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Öğe Batman ilindeki ince film a-Si teknolojili fotovoltaik sistemin performans değerlendirmesi(Balıkesir Üniversitesi, 2018-07-17) Pakma, OsmanBu çalışmada Batman ilinde ince film a-Si teknolojisine sahip 2.16 kWp güce sahip şebeke bağlantılı sistemin bir yıllık elektrik enerjisi üretim verileri alınmış ve modüllerin performansı dış parametrelerde göz önüne alınarak değerlendirilmiştir. Sistem ölçümleri Ocak ayından Aralık ayına kadar tüm 2016 yılını kapsamaktadır. İnce film a-Si PV sistemden 2016 yılı süresince şebekeye 2.631 MWh enerji sağlanmıştır. Sistemin nihai verimi (Yf) 1.13 den 4.89 kWh/KWp/gün’e, performans oranı da (PO) %53 ile %78 arasında değişmektedir. Ortam ve buna bağlı olarak modül sıcaklıklarının sistem performansına etkisinin %6 - %9 arasında olduğu hesaplanmıştır. Ayrıca diğer sistem bölümlerinin de sistem performansı üzerinde değişen oranlarda etkili olduğu belirlenmiştir.Öğe Wet chemical methods for producing mixing crystalline phase ZrO 2 thin film(Elsevier, 2016-07) Pakma, Osman; Özdemir, Cengiz; Kariper, İshak Afşin; Özaydın, Cihat; Güllü, ÖmerThe aim of the study is to develop a more economical and easier method for obtaining ZrO 2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO 2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO 2 /p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.Öğe Improvement of diode parameters in Al/n-Si schottky diodes with coronene interlayer using variation of the illumination intensity(Elsevier, 2017-12-15) Pakma, Osman; Çavdar, Şükrü; Koralay, Haluk; Tuğluoğlu, Nihat; Yüksel, Ömer FarukIn present work, Coronene thin films on Si wafer have been deposited by the spin coating method. It has been ultimately produced Al/Coronene/n-Si/In Schottky diode. Current–voltage (I-V) measurements have been used to determine the effect of illumination intensity in the Schottky diodes. The barrier height (ΦB) values increased as ideality factor (n) values decreased with a increase in illumination intensity. The ΦB values have been found to be 0.697 and 0.755 eV at dark and 100 mW/cm2, respectively. The n values have been found to be 2.81 and 2.07 at dark and 100 mW/cm2, respectively. Additionally, the series resistance (Rs) values from modified Norde method and interface state density (Nss) values using current-voltage measurements have been determined. The values of Rs have been found to be 1924 and 5094 Ω at dark and 100 mW/cm2, respectively. The values of Nss have been found to be 4.76 × 1012 and 3.15 × 1012 eV−1 cm−2 at dark and 100 mW/cm2, respectively. The diode parameters are improved by applying the variation of illumination intensity to the formed Schottky diodes.Öğe Electrical characteristics of the Al/Congo Red (CR)/p-Si semiconductor diodes(Dumlupınar Üniversitesi, 2015-05) Güllü, Ömer; Pakma, Osman; Turut, Abdulmecit; Arsel, İsmailIn this work, we have studied the electrical characteristics of the Al/CR/p-Si MIS Schottky structures formed by coating of the organic material directly on p-Si substrate. It has been seen that the CR thin film on the p-Si substrate has indicated a good rectifying behavior. The barrier height and the ideality factor of the device have been calculated from the I-V characteristic. We have also studied the suitability and possibility of the MIS diodes for use in barrier modification of Si MS diodes. In addition, we have compared the parameters of the Al/CR/p-Si MIS Schottky diodes with those of conventional Al/p-Si MS diodes. We have observed that the b value of 0.77 eV obtained for the Al/CR/p-Si device was significantly larger than BH value of the conventional Al/p-Si MS contact. Thus, the modification of the interfacial potential barrier for metal/Si diodes has been achieved by using the CR organic interlayer. This was attributed to the fact that the CR interlayer increased the effective b by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 eV-1 cm-2 to 2.44×1012 eV-1 cm-2.Öğe Photoelectric and photocapacitance characteristics of Au/pyrene/N-Si MIS structures(Journal of Non-Oxide Glasses, 2017-04-01) Güllü, Ömer; Pakma, Osman; Özaydın, Cihat; Arsel, İsmail; Turmuş, MesutThis paper presents in-depth analysis of the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of identically prepared Au/Pyrene(C16H10)/n-Si hybrid organic-oninorganic semiconductor photovoltaic cells (total 43 diodes). The barrier heights, ideality factors and reverse bias saturation currents of all devices were extracted from the electrical characteristics. The mean barrier height, mean ideality factor and mean saturation current from I-V measurements were calculated as 0.79 ± 0.01 eV, 1.40 ± 0.08 and (1.01 ± 0.46)x10-8 A, respectively. Also, the photoelectric (I-V) and photocapacitance (C-V and conductance (G)-voltage (V)) characteristics of the Au/Pyrene/n-Si device under 100 mW/cm2 light illumination were investigated. It has been seen that the light illumination increases strongly the current, capacitance and conductance values of the device due to electron-hole charge pair generation. The C-V and G-V characteristics under illumination have shown a non-monotonic dependence of capacitance on frequency giving rise to a peak. This is attributed to the existence of electrically active traps. The open circuit voltage and short circuit current of the Au/Pyrene/n-Si device were extracted as 80 mV and 30 µA, respectively.