Browsing by Author "Akkurt, Nihan"

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Detailed transmittance analysis of high-performance SnO₂-doped WO₃thin films in UV-Vis region for electrochromic devices
(Springer, 2020-09-18) Olkun, Ali; Pat, Suat; Akkurt, Nihan; Mohammadigharehbagh, Reza; Demirkol, Uğur; Özgür, Mustafa; Korkmaz, Şadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0003-0061-0573; KVY-3644-2024
WO(3)is a popular electrochromic device and therefore it has extensively used for the electrochromic (EC) devices such as display and smart window applications. In this study, SnO2-doped WO(3)thin films have been deposited to obtain high-performance EC device and detailed transmittance analysis was determined. At the end of this study, general coloring-bleaching mechanism for SnO2-doped WO(3)active layer is presented. Li ion intercalation/de-intercalation is seen in Nyquist graph for the SnO2-doped WO(3)thin film deposited onto ITO coated glass substrate. All tests were done in 80 s in coloring and bleaching of the SnO2-doped WO(3)layer. Reversibility values of the EC devices mounted in this study were calculated to be 79 and 90% for the device with ITO or FTO conductive layers, respectively. According to the morphological analysis, grain distribution on the surfaces defined as to be perfect. Thanks to Raman analyses, the SnO2-WO(3)phases are seen. Finally, the EC devices have been working in the UV-Vis region. As a result, to obtain the high-performance EC device, SnO2-doped WO(3)active layer is a good choice. TVA method is also proper technology to device manufacturing.
Electrochromic properties of graphene doped Nb2O5 thin film
(Electrochemical Society, 2020-12-01) Akkurt, Nihan; Pat, Suat; Korkmaz, Şadan; Olkun, Ali; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi.; 0000-0003-0061-0573; 0000-0002-0333-487X; DJH-5166-2022; X-5375-2018; 57216253716; 57189905524
Electrochromic device plays a key role in energy efficiency management and modern display technology. As a cathodic coloration material, Nb2O5 is one of the important material used in the electrochromic device. The capacity of a layer is related with the intercalation and deintercalation behavior. Graphene Doping is a promising process for the high-capacity ion storage application. Graphene is a two-dimensional material and it possesses excellent mechanical and electrical properties. In this paper, graphene doped Nb2O5 thin films have been deposited onto ITO coated glass substrate by a thermionic vacuum arc (TVA) technique. The coloring efficiency has been calculated as 91 and 56 cm(2) C-1 at 414 and 550 nm, respectively. The transmittance variation of graphene doped Nb2O5 layer have determined as 42%. According to the Raman spectroscopy, the peaks for orthorhombic phase of Nb2O5 and graphene bands have been observed. According to obtained results, graphene is a promising dopant material for the high performance electrochromic device with Nb2O5 active layer.
Investigation of TiO2 thin films as a cathodic material for electrochromic display devices
(Springer, 2020-04-26) Akkurt, Nihan; Pat, Suat; Mohammadigharehbagh, Reza; Özgür, Mustafa; Demirkol, Uğur; Korkmaz, Sadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; DJH-5166-2022; 57216253716
Titanium dioxide is a preferred material in many fields of applications and is also used as one of best electrochromic display (ECD) candidates due to its chemical stability. Electrochromic devices are innovative, low-cost and low energy consumption for using as displays. In this work, electrochromic, morphological, structural, and some optical properties of tandem structures were comprehensively investigated. The mean thicknesses of the samples were measured as 86 and 120 nm on ITO- and FTO-coated glass substrates, respectively. The chronoamperometry test was performed to determine some electrochromic properties of the ECD. It was observed that the amounts of ions intercalated/de-intercalated from the coated TiO2 layer were almost equal to each other. According to the chronocoulometric analysis, the superior reversibility and coloration efficiency of the assembled ECD were found to be 83% and 26 cm(2)/C, respectively, onto ITO substrates. Higher reversibility is revealed in thinner films, which is consistent with the obtained thickness results. In a similar manner, highest coloration efficiency obtained for our ECD has demonstrated good contact between the TiO2-deposited layer and the ITO-coated glass substrate. Also, the highest porosity was reached by taking the highest coloration efficiency value into account. Moreover, coloration efficiencies and Delta T ratios are changed due to the interlayer transparent conductive oxide layers. Raman spectroscopy measurement reveals the anatase phase of TiO2 films on both substrates. Another important finding is related to the defect structures of the TiO2 phase. TiO2, TiO3 and TiO4 mixed phases show the lower coloration efficiency according to the TiO2 phase, for the first time. TiO3 and TiO4 phases were grown by using the FTO-coated glass substrate. Comparing results with reports has shown that our investigated design and technology for ECD applications are good candidates for such applications.
