Mühendislik Fakültesi, Enerji Sistemleri Mühendisliği Bölümü, Makale Koleksiyonu

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https://hdl.handle.net/11492/872

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Disruptive electrochromic materials: carbazole-based conjugated polymers
(Amer Chemical Soc, 2025) Çarbaş, Buket Bezgin
Carbazole-based conjugated polymers are revolutionizing electrochromic technology and becoming indispensable materials for cutting-edge applications. These polymers showcase exceptional electrochromic capabilities, featuring high coloration efficiency, fast switching times, and outstanding stability, all tailored to their unique structure and doping levels. This review explores the innovative realm of EC conjugated polymers, highlighting the charge transport and photoconductive role of carbazole (Cz) as a main chain building block or subunit, making these materials ideal for use in smart windows, displays, and other optoelectronic devices. The resulting polymers of Cz demonstrate diverse electrochromic behaviors, ranging from transparent to green and blue color transitions, depending on the specific structure and doping level. The presence of carbazole units within the polymer backbone or as side chain substituents allows for further tuning of the material's properties through chemical modification. Furthermore, our review emphasizes the importance of understanding the relationship between the molecular structures of the polymers and their resulting electrochromic properties. By systematically studying the effects of different substituents, linkage positions, and polymerization techniques, researchers can gain valuable insights into the design principles that govern the performance of these materials. This knowledge is crucial for the development of next-generation electrochromic devices with improved efficiency, durability, and functionality.
Parameter estimation and validation of cascaded DC-DC boost converters for renewable energy systems using the IGWO optimization algorithm
(Elsevıer Science Sa, 2025) Çeltik, Seyit Alperen; Kül, Seda; Balcı, Selami; Dik, Abdullah
The voltage amplitude generated by renewable energy sources is often unstable, necessitating the use of power electronic circuits for effective grid integration. Among these, DC-DC converters play a critical role in maintaining a constant DC link voltage, typically 400 V or 800 V, at the input of inverter circuits that supply power to the load or the grid. The study focuses on the voltage gain behavior of a high-gain dual cascaded DC-DC boost converter designed for PV (photovoltaic) power systems. Using ANSYS Electronics software with its parametric solver, a comprehensive dataset was generated based on key parameters such as input voltage, power switch duty ratio, and switching frequency. The Improved Grey Wolf Optimizer (IGWO) algorithm was employed to estimate mathematical models for this dataset using linear and quadratic equations. The accuracy of the proposed models was validated across six test scenarios, demonstrating superior performance compared to traditional optimization algorithms, including Harmony Search (HS), Particle Swarm Optimization (PSO), Differential Evolution (DE), and the standard Grey Wolf Optimizer (GWO). Experimental validations yielded output voltages of 23.5 V and 36.1 V for input voltages of 4.8 V and 6.2 V, respectively, closely aligning with simulation results of 23.113 V and 36.447 V. The findings, supported by detailed simulations and graphical analyses, highlight the IGWO algorithm's precision and reliability in predicting converter output voltages under variable input conditions. This work advances renewable energy systems integration by enhancing the modeling and performance of cascaded DC-DC boost converters.
