Browsing by Author "Biber, Mehmet"

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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
On Thermal and Optical Sensor Applications of Chitosan Molecule in the Co/Chitosan Hybrid Heterojunction Design
(Springer, 2021) Kacus, Hatice; Aydogan, Sakir; Incekara, Umit; Yilmaz, Mehmet; Biber, Mehmet
Co/Chitosan/p-Si/Al and Co/p-Si devices were made and barrier height and ideality factor values of both devices were determined at room temperature (dark conditions). After the chitosan interlayer was found to improve the device, the thermal and photosensivity properties of the Co/Chitosan/p-Si/Al device were investigated in detail. The current-voltage measurements of Co/Chitosan/p-Si/Al heterojunction were performed in temperature range of 100-460 K and illumination intensity range of 100-400 mW/cm(2). It was seen that the device parameters such as barrier height, ideality factor, series resistance and interface states density were strongly dependent on temperature. Furthermore, the capacitance-voltage (C-V) characteristics of the device were investigated at various frequencies at room temperature. The responsivity (R), detectivity (D*) and rectification ratio (RR) values of the Co/Chitosan/p-Si/Al heterojunction were found to be as a function of illumination intensity. The experimental results show that the fabricated device with chitosan thin film interlayer can be used in various optoelectronic applications, especially applications in low temperature switching devices, energy generation, photodiode and photodetector.
Phenol Red Based Hybrid Photodiode for Optical Detector Applications
(Pergamon-Elsevier Science Ltd, 2020) Kacus, Hatice; Sahin, Yilmaz; Aydogan, Sakir; Incekara, Umit; Yilmaz, Mehmet; Biber, Mehmet
In this study, the phenol red (PR) dye film has been deposited on n-type silicon wafer and SEM, XRD measurements of the film have taken. Then, the PR/n-Si photodiode has been fabricated and (dark) electrical and photoresponse characterization has been analysed. The current-Voltage (I-V) measurements have been carried out at varied light power ranging from 100 mW/cm 2 to 400 mW/cm(2). Rectification ratios (RR) have been determined as a function of illumination intensities and they are determined as 115.47 for 100 mW/cm(2) and 30.26 for 400 100 mW/cm(2), respectively. The ideality factor and the barrier height of the Co/PR/n-Si photodiode have been determined as 2.80 and 0.52 eV, respectively in dark. Therefore, it has been seen that the PR/n-Si photodiode performances are strongly dependent on the incident optical power. Namely, the current density has increased remarkably with the power of light at the same reverse bias voltage and this behavior is explained by strong capability of converting a light signal into an electrical for the PR/n-Si photodiode device. Responsivity (R) and detectivity (D*) of the PR/n-Si photodiode are also plotted as a function of illumination intensities for reverse biases and it is found that both parameters are dependent on the illumination intensity. Finally, the capacitance-voltage (C-V) characteristics of the device have been carried out at various frequencies. Obtained experimental results indicate that the PR dye can be used in various optoelectronic applications.
Photo-Sensor Characteristics of Tannic Acid (C76H52O46)/N-Si Hybrid Bio-Photodiode for Visible and UV Lights Detection
(Elsevier Sci Ltd, 2022) Yildirim, Fatma; Orhan, Zeynep; Taskin, Mesut; Incekara, Umit; Biber, Mehmet; Aydogan, S.
We present the electo-optical characterization of tannic acid (TA)/n-Si heterojunction for visible and UV lights (365 nm and 395 nm). The TA was deposited on n-Si by spin coating. The morphological and structural analyses of TA film were carried out by Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray (EDX) analyses, respectively. The electro-optical performance of the TA/n-Si bio-photodiode were investigated by I-V measurements for 10 mW/cm(2), 15 mW/cm(2), 20 mW/cm(2) and 30 mW/cm(2) visible light intensities in addition to UV light. Light-dependent the responsivity, ON/OFF ratio, detectivity, shunt resistance and series resistance were calculated. Maximum values of responsivity, detectivity and ON/OFF ratio were determined as 11.9 mA/W (-1.5 V), 3.2 x 109 Jones (at-0.42 V) and 194 (30 mW/cm2) (AM 1.5 G), at-2 V respectively. Whereas, they were determined to be 0.1 A/W, 4 x 109 Jones and 14977, respectively for UV light. Furthermore, the dielectric properties of the TA/n-Si heterostructure also were investigated from the dark Capacitance/Conductance-Voltage measurements. It was seen that both real and imaginary parts of the dielectric constants was frequency dependent. Experimental results show that the TA/n-Si device with a high rectification ratio of 2263 is a potential candidate for detecting visible and UV lights.