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Öğe Combinatorial approach to morphology studies of epitaxial thin films(American Institute of Physics Inc., 2006) Suljovrujic E.; Micic M.; Demic S.; Srdanov V.I.Described is the application of a combinatorial physical vapor deposition (CPVD) method for studying the growth dynamics of epitaxial films. The CPVD method takes advantage of the angle-dependent evaporation rate from a point source to produce thin film libraries whose deposition rate changes continuously for a factor of 50 across a 70-mm long-substrate. The link between the deposition rate and the resulting thin film morphology was made by spatially correlated absorption and atomic force microscopy measurements. It is shown that the growth of tryphenyldiamine derivate on a silica surface proceeds by three-dimensional growth of isolated islands which, at some critical coverage, coalesce to form uniform amorphous film. While the critical coverage of such films depends on the deposition rate in the 0.015-0.4 nms region, the particle size distribution function does not. © 2006 American Institute of Physics.Öğe Effect of TiO 2 modification with amino-based self-assembled monolayer on inverted organic solar cell(Elsevier B.V., 2017) Tozlu C.; Mutlu A.; Can M.; Havare A.K.; Demic S.; Icli 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 A novel high-contrast ratio electrochromic material from spiro[cyclododecane-1,9'-fluorene]bicarbazole(2011) Usluer O.; Koyuncu S.; Demic S.; Janssen R.A.J.A novel electroactive spirocyclododecylfluorene monomer named 2,7-bis(carbazol-9-yl)-9,9'-spiro[cyclododecane-1,9'-fluorene] (SFC) was synthesized and electrochemically polymerized to give a very stable multi-electrochromic polymer (poly-SFC). Two separate oxidation processes were observed for both SFC monomer and poly-SFC that carries two carbazole units. The polymeric film of poly-SFC was coated onto ITO/glass surface, and it shows different colors (transparent, yellowish green, green, and dark green) upon stepwise oxidations. An electrochromic device based on poly-SFC was assembled in the sandwich cell configuration of ITO/poly-SFC//gel electrolyte//PEDOT/ITO. Poly-SFC exhibits 90% of transparency at neutral state and a high contrast ratio (ÎT = 58% at 800 nm). This device constructed from it represents a response time of about 1 s, high coloration efficiency (1377 cm2 C-1) and retained its performance by 96.4% even after 1000 cycles. Exhibiting high transparency at neutral state, reversible redox behavior, resistance to overoxidation, and especially high contrast ratio at near IR region can make poly-SFC be useful and promising candidate for electrochromic applications despite having a relatively slow response time. © 2010 Wiley Periodicals, Inc.Öğe Optical and electrochemical properties of polyether derivatives of perylenediimides adsorbed on nanocrystalline metal oxide films(Elsevier, 2008) Kus M.; Hakli O.; Zafer C.; Varlikli C.; Demic S.; Özçelik S.; Icli S.We report optical and electrochemical properties of polyether derivatives of perylenediimides (PDIs) thin films formed in various materials (semiconductor, insulator, amorphous and self-assembly). Perylenediimides adsorbed on nanocrystalline TiO2 (NT) nanocrystalline alumina (NA), amorphous silicon (PS) and neat self-assemblied (SA) films were prepared and characterized based on spectroscopic, electrochemical, spectro-electrochemical techniques. The absorption and fluorescence spectra of PDIs in chloroform exhibit vibronic features. The fluorescence quantum yields (?f) of PDIs with end amino substituents in chloroform solutions are over 0.95, while the quantum yield of triethoxyphenyl substituted PDI ?f value is 0.024 in solution. Optical spectroscopy proves that PDIs in metal oxide thin films form aggregated type complexes. An electrochromism, a color change from red to blue/violet, is observed on metal oxide films, that indicates existence of mono and dianion forms of PDIs. Reversibility of electrochemical reductions in NT film depends on the scanning rate. However, electrochromism in NA films is stable and reversibility is independent from scanning rate. Stable mono and diaionic species are formed on NA films. SA films show broad absorption peaks during the voltammetric scan. On the other hand, the first reduction onset potentials of PDIs are almost equal to the onset potential of capacitive current of TiO2 which lead to low efficiency in dye-sensitized solar cells. © 2008 Elsevier B.V. All rights reserved.Öğe Push-pull type material having spirobifluorene as ?-spacer for dye sensitized solar cells(Elsevier Ltd, 2016) Can M.; Bilgili H.; Demirak K.; Gultekin B.; Koyuncu S.; Kus M.; Zafer C.; Demic S.; Icli S.Two organic dyes for dye-sensitized solar cells (DSSC) based on spirobifluorene were synthesized and characterized. Electrochemical, spectroscopic and photovoltaic properties of the dyes have been investigated. Hexyloxy substituted triarylamine was used as electron donating moiety in the molecule while spirobifluorene and cyanoacrylic acid were used as ?