Grey Wolf-Based Heuristic Methods For Accurate Parameter Extraction To Optimize The Performance Of PV Modules
(Inst Engineering Technology-Iet, 2024) Çeltek, Seyit Alperen; Kül, Seda; Singla, Manish Kumar; Gupta, Jyoti; Safaraliev, Murodbek; Zeinoddini-Meymand, Hamed
Parameterprediction for PV solar cells plays a crucial role in controlling andoptimizing the performance of PV modules. In this study, the parameter prediction of a four-diode PV model wascarried out using the Improved Grey Wolf Optimization (IGWO) algorithm, whichbuilds upon the Grey Wolf Optimization (GWO) algorithm. The parameters requiredfor the four-diode PV model were optimized based on a predefined objectivefunction. Subsequently, the obtained data were compared with the data from RTCFrance Solar Cell to validate the accuracy and reliability of the optimizationresults. The evaluation of the optimization results revealed that the SumSquare Error (SSE) values for PSOGWO, AGWOCS, GWOCS, and GWO were 3.96E-05, while the MSE value for IGWO was 3.6309E-05. These findings clearly demonstratethat the proposed IGWO algorithm outperforms the other algorithms used in thestudy, based on the minimized SSE values. This study emphasizes the importanceof parameter prediction in optimizing PV performance, and it contributes to thefield by introducing the novel IGWO algorithm for the four-diode PV model. Thealgorithm's superior performance, as demonstrated through extensive testing andcomparison with existing algorithms, validates its efficacy in accuratelypredicting the parameters for the PV solar cell model. This paper presents the parameter prediction of a four-diode PV model using the improved grey wolf optimization (IGWO) algorithm, which builds upon the grey wolf optimization (GWO) algorithm. Initially, the proposed algorithm underwent rigorous testing across ten benchmark test functions. The results of this comprehensive evaluation demonstrated the superiority of the proposed IGWO algorithm over the other algorithms used for comparison. image
A new n-functionalized pyrrole derivative bearing ruthenium tris(2,2'-bipyridine) subunit
(Wiley-V C H Verlag Gmbh, 2024) Çarbaş, Buket Bezgin; Kaya, Yasemin; Yıldız, Hüseyin Bekir; Kıvrak, Arif
In recent years, nitrogen-based ruthenium complexes have become an important material for dye-sensitized solar cells and photo-catalytic H2O and CO2 reduction research and applications, thanks to their charge transfer feature from the metal to the ligand. The electronic and spectral properties of such materials can be easily modified by changing the substituents and ligands. In this study, a new ruthenium (II) complex with N-functionalized pyrrole derivative ([Ru(bpy)(2)(bpyCONHArPy)](+2) complex) was successfully synthesized and characterized. Its optical and electrochemical properties were studied by means of fluorescence, UV-vis spectrometry, FTIR spectroscopy and cyclic voltammetry. These results were compared with that of its components (4-(1H-pyrrol-1-yl) aniline, N-4,N-4 '-bis(4-(1H-pyrrol-1-yl)phenyl)-[2,2 '-bipyridine]-4,4 '-dicarboxamide and ligand [Ru(bpy)(3)](+2)). Related theoretical studies were also studied to find energy levels of complex. The present work is carried out to understand what chemical changes bring when combination of all the pieces of the puzzle into a chemical structure step by step.
Türkiye’nin Enerji Talebi Tahmin Probleminin Çözümünde Regresyon Yöntemlerine Dayalı Yaklaşımlar
(2024) Çeltek, Seyit Alperen
Günümüzde enerji talebi ve bu talebin gelecekteki tahmini, sürdürülebilir enerji politikaları oluşturmak ve enerji kaynaklarının etkin kullanımını sağlamak için hayati bir öneme sahiptir. Bu çalışmada Türkiye’nin 1979-2020 yılları arasına ait gözlemlenen enerji talebi, nüfus, gayri safi yurt içi hasıla, ihracat ve ithalat verileri kullanılarak enerji talep tahmin modelleri oluşturulmuştur. Enerji talep tahmini modellerini oluşturmak için çoklu regresyon ve polinom regresyon yöntemleri kullanılmıştır. Çalışmanın temel hedefi, literatürde bulunan yöntemlere kıyasla doğruluk oranı daha fazla olan bir talep tahmin modeli sunmaktır. Çalışmanın başlıca bulguları, çoklu regresyonun enerji talep tahmininde literatürdeki çalışmaların sonucu yakaladığını ve etkili bir araç olduğunu göstermektedir. Ayrıca, polinom regresyon tabanlı yaklaşımla literatürdeki sonuçlar yaklaşık %4 oranında iyileştirilmiş ve güvenli bir tahmin modeli literatüre sunulmuştur. Ayrıca, elde edilen tahmin modeli kullanılarak Türkiye’nin 2021-2050 arasındaki enerji talebi tahmin edilmiştir. Elde edilen sonuçlar, belirtilen dönemde enerji talebinin önemli ölçüde artacağını ortaya koymaktadır. 2021-2050 yılları arası enerji talebi artış oranının, geçmiş yıllara benzerlik göstermesi, regresyon tabanlı yöntemin güvenilirliğini desteklemektedir. Bu çalışma, enerji planlaması ve politika oluşturmadaki karar alıcılar için önemli bir referans kaynağı olabilir.
