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Öğe Carbon nanotube supported thiospinel quantum dots as counter electrodes for dye sensitized solar cells(Pergamon-Elsevier Science Ltd, 2021) Sarilmaz, Adem; Ozen, Abdurrahman; Akyildiz, Hasan; Gultekin, Sirin Siyahjani; Kus, Mahmut; Ozel, FarukIn the current study, sulfide based ternary and quaternary thiospinel nanocrystals were synthesized by using a simple hot injection method and used as catalyst instead of Pt in a DSSCs application for the first time. CuNiCoS4, CuCo5S8, and CuCo2S4 as thiospinel nanocrystals have been synthesized in crystalline structure, single phase, nearly stoichiometric, and having narrow size distribution below 10 nm. Comparative studies showed that, Carbon Nanotube (CNT)-CuCo2S4 based DSSCs yielded the most favorable results as a potential counter electrode showing very similar power conversion efficiency (eta = 4.99%) in comparison with Pt based DSSCs produced under identical conditions. Therefore, this study implies that the thiospinel nanocrystals and their CNT supported composites can be proposed as novel counter electrode materials for low-cost platinum-free solar cells.Öğe Developing Biopolymer-Based Electrolytes for Supercapacitor and Dye-Sensitized Solar Cell Applications(Amer Chemical Soc, 2023) Konwar, Subhrajit; Singh, Pramod K.; Dhapola, Pawan; Singh, Abhimanyu; Savilov, Serguei V.; Yahya, Muhd Zu Azhan; Gultekin, Sirin SiyahjaniThis paper deals with the synthesis, characterization, and application of low-viscosity ionic liquids as dopants and biopolymers as the host. The biopolymer used in the present study is cornstarch, while the ionic liquid 1-ethyl 3-methylimidazolium thiocyanate (EMIm(+)SCN(-)) is used to develop an electrochemical double-layer capacitor (EDLC) and a dye-sensitized solar cell (DSSC). Different weight ratios of the ionic liquid are incorporated in the polymer host to develop a highly conducting ionic-liquid-doped biopolymer electrolyte (ILBPE). Electrical, structural, and photoelectrochemical characterizations are carried out in detail. Electrochemical impedance spectroscopy (EIS) shows that doping different weight ratios of the ionic liquid enhances the ionic conductivity and conductivity maxima observed at a weight ratio of 80 of the ionic liquid, with an ionic conductivity value of 2.6 x 10(-4) S cm(-1). X-ray diffraction (XRD) and polarized optical microscopy (POM) affirm a reduction in the crystallinity, while thermogravimetric analysis (TGA) shows thermal stability of the ILBPE beyond 200 degrees C. In addition, the 80% ILBPE-based EDLC exhibits a specific capacitance of 140 F g(-1-) , an energy density of 23.13 Wh kg(-1) , and a power density of 3600 W kg(-1) calculated based on galvanostatic charge-discharge (GDC), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) studies. Moreover, the photovoltaic performance of the DSSC is investigated by using J-V analysis and EIS measurements, while the overall power conversion efficiency is determined as 4% under standard conditions (AM 1.5).Öğe Enhanced Hole Mobility of p-Type Materials by Molecular Engineering for Efficient Perovskite Solar Cells(Amer Chemical Soc, 2023) Yeşil, Tamer; Mutlu, Adem; Gultekin, Sirin Siyahjani; Gunel, Zeynep Gulay; Zafer, CeylanStar-shaped triazatruxenederivative hole-transporting materials(HTMs), namely, 3,8,13-tris(4-(8a,9a-dihydro-9H-carbazol-9-yl)phenyl)-5,10,15-trihexyl-10,15-dihydro-5H-diindolo[3,2-a:3 & PRIME;,2 & PRIME;-c]carbazole (TAT-TY1)and 3,8,13-tris(4-(8a,9a-dihydro-9H-carbazol-9-yl)phenyl)-5,10,15-trihexyl-10,15-dihydro-5H-diindolo[3,2-a:3 & PRIME;,2 & PRIME;-c]carbazole (TAT-TY2),containing electron-rich triazatruxene cores and donor carbazole moieties,were synthesized and successfully used in triple-cation perovskitesolar cells. All the HTMs were obtained from relatively inexpensiveprecursor materials using well-known synthesis procedures and uncomplicatedpurification steps. All the HTMs, including the 