefly describes (i) the phase diagrams of Cu–Sn–S, (ii) the bulk properties of Cu2SnS3,Cu3SnS4, and Cu4SnS4, (iii) the effect of deposition conditions on the phase formation, (iv) the physicalproperties of Cu2SnS3, Cu3SnS4, and Cu4SnS4 thinfilms, and (v) the photovoltaic performance of Cu2SnS3,Cu3SnS4, and Cu4SnS4 solar cells.