Elektrokimyasal kaplama yöntemiyle yeni nesil cu2msns4 (m=zn+2,co+2, fe+2, mn+2, ni+2) ince filmlerinin sentezi ve karşıt elektrot olarak boya duyarlı güneş gözesi uygulamaları
(2017) Sönmezoğlu, Savaş; Çarbaş, Buket; Özel, Faruk
Bu projede, yeni nesil CuMSnS4 (M = Zn2+, Co2+, Fe2+, Mn2+, Ni2+) ince filmleri tek-adım ve iki-adım elektrokimyasal depolama yöntemi ile başarılı bir şekilde sentezlenmiş ve boya duyarlı güneş gözelerinde (BDGG) karşıt elektrot olarak kullanılabilirliliği araştırılmıştır. İnce filmlerin yapısal, morfolojik ve kompozisyon özellikleri, X-ışını difraksiyonu (XRD), Raman spektroskopisi, Taramalı elektron mikroskobu (SEM), Atomik kuvvet mikroskobu (AFM), X- ışını fotoelektron spektroskobisi (XPS) ve Enerji-dağılımlı spektrometre (EDS) yardımıyla karakterize edilmiştir. Elde edilen tüm ince filmlerin kesterit fazlı kristal yapıya, uygun stokoyimetriye, 60-300 nm aralığında parçacık boyutlu ve gözenekli yapıda oluştuğu gözlemlenmiştir. Ayrıca, döngüsel voltametri analizlerinden, Cu2CoSnS4 ve Cu2FeSnS4 ince filmlerinin diğer ince filmlere göre iyodür bazlı elektrolitin indirgenmesi için daha iyi elektrokatalitik aktivite sergiledikleri tespit edilmiştir. Fotovoltaik sonuçlarda, tek- ve iki-adımlı elektrokimyasal depolama yöntemi ile sentezlenen Cu2CoSnS4 ve Cu2FeSnS4 ince filmlerinin karşıt elektrot olarak kullanıldığı boya-duyarlı güneş gözelerinin sırasıyla 3% - 5.55% ve 2.94% - 5.14% ile Cu2ZnSnS4 ince filmine (1.93% - 2.87%) göre daha iyi verimlilik değerlerine ulaştığı gözlemlenmiştir. Aynı zamanda, akım ve gerilim için gerçekleştirilen kararlılık testlerine göre de Cu2CoSnS4 filmi en uzun elektron yaşam ömrü ve kararlı anahtarlama performansına sahipken, Cu2MnSnS4 filmi en kısa yaşam ömrü ve daha kararsız anahtarlama performansına sahiptir. Bu umut verici sonuçlar, düşük maliyetli, yüksek verimli Pt-karşıt elektrotsuz boya-duyarlı güneş gözelerinde yeni nesil CuMSnS4 ince filmlerinin potansiyel bir uygulamasını vurgulamaktadır.
Determination of solar reflection coefficients (albedo) from satellite images using google earth engine platform
(2024) Yıldız, Mehmet Alper; Karabörk, Hakan; Rüşen, Selmin Ener
In many models calculating solar radiation, a combination of physical measurements and mathematical models is used to achieve results close to reality. In these calculations, the slope values and shading effects in the region being analyzed are often disregarded. Mathematical models such as ArcGIS's Area Solar Radiation (ASR) can calculate shading effects on three-dimensional surfaces. When solar radiation models are computed in three dimensions, accounting for solar rays reflected from the ground, in addition to atmospheric reflections, will increase accuracy. This study aimed to determine the surface reflectance coefficients that should be added in three-dimensional radiation models. In literature, general assumptions exist for surface reflectance coefficients, which represent very broad average values. However, this study aimed to establish precise albedo values for all land classes and surfaces. An area of approximately 1600 km² located in the mountainous region south of Karaman was chosen as the test area. This area was chosen in Karaman province because, as is known, this region has high solar energy potential. Sentinel 2A satellite images with a spatial resolution of 10 meters were used for both summer and winter seasons through the Google Earth Engine (GEE) platform. For the summer and winter applications, the albedo value for snowy surfaces was calculated as 0.86, while for light-colored buildings, it was 0.36 for summer and 0.28 for winter. Although examples were provided for some land classes, the study ultimately determined albedo values for all land surfaces without differentiation between classes.
