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Öğe Aktif tabakaya Ag nanopartikül katkısının organik güneş hücrelerinin fotovoltaik verimine etkisi(Bilecik Şeyh Edebali Üniversitesi, 2022) Yurtdaş, Semih; Ünal, Muhittin; Tozlu, CemOrganik güneş hücreleri alternatif enerji kaynaklarından bir tanesidir. Bu teknolojinin ticarileşebilmesinin önündeki tek engel düşük verimlilik değerleridir. Bu çalışmada evrik yapıdaki organik güneş hücrelerinin verimi Ag nanopartiküllerin (np) plazmonik etkilerinden yararlanarak arttırılmıştır. Aygıt konfigürasyonu ITO/ZnO/poli(3-hekziltiofen-2,5-diil) (P3HT): (6,6)-fenil C61 bütirik asit metil ester (PCBM)/MoO3/Ag şeklindedir. Ag np’ler poliol yöntemi ile sentezlenmiş ve X-Işını difraktometresi (XRD) UV-Vis spektrofotometre ve alan emisyonlu taramalı elektron mikroskopu (FESEM) ile karakterize edilmiştir. Daha sonrasında Ag, kütlece %0,125-0,25-0,5 oranlarında P3HT:PCBM’e katkılanmıştır. Referans hücrede verim değeri %3,21 iken %0,25 Ag katkılı aygıtta yaklaşık %7’lik bir verim artışı ile %3,43 değerine ulaşılmıştır.Öğe Ara Yüzey Etkin Molibden Oksit/Organik Hibrit Anot Tampon Tabakaların Sentezi ve Organik Fotovoltaik Hücrelere Uygulanması(2016) Tozlu, Cem; Zafer, Ceylan; Can, Mustafa; Yiğit, Mesude Zeliha; Mutlu, AdemBu projede, indiyum katkılı kalay oksit (ITO, InSnO2) elektrot tabaka üzerinde kendiliğinden organize olan tek tabaka moleküller (SAM) ile MoO3 tabakaların bir araya gelmesi ile oluşan hibrit anot katmanın organik güneş hücre verimliliği üzerine etkileri çalışmaları yapılmıştır. Bu amaçla karboksilik asit türevli ve merkezde tiyofen molekülü içeren donör ve akseptör özellikli kendiliğinden organize olan tek tabaka moleküller sentezlenmiştir. Organik güneş hücrelerinde etkin yük transferi için metal kontaklar ile yarıiletken malzemeler arasında omik kontak yapısının oluşması gerekmektedir. Projemizde özellikle anot tampon tabakada etkin yük transferini gerçekleştirmek için MoO3 ile InSnO2 metal oksitleri ve yeni SAM molekül yapıları arasında monodante bağ yapısı oluşturalarak hibrit elektrotlar üretilmiştir. Yedi adet birbirinden farklı SAM molekülleri metal oksit katman üzerine çözelti ortamında büyütülmüş ve bu yapı üzerine PCBM ve P3HT fotoaktif katmanlar büyütelerek güneş hücreleri üretilmiştir. Yapılan sentez çalışmalarında moleküllerin optik özellikleri UV-Vis, elektro- kimyasal özellikler döngüsel voltametri, yüzey özellikleri Kelvin Uç Mikroskopu ve temas açısı ölçer, molekül yapıları FT-IR ve 1H-NMR analizleriyle aydınlatılmıştır. Çalışmalarda MoO3 üzerine dizilen SAM molekülleri (ITO/MoO3/SAM) ile SAM molekülleri üzerinde MoO3 ince film oksit tabakanın büyütülmesi sonucu oluşan (ITO/SAM/MoO3) iki farklı hibrit elektrot yapısı üretilmiştir. ITO/SAM/MoO3 hibrit anot tabakasının güneş hücre verimlilikleri üzerine yapılan çalışmalarda yük taşıyıcı transferi için SAM moleküllerinin ITO ile MoO3 arayüzeyinde uygun enerji band profilini sağladığı ortaya çıkmıştır. Elde edilen sonuçlar neticesinde standart ITO/MoO3/P3HT:PCBM/Ca/Ag güneş hücresi yapısından ortalama %1.85 verimlilik elde edilmiş olup, 4-[5'-(3,5-metoksifenil)-2,2'bitien-5-il]benzoik asit’in (ZE-1MeO) ve 4-[5'-(3,4,5-triflorofenil)-2,2'-bitien-5-il]benzoik asit (ZE-3F) molekülleri haricinde diğer SAM moleküllerinin kullanılması ile elde edilen ITO/SAM/MoO3/P3HT:PCBM/Ca/Ag yapısındaki güneş hücrelerin verimlilik değerleri standart güneş hücre verimlilik değerini geçmiştir. En yüksek verimlilik değeri tek Florlu SAM molekülünden %2.22 olarak ortaya çıkmıştır. Projenin nihai hedeflerinden biri olan kısa devre akım (Jsc) yoğunluğunun arttırılması, SAM molekülleri kullanılması ile sağlanmıştır. Ortalama 6.02 mA/cm2 olan standart hücrenin Jsc değeri, 4-2,2'-bitien-5-il]benzoik asit’in ZE-Ph SAM molekülü kullanılması ile ortalama 6.93 mA/cm2 değerine kadar çıkmıştır.