Yazar "Tomakin, Murat" seçeneğine göre listele

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    A Study on Hydrothermal Grown CdS Nanospheres: Effects of Cd/S Molar Ratio
    (Gazi Univ, 2019) Yilmaz, Salih; Tomakin, Murat; Unverdi, Ahmet; Aboghalon, Abdulaziz
    The study reports the influences of altering of Cd/S molar ratio on some physical properties of hydrothermal grown CdS nanospheres. Cd/S molar ratios were chosen as 1:0.5, 1:1, 1:2, 1:3 and 1:4 in the stock solution. X-ray diffraction (XRD) data showed the occurrence of nano-amorphous CdS structure. Scanning electron microscopy (SEM) conclusions illustrated that increasing Cd/S molar ratio up to 1:3 caused a growth in the sphere size whereas further rising of Cd/S molar ratio led to smaller sphere size. The presence of Cd and S atoms in CdS structure was approved by Energy dispersive x-ray spectroscopy (EDS) analysis. Optimum transparency was found by Cd/S molar ratio of 1:3. Band gap scores of CdS nanospheres were determined to be above 2.60 eV that was bigger than bulk CdS (2.42 eV) because of quantum confinement effect. Photoluminescence (PL) results showed that a gradual decrease in each peak was attained upon increasing Cd/S molar ratio, which could be due to the formation non-radiative recombination phenomenon. Electrical data demonstrated that CdS nanosphere having Cd/S molar ratio of 1:1 exhibited the best carrier density (1.48 x 10(15)cm(-3)) and resistivity (1.27x10(3)Omega.cm) values. Thus, it can be deduced that Cd/S molar ratio of 1:3 was obtained to be optimum one since it possesses both bigger sphere size and better transparency, facilitating the effective use of CdS nanospheres in the solar cells.
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    Enhanced efficiency of CdS/P3HT hybrid solar cells via interfacial modification
    (Tubitak Scientific & Technological Research Council Turkey, 2019) Yilmaz, Salih; Polat, Ismail; Tomakin, Murat; Unverdi, Ahmet; Bacaksiz, Emin
    The present paper examines the effects of surface modification of CdS with diverse dyes on fabricated CdS-based hybrid solar cells. The X-ray diffraction results showed that CdS thin films had a hexagonal phase with a preferred orientation along the (101) plane. Scanning electron microscopy indicated that the CdS specimen was composed of a granular structure while a P3HT layer was formed from tiny grains. Band gaps of the CdS thin films and the P3HT layer were 2.45 eV and 1.98 eV, respectively. The absorption spectra showed that different dye loading caused an increase in the absorbance of CdS thin films in the wavelength range of 400-650 nm. The photoluminescence of the CdS/P3HT structure including various dyes was lower than that of the pristine one, implying that efficient charge separation was achieved upon surface modification. Current density-voltage curves showed that the ITO/CdS/N719/Ag hybrid solar cell exhibited the best overall efficiency of 0.082%, which can be attributed to improvements in both short circuit current density (J(sc)) and open circuit voltage (V-oc). These enhancements can be attributed to the creation of better interfacial contact between CdS and P3HT layers after dye loading.
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    Improved performance of CdS powder-based hybrid solar cells through surface modification
    (2021) Ünverdi, Ahmet; Yılmaz, Salih; Tomakin, Murat; Polat, İsmail; Bacaksız, Emın
    The effects of surface modification of CdS through organic Eosin-Y, indoline D205, and Ru-based complex N719 and N3 dyes on CdS-based hybrid solar cells were studied. Chemical bath deposition (CBD) and doctor blade methods were in turn employed to fabricate the CdS specimens on Indium-Tin Oxide (ITO) covered glass substrates. P3HT material with and without dye coatings was covered through a spin-coater on the surface of CdS specimens. Ag paste was then deposited on the surface of P3HT to obtain hybrid solar cells. Structural analysis indicated that CdS powders showed a cubic growth with the preferred orientation of (111). Morphological analysis demonstrated that CdS powders exhibited hierarchical morphology and the morphology turned to granular structure with some porosity upon deposition of both N3 dye and P3HT layers. Absorption plots indicated that Eosin-Y dye loading led to a rise in the absorbance values of CdS specimens. After dye loading, photoluminescence data of CdS-based heterostructure illustrated a decrement in the luminescence intensity, implying that effective exciton dissociation was obtained. Current density-voltage (J-V) characteristics of the hybrid solar cells depicted that the best overall efficiency was observed for Eosin-Y-modified cell as 0.135%. This proved that surface modification by Eosin-Y dye led to a better interfacial contact between CdS and P3HT bilayer due to the enhancement in the charge separation.
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    Role of Mg doping in the structural, optical, and electrical characteristics of ZnO-based DSSCs
    (Tubitak Scientific & Technological Research Council Turkey, 2017) Polat, Ismail; Yilmaz, Salih; Tomakin, Murat; Bacaksiz, Emin
    ZnO- and Mg-doped ZnO samples are prepared by spray pyrolysis on conducting glass substrates to fabricate ZnO-based dye-sensitized solar cells (DSSCs). Influences of Mg-doping content on the power conversion efficiencies of ZnO-based DSSCs are investigated. X-ray diffraction results show that all the samples exhibit a hexagonal wurtzite structure. Scanning electron microscopy data indicate that the ZnO sample has uniform rods with 1 mu m diameter. With respect to ZnO, the band gap value of 4 at.% Mg-doped ZnO samples improves to the value of 3.27 eV and a further increase in Mg level up to 6 at.% gives rise to a decline in the band gap value of 3.22 eV. Photoltuminescence measurements illustrate that intensities of the ultraviolet peak and a red luminescence peak take their maximum values for 4 at.% Mg doping. From solar cell performance measurements, the best power conversion efficiency of 0.08% is obtained for the doping amount of 4 at.% Mg.
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    Öğe
    Role of Mg doping in the structural, optical, and electrical characteristics of ZnO-based DSSCs
    (2017) Polat, İsmail; Yılmaz, Salih; Tomakin, Murat; Bacaksız, Emin
    ZnO- and Mg-doped ZnO samples are prepared by spray pyrolysis on conducting glass substrates to fabricate ZnO-based dye-sensitized solar cells (DSSCs). In uences of Mg-doping content on the power conversion efficiencies of ZnO-based DSSCs are investigated. X-ray diffraction results show that all the samples exhibit a hexagonal wurtzite structure. Scanning electron microscopy data indicate that the ZnO sample has uniform rods with 1 m diameter. With respect to ZnO, the band gap value of 4 at.% Mg-doped ZnO samples improves to the value of 3.27 eV and a further increase in Mg level up to 6 at.% gives rise to a decline in the band gap value of 3.22 eV. Photoluminescence measurements illustrate that intensities of the ultraviolet peak and a red luminescence peak take their maximum values for 4 at.% Mg doping. From solar cell performance measurements, the best power conversion efficiency of 0.08% is obtained for the doping amount of 4 at.% Mg.