Detection of vortex cavitation with the method adaptive neural fuzzy networks in the deep well pumps
(2021) Durdu, Akif; Çeltek, Seyit Alperen; Orhan, Nuri
Nowadays submersible deep well pumps are the most used irrigation systems in agriculture field. Efficient operation and economical life of pumps is an important issue. One of the most important parameters affecting pump efficiency and life is cavitation The cavitation is one of the problems frequently faced in the pump systems that widely used in the agriculture field. The cavitation could cause more undesired effects such as loss of hydraulic performance, erosion, vibration and noise. This paper presents a novel model for the detection of vortex cavitation in the deep well pump used in the agriculture system using adaptive neural fuzzy networks. The data submergence, flow rate, power consumption, pressure values, and noise values used for training the ANFIS (Adaptive-Network Based Fuzzy Inference Systems) network are acquired from an experimental pump. In this study, we use to the sixty-seven data for training process, while the fifteen data have used for testing of our model. The average percentage error (APE) has obtained as 0.08 % and as 0.34 % respectively for 67 training data and for 15 test data. The performance of the implemented model shows the advantages of ANFIS. The result of this study shows that ANFIS can be successfully used to detect vortex cavitation. This paper has two novel contributions which are the usage of noise value on cavitation detection and find out cavitation by using adaptive neural fuzzy networks. During the cavitation, the pump parameters must change by controller for prevent unwanted pump errors. The strategy proposed could be preliminary study of automatic pump control. Also proposed novel control strategy can be used for cavitation control in agriculture irrigation pumps, because of easy set up and no need extra cost. The ANFIS based model has real-time applicable thanks to rapid and easy control. It is possible to set safe boundaries in submergence in this model. Thus, users by adjusting controllable parameters can prevent cavitation and increase pump efficiency.
AN OPERANT CONDITIONING APPROACH FOR LARGE SCALE SOCIAL OPTIMIZATION ALGORITHMS
(2020) Çeltek, Seyit Alperen; Durdu, Akif
The changes that positive or negative results cause in an individual's behavior are called Operant Conditioning. This paper introduces an operant conditioning approach (OCA) for large scale swarm optimization models. The proposed approach has been applied to social learning particle swarm optimization (SL-PSO), a variant of the PSO algorithm. In SL-PSO, the swarm particles are sorted according to the objective function and all particles are updated with learning from the others. In this study, each particle's learning rate is determined by the mathematical functions that are inspired by the operant conditioning. The proposed approach adjusts the learning rate for each particle. By using the learning rate, a particle close to the optimum solution is aimed to learn less. Thanks to the learning rate, a particle is prevented from being affected by particles close to the optimum point and particles far from the optimum point at the same rate. The proposed OCA-SL-PSO is compared with SL- PSO and pure PSO on CEC 13 functions. Also, the proposed OCA-SL-PSO is tested for large-scale optimization (100-D, 500-D, and 1000-D) benchmark functions. This paper has a novel contribution which is the usage of OCA on Social Optimization Algorithms. The results clearly indicate that the OCA is increasing the results of largescale SL-PSO.
Evaluating action durations for adaptive traffic signal control based on deep q-learning
(Springer, 2021) Celtek, Seyit Alperen; Durdu, Akif; Ali, Muzamil Eltejani Mohammed
Adaptive traffic signal control is the control technique that adjusts the signal times according to traffic conditions and manages the traffic flow. Reinforcement learning is one of the best algorithms used for adaptive traffic signal controllers. Despite many successful studies about Reinforcement Learning based traffic control, there remains uncertainty about what the best actions to actualize adaptive traffic signal control. This paper seeks to understand the performance differences in different action durations for adaptive traffic management. Deep Q-Learning has been applied to a traffic environment for adaptive learning. This study evaluates five different action durations. Also, this study proposes a novel approach to the Deep Q-Learning based adaptive traffic control system for determine the best action. Our approach does not just aim to minimize delay time by waiting time during the red-light signal also aims to decrease delay time caused by vehicles slowing down when approaching the intersection and caused by the required time to accelerate after the green light signal. Thus the proposed strategy uses not just information of intersection also uses the data of adjacent intersection as an input. The performances of these methods are evaluated in real-time through the Simulation of Urban Mobility traffic simulator. The output of this paper indicate that the short action times increase the traffic control system performances despite more yellow signal duration. The results clearly shows that proposed method decreases the delay time. © 2021, Springer Science+Business Media, LLC, part of Springer Nature.