Öğe Comparative study of arylene bisimides substituted with imidazole side group for different dielectrics on the OFET application(Elsevier Science SA, 2013) Tozlu, Cem; Erten-Ela, Şule; Singh, Th. Birendra; Sarıçiftçi, N. Serdar; İçli, SıddıkWe analyzed the effect of polymeric dielectric with hydroxyl and hydroxyl-free group on current-voltage characteristics of organic thin film transistor by the use of benzimidazole-derived arylene bisimide derivatives. Polyvinyl alcohol (PVA) with polar group and benzocyclobutene (BCB) with non-polar group were used as solution processed dielectric materials to compare with each other in thin film transistor application. The hydroxyl group has a significant effect on turn-on voltage and turn-off current in depletion regime due to hydroxyl group. It is observed that the surface morphology is influenced by the chemical structure of polymeric dielectric concerning surface energy. The electron field effect mobility of both arylene bisimides is enhanced by decreased surface energy of dielectric. The highest mobility was obtained by employing naphthalene bis-benzimidazole as an active layer on both dielectrics compared with perylene bis-benzimidazole semiconductor. The electrical behaviors of these semiconductors are discussed in relation to gate dielectric surface properties. (c) 2013 Elsevier B.V. All rights reserved.Öğe Effect of Au nanoparticle doped ZnO buffer layer on efficiency in organic solar cells(Elsevier B.V., 2023) Yurtdaş, Semih; Karaman, Mustafa; Tozlu, CemAlthough organic solar cells have great potential, there is a need to increase their efficiency values. In this study, ITO/ZnO/P3HT:PCBM/MoO3/Ag structure was used and it was aimed to increase the efficiency by adding different percentages of Au nanoparticles (nps) into the ZnO electron transport layer. According to the best results, adding 10% (V/V) Au into ZnO increased the power conversion efficiency from 2.94% to 3.48%. Thus, efficiency increase of nearly 20% was achieved. The main reason for the increase in efficiency is the increase in current density by utilizing the plasmonic effects of Au nps. While the current density was 8.14 mA/cm2 in the device without Au nps, the 10% Au doping increased to 8.58 mA/cm2 in the device.Öğe Effect of functional groups of self assembled monolayer molecules on the performance of inverted perovskite solar cell(Elsevier, 2020) Arkan, Emre; Yalçın, Eyup; Ünal, Muhittin; Arkan, M. Zeliha Yiğit; Can, Mustafa; Tozlu, Cem; Demic, ŞerafettinOrganic-inorganic halide structure such as hybrid perovskite materials has been appeared as a pioneering approach to be used as a light harvester for cost-effective photovoltaic devices. Since light-absorber material is sandwiched between hole and electron transport layers, interfacial engineering starts playing significant role to develop high efficient perovskite solar cell (PSCs). Specifically, poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) is used commonly as both electrode modifier material and hole transport layer in inverter type device architecture, but it also suffers from instability of PEDOT:PSS due to its ionic nature. Therefore, self-assembled monolayer (SAM) technic is regarded as a proper approach to overcome this problem. In this work, we present five novel SAM molecules with a feasible methodology to compare effect of electron donating and withdrawing terminal groups on the efficiency of inverted PSCs. Depending on the end group, SAM customization indicates a change in the work function of indium tin oxide (ITO) electrode, rectification of device parameters and passivation of the surface trap states. The present study fills a gap in the literature by indicating a comparative treatment route to more clearly understand interfacial issues between electrode-organic layers and perovskite structure for the fabrication of efficient inverted PSCs. This is the first study to undertake a longitudinal evaluation of the influence of both electron-donating and withdrawing terminal groups on the efficiency of inverted type PSCs.Öğe Effect of TiO 2 modification with amino-based self-assembled monolayer on inverted organic solar cell(Elsevier B.V., 2017) Tozlu, Cem; Mutlu, Adem; Can, Mustafa; Havare, Ali Kemal; Demic, S.; İçli, S.The effects of surface modification of titanium dioxide (TiO 2 ) on the performance of inverted type organic solar cells (i-OSCs) was investigated in this study. A series of benzoic acid derivatized self-assembled monolayer (SAM) molecules of 4?-[(hexyloxy)phenyl]amino-3,5-biphenyl dicarboxylic acid (CT17) and 4?