Studies on the morphological, structural, optical and electrical properties of Fe-doped Zno magnetic nano-crystal thin films
(Elsevier, 2021-02-27) Mohammadigharehbagh, Reza; Pat, Suat; Akkurt, Nihan; Korkmaz, Şadan; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0002-0333-487X; X-5375-2018
In this work, the effect of substrate material on the morphological, structural, optical and electrical properties of Fe-doped ZnO magnetic nano-crystal thin films was investigated. Fe-doped ZnO is a magnetic material and shows ferromagnetism at room temperature. FeO phases were detected in x-ray diffraction patterns. The surfaces of the films are fully occupied-spherical-like nano crystalline. The Fe/Zn ratios were calculated 1.6 and 5.9%. The optical transmittance value of the film is approximately 40%. The band gap value was shifted toward to lower value and the value was found as 3.15 eV. The maximum magnetic moments were obtained at 4000 and 2500 Oe for the film deposited onto glass and Si substrates, respectively. The electrical properties were determined at the maximum magnetic moment situation for the nano crystallites. It was found that diluted Fe-doped ZnO magnetic semiconductors have giant magnetic moment and electrical conductivity.
Studies on the surface and optical properties of ta-doped zno thin films deposited by thermionic vacuum arc
(Springer, 2021-11-09) Pat, Suat; Mohammadigharehbagh, Reza; Akkurt, Nihan; Korkmaz, Şadan; Mohammadigharehbagh, Reza; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0333-487X; X-5375-2018
In this research, Ta doped ZnO thin films have been deposited onto glass and Si substrates by Thermionic vacuum arc (TVA) thin film deposition system. TVA is an anodic plasma thin film deposition system and it is used to relatively high-quality thin films deposition. ZnO thin films have direct optical band gap of 3.37 eV. Tantalum is an efficient higher-valance element. Ta atom gives the more electrons compared to Zinc atom and their ionic radius are very close to each other, so substituted element does not bring into additional stress in crystal network. The deposited thin films were analyzed by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, UV-Vis spectrophotometry and interferometer. To change the band gap properties of the ZnO thin film, Ta doping was used and band gap of Ta doped ZnO thin film was obtained 3.1 eV by Tauc's method. The wt% ratios for Zn/Ta were calculated as 0.45 and 0.42 for the films deposited onto glass and Si substrates, respectively. Crystallite sizes of Ta doped ZnO thin film was decreased by changing substrate material. To the best of our knowledge, substituted Ta elements connected to the oxygen atom in crystal network and orthorhombic beta '-Ta₂O₅ were detected in the all films structure. Their band gaps of the beta '-Ta₂O₅ were measured as 2.70 eV and 2.60 eV for Ta-doped ZnO thin films deposited onto glass and Si substrates, respectively. Up to day, the band gap of the beta '-Ta₂O₅ was calculated by density function theory. According to results, beta '-Ta₂O₅ structure was found as embedded from in the ZnO crystal network.
Surface, optical and electrochemical performance of indium-doped ZnO/WO3 nano-composite thin films
(Springer, 2020-10-06) Mohammadigharehbagh, Reza; Pat, Suat; Akkurt, Nihan; Olkun, Ali; Özgür, Mustafa; Demirkol, Uğur; özen, Soner; Korkmaz, Şadan; Olkun, Ali; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0003-0061-0573; KVY-3644-2024
Great demand on replacing emission and pollution-free materials for energy storage by traditional fossil fuels has led to investigating of high-performance electrochromic materials. Nano-composite for electrochromic device may be a good choice. In this paper, stack-structured indium-doped ZnO/WO3 nano-composite thin films were deposited on glass, indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO)-coated glass substrates, respectively. Surface, optical and electrochromic (EC) performance of the prepared nano-composite films has been investigated. Electrochromic impedance spectroscopy (EIS), cyclic voltammetry, repeating chronoamperometry (CA) and chronocoulometry (CC) measurements were taken.The Raman spectroscopy measurement shows that high-intensity peaks are related to ZnO wurtzite structure for all substrates. In the CA measurement, the rate of Li+ transfer between surface and electrolyte was faster for films coated onto ITO substrate. In addition, the intercalation/deintercalation of Li+ was obviously found faster for films onto ITO substrate due to roughness, structure differences than the other sample. As an advantage of our nano-composite material, the absence of current decay in the both coloration and bleaching stages has proved superiority and stability of films as well as indium contribution. The reversibility of stack-structured InZnO/WO3 nano-composite films was computed as 30 and 50% for the film with ITO and FTO substrates. The highest coloration efficiency value has calculated as 80 and 69 cm(2)/C for nano-composite thin films deposited onto FTO substrate @ 632 and 550 nm, respectively. Warburg impedance element values were determined from the equivalent circuit model. Also, calculated charges were determined for bleaching or coloring process for all films.