Farklı lokasyonlarda yetiştirilen şeker pancarı bitkisinin (Beta vulgaris L.) bazı morfolojik ve teknolojik karakterlerinin hasat zamanlarına göre değişiminin incelenmesi
(Karamanoğlu Mehmetbey Üniversitesi, 2023) Cesur, Cüneyt
Bu araştırma 2014–2015 yıllarında, Orta Anadolu bölgesinde, şeker pancarı bitkisinin verim ve verim unsurları üzerine genotip–çevre ilişkilerinin etkisinin incelenmesi amacıyla yapılmıştır. Araştırmada bölgeye uyumlu Turbata çeşidi kullanılmıştır. Nisan ayının ilk günlerinde yapılan ekimlerde lokasyonlar (Şefaatli ve Sarıkaya) ana parselde, hasat zamanları (15 Eylül, 1 Ekim, 15 Ekim ve 1 Kasım) ise alt parsellerde oluşturulmuştur. Farklı lokasyon ve hasat zamanlarının kök (gövde) boyu, kök (gövde) ağırlığı, kök (gövde) çapı, biyokütle ağırlığı, şeker oranı, kuru madde, usare safiyeti, α amino azot (N), melas oranı, yaprak ağırlığı, kül oranı, pancar verimi özelliklerine etkisi incelenmiştir. Elde edilen neticelere göre lokasyonlara göre şefaatli lokasyonun kök (gövde) ağırlığı (751.7 kg/da), kök (gövde) çapı (11.8 cm) biyokütle ağırlığı (902.8 kg/da), α amino N (0.050), yaprak ağırlığı (287.29 kg/da) ve pancar verimi (644.3 kg/da) özellikleri daha yüksek değerler oluştururken, Sarıkaya lokasyonunda ise kök (gövde) yüksekliği (18.3 cm), şeker oranı (16.5%), kül oranı (3.134%), usare safiyeti (89.5%), şeker oranı ve kuru madde (19.98%) özellikleri daha yüksek değerler oluşturmuştur. Temel bileşen analizine göre PC1 %50.03 olarak gerçekleşirken, PC2 %17.11 olarak gerçekleşmiştir.
Electrochemical and optical properties of poly(4-(4-(1H-pyrrol-1-yl)phenyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole
(Springer, 2024) Çarbaş, Buket Bezgin; Ergin, Nurseli Mislina; Yıldız, Hüseyin Bekir; Kıvrak, Arif
A novel dithieno[3,2-b:2',3'-d]pyrrole (DTP) derivative, namely, 4-(4-(1H-pyrrol-1-yl)phenyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole (DTP-Ph-Pyr) was synthesized, and its corresponding polymer (P(DTP-Ph-Pyr)) was successfully obtained via electrochemical polymerization. Electrochemical and optical properties of this novel polymer were discussed in detail. It was found that the polymer film also exhibited a reversible electrochromic behavior (orange color in the neutral state and blue color in the oxidized state) with a high optical contrast (52.5% at 950 nm) and coloration efficiency (123 cm2/C at 950 nm). Moreover, the electrochemical and optical properties of the polymer were compared with both its electrochromic P(DTP) analogues and its sister polymer structure, poly(1-(4-(1H-pyrrol-1-yl)phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole) (P(SNS-Ph-Pyr)), possessing same subunit. Graphical abstract: [Figure not available: see fulltext.
Estimation of PEMFC design parameters with social learning-based optimization
(Springer Science and Business Media Deutschland GmbH, 2024) Çeltek, Seyit Alperen
Parameter estimation of proton exchange membrane fuel cell (PEMFC) design is crucial in developing and optimizing PEMFC technology. This study proposes a social learning-based swarm optimization technique to solve the PEMFC design problem. Social learning is based on particles learning from each other and sharing information in a swarm. This allows better solutions found by one particle in the swarm to be used by others, allowing them to arrive at a globally better solution in less iteration. The proposed approach uses the social learning particle swarm optimization (SL-PSO) algorithm to minimize the sum of squared errors (SSE) between the calculated and experimental voltage for the PEMFC parameter extraction problem. The study was carried out on two types of PEMFC (500 W Horizon and BCS 500 W) and compared with heuristic methods commonly used in the literature. This study is the first time in the literature that SL-PSO has been used to optimize PEMFC design parameters. The results show that the SL-PSO-based approach achieves SSE values of 3.8 × 10 - 2 and 4.903 × 10 - 2 for BCS 500 W and 500 W Horizon, respectively. The output reveals that the SL-PSO-based method is an effective optimization tool in PEMFC design by achieving better SSE value in minimum iteration than other comparative algorithms. The proposed approach is expected to be more helpful in making highly efficient fuel cell-based energy systems because of promising results.