-[1-naphthyl (phenyl)amino]biphenyl-4-carboxylic acid (CT19) were utilized to modify the interface between TiO 2 buffer layer and poly-3 hexylthiophene (P3HT):[6,6]-phenyl C 61 butyric acid methyl ester (PC 61 BM) active layer having the device structure of ITO/TiO 2 /SAM/P3HT:PC 61 BM/MoO 3 /Ag. The work function and surface wetting properties of TiO 2 buffer layer served as electron transporting layer between ITO and PC 61 BM active layer were tuned by SAM method. The solar cell of the SAM modified devices exhibited better performance. The power conversion efficiency (PCE) of i-OSCs devices with bare TiO 2 electrodes enhanced from 2.00% to 2.21% and 2.43% with CT17 and CT19 treated TiO 2 electrodes, respectively. The open circuit voltage (V oc ) of the SAM treated TiO 2 devices reached to 0.60 V and 0.61 V, respectively, while the V oc of untreated TiO 2 was 0.57 V. The water contact angle of i-OSCs with CT17 and CT19 SAMs was also higher than the value of the unmodified TiO 2 electrode. These results show that inserting a monolayer at the interface between organic and inorganic layers is an useful alternative method to improve the performance of i-OSCs. © 2017 Elsevier B.V.Öğe Electrospinning of Cu2ZnSnSe4-xSx nanofibers by using PAN as template(Elsevier Science Bv, 2015) Özel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Yigit, M. Zeliha; Aljabour, Abdalaziz; Buyukcelebi, Sumeyra; Tozlu, CemWe firstly demonstrate the synthesis of Cu2ZnSnSe4-xSx (CZTSeS) nanofibers through versatile electrospinning technique. Polyacrylonitrile (PAN) was used as templating polymer that leads to decrease in imperfections on crystal fibers and yields outstanding structure including a few defects with diameter around 250 nm. Sulfurization and/or selenization processes were carried out separately and simultaneously depending upon the demanded chemical structure. Detailed characterization and electrochemical response indicate their potential application for solar cells as p-type semiconductors. (C) 2014 Elsevier B.V. All rights reserved.Öğe Farklı yöntemlerle sentezlenmiş olan ZnO’in organik güneş hücrelerinde verim üzerine etkisi(2021) Yurtdaş, Semih; Karaman, Mustafa; Tozlu, CemBu çalışmada ITO/ZnO/P3HT:PCBM/MoO3/Ag yapısına sahip güneş hücresi üretilmiş olup farklı yöntemlerle sentezlenmiş olan ZnO’in aygıt verimi üzerindeki etkisi incelenmiştir. Sentez yöntemi olarak, sol-jel, nanokristal ve çözelti prosesi kullanılmıştır. Öncelikle her bir farklı sentez yöntemi için XRD ile karakterizasyon yapılmıştır. Daha sonrasında ise elde edilen ZnO çözeltileri ile kaplamalar yapılarak aygıtlar üretilmiştir. Yapılan aygıtların verim değerleri, 100 mw/cm2 güneş ışıması altında Keithley 2400 kaynak ölçer cihazı yardımı ile belirlenmiştir. Elde edilen bulgulara göre en yüksek verime (%2,90) sol-jel yöntemiyle sentezlenen ZnO ile ulaşılmıştır. Ayrıca sol-jel yönteminin, diğer yöntemlere göre daha ucuz ekipmanlara ve nispeten zararsız kimyasallara gereksinim duymasından dolayı ekstra avantajları vardır. Sonuç olarak organik güneş hücrelerinde kullanılacak olan ZnO için en uygun sentez yöntemi sol-jel yöntemi olduğu belirlenmiştir.Öğe Functionalized organic semiconductor molecules to enhance charge carrier injection in electroluminescent cell(Elsevier Science Bv, 2017) Yalçın, Eyyüp; Kara, Duygu Akın; Karakaya, Caner; Yiğit, Mesude Zeliha; Havare, Ali Kemal; Can, Mustafa; Tozlu, CemOrganic semiconductor (OSC) materials as a charge carrier interface play an important role to improve the device performance of organic electroluminescent cells. In this study, 4,4"-bis(diphenyl amino)-1,1':3',1"-terphenyl-5'-carboxylic acid (TPA) and 4,4"-di-9H-carbazol-9-yl-1,1':3',1"-terphenyl-5'-carboxylic acid (CAR) has been designed and synthesized to modify indium tin oxide (ITO) layer as interface. Bare ITO and PEDOT:PSS coated on ITO was used as reference anode electrodes for comparison. Furthermore, PEDOT:PSS coated over CAR/ITO and TPA/ITO to observe stability of OSC molecules and to completely cover the ITO surface. Electrical, optical and surface characterizations were performed for each device. Almost all modified devices showed around 36% decrease at the turn on voltage with respect to bare ITO. The current density of bare ITO, ITO/CAR and ITO/TPA were measured as 288, 1525 and 1869 A/m(2), respectively. By increasing current density, luminance of modified devices showed much better performance with respect to unmodified devices. (C) 2017 Elsevier B.V. All rights reserved.