Yazar "Biber, M." seçeneğine göre listele

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    Effects of PEDOT:PSS and crystal violet interface layers on current-voltage performance of Schottky barrier diodes as a function of temperature and variation of diode capacitance with frequency
    (Elsevier, 2022) Deniz, A. R.; Tas, A. I.; Caldiran, Z.; Incekara, U.; Biber, M.; Aydogan, S.; Turut, A.
    In this study, diode applications of Crystal Violet (CV) and PEDOT materials were studied. The Ni/p-Si/Al, Ni/CV/p-Si/Al and Ni/PEDOT:PSS/CV/p-Si/Al diodes were fabricated. The I-V (current-voltage) characteristics of all diodes were analyzed at room temperature, it was determined that the PEDOT:PSS and CV materials improved the basic diode parameters. Also, I-V characteristics of Ni/PEDOT:PSS/CV/p-Si/Al of diode were investigated for different temperature values. It has been determined that the basic diode parameters are strongly dependent on temperature. It was determined that while the barrier height (Fb) increased with increasing temperature, the ideality factor (n) and the series resistance (Rs) values decreased. Using temperature-dependent measurements, it was determined that the potential barrier and ideality factor values at the contact interface has a double Gaussian distribution. In addition, C-V (capacitance-voltage) measurements of these diodes were analyzed depending on the frequency. It was found that the diode capacitance decreased with increasing frequency.
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    Effects of the PENTACENE as doping material on the power conversion efficiency of P3HT:PCBM based ternary organic solar cells
    (Elsevier, 2021) Caldiran, Z.; Erkem, U.; Baltakesmez, A.; Biber, M.
    In organic solar cells (OSCs), changing the device geometry and the photophysical properties of the active layer is an effective way to change the power conversion efficiency (PCE). For this purpose, both the buffer layer was coated between the active layer and the metal and the organic material was doped to the active layer to obtain the ternary structure. In this study, for the fabrication of bulk-heterojunction (BHJ) organic solar cell, the PEDOT:PSS layer was coated on chemically cleaned ITO coated glass substrates by the spin coating method. Subsequently, the P3HT:PCBM blend as an active layer was coated on top of PEDOT:PSS in the glove box using the same method. Finally, aluminum (Al) was coated using thermal evaporation and ITO/PEDOT:PSS/P3HT: PCBM/Al organic solar cells structure as reference device were obtained. Then, PENTACENE material with an organic semiconductor property was doped into P3HT:PCBM blend and ITO/PEDOT:PSS/P3HT:PCBM:PENTACENE/Al bulk heterojunction organic solar cell structure was obtained using the same method. In addition, the effects of OSC on PCE were investigated by coating the 2 nm lithium fluoride layer between the Al and the active layer. For devices, dark and light current density-voltage (J-V) measurements were performed under 100 mW/ cm2 in the glove box, and device parameters were calculated by the J-V curve. It was observed that the reference device showed photovoltaic properties under light and its PCE was 0.64%. When the experimental findings obtained were examined, both the LiF buffer layer and PENTACENE doping material improved the ternary OSC device performance and increased the PCE from 0.64% to 2.65%, according to the reference device. As a result of the doping, the mobility of the carrier increased with the increase of photon absorption and the presence of the buffer layer increased the carrier injection. Changing device properties can be explained with these results.
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    The electrical current characteristics of thermally annealed Co/anodic oxide layer/n-GaAs sandwich structures
    (World Scientific Publ Co Pte Ltd, 2019) Yildirm, N.; Turut, A.; Biber, M.; Saglam, M.; Guzeldir, B.
    The Co/anodic oxide layer/n-GaAs MOS structures have been fabricated by us. The MOS structures have shown an excellent rectifying behavior before and after thermal annealing of 500 degrees C for 2 min. It has been stated in the literature that the thermal annealing at a relatively low-temperature can improve the quality and performance of the anodic MOS structure. The current-voltage (I-V) measurements of the annealed MOS structure have been attempted in the measurement temperature range 60-320 K with the steps of 20 K. The I-V plot at 300 K has given the diode parameter values as barrier height (Phi(b0) = 0.96 eV and ideality factor n = 1.22, diode series resistance R-s = 124 Omega for the annealed sample, and (Phi(b0) = 0.87 eV and n = 2.11, R-s = 204 Omega for the nonannealed structure. A mean tunneling potential barrier value of 0.59 eV for the anodic oxide layer at the Co/n-GaAs interface has been calculated from the current- voltage-temperature curves. Furthermore, Phi(b0)(T) versus (2kT)(-1) curve has followed a double Gaussian distribution (GD) of the barrier heights. It has been stated that the double GD may be originated from the presence of the surface patches and phases arisen at the anodic oxide layer/n-GaAs interface.
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    THE INFLUENCE OF HIGH-ENERGY ELECTRONS IRRADIATION ON SURFACE OF n-GaP AND ON Au/n-GaP/Al SCHOTTKY BARRIER DIODE
    (World Scientific Publ Co Pte Ltd, 2018) Demir, K. Cinar; Kurudirek, S. V.; Oz, S.; Biber, M.; Aydogan, S.; Sahin, Y.; Coskun, C.
