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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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    Öğe
    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.