Öğe Illumination and dipole layer effects on the density of state distribution in n-type organic thin film phototransistors based on naphthalene bis-benzimidazole: Experiment and modeling(Elsevier Science BV, 2017) Boukhili, W.; Tozlu, Cem; Mandouani, M.; Erten-Ela, S.; Bourguiga, R.The electrical and optoelectrical properties of naphthalene bis-benzimidazole (NBBI) based organic thin film phototransistors (photoTFTs) with divinyl tetramethyl disiloxane-bis (benzo-cyclobutene) (BCB) as a gate insulator layer were investigated in detail under dark and various white light illumination conditions. One of the most apparent effects on devices under illumination is the shifting of the threshold voltage from positive values to negative values with increasing the light intensity. The calculated values by the proposed expression of the threshold voltage under illumination are fitted well with the experimental data. The photoTFTs exhibited a photoconduction behavior with a high photosensitivity value of 5.45 x 10(4) under 80 mW cm(-2) in off-state (V-G = 0 V) and a high responsivity value of 34.4 AW(-1) under 50 mW cm(-2) in the on-state that demonstrate the NBBI is promising material to be used on the optoelectronic applications. The combination of illumination-induced effect and dipole layer has been also studied to see how DOS distribution changes. When the dipole moment increased from P = 2D to P = 6D, the DOS distribution is more broadened and the DOS decrease with increasing the white light intensity. The used model gives a good agreement between the measured current voltage characteristics of the NBBI-photoTFTs and those modeled in all measurement conditions (in dark and under illumination). (C) 2017 Elsevier B.V. All rights reserved.Öğe Organic insulator layer influence on the electrical properties of N, N’-di (2-ethylhexyl) - 3, 4, 9, 10-perylene diimide organic thin-film transistors: Experiment and modeling(Physical Society of the Republic of China, 2018) Boukhili, W.; Tozlu, Cem; Bourguiga, R.; Wageh, S.In this work, n- type organic thin film transistors (OTFTs) based on different kinds of organic dielectrics were fabricated, characterized and theoretically investigated. Three kinds of organic insulators were applied as dielectric gate which are: divinyl tetramethyl disiloxane-bis (benzo-cyclobutene) (BCB), poly(vinylalcohol) (PVA) and poly (4-vinyl phenol) (PVP). Analytical model was applied to describe the electrical behavior of the fabricated OTFTs and to explain the absence of saturation of the drain current for the device based on PVA dielectric. In addition, Meyer–Neldel rule-grain boundary model was applied for the calculation of total resistance of OTFTs based on different dielectrics materials. The theoretical results of output characteristics and total resistance showed an excellent agreement with the experimental measurements. The experimental and theoretical calculations revealed that the n-channel OTFTs based on BCB as an insulator layer exhibited superior electrical characteristics in terms of threshold voltage, mobility and drain current compared with the devices based on PVA and PVP as a gate insulator layer. The device based on BCB organic insulator layer has the largest mobility of 4 × 10 ?3 cm 2 V ? 1 s ?1 , the smallest leakage current relative to the devices based on PVA and PVP. While, the device fabricated with PVP organic insulator gate has a large trap density on the PVP-EHPDI interface which causes a pronounced decrease in field effect mobility and consequently drain current.