Yazar "Sefer, Emre" seçeneğine göre listele

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    A narrow range multielectrochromism from 2,5-di-(2-thienyl)-1H-pyrrole polymer bearing pendant perylenediimide moiety
    (Elsevier Sci Ltd, 2015) Sefer, Emre; Bilgili, Hakan; Gultekin, Burak; Tonga, Murat; Koyuncu, Sermet
    A new 2,5-di-(2-thienyl)-1H-pyrrole (SNS) moiety containing perylenediimide (PDI) acceptor as pendant side chain has been synthesized for an electroactive monomer and then directly deposited onto ITO/glass surface via electrochemical polymerization process. The observed electronic interaction only at the excited state due to the presence of phenylene spacer between SNS-donor and PDI-acceptor moiety leads to efficient fluorescence quenching. This charge separation behavior was also proved by theoretical DFT calculations. Thin films of the polymer electropolymerized onto transparent electrode exhibited ambipolar multi-electrochromic behavior including purple, violet-red-khaki-blue colors in both anodic and cathodic regime only between -1.2 and 1.0 V. We further demonstrated that this polymer film has a high contrast ratio (Delta T = 45% at 900 nm), a faster response (0.5 s), high coloration efficiency (254 cm(2) C-1) and retained its performance by 92% even after 5000 cycles. (C) 2014 Elsevier Ltd. All rights reserved.
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    A new conducting polymer of 2,5-bis(2-thienyl)-1H-(pyrrole) (SNS) containing carbazole subunit: Electrochemical, optical and electrochromic properties
    (Elsevier Science Sa, 2009) Koyuncu, Sermet; Zafer, Ceylan; Sefer, Emre; Koyuncu, Fatma Baycan; Demic, Serafettin; Kaya, İsmet; Ozdemir, Eyup
    We report here the synthesis of a new electroactive monomer 3,6-di-tert-butyl-[4-(2,5-di-2-thienyl-1H-pyrrol-1-yl)phenyl]-9H-carbazole in five steps and polymerization of this monomer by two different procceses: Kumada Coupling and electro-oxidative. The product obtained by chemical polymerization exhibits a high thermal stability and narrow molecular weight distribution. While, in the UV-vis absorption spectrum of monomer the absorption peaks appear at 338 nm, the chemically synthesized polymer absorbs at 428 nm with 90 nm red shift. Cyclic voltammogram of monomer shows two separate oxidation processes which reflect the first oxidation at +0.84 V and a second one at +1.43 V. When the polymeric film prepared by electrochemical process was subjected to a repeated cyclic scan between -0.2V and +1.0V, it switches among three different colors (orange, green and blue). The oxidation and reduction response times were calculated as 2.0 s for this polymer film and exhibits high redox stability. The results anticipate that this kind of polymers can be used for designing electrochromics based on the use of one molecule for the generation of three basic colors (RGB). (C) 2009 Elsevier B.V. All rights reserved.
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    A New Donor-Acceptor Double-Cable Carbazole Polymer with Perylene Bisimide Pendant Group: Synthesis, Electrochemical, and Photovoltaic Properties
    (John Wiley & Sons Inc, 2009) Koyuncu, Sermet; Zafer, Ceylan; Koyuncu, Fatma Baycan; Aydin, Banu; Can, Mustafa; Sefer, Emre; Ozdemir, Eyup
    We report here electrochemical synthesis of novel soluble donor-acceptor (D-A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz-PDI). The band gap, E, was measured using UV-Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole-donor to perynediimide-acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV-Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D-A double-cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm(2) radiation power. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280-6291, 2009
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    A new low band gap electrochromic polymer containing 2,5-bis-dithienyl-1H-pyrrole and 2,1,3-benzoselenadiazole moiety with high contrast ratio
    (Elsevier Sci Ltd, 2011) Koyuncu, Fatma Baycan; Sefer, Emre; Koyuncu, Sermet; Ozdemir, Eyup
    A new low band gap electrochromic polymer containing of 3-(2,5-di-2-thienyl-1H-pyrrol-1-yl)-9-ethyl-9H-carbazole (SNSC) and 2,1,3-benzoselenadiazole (BSe) moiety has been reported. Structural identification of initial compounds and product were carried out by using FT-IR and H-1 NMR spectroscopy results. The resulting polymer, poly(SNSC-BSe), was completely soluble in various common organic solvents and its weight-average molecular weight (M-w) were 9420 (PDI: 1.22). According to AFM results, the RMS (root mean surface) roughness of poly-(SNSC-BSe) was found to be 48.6 nm. Besides, the thermogravimetric analysis presented that the poly(SNSC-BSe) is moderately stable against to thermal effect with the initial degradation temperature at 182 degrees C. The lowest energy transition band maxima of poly(SNSC-BSe) was 498 nm in thin film and the optical band gap calculated from the onset wavelength of the optical absorption was 1.77 eV. On the other hand, the electrochemical band gap calculated from oxidation and reduction onset values was 1.60 eV, respectively. Finally, the electrochromic performance of the polymer film represents a high contrast ratio in the NIR region (51%), fast response time of about 1 s, high coloration efficiency (274 cm(2) C-1) and retained its performance by 94.6% even after 1000 cycles. (C) 2011 Elsevier Ltd. All rights reserved.
