Yazar "Gundogdu, Yasemin" seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim Yok
    Öğe
    Determination of photovoltaic parameters of CIGS hetero junction solar cells produced by PLD technique, using SCAPS simulation program
    (Pergamon-Elsevier Science Ltd, 2021) Gezgin, Serap Yigit; Houimi, Amina; Gundogdu, Yasemin; Mercimek, Bedrettin; Kilic, Hamdi Sukur
    In this study, CIGS ultrathin films of 52 nm, 89 nm, 183 nm and 244 nm thicknesses were grown on a n-Si substrate using PLD technique, then Ag/CIGS/Si/Al hetero-junction solar cells were formed by producing front finger and back contact. While the thickness of CIGS ultrathin film is increased, their grain sizes are also increased, crystal structures are developed and more light is absorbed within the thin film. The straight characteristics of hetero-junctions have been improved while the thicknesses of CIGS ultrathin film is decreased according to J-V characteristics of the hetero-junctions in the darkness. In addition, depending on CIGS ultrathin film thickness, the photovoltaic behavior of CIGS/Si hetero junction solar cells has been studied and interpreted in detail in this article. It can be concluded that CIGS/Si hetero-junction solar cell device produced based on CIGS ultrathin film of 183 nm thickness shows the highest short circuit current density and power conversion efficiency values among other thicknesses, with respect to J-V curve under the illumination (AM 1.5 solar radiation in 80 mW/cm2). Using SCAPS 1-D program, we have been able to successfully simulate CIGS/Si hetero-junction of 183 nm thickness.
  • Küçük Resim Yok
    Öğe
    The electrical properties of ZnO/Si heterojunction diode depending on thin film thickness
    (Korean Physical Soc, 2022) Akin, Ummuhan; Houimi, Amina; Gezgin, Bahri; Gundogdu, Yasemin; Kilic, Sumeyye; Mercimek, Bedrettin; Berber, Adnan
    In this work, ZnO thin films have been produced on p-Si wafer depending on number of laser pulses applied using pulse laser deposition (PLD) technique at room temperature conditions. Three different thicknesses of ZnO thin films (ZnO1, ZnO2 and ZnO3) have been produced by applying 18,000, 36,000 and 54,000 laser pulses and thicknesses of these produced three thin films have been measured to be 41 nm, 70 nm, 197 nm, respectively. It is observed in this work that while thicknesses of ZnO thin films increases, crystal structure of thin films develops, their grain size increase while their band gaps decrease. Ag/ZnO/Si/Au heterojunction diodes have been produced based on ZnO1, ZnO2 and ZnO3 thin films. After that, effect of thickness of thin film on electrical properties of diodes produced depending on number of laser pulses has been analyzed in detail. I-V characteristics of ZnO/Si heterojunction diodes produced have also been measured in darkness environment and under illumination conditions (AM 1.5 solar radiation of 80 mW/cm(2)) and results obtained have been interpreted and a conclusion has been made in this work. Furthermore, ideality factors, barrier heights and serial resistivities of these diodes have been calculated using conventional thermionic emission theory, Norde and Cheung-Cheung methods and then results obtained from analytical methods have been interpreted in detail in the present article. ZnO heterojunction diodes have exhibited photovoltaic properties under illumination conditions. It has been observed that as thickness of ZnO thin film is increased, J(sc) and eta values of the hetero junction diodes are increased. ZnO-3A hetero junction diode has exhibited the most improved photovoltaic performance. We have also theoretically investigated photo-electric properties of ZnO-3A heterojunction diode using SCAPS-1D packed software. The resulted J-V characteristics have been found very similar to measured counterparts.
  • Küçük Resim Yok
    Öğe
    Molecular Structure and TD-DFT Study of the Xylene Isomers
    (Gazi Univ, 2019) Kepceoglu, Abdullah; Gundogdu, Yasemin; Dereli, Omer; Kilic, Hamdi Sukur
    In this work, we have investigated the xylene isomers in concepts of vertical and adiabatic ionization energy parameters and molecular orbital (HOMO-1, HOMO/SOMO, LUMO, LUMO+1) energies of the neutrals and singly charged cation radicals. As a first step of the calculations, conformational analysis has been performed for all isomers using the semi-empirical method with PM3 core type Hamiltonian. Geometry optimization and frequency calculations were performed by using Density Functional Theory (DFT) with Becke, three-parameter, Lee-Yang-Parr (B3LYP) exchange-correlation functional and 6-311++G(d,p) basis sets. UV-Vis electronic spectra of the neutral xylene isomers were calculated by using the TD-DFT method with cam-B3LYP functional and 6-311++G(2d,2p) basis set.
  • Küçük Resim Yok
    Öğe
    Optical, Optoelectronic, and Third-Order Nonlinear Photonics of Ultrathin Molybdenum Oxide Film Deposited by Atomic Layer Deposition
    (Wiley-V C H Verlag Gmbh, 2023) Basyooni, Mohamed A. A.; Gundogdu, Yasemin; Kilic, Hamdi Sukur; Eker, Yasin Ramazan
    The atomic layer deposition (ALD) technique has attracted significant attention because it enables the control of film synthesis at the subnanometre scale. Herein, molybdenum oxide (MoO3) ultrathin films using the ALD system through Bis(t-butylimido)bis(dimethylamino)molybdenum (VI) as a molybdenum (Mo) source are prepared. To understand the effect of deposition temperature, thin films are prepared at three different temperatures 100, 150, and 250 degrees C. The morphological and elemental properties are assessed using a field emission scanning electron microscope, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy techniques. It is observed that the film thicknesses increase with the increase in the deposition temperature. It is found that the film growth at 150 degrees C is the most potential one for UV optoelectronic applications with high stability even under low applied bias voltages. Moreover, these films show interesting nonlinear optical behaviors as investigated with the z-scan technique applying open and closed aperture methods. The calculated nonlinear optical parameters including nonlinear absorption coefficient (beta), nonlinear refractive index (n(2)), nonlinear refractive coefficient (gamma), and third-order nonlinear susceptibility (chi((3))) are 10(-11) m W-1, 10(-16) cm(2) W-1, 10(-11) cm(2) W-1, and 10(-11) esu, respectively.