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    Improving the performance of the organic solar cell and the inorganic heterojunction devices using monodisperse Fe3O4 nanoparticles
    (Elsevier Gmbh, Urban & Fischer Verlag, 2017) Caldiran, Zakir; Biber, Mehmet; Metin, Onder; Aydogan, Sakir
    8 nm Fe3O4 nanoparticles (NPs) were successfully doped into poly(3hexylthiophene):phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) to fabricate ITO/PEDOT:PSS/P3HT:PCBM:Fe3O4/AI solar cell along with a heterojunction device of Fe3O4/p-GaAs by depositing them on p-GaAs substrates. The experimental results revealed that the presence of Fe3O4 nanoparticles (NPs) in the ITO/PEDOT:PSS/P3HT:PCBM/A1 solar cell improved its performance with respect to the one without Fe3O4. For example, power conversion efficiency was increased from 1.09% to 2.22% when doping 5 wt% of Fe3O4 NPs to P3HT:PCBM. This was attributed to increase of the light absorption in the presence of Fe3O4 NPs doping. Furthermore, the analysis of the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the Fe3O4/p-GaAs heterojunction have been studied successfully. The experimental barrier height Ob and ideality factor n were determined as 0.80 eV and 1.53, respectively, from the experimental I-V plots. In addition, the value of the Phi(b) obtained from the C-V characteristics was 0.95 eV (f= 500 kHz). The mismatch between barrier heights obtained from both measurements was explained by the two techniques are based on different nature. The interface state density of the Fe3O4/p-GaAs heterojunction was determined from 5.16 x 10(14) cm(-2)eV(-1) to 1.34 x 10(15) cm(-2)eV(-1). (C) 2017 Elsevier GmbH. All rights reserved.
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    The influence of annealing temperature and time on the efficiency of pentacene: PTCDI organic solar cells
    (Elsevier Science Bv, 2017) Biber, Mehmet; Aydogan, Sakir; Caldiran, Zakir; Cakmak, Bulent; Karacali, Tevhit; Turut, Abdulmecit
    In this study, fabrication of a polycyclic aromatic hydrocarbon/Perylene Tetracarboxylic Di-Imide (PTCDI), donor/acceptor solar cells are presented using physical vapour deposition technique in a 1000 class glove box. An ITO/PEDOT:PSS/Pentacene/PTCDI/Al (ITO = Indium Tin Oxide and PEDOT:PSS = poly(3,4-ethylene dioxythiophene) polystyrene sulfonate) solar cell has been obtained and the power conversion efficiency, PCE (eta) of about 0.33% has been obtained under simulated solar illumination of 300 W/m(2). Furthermore, the effects of annealing temperatures (at 100 and 150 degrees C) and of annealing (at 100 degrees C) times for 5 and 10 min. on the power conversion efficiency, eta of the solar cells have also been investigated. In general, it has been seen that the thermal annealing deteriorated the characteristics parameters of Pentacene/PTCDI solar cell such that both fill factor, FF and eta decreased after annealing and with increase of annealing time. Atomic force microscopy (AFM) images showed that the phase segregation and grain size increased and the surface roughness of Pentacene film decreased and these effects reduced the eta value. The eta values of the solar cell have been determined as 0.33%, 0.12% and 0.06% for pre-annealing, annealing at 100 and 150 degrees C, respectively. (C) 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
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    Investigation of electrical properties of Ni/Crystal Violet (C25H30CIN3)/n-Si/Al diode as a function of temperature
    (Elsevier Science Sa, 2018) Deniz, Ali Riza; Caldiran, Zakir; Biber, Mehmet; Incekara, Umit; Aydogan, Sakir
    In this study, Crystal Violet material was used for interface layer of Schottky diode applications. Firtly, chemical cleaning process have been made for boron doped n-Si crystals. After, Al metal was coated on the one surface of crystals by thermal evaporation and crystal violet materials were coated on other surface of crystals with spin coating method (coating parameters; 800 rpm for 60 s). Lastly, Ni metal was coated on Crystal Violet by sputtering. So, we obtained the Ni/Crystal Violet/n-Si/Al Schottky type diode. After the fabrication process of diode, the current-voltage (I-V) and capacity-voltage (C-V) measurements of Ni/Crystal Violet/n-Si/Al Schottky type diode were taken for various temperatures. The some basic diode parameters such as ideality factor (n), barrier height (Phi(b)) and series resistance (Rs) of Ni/Crystal Violet/n-Si/Al were calculated from I-V measurements using different methods (Thermionic Emission, Cheung and Norde functions). Also, diode parameters such as Fermi energy level, diffusion potential, carrier concentration and barrier height were calculated from the C-V measurements of diode as a function of temperature. (C) 2018 Elsevier B.V. All rights reserved.