Faculty Publications
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Item Synthesis and characterization of Cu doped CdTe thin films for solar cell application(Elsevier Ltd, 2019) Ray, S.; Bangera, K.V.; Tarafder, K.Synthesis and characterization of thin-film based photovoltaic materials attract with great research interest for the past few years as the efficiency of the photovoltaic cell can be improved systematically with a proper functionalization of the films and making multilayers. We have synthesized Cu-doped CdTe thin films with different doping concentrations using the PVD technique. The structural, morphological, and optical properties of synthesized films were carefully investigated. Our study shows that all the prepared films are polycrystalline with a cubic structure. The morphological studies (SEM) reveal that all the films are crack and pinhole-free. The composition and stoichiometry of the film were confirmed by energy dispersive spectroscopy (EDS) study. The optical characterization of the samples is performed by using UV- VIS-NIR spectrometer. The result shows interesting optical behavior of the film suitable for solar cell applications. © 2019 Elsevier Ltd. All rights reserved.Item ZnSxSe1−x thin films: A study into its tunable energy band gap property using an experimental and theoretical approach(Elsevier Ltd, 2022) Ray, S.; Barman, B.; Darshan, C.; Tarafder, K.; Bangera, K.V.In recent times, ZnS and ZnSe thin films are drawing tremendous attention towards opto-electrical devices due to their optimal wide band gap energy. By alloying ZnS and ZnSe films to obtain ZnSxSe1−x thin films, the band gap of the ZnSxSe1−x film can be tuned to a value according to the device requirements. Herein, ZnSxSe1−x thin films were deposited on pre-cleaned glass substrates using a thermal evaporation system and the various properties of the obtained thin films were analyzed by altering the percentage of sulfur concentration in the films. The XRD analysis illustrated that the prepared films are polycrystalline in nature and oriented along cubic (1 1 1) plane. The deviation of (1 1 1) preferential peak position with composition ‘x’ along the absence of any secondary peaks confirms the formation of ternary ZnSxSe1−x thin films. DFT analysis verifies the formation of pristine ZnSxSe1−x alloy system. FESEM micrographs displayed that the ZnSxSe1−x thin films do not have any cracks or pinholes. EDAX analysis of the films revealed the existence of Zn, Se and S in an appropriate quantity. Optical analysis revealed the effective band gap tailoring of ZnSxSe1−x thin films. The band gap of the ZnSxSe1−x thin films increases from 2.59 eV to 3.38 eV as the composition ‘x’ varied from 0 to 1 and band composition was determined using the DOS plot obtained using VASP. © 2022 International Solar Energy SocietyItem Validation of ZnTe as back surface field layer for CdTe solar cells: A combined experimental and theoretical study(Elsevier Ltd, 2023) Ray, S.; Tarafder, K.An excellent back contact layer is one of the key requirements for thin-film solar cells with a high energy conversion efficiency. For a highly resistive compound such as CdTe thin-film, fabrication of contact with low electrical contact resistance along with a high electron affinity is very difficult. Herein, we have thoroughly investigated the possibility of using ZnTe as a back contact layer for CdTe-based solar cells through combined experimental and first-principle studies. CdTe and ZnTe thin films were deposited on the glass substrate. Detailed structural, morphological, elemental, electrical, and optical properties are investigated through different experimental techniques. Then p-ZnTe/n-CdTe heterojunction was fabricated, and junction properties were studied. Precise electronic band-structures were obtained for CdTe, ZnTe, and CeTe/ZnTe heterojunctions. The interface properties, band edge position, and band alignments were estimated by using the HSE06 hybrid functional method. Detailed theoretical results substantiate our experimental findings. © 2023 Elsevier B.V.