    We fabricated 25 Au/n-GaP/Al Schottky devices and investigated the influence of high electron irradiation, which has 12MeV on the devices, at room temperature. The X-ray diffraction patterns, scanning electron microscopic images and Raman spectra of a gallium phosphide (GaP) semiconductor before and after electron irradiation have been analyzed. Furthermore, some electrical measurements of the devices were carried out through the current-voltage (I-V) and capacitance-voltage (C-V) measurements. From the I-V characteristics, experimental ideality factor n and barrier height Phi values of these Schottky diodes have been determined before and after irradiation, respectively. The results have also been analyzed statically, and a gauss distribution has been obtained. The built-in potential V-bi, barrier height Phi, Fermi level E-F and donor concentration N-d values have been determined from the reverse bias C-V and C-2-V curves of Au/n-GaP/Al Schottky barrier diodes at 100 kHz before and after 12MeV electron irradiation. Furthermore, we obtained the series resistance values of Au/n-GaP/Al Schottky barrier diodes with the help of different methods. Experimental results confirmed that the electrical characterization of the device changed with the electron irradiation.
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    Interpretation of the I-V, C-V and G/?-V characteristics of the Au/ZnS/n-GaAs/In structure depending on annealing temperature
    (Elsevier, 2021) Baltakesmez, A.; Guzeldir, B.; Saglam, M.; Biber, M.
    The Zinc Sulphide (ZnS) thin film, which is included in the Au/n-GaAs/In diode as the interface layer, was grown on the n-GaAs semiconductor substrate by the spray pyrolysis method. First, to reveal some structural, surface and optical properties of the ZnS thin film, XRD, SEM and absorption measurements were taken. It was determined that the ZnS thin film completely covering the surface of the n-GaAs semiconductor substrate has a hexagonal structure and a forbidden energy range of 3.83 eV. Later, the current-voltage (I?V), the capacitancevoltage (C?V) and the conductance-voltage (G/?-V) measurements of the Au/ZnS/n-GaAs/In structure were taken at room temperature, and various important parameters of the structure were calculated with different methods. In order to reveal the effects of annealing temperature on the I?V, C?V and G/?-V measurements of Au/ ZnS/n-GaAs/In structure, the device was annealed at 100, 200 and 300 ?C respectively for 5 min in nitrogen gas environment. The characteristic parameters were calculated again and the results were interpreted comparatively. At the same time, with the help of the C?V and G/?-V characteristics, the dependence on applied bias voltage and frequency of the parameters such as dielectric constant, dielectric loss, loss tangent, ac electrical conductivity and real and imaginary part of electric modulus of the diode have been revealed. After thermal annealing at 200 ?C, it has been determined that the ideality factor, turn-on voltage and leakage current values are at minimum level and the barrier height and rectification ratio values are at maximum level. In other words, it has been revealed that the optimum thermal annealing temperature for this device is 200 ?C.
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    Inverted planar perovskite solar cells based on Al doped ZnO substrate
    (Elsevier Science Bv, 2018) Baltakesmez, A.; Biber, M.; Tuzemen, S.
    In this study, we present an inverted hybrid perovskite solar cell using Al doped Zinc Oxide (AZO) transparent metal oxide as substrate and anode electrode. Obtained results revealed that the AZO substrates prepared by RF magnetron sputtering with the optimal growth parameters have electrical and optical properties similar to properties of commercial Indium Tin Oxide (ITO), resistivity around 0.5 m Omega cm and transparency around 85%. Hybrid perovskite thin films were coated onto the PEDOT:PSS/AZO and PEDOT:PSS/ITO substrates. The morphological, structural and optical properties of the perovskite films were comparatively studied by SEM, XRD, and UV-visible spectroscopy. Besides, inverted planar perovskite solar cells were fabricated on AZO and on ITO substrates by single solution coating. The champion cell exhibited short-circuit current of 22.26 mA/cm(2), an open-circuit voltage of 0.87 V, and a fill factor of 0.51, led to a power conversion efficiency (PCE) 9.88% which is obtained by cell based on AZO substrate. The PCE value is comparable to efficiency of cell based on ITO, 12.82%. (c) 2017 The Egyptian Society of Radiation Sciences and Applications. Production and hosting by Elsevier B.V.
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    The power conversion efficiency optimization of the solar cells by doping of (Au:Ag) nanoparticles into P3HT:PCBM active layer prepared with chlorobenzene and chloroform solvents
    (Iop Publishing Ltd, 2019) Kacus, H.; Aydogan, S.; Biber, M.; Metin, O.; Sevim, M.
    We report to enhance the power conversion efficiency of organic solar cells by embedding of (Au:Ag) nanoparticles (NPs) into P3HT:PCBM active layer of the organic solar cells. Furthermore, the effect of solvents based on chlorobenzene and chloroform on the P3HT:PCBM active layer has been investigated for comparison. As known, the performance of organic solar cells based on the blend of regioregular P3HT:PCBM is strongly influenced by blend composition. For this purpose, ITO/PEDOT:PSS/P3HT:PCBM/(Au: Ag) NPs/LiF/Al quaternary hybrid solar cells were fabricated. Absorption, AFM, SEM and XRD measurements of the quaternary hydride active layers prepared with chlorobenzene (CB) and chloroform(CF) solvents were obtained. The optical energy band gap of the hybrid active layer was calculated. The highest PCE values were obtained for 1.2% Au:0.3% AgNPs ratios and the study has been focused on these values. (Au:Ag) NPs in the active layer increased the power conversion efficiency (PCE) of the device from 2.11% to 3.29% and to 2.27% for prepared with CB and CF solvents, respectively. This increase was explained by the scatter of the incident light from the NPs and an enhancement of light absorption in the active layer of the solar cell, increasing the optical path distance.