Yazar "Zafer, Ceylan" seçeneğine göre listele

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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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    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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    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.
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    Electrochemical and optical properties of biphenyl bridged-dicarbazole oligomer films: Electropolymerization and electrochromism
    (Pergamon-Elsevier Science Ltd, 2009) Koyuncu, Sermet; Gultekin, Burak; Zafer, Ceylan; Bilgili, Hakan; Can, Mustafa; Demic, Serafettin; Kaya, İsmet
    4,4'-Di(N-carbazoyl)biphenyl monomer (CBP) was synthesized and coated onto ITO-glass surface by electrochemical oxidative polymerization. Its CV shows two distinct one-electron and stepwise oxidation processes occurred at 1.29 and 1.61 V. By using this property, the monomer was electrochemically polymerized separately at these oxidation states and thus, two different oligomer films were obtained afterwards. Their spectro-electrochemical and electrochromic properties were also investigated. Switching ability of the oligomers was evaluated by kinetic studies upon measuring the percent transmittance (%T) at their maximum contrast point, indicating that these oligomers were found to be suitable material for electrochromic devices. (C) 2009 Elsevier Ltd. All rights reserved.
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    Fenantren Merkezli Multi Fonksiyonel Donor-Akseptör Tipi Makro Moleku?llerin Sentezi ve Opto-elektronik Uygulamaları
    (2016) Koyuncu, Sermet; Zafer, Ceylan; Koyuncu, Fatma Baycan; Can, Mustafa
    Bu projede, merkezde du?zlemsel yapıda fenantren moleku?lu? içeren farklı absorbsiyon ve emisyon bandlarına sahip bir dizi elektroaktif makromoleku?l ve polimer (AKD-X ve MGCX) sentezlenmiştir. Sentezlenen çıkış bileşikleri ve nihayi u?ru?nlerin kimyasal yapıları, FT-IR ve 1H-NMR analizleriyle aydınlatılmıştır. AKD-X ve MGC-X elektroaktif moleku?llerin optik özellikleri UV-Vis ve UV-floresas ölçu?mleriyle, elektrokimyasal özellikleri ise döngu?sel voltametri ölçu?mleriyle incelenmiştir. Elde edilen verilerden optik ve elektrokimyasal HOMOLUMO band boşluğu değerleri hesaplanmış, ayrıca temel hal ve uyarılmış haldeki yu?k dağılımları DFT hesaplamalarıyla belirlenmiştir. Elektroaktif özellikteki AKD-X moleku?llerinin Organik boya sensörlu? gu?neş hu?cresi (DSSC) uygulamalarında, MGC-X polimerleri ise elektrokromik uygulamalarda kullanılabileceği elde edilen sonuçlarla ortaya konulmuştur.
  • Küçük Resim
    Öğe
    Highly conjugated isoindigo and quinoxaline dyes as sunlight photosensitizers for onium salt-photoinitiated cationic polymerization of epoxy resins
    (John Wiley and Sons Ltd, 2022) Ercan, Bahar T.; Gültekin, Şirin S.; Yeşil, Tamer; Dinçalp, Haluk; Koyuncu, Sermet; Yağcı, Yusuf; Zafer, Ceylan
    In this study, photoinitiated cationic polymerization of epoxy resins by photoinduced electron transfer reactions using four new chromophoric dyes, namely (3E)-1,1′-bis(2-ethylhexyl)-6,6′-dipyren-1-yl-3,3′-biindole-2,2′(1H,1′H)-dione (ISOIV), (3′E)-1,1′′′-diethyl-1′,1′′-bis(2-ethylhexyl)-1H,1′′′H-5,6′:3′,3′′:6′′,5′′′-quaterindole-2′,2′′(1′H,1′′H)-dione (ISOV), (3E)-6,6′-bis(9-ethyl-9H-carbazole-3-yl)-1-[(2R)-2-ethylhexyl]-1′-[(2S)-2-ethylhexyl]-3,3′-biindole-2,2′(1H,1′H)-dione (ISOVIII) and 3,3′-(6-bromokinoksalin-2,3-diyl)bis(9-ethyl-9H-carbazole) (TPDC6), and diphenyliodonium hexafluorophosphate (Ph2I+PF6−; DPI) under sunlight is reported. Upon irradiation, photoexcited dye forms an exciplex with DPI. Electron transfer reactions within the exciplex result in the formation of ionic species capable of initiating ring-opening polymerization of an epoxy resin. It is shown that among the investigated dyes, ISOVIII and TPDC6 exhibited higher initiation efficiency in accordance with their stronger electron-donating nature due to the presence of carbazole groups. © 2021 Society of Industrial Chemistry.
