Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
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Article Citation - WoS: 24Citation - Scopus: 23Photovoltaic Performance of Magnetron Sputtered Antimony Selenide Thin Film Solar Cells Buffered by Cadmium Sulfide and Cadmium Sulfide /Zinc Sulfide(Elsevier B.V., 2023) Cantas, A.; Gundogan, S.H.; Turkoglu, F.; Koseoglu, H.; Aygun, G.; Ozyuzer, L.Antimony selenide (Sb2Se3)-based thin-film solar cells have recently attracted worldwide attention as an abundant, low-cost, and efficient photovoltaic technology. The highest efficiencies recorded for Sb2Se3 solar cells have been obtained using cadmium sulfide (CdS) as a buffer layer. The Cd-included hybrid buffer layers could be one option to increase device efficiency through more effective usage of light. Therefore, in this work, the effect of single CdS and hybrid CdS/zinc sulfide (ZnS) buffer layers on the photovoltaic performance of Sb2Se3 thin-film solar cells has been investigated in detail. Sb2Se3 thin films have been deposited on molybdenum (Mo)-coated soda-lime glass (SLG) substrates by radio frequency magnetron sputtering technique followed by a post-heat treatment process. The morphological, and structural properties of Sb2Se3 thin films have been investigated by X-Ray Diffraction and Scanning Electron Microscopy. To compare the device performances of single CdS and hybrid CdS/ZnS buffered Sb2Se3 thin-film solar cells, SLG/Mo/Sb2Se3/CdS/ZnS/indium tin oxide (ITO) and SLG/Mo/Sb2Se3/CdS/ITO structures have been fabricated. The findings of this study have revealed a reduction in solar cells’ performance from η=3.93% for CdS buffer to η=0.13% for CdS/ZnS hybrid buffer. The change in the solar cell performance using the CdS/ZnS hybrid buffer has been discussed in detail. © 2023 Elsevier B.V.Article Citation - WoS: 171Citation - Scopus: 169Janus Single Layers of In2sse: a First-Principles Study(American Physical Society, 2018) Kandemir, Ali; Şahin, HasanBy performing first-principles calculations, we propose a stable direct band gap semiconductor Janus single-layer structure, In2SSe. The binary analogs of the Janus structure, InS and InSe single layers are reviewed to evince the structural and electronic relation with In2SSe. The structural optimization calculations reveal that a Janus In2SSe single layer has hexagonal geometry like the InS and InSe single layers, which are also its structural analogs. The Janus single layer is dynamically stable, as indicated by the phonon spectrum. The electronic band diagram of the Janus structure shows that an In2SSe single layer is a direct band gap semiconductor, in contrast to its analogs, InS and InSe single layers, which are indirect band gap semiconductors. Nevertheless, it is found that the strain effect on electronic properties of the InS and InSe single layers designates the electronic structure of the Janus single layer. A rough model for the construction of the electronic band diagram of the Janus structures is discussed, and it is indicated that the difference in work functions of chalcogenide sides in the Janus structure determines the construction of the electronic structure. It is found that the Janus structure is a robust direct gap semiconductor under tolerable strain; for that reason, the Janus In2SSe single layer is a candidate for optoelectronic nanodevice applications.Article Citation - WoS: 50Citation - Scopus: 49Validation of Inter-Atomic Potential for Ws2 and Wse2 Crystals Through Assessment of Thermal Transport Properties(Elsevier Ltd., 2018) Mobaraki, Arash; Kandemir, Ali; Yapıcıoğlu, Haluk; Gülseren, Oğuz; Sevik, CemIn recent years, transition metal dichalcogenides (TMDs) displaying astonishing properties are emerged as a new class of two-dimensional layered materials. The understanding and characterization of thermal transport in these materials are crucial for efficient engineering of 2D TMD materials for applications such as thermoelectric devices or overcoming general overheating issues. In this work, we obtain accurate Stillinger-Weber type empirical potential parameter sets for single-layer WS2 and WSe2 crystals by utilizing particle swarm optimization, a stochastic search algorithm. For both systems, our results are quite consistent with first-principles calculations in terms of bond distances, lattice parameters, elastic constants and vibrational properties. Using the generated potentials, we investigate the effect of temperature on phonon energies and phonon linewidth by employing spectral energy density analysis. We compare the calculated frequency shift with respect to temperature with corresponding experimental data, clearly demonstrating the accuracy of the generated inter-atomic potentials in this study. Also, we evaluate the lattice thermal conductivities of these materials by means of classical molecular dynamics simulations. The predicted thermal properties are in very good agreement with the ones calculated from first-principles.Article Citation - WoS: 7Citation - Scopus: 8Hydrogenation-driven phase transition in single-layer TiSe2(IOP Publishing Ltd., 2017) İyikanat, Fadıl; Kandemir, Ali; Özaydın, H. Duygu; Senger, Ramazan Tuğrul; Şahin, HasanFirst-principles calculations based on density-functional theory are used to investigate the effects of hydrogenation on the structural, vibrational, thermal and electronic properties of the charge density wave (CDW) phase of single-layer TiSe2. It is found that hydrogenation of single-layer TiSe2 is possible through adsorption of a H atom on each Se site. Our total energy and phonon calculations reveal that a structural phase transition occurs from the CDW phase to the T d phase upon full hydrogenation. Fully hydrogenated TiSe2 presents a direct gap semiconducting behavior with a band gap of 119 meV. Full hydrogenation also leads to a significant decrease in the heat capacity of single-layer TiSe2.Article Citation - WoS: 14Citation - Scopus: 14Two-Dimensional Finite Elements Model for Selenium Transport in Saturated and Unsaturated Zones(Springer Verlag, 2010) Tayfur, Gökmen; Tanji, Kenneth K.; Baba, AlperA two-dimensional finite element model was developed to simulate species of selenium transport in two dimensions in both saturated and unsaturated soil zones. The model considers water, selenate, selenite, and selenomethionine uptake by plants. It also considers adsorption and desorption, oxidation and reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. In addition to simulating water flow, selenate, selenite, and selenomethionine transport, the model also simulates organic and gaseous selenium transport. The developed model was applied to simulate two different observed field data. The simulation of the observed data was satisfactory, with mean absolute error of 48.5 μg/l and mean relative error of 8.9%. © 2009 Springer