Öğe Organic Thin Film Phototransistor Based On Arylene Derivatives(Türk Fizik Derneği, 2014) Tozlu, Cem; S. Erten, ElaThe research and development of organic electronic has been impressive grown at last decade because of the cost effective and easy production in comparison with inorganic electronic. The one of organic electronic component is organic thin film phototransistors that are one of the most tremendous progress topics in semiconductor technologies because of their potential for use as low cost alternative to conventional amorphous silicon transistors. Three-terminal phototransistor is a key component for light detection and photoswitching in an optoelectronic circuit. We have prepared naphthalene bis benzimidazole (NBBI) thin-film photo-transistor with top contact/bottom gate geometry in order to sense visible light. The soluble dielectric that is poly-vinyl alcohol (PVA) was used to obtain high transparency of dielectric on indium tin oxide (ITO) to penetrate light through the device. The photosensing characteristics of NBBI based field effect transistor are investigated under 100 mW/cm2 illumination of visible light and dark. The mobility of NBI on PVA dielectric is measured as 10-5 cm2 V-1s-1.Öğe Polimerik güneş hücrelerinde ag nanopartikül katkılı tio2 tampon tabakasının kendiliğinden organize olan tek tabaka moleküller (SAM) ile modifiye edilmesi(Düzce Üniversitesi, 2020) Yurtdaş, Semih; Can, Mustafa; Karaman, Mustafa; Tozlu, CemOrganik güneş hücrelerinin performansları üzerinde yüzey modifikasyonu ve metal nanopartiküller önemli birrol oynamaktadır. Tek tabaka kendiliğinden organize olan (self assembly monolayer, SAM) organik malzemelerucuz ve kolay uygulanabilir olmaları nedenleriyle diğer yüzey uygulama tekniklerine alternatif birmalzemelerdir. Metal nanopartiküllerin organik güneş hücrelerinde uygulama alanlarının geliştirilmesi sonyıllarda önemli bir başlık haline gelmiştir. Bu çalışmada, sol-jel yöntemi ile sentezlenen TiO2 elektrot yapısınaAg np’ler katkılanmış ve Ag-/TiO2 yüzeyi SAM molekülü ile modifiye edilerek yeni bir tür elektrottasarlanmıştır. TiO2 elektrotlu güneş hücresinde elde edilen verimlilik değeri % 2,25 iken, bu çalışmadatasarlanan Ag-TiO2/SAM elektrot yapısından elde edilen güneş hücre verimliliği % 2,84 olarak bulunmuştur.Öğe Poly(melamine-co-formaldehyde) methylated effect on the interface states of metal/polymer/p-Si Schottky barrier diode(Elsevier Science SA, 2016) Tozlu, Cem; Mutlu, AdemThe deposition technique and interface effect of polymeric molecules onto silicon surface is crucial topic for organic/inorganic hybrid technologies. In this study, the chemical structure of poly(4-vinyl phenol) (PVP) has been modified by cross-linked agent in solution for deposition onto p-Si surface. The poly (melamine-co-formaldehyde) methylated (PMF) has been used as a cross-linked agent for PVP polymeric molecules to apply spin cast deposition technique. The rectification ratio and interface states have been improved with PMF cross-link agent compared with only PVP polymeric layer. Some important diode parameters such as diode ideality factor (eta), barrier height (phi(b)), interface state density (N-ss), series resistance (R-s) of the Au/PVP:PMF/p-Si structure were calculated from the current-voltage (I-V) characteristics. The ideality factor and barrier height were found to be 2.37 and 0.71. For the explanation of the deviation of ideality factor value from 1, the interface states has been investigated by the frequency dependent capacitance (C-f-V) and conductance (G-f-V) techniques at room temperature. It is found that the interface states and R-s which indicate the deviation of the ideality factor of Au/PVP:PMF/p-Si structure is strongly depended on bias voltage and frequency. (C) 2015 Elsevier B.V. All rights reserved.Öğe Solution processed white light photodetector based N, N '-di(2-ethylhexyl)-3,4,9,10-perylene diimide thin film phototransistor(Elsevier Science SA, 2014) Tozlu, Cem; Kuş, Mahmut; Can, Mustafa; Ersöz, MustafaIn this study, a solution-processed n-type photo-sensing organic thin film transistor was investigated using polymeric dielectric under different white light illuminations. N, N'-di (2-ethylhexyl)-3,4,9,10-perylene diimide and divinyl tetramethyl disiloxane-bis (benzo-cyclobutene) were used as a soluble active organic semiconductor and as a dielectric material, respectively. Stable amplification was observed in the visible region without gate bias by the device. The electrical characterization results showed that an n-type phototransistor with a saturated electron mobility of 0.6 x 10(-3) cm(2)/V.s and a threshold voltage of 1.8 V was obtained. The charge carrier density of the channel of the device exhibited photo-induced behaviors that strongly affected the electrical properties of the transistor. The photosensitivity and photoresponsivity values of the device were 63.82 and 24 mA/W, respectively. These findings indicate that perylene diimide is a promising material for use on organic based phototransistors. (C) 2014 Elsevier B.V. All rights reserved.