Yazar "Baltakesmez, Ali" seçeneğine göre listele

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    A comparative study on the effect of monodisperse Au and Ag nanoparticles on the performance of organic photovoltaic devices
    (Elsevier, 2021) Kacus, Hatice; Metin, Onder; Sevim, Melike; Biber, Mehmet; Baltakesmez, Ali; Aydogan, Sakir
    The monodisperse Au (similar to 5 nm) and Ag (similar to 3 nm) nanoparticles used in this study were obtained using surfactant-assistant solvothermal methods and characterized by XRD TEM and SEM. Then, these nanoparticles were embedded into the P3HT:PCBM photoactive layer at different ratios and the effects of the nanoparticles on the performance of the organic solar cells have been studied by varying the loading percent of the NPs in the range of 0.5-2 wt%. The best solar cell composition was determined to be 1 wt% for Au NPs and 0.5 wt% for Ag NPs. Optical absorption spectrum of P3HT:PCBM, P3HT:PCBM:AuNPs and P3HT:PCBM:AgNPs active layers were obtained using UV-visible spectroscopy. The J-V plots of ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al solar cells having 1.10(-6) m(2) OSC area and with different Au NPs and Ag NPs loading ratios in the P3HT:PCBM were obtained under air mass (AM) 1.5G illumination. Open circuit voltage, short-circuit current density, fill factor, and power conversion efficiency of the OSC were calculated. The highest PCE values were obtained as 3.35% for Au NPs and as 3.50% for Ag NPs doped devices. This increase in PCEs was explained by a plasmonic effect that stems from the metallic NPs.
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    Determination of albedo parameters of the organometallic halide perovskite films
    (Pergamon-Elsevier Science Ltd, 2020) Yilmaz, Demet; Baltakesmez, Ali; Uzunoglu, Zeynep; Biber, Mehmet
    In this work, albedo number, energy and dose of the perovskite films were determined by the gamma ray spectrometry. The MAPbBr(3-x)Cl(x), MAPbBr(3-x)I(x), MAPbl(3-x)Cl(x) and MAPbl(3) thin films were coated on the Pedot:PSS/ITO substrates by static spin coating technique. The structural properties of the films were determined with field emission scanning electron microscopy (FE-SEM) images and X-ray diffraction (XRD) patterns. Albedo parameters of perovskite films were carried out by using a high purity germanium detector with a resolution of 182 eV at 5.9 keV and 59.54 keV gamma-rays emitted from a radioactive source of Am-241 (59.54 keV). In XRF experiments, the scattering angle was set 168 degrees. XRD patterns show that perovskite structure has forming tetragonal with high crystallinity. Also, the perovskite layer has compact and high coverage capability and uniform surface feature in terms of FE-SEM morphology. It is observed that albedo parameters are dependent on the density, the mean atomic number and the average band gap energy of perovskite films. Also, high energy radiation scattering from the perovskite films appears to be enhanced significantly with the MABr treatment.
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    Improved perovskite film quality and solar cell performances using dual single solution coating
    (Aip Publishing, 2017) Baltakesmez, Ali; Biber, Mehmet; Tuzemen, Sebahattin
    In this study, we present high quality perovskite CH3NH3PbI3-xClx thin films prepared by a combination of static and dynamic coating approaches, named dual single solution coating. Static coating, dynamic coating and the combination of these are comparatively studied. Scanning electron microscopy, X-ray diffraction, atomic force microscopy, UV-visible spectroscopy, and photoluminescence techniques are used for the determination of morphological, structural, and optical properties of thin films prepared using different coating approaches and deposition temperatures. All the coating approaches are repeated at room temperature and with hot deposition. The high quality and density CH3NH3PbI3-xClx films with full surface coverage are obtained using thedual single solution coating, particularly with hot-deposition. The perovskite solar cells prepared by the dual coating approach with hot deposition have better values for all the performance parameters in comparison to the other coating approaches, resulting in high efficiencies. The best device has a short circuit current of 22.03 mA/cm(2), an open circuit voltage of 0.91V, a fill factor of 0.73, and a power conversion efficiency of 14.68% from short-circuit to forward bias, and 22.39 mA/cm(2), 0.91 V, 75% and 15.32% for the vice-versa, respectively. Published by AIP Publishing.