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    A New Near-Infrared Switchable Electrochromic Polymer and Its Device Application
    (Wiley, 2010) Sefer, Emre; Koyuncu, Fatma Baycan; Oguzhan, Eda; Koyuncu, Sermet
    A new near-infrared switchable electrochromic polymer containing carbazole pendant (poly-SNSC), synthesized by electrochemical polymerization of 2,5-bis-dithienyl-1H-pyrrole (SNS) main chain, has been prepared. The electrochemical and optical properties of SNSC monomer and its polymer have been investigated. Because of having two different electro-donor moieties; that is, carbazole and SNS, SNSC gave two separate electrochemical oxidation and also light brown color of the film in the neutral state turn into gray on oxidation. An electrochromic device, contructed in the sandwich configuration [indium tin oxide (ITO)-coated glass/anodically coloring polymer (poly-SNSC)//gel electrolyte//cathodically coloring polymer (PEDOT)/ITO-coated glass] and exhibited a high coloration efficiency (1216 cm(2) C-1), a very short response time (about 0.3 s), low driving voltage, and a high redox stability. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4419-4427, 2010
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    A Novel Near-IR Effective Pyrene-Based Donor-Acceptor Electrochrome
    (Wiley-V C H Verlag Gmbh, 2015) Sefer, Emre; Hacioglu, Serife O.; Tonga, Murat; Toppare, Levent; Cirpan, Ali; Koyuncu, Sermet
    In this work, a novel donor-acceptor electrochromic monomer (3HTP), containing a pyrene subunit connected to a quinoxaline acceptor bridge, is synthesized. The corresponding polymer, poly-(3HTP), is directly deposited onto an indium tin oxide (ITO)/glass surface via an electrochemical process. Atomic force microscopy (AFM) images reveal that the electrochemically deposited poly-(3HTP) has a smooth surface due to self-assembly of the planar pyrene subunit. Electrochemical and optical properties are investigated via cyclic voltammetry and UV-vis absorption measurements. The polymer film shows a multielectrochromic feature at both anodic and cathodic regimes. Poly-(3HTP) exhibits a strong near-infrared (NIR) absorption at the oxidized state with an optical contrast of 88% (at 1800 nm), a very fast response time of 0.5 s and fast switching times, and long-term stability. Density functional theory calculations reveal that the molecule has a high planarity, and the NIR absorption arises from a strong intramolecular charge transfer from the polymer backbone to the planar pyrene subunit.
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    Carbazole based D-A-?-A chromophores for dye sensitized solar cells: Effect of the side alkyl chain length on device performance
    (Pergamon-Elsevier Science Ltd, 2017) Kiymaz, Deniz; Sezgin, Meryem; Sefer, Emre; Zafer, Ceylan; Koyuncu, Sermet
    A series of Carbazole based Donor-Acceptor-pi Bridge-Acceptor (D-A-pi-A) dyes that contain different alkyl side chains with different lengths have been synthesized. Electrochemical and optical properties of these dyes were demonstrated by impedance spectroscopy, cyclic voltammetry, UV-Vis absorption and fluorescence spectroscopy, respectively. Herein, we report PV performance of dye-sensitized solar cells depending on the molecular structure of the dyes in terms of comparison of alkyl chain length on the carbazole moiety using an ionic liquid based electrolyte under standard AM 1.5 illumination. The results demonstrate that the dye containing alkyl chain with 4C atoms exhibited better performance compared to alkyl chains with 2C, 6C and 12C atoms. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Donor-akseptör tipi yeni tür dendrimerik moleküllerin sentezi ve bazı özelliklerinin incelenmesi
    (Çanakkale Onsekiz Mart Üniversitesi, 2010) Sefer, Emre; Özdemir, Eyüp
    Bu çalışmada fluoren-karbazol'den oluşan çekirdek etrafında son grup olarak yer alacak perilen tetrakarboksi diimit ve naftalimit ile dendrimerik moleküller sentezlenmiştir. UV-Vis, FT-IR, 1H-NMR teknikleri yapısal karakterizasyon için kullanılırken molekül ağırlığı MALDİ TOF-MS ile belirlenmiştir. Opto-elektronik teknolojilere uygulanabilmesi için en yüksek enerjili dolu molekül orbital ( HOMO), en düşük enerjili boş molekül orbital ( LUMO) enerji seviyeleri, buna bağlı olarak elektrokimyasal (Eg') ve optik bant boşluğu (Eg) değerleri sırasıyla döngüsel voltametri (CV) ve UV-Vis absorbsiyon spekroskopi ölçümlerinin sonuçları kullanılarak hesaplanmıştır. Ayrıca dendrimerlerin emisyon ölçümleri alınmış ve bütün bu bilgilerle elektron transfer mekanizmaları belirlenmiştir.