Öğe Solution-processed small-molecule organic solar cells based on non-aggregated zinc phthalocyanine derivatives: A comparative experimental and theoretical study(Elsevier, 2021) Yüzer, A. Celil; Kurtay, Gülbin; İnce, Tuncay; Yurtdaş, Semih; Harputlu, Ersan; Ocakoglu, Kasım; Güllü, Mustafa; Tozlu, Cem; İnce, MineA series of non-aggregated zinc phthalocyanine derivatives containing either bulky thiophenol or phenol substituents were synthesized as a novel donor component for bulk heterojunction (BHJ) solar cell applications. The molecular structure and photophysical properties of ZnPc derivatives were investigated by combined experimental and theoretical studies using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In order to evaluate the physical properties of ZnPcs in the solvent environment, we applied the conductor-like polarizable continuum model (CPCM). Within this scope, light-harvesting efficiency (LHE), excited-state lifetime (τ), maximum absorption wavelengths (λmax), oscillator strength (f) and hyperpolarizability (β tensors) were calculated both in vacuum and chloroform (ε = 4.9) medium. Furthermore, divergent types of global descriptors such as EHOMO, ELUMO, and bandgap (Egap) energies, ionization potential (I), electron affinity (A), hardness (η), and electrophilicity index (ω) were also calculated. Our computational findings revealed that the linker heteroatoms [sulfur for the ZnPc (1–2); oxygen for the ZnPc (3–4) including the substituent type (isopropyl for the ZnPc (2–4), and phenyl for the ZnPc (1–3] severely affected the photophysical properties of the dyes. In relation, theoretical results are in good accordance with our experimental observations. Finally, ZnPc derivatives were used as a donor component and PC61BM as an acceptor material in BHJ solar cells, displaying a maximum power conversion efficiency of 0.8%. Compared with ZnPcs 1–2, ZnPc 3–4 based cells showed an inferior photovoltaic performance. These results are promising and should encourage further studies on BHJ solar cells using near-infrared absorbing and non-aggregated ZnPcs.Öğe Structural properties of cadmium selenide nanowires prepared by chemical bath deposition for the electrical and photosensitive characteristics of the p-Si/CdSe heterojunction(Society of Photo-optical Instrumentation Engineers, 2020) Öksüzoğlu, Fatih; Gubur, Hülya Metin; Havare, Ali Kemal; Özmen, Sevda Ildan; Ünal, Muhittin; Tozlu, CemCadmium selenide (n-CdSe) thin films were grown on a silicon substrate with a polished surface and applied to the Schottky type device structure. The n-CdSe thin films produced depended on various deposition times at 70 degrees C by the use of the chemical bath deposition technique. XRD results show that the fabricated thin films consist of both cubic and hexagonal crystal systems. The morphology of CdSe was formed in nanograins and nanowire structures with respect to deposition times of 6 and 10 h, respectively. In addition to structural analysis of CdSe thin films, CdSe nanowires were used as an interfacial layer in a metal-semiconductor device to investigate its effects on the electrical and photosensitive characteristics of the device. As well as under forward bias current-voltage (I - V) conditions, the space charge limited current conduction behaviors were identified at low voltages. The results showed that the film produced at 10 h has a better performance compared to that produced at 6 h in terms of increased electric current.