-bridge and acceptor groups, respectively. MK162-sensitized solar cells exhibited a short-circuit current (ISC) of 4,92 mA cm-2, an open-circuit voltage (VOC) of 520 mV and a fill factor (FF) of 0.59, resulting an overall power conversion efficiency of 1,52 where the reference cell, Z907 was yielded an overall conversion efficiency of 4.08% efficiency with 620 mV of VOC and 14.51 mA cm-2 of ISC under standard AM 1.5 illumination. © 2016 Hydrogen Energy Publications LLCÖğe Structural and vibrational spectroscopy investigation of the 5-[(diphenyl) amino] isophthalic acid molecule(American Institute of Physics Inc., 2014) Kurt M.; Şaş E.B.; Can M.; Okur S.; Icli S.; Demic S.The molecular structure and vibrations of 5-(diphenyl) amino] isophthalic acid (DPIFA) were investigated by different spectroscopic techniques (such as infrared and Raman). FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. HOMO-LUMO analyses were performed. The theoretical calculations for the molecular structure and spectroscopic studies were performed with DFT (B3LYP) and 6-311G(d,p) basis set calculations using the Gaussian 09 program. After optimizing the geometry of the molecule, vibration wavenumbers and fundamental vibrations wavenumbers were assigned on the basis of the potential energy distribution (PED) of the vibrational modes calculated with VEDA 4 program. The results of theoretical calculations for the spectra of the title compound were compared with the observed spectra. © 2014 AIP Publishing LLC.Öğe Structure-Property Relationship in Amber Color Light-Emitting Electrochemical Cell with TFSI Counteranion: Enhancing Device Performance by Different Substituents on N^N Ligand(American Chemical Society, 2021) Demir N.; Karaman M.; Yakali G.; Tugsuz T.; Denizalti S.; Demic S.; Can M.Amber color emitting novel Ir(III) complexes were synthesized: [Ir(Meppy)2(Fpbpy)][PF6] (1bPF6), [Ir(Meppy)2(Fpbpy)][TFSI] (1bTFSI), [Ir(Meppy)2(MeObpy)][PF6] (2bPF6) and [Ir(Meppy)2(MeObpy)][TFSI] (2bTFSI), where Meppy = 2-(p-methylphenyl)-pyridine (b), Fpbpy = 4,4?-bis(4-fluorophenyl)-2,2?-bipyridine (1), and MeObpy = 4,4?-bis(4-methoxy)-2,2?-bipyridine (2). The photophysical and X-ray results showed that the complexes have aggregation-induced phosphorescent emission (AIPE) and a salt-induced polymorphism effect. The highest photoluminescence intensity was observed in complex 2bTFSI compared to other complexes in the solid state. Their theoretical absorption and phosphorescence emission transitions in acetonitrile were also investigated by using double- and triple-? basis sets with B3LYP and PBE0 hybrid functional. The best light-emitting electrochemical cell (LEC) performance was exhibited by complex 2bTFSI, and the data obtained were as follows: Luminance, current density, luminous efficiency, turn-on time, power efficiency, and external quantum efficiency were measured as 16 156 cd/m2, 554 mA/cm2, 8.49 cd/A, 17 s, 3.95 lm/W and 6.37%, respectively. The investigation of crystallographic characteristics have shown that the LEC performance of these complexes depends on cationic-anionic interaction which has a significant influence on molecular stacking of the molecules. Because, complex 2bTFSI, with weak cationic-anionic interactions, shows strong ?···?stacking interactions between the adjacent molecules, it is the best lighting application candidate among the complexes. © 2021 American Chemical Society.Öğe Synthesis and properties of alkyl chain substituted naphthalenetetracarboxylic monoanhydride monoimides and unsymmetrically substituted naphthalene derivatives(Chemical Publishing Co., 2016) Koz B.; Demic S.; Icli S.1,4,5,8-Naphthalenedianhydride is converted to N-(2-ethylhexyl)-1,4,5,8-naphthalenetetracarboxylic monoanhydride monoimide (2a) and N-(2-hydroxyethyl)-1,4,5,8-naphthalenetetracarboxylic monoanhydride monoimide (2c) through the potassium salt prepared from a reaction with potassium hydroxide. N-Dodecyl-1,4,5,8-naphthalenetetracarboxylic monoanhydride monoimide (2b) was prepared by the condensation reaction of 1,4,5,8-naphthalenedianhydride with dodecylamine. Naphthalene-1,4-N-(2-ethylhexyl)-imide-N-ethyl-1H-benzo[d]imidazol-5-carboxylate and naphthalene-1,4-N-dodecyl-imide-N-ethyl-1H-benzo[d]imidazol-5-carboxylate were prepared by the condensation reaction of N-alkyl-1,4,5,8-naphthalenetetracarboxylic monoanhydride monoimide (alkyl = 2-ethylhexyl and dodecyl) with ethyl 3,4-diaminobenzoate. Molecular structures and electrochemical properties of all naphthalene derivatives were determined. Their thermal properties were also studied by thermal gravimetric analysis. © 2016, Chemical Publishing Co. All rights reserved.
