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    Effects of different formulation PEDOT:PSS hole transport layers on photovoltaic performance of organic solar cells
    (John Wiley and Sons, August 2017) Ongul, Fatih; Yuksel, Sureyya Aydin; Kazici, Mehmet; Bozar, Sinem; Gunbatti, Anil; Gunes, Serap
    In this study, the effects of the various types of PEDOT:PSS with different conductivities on the photovoltaic parameters of organic solar cells were investigated. The performances of five various commercially available PEDOT:PSS with formulations such as FET, PT2, PH1000, PH500 and PH were compared. It was observed that the device employing PH1000 as an interlayer between ITO and the active layer exhibited the highest photovoltaic performance as compared to other devices with FET, PT2, PH500 and PH.
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    Influences of CdSe NCs on the photovoltaic parameters of BHJ organic solar cells
    (Pergamon-Elsevier Science Ltd, 2018) Ongul, Fatih; Yuksel, Sureyya Aydin; Allahverdi, Cagdas; Bozar, Sinem; Kazici, Mehmet; Gunes, Serap
    In this study, the high quality CdSe nanocrystals (NCs) capped with stearic acid were synthesized in a solvent and then purified four times by using the precipitation and redissolution process. The average size of the synthesized CdSe NCs was determined similar to 3.0 nm via transmission electron microscopy (TEM) measurement and their corresponding optical band edge energy was also calculated as similar to 2.1 eV using ultraviolet-visible (UV-Vis) absorption spectroscopy. The bulk heterojunction (BHJ) hybrid solar cells based on a ternary system including P3HT, PCBM and CdSe NCs at different weight concentrations (0 wt%, 0.1 wt%, 0.5 wt%, 1 wt% and 2 wt%) were fabricated by spin-casting process. The effect of the concentration of CdSe NCs on the photovoltaic parameters of these BHJ organic solar cells was investigated. The surface morphology of the photoactive layer modified by the incorporation of CdSe NCs into P3HT:PCBM matrix was observed with scanning electron microscopy (SEM). It was shown that when the concentration of CdSe NCs increases above 0.1 wt% in this ternary system, the photovoltaic performance of the devices significantly decreases. The power conversion efficiency of the organic photovoltaic (OPV) device was enhanced similar to 20% by incorporating CdSe NCs with 0.1 wt% with respect to those without CdSe NCs. (C) 2017 Elsevier B.V. All rights reserved.
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    Structural, spectroscopic, electronic, nonlinear optical and thermodynamic properties of a synthesized Schiff base compound: A combined experimental and theoretical approach
    (Elsevier, 2017) Gokce, Halil; Ozturk, Nuri; Kazici, Mehmet; Goreci, Cigdem Yorur; Gunes, Serap
    A Schiff base compound, 2-[(1H-benzimidazol-2-ylimino)methy1]-4-bromophenol (BISB), was synthesized and its spectroscopic characterization was performed using experimental methods such as FT-IR, Raman, proton and carbon -13 NMR chemical shifts and UV Vis. spectroscopies. Density functional theory (DFT/B3LYP/6-311G(d,p)) computations were used to investigate the optimized molecular geometry, conformational forms, harmonic vibrational wavenumbers, NMR chemical shifts, UV Vis. spectroscopic parameters, natural bond orbital (NBO) analysis, HOMO-LUMO energies, nonlinear optical (NLO) properties, molecular electrostatic potential (MEP) map, atomic charges and thermodynamic properties of the BISB molecule. The assignments of vibrational modes were performed by means of potential energy distribution (PED) using VEDA4 program, The NBO analysis was used to investigate intramolecular hyrogen bonding (O-H center dot center dot center dot N), bond species, hyperconjugation interactions and intramolecular charge transfers (ICTs). Considering the computed HOMO and LUMO energies, the quantum molecular descriptors such as ionization potential (I), electron affinity (A), chemical hardness (eta), chemical softness (zeta), electronegativity (chi), chemical potential (mu) and electrophilicity index (omega) parameters were investigated for the BISB molecule. DFT computations were also performed to determine the dipole moment (mu) the mean polarizability (alpha), the anisotropy of the polarizability (Delta alpha) and the first hyperpolarizability (beta(0)) values. The recorded experimental spectroscopic results are in a good harmony with the computed data. (C) 2017 Elsevier B.V. All rights reserved.
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    Öğe
    Theoretical and experimental investigations of the 2-(4-chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile molecule as a potential acceptor in organic solar cells
    (Iop Publishing Ltd, 2016) Kazici, Mehmet; Bozar, Sinem; Yuksel, Sureyya Aydin; Ongul, Fatih; Gokce, Halil; Gunes, Serap; Goreci, Cigdem Yorur
    A novel soluble asymmetric acrylonitrile derivative, 2-(4-Chlorophenyl)-3-{[5-(2-cyano-2-phenylethenyl)]furan-2-yl}acrylonitrile (CPCPFA, 3) was synthesized in three steps by Knoevenagel condensation. The structure of the CPCPFA was characterized using UV-vis, FTIR, H-1 NMR, C-13 NMR, and LC-MS. CPCPFA was evaluated as an electron acceptor in bulk heterojunction organic solar cells. Its optical and electronic properties as well as photovoltaic performance were investigated.