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    Effect of a pi-bridging unit in triphenylamine-benzothiadiazole based donor acceptor chromophores for dye-sensitized solar cells
    (Pergamon-Elsevier Science Ltd, 2014) Yigit, Mesude Zeliha; Bilgili, Hakan; Sefer, Emre; Demic, Serafettin; Zafer, Ceylan; Can, Mustafa; Koyuncu, Sermet
    Two new metal free sensitizers based on triphenylamine-benzothiadiazole were synthesized and used in dye sensitized solar cells (DSSCs). Electrochemical and optical properties of the dyes were studied by cyclic voltammetry, UV-vis absorption and fluorescence spectroscopy. A red shift was observed by the attachment of a thiophene (MZ-259) instead of a phenylene (MZ-255) bridge. The reverse effect was observed in the electrochemical properties because of the more electron-donating thiophene incorporated into the cyanoacrylic acid as an anchoring-acceptor unit in this system resulted in a higher LUMO level. The charge distribution of the dyes was also proved by DFT calculations using the Spartan10 program with the parameters of B3LYP and 6-31G** basis set. Finally the photovoltaic performances were investigated under standard AM 1.5 illumination with a power of 100 mW/cm(2) using an ionic liquid based electrolyte. The power conversion efficiencies, eta, were increased from 3.16% to 3.81% by using thiophene instead of phenylene as a pi-bridge unit. (C) 2014 Elsevier Ltd. All rights reserved.
  • Küçük Resim
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    Metal içermeyen organik makro moleküllerin sentezi, karakterizasyonu ve optoelektronik uygulamaları
    (Çanakkale Onsekiz Mart Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2015) Sefer, Emre; Koyuncu, Sermet
    Bu tez çalışmasında kendi kendine düzenlenme özelliğine sahip ana ve yan grup olarak piren molekülü içeren makro moleküllerin sentezi, karakterizasyonu ve opto elektronik performansları üzerine çalışmalar yapılmıştır. İlk olarak kinoksalin akseptör ana merkeze piren molekülü Paal knorr halkalaşma reaksiyonu ile bağlanmış sonra ana merkez tiyofen (PE3), 3-hegzil tiyofen (PE4) ve 3,4-etilendioksi tiyofen (PE5) donor birimleri ile sübstitüe edilerek üç adet donör akseptör tipi monomer sentezi gerçekleştirilmiştir. İkinci adımda organik günüş pillerinde kullanılmak üzere çözünebilir makro molekül (PSM2) sentezi gerçekleştirilmiştir. Son olarak çapraz bağlanabilir vinil grupları içeren makro molekül (PO3) sentezi gerçekleştirilmiştir. Yapısal karakterizasyon işlemlerinde UV-Vis, FT-IR, 1H-NMR teknikleri kullanılmıştır. Opto-elektronik teknolojilere uygulanabilmesi için en yüksek enerjili dolu molekül orbital ( HOMO), en düşük enerjili boş molekül orbital ( LUMO) enerji seviyeleri, buna bağlı olarak elektrokimyasal (Eg') ve optik bant boşluğu (Eg) değerleri sırasıyla döngüsel voltametri (CV) ve UV-Vis absorbsiyon spekroskopi ölçümlerinin sonuçları kullanılarak hesaplanmıştır. PE3, PE4 vePE5 kodlu monomerlerin elektrokromik performansları üzerine çalışmalar yapılmıştır. PSM2 kodlu molekülden çeşitli bileşimlerde 4 adet güneş hücresii denemesi yapılarak foto fiziksel performansları incelenmiş filmlerin yüzey karakterizasyonları AFM ölçümleri ile gerçekleştirilmiştir. PO3 kodlu makro makro molekülden de OLED cihaz denemesi gerçekleştirilmiştir.