Fatty Acid Composition of Seed Oil from Cocklebur (Xantium Strumarium Subsp. Strumarium) Grown in Turkey
(Sivas Cumhuriyet Üniversitesi, 2022) Cesur, Cüneyt; Coşge Şenkal, Belgin; Uskutoğlu, Tansu
Vegetable oils are not only used for human consumption but also used for industrial purposes (soaps, biodiesel, painting, cosmetics, etc.). One of the most important criteria in determining the usage areas of vegetable oils is the fatty acid composition it contains. Turkey supplies its edible oil needs with both seed and vegetable oil imports. To meet this vegetable oil need of Turkey, vegetable oils obtained from different plants are of great importance. This study, it was aimed to determine the oil content, fatty acid composition, and some properties of cocklebur (Xantium strumarium subsp. strumarium) seeds collected from the natural area. 100 fruit weight (g), seed weight (g), and hull ratio (%) were determined as 32.23±2.66, 7.17±0.99, and 77.70±2.84, respectively. Cocklebur seeds contain 24.19% seed oil. Its oil is rich in linoleic (%76.97) and oleic (%11.91) acids.
Construction of novel cyanobacteria-based biological photovoltaic solar cells: Hydrogen and photocurrent generated via both photosynthesis and respiratory system
(Elsevier B.V., 2023) Çarbaş, Buket Bezgin; Güler, Menşure; Yücel, Kamile; Yıldız, Hüseyin Bekir
Biological photovoltaic (BPV) cells use biological organisms in order to produce clean electrical power by capturing solar energy. In this study, a cyanobacteria based BPV cell was constructed and it generated H2 gas and photocurrent via photosynthesis and respiratory system. This kind of BPV cell was constructed in which the cathode and photoanode are gold electrodes coated with different conjugated polymers and these polymers are combined to Pt or Au nanoparticles with oligoaniline bonds. Unlike the cathode electrode, a kind of cyanobacteria (Leptolyngbia sp.) was used in the design of photoanode and bounded to Au NPs with oligoaniline bonds. For the configuration of cathode in BPV cell, a gold electrode was first coated with a dithienylpyrrole-based conductive polymer with an amine open-ended aniline functional group. This conductive polymer was then attached to mercapto-aniline functionalized Pt nanoparticles with oligoaniline bonds. In the case of photoanode in BPV cell, this time, a dithienopyrrole-based conductive polymer with an aniline subunit was coated on another Au electrode surface via electrochemical polymerization. This polymer provides to connect oligoaniline modified Au nanoparticles with coating cyanobacteria. Some control and optimization experiments for photoanode of the system were done in order to understand photosynthesis formation and get efficient photocurrent from BPV cell. The system was illuminated under visible light and a constant potential and then the decomposition of water in BPV solar cell system was observed via photosynthesis by cyanobacteria with the formation of H2 and O2 gases besides photocurrent generation. Another photocurrent generation via respiratory system of cyanaobacteria was also investigated in the medium of glucose after diuron (PS II inhibitor an inhibitor) was added into medium. By using two different properties (photosynthesis and respiratory system) of cyanobacteria, BPV solar system generates high amount of photocurrent and hydrogen.
Effect of Au nanoparticle doped ZnO buffer layer on efficiency in organic solar cells
(Elsevier B.V., 2023) Yurtdaş, Semih; Karaman, Mustafa; Tozlu, Cem
Although 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.
A comprehensive overview of carbazole-EDOT based electrochromic copolymers: A new candidate for carbazole-EDOT based electrochromic copolymer
(Elsevier Ltd., 2023) Çarbaş, Buket Bezgin; Özbakır, Sinan; Kaya, Yasemin
In recent years, there has been an increase in the demand for the synthesis of carbazole-EDOT based electrochromic copolymers since this combination of structures facilitates the obtaining of a free standing film on the working electrode and improves the electrochromic properties of the polycarbazole (PC) polymer. In this study, carbazole-EDOT based copolymers with electrochromic properties in the literature were classified into three groups and the effect of changing the carbazole/EDOT order on the polymer chain on the electrochromic properties of the obtained copolymer was tried to be revealed. Moreover, as an example, a new candidate for carbazole-EDOT based electrochromic random copolymer was introduced. Carbazole and EDOT monomers were copolymerized electrochemically in nonacidic medium for a clear and basic comparison. The electrochemical and spectroelectrochemical studies show that the corresponding copolymer, poly(C-co-EDOT), contains freestanding property on working electrode and shows multielectrochromic property. The copolymer gave a λmax value at about 545 nm with a band gap of 1.74 eV. As expected, EDOT monomer inserting to the polycarbazole chain improves electrochemical and optical properties of homopolymer PC. The electrochromic performance of new copolymer was also compared with its homopolymers components (polymer of carbazole (C) and EDOT) and carbazole-EDOT based electrochromic random copolymers in literature. The experiments showed that poly(C-co-EDOT) was an electroactive material with higher coloration efficiency (CE) (258 cm2/C at 900 nm) than that of PC and carbazole-EDOT based random copolymers in literature. DFT theoretical and experimental calculations were also achieved in order to find HOMO and LUMO energy levels besides band gap and compared with each other. No such a theoretical calculation related electrochromic PC polymer and that kind of random electrochromic copolymer has ever been encountered in the studies carried out so far. Since this research is a baseline study for the valuable design of carbazole-EDOT based electrochromic copolymer, it is thought to shed light on the scientists who will work on this subject in the future.