5,10,15-trihexyl-10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazole(TAT-H) main core, had suitable highest occupied molecular orbitals(HOMOs) for perovskite (TAT-H: -5.15 eV, TAT-TY1: -5.17eV, and TAT-TY2: -5.2 eV). Steady-state and time-resolved photoluminescenceresults revealed that hole transport from the valence band of theperovskite into the HOMO of the new triazatruxene derivatives wasmore efficient than with TAT-H. Furthermore, the substitution of n-hexylcarbazole and 9-phenylcarbazole in triazatruxenealtered the crystalline nature of the main core, resulting in a smoothand pinhole-free thin-film morphology. As a result, the hole mobilitiesof TAT-TY1 and TAT-TY2 were measured to be one order of magnitudehigher than that of TAT-H. Finally, TAT-TY1 and TAT-TY2 achieved powerconversion efficiencies of up to 17.5 and 16.3%, respectively, comparedto the reference Spiro-OMeTAD. These results demonstrate that thenew star-shaped triazatruxene derivative HTMs can be synthesized withoutusing complicated synthesis strategies by controlling the intrinsicmorphology of the TAT-H main core.Öğe A Facile Approach to Produce Activated Carbon from Waste Textiles via Self-Purging Microwave Pyrolysis and FeCl3 Activation for Electromagnetic Shielding Applications(Mdpi, 2024) Sert, Sema; Gultekin, Sirin Siyahjani; Gultekin, Burak; Kaya, Deniz Duran; Korlu, AysegulThis study aims to convert composite textile structures composed of nonwoven and woven fabrics produced from cotton-jute wastes into activated carbon textile structures and investigate the possibilities of using them for electromagnetic shielding applications. To this end, the novel contribution of this study is that it shows that directly carbonized nonwoven textile via self-purging microwave pyrolysis can provide Electromagnetic Interference (EMI) shielding without any processing, including cleaning. Textile carbonization is generally achieved with conventional heating methods, using inert gas and long processing times. In the present study, nonwoven fabric from cotton-jute waste was converted into an activated carbon textile structure in a shorter time via microwaves without inert gas. Due to its polar structure, FeCl3 has been used as a microwave absorbent, providing homogeneous heating in the microwave and acting as an activating agent to serve dual purposes in the carbonization process. The maximum surface area (789.9 m(2)/g) was obtained for 5% FeCl3. The carbonized composite textile structure has a maximum of 39.4 dB at 1 GHz of EMI shielding effectiveness for 10% FeCl3, which corresponds to an excellent grade for general use and a moderate grade for professional use, exceeding the acceptable range for industrial and commercial applications of 20 dB, according to FTTS-FA-003.Öğe One-step preparation of binder-free nickel-containing graphene foam electrode for supercapacitors(Wiley, 2024) Gultekin, Sirin Siyahjani; Karimi, Aziz Ahmad; Can, Mustafa; Demic, SerafettinIn this study, a nickel hydroxide (Ni(OH)2)-modified reduced graphene oxide (rGO) foam electrode for supercapacitor application is presented. The electrode was prepared without using a binder through a one-step process with three different ratios (NirGO1, NirGO2, and NirGo3). To compare the supercapacitor performance of the obtained graphene foam electrodes, rGO and rGO:carbon black (CB) standard electrodes with PVDF-HFP binder were also prepared. All electrodes were then characterized structurally (XPS, EDS, RAMAN, XRD, and FT-IR) and morphologically (SEM). Structural characterizations demonstrated that the Ni-containing electrodes were in alpha-Ni(OH)2:rGO structure. In addition, NirGO3 exhibited a specific capacitance of 800 F g-1 which is relatively the highest performance between the foam electrodes, while rGO:CB presented a specific capacitance of 900 F g-1. The results demonstrated that with the method proposed for electrode development, it was possible to obtain comparable results with the standard electrode rGO:CB. image