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    Interface application of NiPt alloy nanoparticles decorated rGO nanocomposite to eliminate of contact problem between metal and inorganic/organic semiconductor
    (Elsevier Science Sa, 2021) Baltakesmez, Ali; Sevim, Melike; Guzeldir, Betul; Aykac, Cengiz; Biber, Mehmet
    In this study, synthesis of monodisperse NiPt alloy NPs, preparation of rGO, decoration of the NPs onto the rGO and interface application of the NiPt/rGO nanocomposite material were presented. Morphological and structural analysis showed that Ni70Pt30 NPs having particle size of 2.2 +/- 0.4 nm were obtained and de-corated onto the rGO. The I-D/I-G intensity ratio of the rGO was determined to be 1.02. On the other hand, the Ni70Pt30/rGO nanocomposite was used as interface layer in junctions of the Al/lnP and P3HT:PCBM/Al. In the Al/lnP as inorganic metal-semiconductor junction, the interface layer caused an increase in rectification ratio of up to 10(3). Moreover, the ideality factor and barrier height enhanced from 1.47 and 0.49 eV to 1.24 and 0.67 eV at 300 K. It is attributed to eliminate of metal diffusion in lnP and passivation of pinning Fermi level. Additionally, the Ni70Pt30/rGO nanocomposite layer was used fabrication of the P3HT:PCBM solar cell to eliminate of S-shaped J-V curve. The reference solar cell having S-shaped J-V curve showed 6.081 mA/cm(2) short circuit current density, 0.572 V open circuit voltage, 31.4% fill-factor and then 1.092% power conversion efficiency. The presence of the interface layer has caused an increase in the fill-factor value of more than 30%, while the PCE value increased by 15%. The best cell has 1.244% power conversion efficiency with 5.554 mA/cm(2) short circuit current density, 0.544 V open circuit voltage, 41.2% fill-factor. (C) 2021 Elsevier B.V. All rights reserved.
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    Optimizing quality of lead-free perovskite thin film with anti-solvent engineering and co-doping SnBr2/SnF2; its solar cell performance
    (Elsevier, 2020) Baltakesmez, Ali; Guezeldir, Betuel; Alkan, Yunus; Saglam, Mustafa; Biber, Mehmet
    Lead-free perovskite film is crucial for non-toxicity device applications and tin-based perovskite is one of most promising non-toxic perovskites. In this study, Br and F doping and anti-solvent washing process were investigated for suitable MASnI3 perovskite film. The structural, morphological and optical analyses showed the only Br or F doping is not enough to obtain of tin-based perovskite films having high crystallinity, surface coverage and absorbance properties. The Br and F co-doping (1 M(MAI):0.6 M(SnI2):0.2 M(SnBr2):0.2 M(SnF2)) has caused significantly decrease in morphological defects and increase crystallinity. Moreover, addition to the co-doping, void-free film morphology has been obtained by anti-solvent washing process: toluene:chloroform (1:1 vol%). Thus, oxidation of Sn2+ to Sn4+ was successfully suppressed. The optimized Sn-based perovskite film has band gap energy of 1.31 eV and atomic ratio determined to be 1.00:0.15:0.03 from the EDS and 1.00:0.16:0.07 from the XPS for I:Br:F, which indicates I-rich stoichiometric content. The solar cell application has been also performed in device structure of ITO/PEDOT:PSS (60 nm)/perovskite (272 nm)/PCBM (70 nm)/Al (100 nm). The best solar cells prepared using the co-doped perovskite films without and with anti-solvent washing process have PCE values of 2.25% with Jsc 14.9 mA/cm(2), Voc 0.42 V and FF 36% and 4.45% with Jsc 17.8 mA/cm(2), Voc 0.48 V and FF 52%, respectively.
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    Review of the fundamental issues in new generation high efficiency perovskite solar cells
    (Elsevier, 2019) Baltakesmez, Ali; Biber, Mehmet; Tuzemen, Sebahattin
    This is a mini review of the fundamental issues in producing high efficiency solar cells. We have raised many important issues that limit the power conversion efficiency, and introduced the solutions in particular to perovskite solar cell structures. We supposedly estimate very high efficiencies over detailed balance or Schockley-Quessier limit up to 50 %, having applications such as tandem cells, light concentration, inter-band activities with deep levels, photon upconversion and quantum dots together with some unique processing systems. (C) 2019 Elsevier Ltd. All rights reserved.