Vapor deposition of poly(hexafluorobutyl acrylate) nanocoating for encapsulation of organic solar cells
(Elsevier B.V., 2023) Yurtdaş, Semih; Tozlu, Cem; Karaman, Mustafa
The 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.
Enhanced photocatalytic hydrogen evolution and antibacterial activities of ternary chevrel phases
(John Wiley and Sons Inc, 2023) Genç Acar, Eminegül; Kuru, Talha; Sarılmaz, Adem; Süleyman Özel, Sultan; Karanfil Kaçmaz, Gamze; Özel, Faruk
Chevrel phases consisted of abundant materials, are of great interest in a variety of energy conversion and storage technologies because of unique structural and electronic features. Herein, crystalline Mn2Mo6S8, Fe2Mo6S8 and Cu2Mo6S8 Chevrel phases with cubic shapes and homogeneous atomic distribution have been synthesized by solid state method and characterized by advanced analytical techniques. These Chevrel phase catalysts have been investigated for the photocatalytic hydrogen evolution in eosin-Y and triethanolamine media as sensitizer and sacrificial agent, respectively, under visible light irradiation. Mn2Mo6S8 showed the highest photocatalytic hydrogen evolution activity, which is 2.5-fold and 3-fold greater than that of Fe2Mo6S8 and Cu2Mo6S8, respectively. The photocatalytic activity differences of Chevrel phase catalysts can be explained by atomic properties of Mn, Fe and Cu metals. Moreover, the antibacterial efficiencies of Mn2Mo6S8, Fe2Mo6S8 and Cu2Mo6S8 have been also examined on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, as model microorganisms. Accordingly, Mn2Mo6S8 exhibited physical membrane damages such as dents, wrinkled cells and cell elongation and has the most superior antibacterial activity under NIR irradiation.
Optical, electrochemical and DFT studies of donor-acceptor typed indole derivatives
(Univ Ljubljana, 2022) Çarbaş, Buket Bezgin; Noori, Hussein Ali; Kavak, Emrah; Kaya, Yasemin; Kıvrak, Arif
The donor-acceptor type indole chromophore motif presents an interesting molecular architecture to the scientific world, unfortunately, as in every special and beautiful formation needed; their synthesis represents a synthesis challenge. In the current search, new donor-acceptor typed indole derivatives, 1-methyl-phenyl-3-aldehyde indole (HAN-1), 2-(((1-methyl-2-phenyl-1H-indol-3-yl)methylene)malononitrile ( HAN-2), 1-ethyl-2-phenyl-3-aldehyde indole (HAN-3), 2-((1-ethyl-2-phenyl-1H-indol-3-yl)methylene)malononitrile (HAN-4) were successfully synthesized and the results supported with FTIR and NMR spectra analysis. All the molecules undergo excited state intramolecular electron transfer with unique charge transfer reaction. Their electrochemical and optical properties were investigated in relation to the acceptor effect of functional groups on the indole units in the conjugated structure. Density functional theory (DFT) calculations exhibited that higher electron withdrawing ability strength resulted in decreased HOMO-LUMU gaps of the molecules. Futhermore, donor acceptor typed indole derivatives undergo irreversibly one electron oxidation in the medium of 0.1 M TBAPF(6)/ACN solution with a similar onset oxidation potentials. Both experimental and theoretical studies showed that the electron withdrawing ability of the molecules affect more LUMO energy level of the molecules. Moreover, they suggest that donor acceptor indole molecules herein are potential candidates for fabrication of dye synthesized solar cells.

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