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    Naphthalenediimide bridged D-A polymers: Design, synthesis and electrochromic properties
    (Pergamon-Elsevier Science Ltd, 2014) Sefer, Emre; Koyuncu, Fatma Baycan
    We have synthesized two new D-A electrochromic polymers; poly(N,N'-bis(2-hexyl)-2,6-dithiophene-1,4,5,8-naphthalenediimide) (PTNDI) and poly(N,N'-bis(2-hexyl)-2,6-(3,4-ethylenedioxythiophene)-1,4,5,8-naphthalenedimiide) (PENDI) bearing a naphthalenedimiide chromophore in the backbone. Structural characterization of initial compounds and products were carried out by using FT-IR and H-1-NMR spectroscopies. The optical and electrochemical properties of these polymers were investigated by UV-Vis absorption spectroscopy and cyclic voltammetry, respectively. The results of spectroelectrochemical studies indicate that both polymers reveal various colors due to ambipolar redox behavior at cathodic and anodic regime. Both polymer films have reasonable redox stability (in the range of 75-80% after 1000 cycles), coloration efficiency (in the range of 80-100 cm(2) C-1), and response time (approx. 1s). Moreover, it is clearly seen that replacing donor unit from thiophene to EDOT results in change only in neutral state color. (C) 2014 Elsevier Ltd. All rights reserved.
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    Neutral state colorless electrochromic polymer networks: Spacer effect on electrochromic performance
    (Elsevier Sci Ltd, 2014) Gulfidan, Damla; Sefer, Emre; Koyuncu, Sermet; Acar, Metin H.
    A series of carbazole-based monomers and their corresponding polymers with various spacer units were synthesized and coated onto ITO-glass surface via an electrochemical cross-linking process. All carbazole-based polymers exhibited multi-electrochromic behavior thanks to two separate oxidation processes. All materials were characterized by FT-IR. H-1 NMR, GPC, DSC, UV-vis, Florescence and CV. In addition, electrochromic properties of the cross-linked polymer films were investigated via spectro-electrochemical measurements. The colorless films were converted to yellowish green and greenish blue colors at the anodic regime. The results indicate that the spacer unit between the carbazole unit and the polymer backbone has a great impact on the optical and electrochemical properties and also on the electrochromic performance of these polymers. PVBEC with benzyloxy based spacer exhibits a high contrast ratio (Delta T% = 55 at 690 nm), a faster response time of about 2.1 s, a higher coloration efficiency (331 cm(2) C-1) and a better stability (retains its performance by 94.3% even after 1000 cycles). (C) 2014 Elsevier Ltd. All rights reserved.
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    The New Branched Multielectrochromic Materials: Enhancing the Electrochromic Performance via Longer Side Alkyl Chain
    (Amer Chemical Soc, 2011) Koyuncu, Fatma Baycan; Sefer, Emre; Koyuncu, Sermet; Ozdemir, Eyup
    We describe the synthesis and structure property relationships of two branched electroactive monomers containing carbazole core, 2,5-di(2-thienyl)-1H-pyrrole, differentiated by the length of side alkyl chains (DSNSC-1 and DSNSC-2). Structural identification of initial compounds and products were carried out by using FT-IR and H-1 and C-13 NMR spectroscopy. The electroactive materials DSNSC-1 and DSNSC-2 were directly coated on to ITO glass surface by using electrochemical polymerization process. The results clearly indicate that the length of side alkyl chain has a major impact on optical and electrochemical properties of these polymers. Poly-DSNC-2 with longer side alkyl chain exhibits a high contrast ratio (Delta T% = 68% at 850 nm), a response time of about 0.8 s, and high coloration efficiency (352 cm(2) C-1) and retained its performance by 97.1% even after 5000 cycles.
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    Toward Purple-to-Green-to-Transmissive-to-Black Color Switching in Polymeric Electrochrome
    (Amer Chemical Soc, 2014) Karabiyik, Elif; Sefer, Emre; Koyuncu, Fatma Baycan; Tonga, Murat; Ozdemir, Eyup; Koyuncu, Sermet
    A novel 3,4-ethylenedioxythiophene (EDOT)-based donoracceptor electroactive monomer (HCQE) bearing carbazole subunit is synthesized, and then the corresponding polymer, poly(HCQE), is directly deposited onto ITO/glass surface via electrochemical process. Spectroelectrochemical studies demonstrate that poly(HCQE) is capable of showing both n- and p-doping processes. Hence, this low band polymer serves the multielectrochromic feature at three separate states (-0.4 to -2.0 V, -0.4 to 1.2 V, and 1.2 to 2.0 V) with a highly unique near colorless and colored states, fast switching times, redox switching stability, and exceptional transmittance change. To the best of our knowledge, this is the first report of a neutral state green multielectrochromic polymer exhibiting successive switching of colored-to-bleached-to-colored in three distinct regimes.