Öğe Current density-voltage analyses and interface characterization in Ag/DNA/p-InP structures(American Institute of Physics, 2012-02-15) Güllü, Ömer; Pakma, Osman; Türüt, AbdülmecitThe current density-voltage (J-V) characteristics of Ag/DNA/p-InP metal-insulator-semiconductor (MIS) structures have been investigated in room temperature. We have observed that the Ag/DNA/p-InP structure shows an excellent rectifying behavior and that this structure increases the barrier height (φ b0). The main electrical parameters of these structures, such as ideality factor (n), barrier height, and average series resistance values were found to be 1.087, 0.726 eV, and 66.92Ω. This value of n was attributed to the presence of an interfacial insulator layer at the Ag/p-InP interface and the density of interface states (N ss) localized at the InP/DNA interface. The values of N ss localized at the InP/DNA interface were found at 0.675-E v in the 1.38 × 10 12 eV -1 cm -2.Öğe Synthesis and characterization of vanadium oxide thin films on different substrates(Springer Nature, 2017-04-11) Güllü, Ömer; Pakma, Osman; Özaydın, Cihat; Özden, Şadan; Kariper, İshak AfşinIn this study, the V8O15 derivative of vanadium oxide was produced on plain glass, indium tin oxide and silicon wafer substrate layers by taking advantage of wet chemical synthesis which is an easy and economical method. The structural properties of the produced films were examined by XRD and SEM analyses. Besides, Al/VOx/p-Si metal-oxide-semiconductor (MOS) structure was obtained by the same synthesis method. Doping densities of these MOS structures were calculated from frequency dependent capacitance–voltage measurements. It was determined that the interface states which were assigned with the help of these parameters vary according to frequency.Öğe Current mechanism in HfO 2-gated metal-oxide-semiconductor devices(Hindawi, 2012-06-19) Pakma, OsmanThe present study aimed to examine the current density-voltage (J-V) characteristics of Al/HfO2/p-Si (MOS) structure at temperatures ranging between 100 and 320 K and to determine the structure’s current transport mechanism. The HfO2 film was coated on a single side of the p-Si (111) crystal using the spin coating method. The J-V measurements of the obtained structure at the temperatures between 100 and 320 K revealed that the current transport mechanism in the structure was compatible with the Schottky emission theory. The Schottky emission theory was also used to calculate the structure’s Schottky barrier heights (φB), dielectric constants (εr) and refractive index values of the thin films at each temperature value. The dielectric constant and refractive index values were observed to decrease at decreasing temperatures. The capacitance-voltage (C-V) and conductancevoltage (G/ω-V) characteristics of Al/HfO2/p-Si (MOS) structure was measured in the temperature range of 100–320 K. The values of measured C and G/ω decrease in accumulation and depletion regions with decreasing temperature due to localized Nss at Si/HfO2 interface.Öğe On the energy distribution profile of interface states obtained by taking into account of series resistance in Al/TiO2/p–Si (MIS) structures(Elsevier, 2011-02-15) Pakma, Osman; Serin, Necmi; Serin, Saliha Tülay; Altındal, ŞemsettinThe energy distribution profile of the interface states (Nss) of Al/TiO2/pSi (MIS) structures prepared using the solgel method was obtained from the forward bias currentvoltage (IV) characteristics by taking into account both the bias dependence of the effective barrier height (φe) and series resistance (Rs) at room temperature. The main electrical parameters of the MIS structure such as ideality factor (n), zero-bias barrier height (φb0) and average series resistance values were found to be 1.69, 0.519 eV and 659 Ω, respectively. This high value of n was attributed to the presence of an interfacial insulator layer at the Al/pSi interface and the density of interface states (Nss) localized at the Si/TiO2 interface. The values of Nss localized at the Si/TiO2 interface were found with and without the Rs at 0.25-Ev in the range between 8.4×10 13 and 4.9×1013 eV-1 cm-2. In addition, the frequency dependence of capacitancevoltage (CV) and conductancevoltage (G/ω-V) characteristics of the structures have been investigated by taking into account the effect of Nss and R s at room temperature. It can be found out that the measured C and G/ω are strongly dependent on bias voltage and frequency.Öğe I-V-T analysing an inhomogeneous Au/Poly(4-vinyl phenol)/p-Si structure with a double gaussian distribution of barrier heights(Springer Nature, 2010-12-29) Pakma, Osman; Tozlu, Cem; Kavasoğlu, Neşe; Kavasoğlu, Abdülkadir Sertap; Özden, ŞadanIn this study, the current-voltage (I-V) characteristics of Au/Poly(4-vinyl phenol)/p-Si structures have been measured over a wide temperature range (100-300 K). These structures have been analyzed according to thermionic emission (TE) theory, as a result of which an abnormal decrease occurred in the zero-bias barrier height (φb0) and an increase in the ideality factor (n) was observed with temperature decrease and nonlinearity in the activation energy plot. By assuming a Gaussian distribution (GD) of barrier heights of the Au/Poly(4-vinyl phenol)/p-Si structures, barrier inhomogeneities are believed to responsible for this behavior. Evidence is given for the existence of a double GD with mean barrier heights (φ̄b0) of 1.042 and 0.623 eV, standard deviations of 0.138 and 0.081 V, and ideality factors 2.76 and 7.26, which remain effective in the temperature ranges of 180-300 and 100-160 K, respectively. As a result, without using the temperature coefficient of the barrier height, the modified ln(Io/T 2)-q2σo 2/2(kT)2 vs. q/kT plot gives φ̄b0 values and Richardson constants (A *) as 1.036 and 0.623 eV, and 36.20 and 19.99 A/cm2 K2, respectively. The effective Richardson constant value of 36.20 A/cm2 K2 is very similar to the theoretical value of 32 A/cm2K2 for p-Si. Consequently, the temperature dependence of the forward bias I-V characteristics of Au/Poly(4-vinyl phenol)//p-Si (MIS) structure could be attributed to the thermionic emission (TE) mechanism with double GD of the barrier heights.