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    Kendiliğinden Organize Olabilen Donör-Akseptör Tipi Konjuge Polimerler ve Fotovoltaik Uygulamaları
    (2016) Koyuncu, Sermet; Bilgili, Hakan; Gültekin, Burak; Zafer, Ceylan
    Bu projede, ilk olarak kendiliğinden organize olabilen yan zincirler ile fonksiyonlandırılmış, du?şu?k bant aralığına sahip bir seri donör-akseptör tipi polimer tasarlanmış ve sentezlenmiştir. Sentezlenen bu polimerlerin optik ve elektrokimyasal özellikleri UV-Vis absorbsiyon ve döngu?sel voltametri ölçu?mleri vasıtasıyla incelenmiştir. Daha sonra ise sentezlenen yarıiletken polimerlerden hem siloksan içerenleri hem de siloksanlamadan önceki basamak olan allil grubu içeren polimerlerle, hacimsel heteroeklemli organik fotovoltaik hu?cre denemeleri gerçekleştirilmiştir. Denemelerde en yu?ksek gu?ç dönu?şu?m verimi, %6,06 (ortalama: %5,74) ile allil içeren diketopirolpirol ve karbazol tu?revi, BP-3 polimeri ile elde edilmiştir. Elde edilen yu?ksek verimin nedenleri, sonuç ve artışma bölu?mu?nde morfoloji analizleriyle açıklanmıştır. Polimerlerin yan zincirleri u?zerinde bulunan siloksan gruplarının film fazında kendiliğinden organize olmaları sayesinde, fotovoltaik hu?crenin aktif tabakasında, donör ve akseptör arasında bir nanofaz ayrımının sağlanması ve moleku?ller arasındaki etkileşimin artırılması ile hu?cre kararlılığın iyileştirilmesi amaçlanmıştır. Film morfolojisi optimizasyonu, diferansiyel taramalı kalorimetre (DSC) ile belirlenen camsı geçiş sıcaklıkları (Tg) kullanılarak yapılmıştır. Termal tavlama (thermal annealing) sonucunda, aktif tabakada gözlenen değişimler, atomik kuvvet mikroskopu (AFM) ve X-ışını difraktometresi ile takip edilmiştir. Son olarak, analiz sonuçları kullanılarak, polimerlerin fotovoltaik performansları değerlendirilmiştir.
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    Push-pull type material having spirobifluorene as ?-spacer for dye sensitized solar cells
    (Pergamon-Elsevier Science Ltd, 2016) Can, Mustafa; Bilgili, Hakan; Demirak, Kadir; Gultekin, Burak; Koyuncu, Sermet; Kus, Mahmut; Zafer, Ceylan
    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 pi-bridge and acceptor groups, respectively. MK162-sensitized solar cells exhibited a short-circuit current (I-SC) of 4,92 mA cm(-2), an open-circuit voltage (V-OC) 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 V-OC and 14.51 mA cm(-2) of Isc under standard AM 1.5 illumination. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Quantification of the Effects of Recombination and Injection in the Performance of Dye-Sensitized Solar Cells Based on N-Substituted Carbazole Dyes
    (Amer Chemical Soc, 2010) Barea, Eva M.; Zafer, Ceylan; Gultekin, Burak; Aydin, Banu; Koyuncu, Sermet; Icli, Siddik; Fabregat Santiago, Francisco
    Two new sensitizers for dye sensitized solar cells have been designed consisting of thiophene units asymmetrically functionalized by N-aryl carbazole. The di(tert-butyl) carbazole moieties acts as an electron donor group, the thiophene chain as a bridge group, and the cyanoacrylic acid as an anchoring and electron acceptor group. An increase of the conjugation length produces two main effects: first, it leads to a red-shift of the optical absorption of the dyes, resulting in an improved overlap of the absorption with the solar spectrum. Second, the oxidation potential decreases. The photovoltaic performance of this set of dyes as sensitizers in mesoporous TiO2 solar cells was investigated using electrolytes containing the iodide/triiodide redox couple. The dye with the best absorption characteristics showed the highest photocurrent but lower open circuit voltage due to more losses by recombination. A trend between structure (molecule dyes size) and recombination is demostrated using an analysis procedure based on beta-recombination model that combines impedance spectroscopy and density current-voltage data.