Öğe Synthesis, characterization, and DFT study of novel metallo phtalocyanines with four carboranyl clusters as photosensitisers for the photodynamic therapy of breast cancer cells(Elsevier Science Bv, 2019) Şener, Sevil; Bayraç, Abdullah Tahir; Şener, Berke Bilgenur; Tozlu, Cem; Acar, Nursel; Salih, Bekir; Yüksel, MithatThe synthesis and characterization of novel Zn(II) and Co(II) phthalocyanines 4 and 5, respectively containing four o-carboranyl units (40 boron atoms, 32.5% boron by weight) at the peripheral positions are described. The phthalocyanines (Pcs) were synthesized by cyclotetramerization of the previously prepared precursor 4-(2-thiol-o-carboranyl)thiolato-phthalonitrile 3 with the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. They were characterized by elemental analysis, UV-Vis, FT-IR, MALDI-TOF mass and H-1 NMR spectrometry. To elucidate the structural, spectroscopic and bonding properties of the obtained compounds, calculations with DFT/TD-DFT(Density Functional Theory/Time Dependent-Density Functional Theory) were performed. The cytotoxic effects of 4 and 5 on cancer cells and epithelial cells were determined. The targeted cytotoxicities of both compounds against cancer cells were analyzed with the cell viability test. Although, 4 caused less PDT (Photodynamic therapy) based decrease in cell viability of cancer cell line in comparison to 5, it showed comparatively high cytotoxicity against cancer cells but not epithelial cells. The IC50 (half maximal inhibitory concentration) values indicate that 4 with PDT shows 17.3 fold more cytotoxicity to breast cancer cells than epithelial cells. The selectivity in cytotoxicity of 4 makes it a good candidate for cancer treatment. Interestingly, 5 was found to be highly cytotoxic for both cancer and epithelial cell lines. Considerably, 5 might be used as a cancer drug when combined with targeting agents such as antibodies and aptamers.Öğe Temperature dependent electrical transport in Al/Poly(4-vinyl phenol)/ p -GaAs metal-oxide-semiconductor by sol-gel spin coating method(Hindawi Publishing Corporation, 2016) Özden, Ş.; Tozlu, Cem; Pakma, O.Deposition of poly(4-vinyl phenol) insulator layer is carried out by applying the spin coating technique onto p-type GaAs substrate so as to create Al/poly(4-vinyl phenol)/p-GaAs metal-oxide-semiconductor (MOS) structure. Temperature was set to 80-320 K while the current-voltage (I-V) characteristics of the structure were examined in the study. Ideality factor (n) and barrier height (? b) values found in the experiment ranged from 3.13 and 0.616 eV (320 K) to 11.56 and 0.147 eV (80 K). Comparing the thermionic field emission theory and thermionic emission theory, the temperature dependent ideality factor behavior displayed that thermionic field emission theory is more valid than the latter. The calculated tunneling energy was 96 meV. © 2016 Şadan Özden et al.Öğe Vapor deposition of poly(hexafluorobutyl acrylate) nanocoating for encapsulation of organic solar cells(Elsevier B.V., 2023) Yurtdaş, Semih; Tozlu, Cem; Karaman, MustafaThe biggest problem of organic photovoltaics is their quickly deterioration in atmospheric conditions. O2 and moisture in the air affect device performance negatively. In this study, at first, it is determined which electrical parameter used in the device efficiency calculation is affected by atmospheric conditions. For this context, produced devices were kept in room conditions, desiccator, and glovebox, respectively. Stability tests were performed for 8 weeks. According to the results, predominantly, current density (Jsc) is affected by O2, open circuit voltage (Voc) is affected by moisture while fill factor (FF) is affected by both O2 and moisture. Normalized efficiency (η) values are decreased, the devices kept in room conditions, desiccator, and glovebox, 90 %, 60 %, and 20 %, respectively. In the second part, devices were encapsulated with poly(Hexafluorobutylacrylate) (PHFBA) using batch initiated chemical vapor deposition (iCVD) technique at varying thicknesses. FTIR and XPS studies revealed successful PHFBA polymerization coatings. Efficiency losses for encapsulated devices was measured as between 30 and 35 %. When the non-encapsulated and encapsulated devices kept under room conditions were compared, the reductions in efficiency were found to be 90 % versus 30 %. According to the results, PHFBA has good barrier properties against O2 and moisture.
