Yazar "Bilgili, Hakan" 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 processable donor-acceptor polymer displaying neutral state yellow electrochromism
    (Elsevier Sci Ltd, 2013) Oguzhan, Eda; Bilgili, Hakan; Koyuncu, Fatma Baycan; Ozdemir, Eyup; Koyuncu, Sermet
    We report here the synthesis of a new solution processable neutral state yellow polymeric electrochromic material containing 2,5-bis-dithienyl-1H-pyrrole (SNS)-donor and 1,8 naphthalimide-acceptor (SNS-NI) as a subunit. The electrochemical and optical properties were investigated via cyclic voltammetry (CV), UV Vis absorption and fluorescence emission measurements, respectively. Besides, electrochromic performance of poly(SNS NI) has been compared to the both the film preparation method and poly(1-phenyl-2,5-dithiophen-2-ylpyrrole) [poly(SNS-P)] as a standard polymer. In the poly(SNS-NI), yellow color of the polymer film at neutral state converted to green and then dark blue upon the polymer film fully oxidized in the positive regime. SNS NI polymer film prepared via spin casting process exhibits a high contrast ratio in the near-IR region (Delta T% = 56% at 890 nm), a response time of about 1 s, high coloration efficiency (299 cm(2) C-1) and retained its performance by 98.6% even after 5000 cycles. Finally, the results clearly indicate that both electronic nature of the molecule and film preparation method have a major impact on electrochromic performance of these polymers. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
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    Conventional and inverted organic light emitting diodes based on bright green emmisive polyfluorene derivatives
    (Elsevier Sci Ltd, 2018) Mucur, Selin Piravadili; Kok, Cansu; Bilgili, Hakan; Canimkurbey, Betul; Koyuncu, Sermet
    Electro-active green light-emitting polymers based on polyfluorene derivatives (SF5 and SF6) were synthesized by Suzuki coupling reaction. Effect of fluorenone moiety on the main chain of the polyfluorene with allyl subunit was investigated against to performance of both inverted bottom emission and conventional organic light emitting diodes (IBOLEDs and OLEDs, respectively). 2,2',2-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H- benzimidazole) (TPBI) was then utilized as an electron transport layer (ETL) to analyze the change in transport characteristics of the devices with a structure of ITO/PEDOT:PSS/polyfluorene/TPBI/Ca/Al. The results showed that efficiency enhanced nearly four times while the light output values were lowered with the insertion of TPBI as an ETL. In addition, IBOLEDs were also fabricated with a device architecture of ITO/ZnO/polyfluorene/V2O5 /Al being keen on backwards charge injection behavior of the polymers. IBOLEDs were fabricated by using synthesized zinc oxide (ZnO) as the electron-injecting layer. Luminance and luminous efficiency were significantly low while turn on voltages were too low with respect to the conventional devices fabricated. Further, annealing treatment were optimized for light output characteristics of the fabricated OLEDs. This study revealed the importance of charge transport feature of the synthesized polyfluorene derivatives in electroluminescent devices with variant architecture. (C) 2018 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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    Electroluminescence performance of a series of fluorene/2,5-di(2-thienyl)-1H-pyrrole polymers
    (Wiley, 2020) Bilgili, Hakan; Kara, Koray; Yenel, Esma; Demic, Serafettin; Kus, Mahmut; Koyuncu, Sermet
    In this article, a series of fluorene/2,5-dithenyl-1H-pyrrole-based electroactive polymers (HS-X) with different feed ratio of SC12F/OF were synthesized via Suzuki coupling reactions. Chemical characterization of polymers was elucidated by(1)H NMR and Fourier-transform infrared spectroscopy. Electrochemical and electrophysical characterization of the synthesized polymers were investigated by cyclic voltammetry, UV-vis spectroscopy, and fluorescence spectroscopy. Thermal stability of polymers were studied with differential scanning calorimetry and manipulation of the Tg values of HS-X polymers was managed by increasing the numbers of the spiroalkylated fluorene (SAF) moieties incorporated into the polymer backbone. Five different conjugated polymers (HS-1, HS-2, HS-3, HS-4, and HS-5) were used as hole transport layer material in the fabrication of organic light-emitting diode (OLED) devices. The energy levels of the highest occupied molecular orbital as well as the lowest unoccupied molecular orbital and photoluminescence intensities were independent of the number of SAF units. OLED devices based on HS-X polymers were fabricated according to ITO/PEDOT:PSS/HS-X/Alq3/LiF:Al device configuration. Their electroluminescence performances were investigated and the best performance were obtained with the polymer containing 20% SC12F (HS-4) in an OLED device with a turn on voltage of 11.8 V, a maximum luminance of 1202 cd/m(2)and a maximum luminous efficiency of 0.30 cd/A compared to other polymers with different feed ratio.
  • Küçük Resim
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    Fluorene-based donor-acceptor-type multifunctional polymer with bicarbazole pendant moiety for optoelectronic applications
    (John Wiley and Sons Inc, 2021) Pıravadılı, Selin; Doyranlı, Ceylan; Altınışık, Sinem; Bilgili, Hakan; Canımkurbey, Betül; Koyuncu, Sermet
    Since limited examples are in the literature in which both organic light-emitting diodes (OLEDs) and electrochromic (EC) applications were performed using the same conjugated polymer, we presented comprehensive EC and electroluminescence (EL) studies of fluorene-based electroactive polymer (e.g., CFP6) consisting of a bicarbazole pendant moiety with quinoxaline as an acceptor bridge. CFP6 was synthesized by a Suzuki cross-coupling polymerization reaction and utilized as an active and emissive layers of the electrochromic device (ECD) and OLED, respectively, due to its high photoluminescence quantum yield intensity and fine thin film forming capability. The optical, electrochemical, cyclic voltammetry measurements, and density functional theory calculations were realized. Electrochemical cross-linking process was applied over the electroactive carbazole subunit of the CFP6 polymer. After the crosslinking process, EC performance was greatly improved. On the other hand, light emission and EL characteristics of OLEDs based on CFP6 emissive layer were realized in detail with six different device architectures to understand light output profile behavior. As a result, CFP6 emitted bright greenish yellow emission with a maximum brightness of 1777 cd/m2 at 215 mA/cm2 in the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/CFP6:%10 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP)/Alq3/LiF/Al device architecture.
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    Fluorene-Carbazole-Based Porous Polymers by Photoinduced Electron Transfer Reactions
    (Amer Chemical Soc, 2020) Koyuncu, Sermet; Hu, Peng; Li, Zhiquan; Liu, Ren; Bilgili, Hakan; Yagci, Yusuf
    A new photoinitiating system for the metal-free preparation of conjugated microporous polymers (CMPs) is reported. In this approach, irradiation of solutions containing an electroactive monomer, possessing both carbazole and fluorene units, 9,9'-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis-9H-carbazole (CFD), and the iodonium salt (Ph2I+PF6-) as the oxidizing agent resulted in the formation of CMPs. Photoinduced step-growth polymerization proceeded through the successive electron transfer between the excited CFD and iodonium salt, proton release, and coupling reactions. The polymers formed were characterized by FT-IR and H-1 NMR analyses. The electrochemical and optical properties of CMPs before and after the dedoping process were evaluated by cyclic voltammetry, differential pulse voltammetry, and UV-vis absorption and photoluminescence techniques. The porous structure of the obtained polymers was confirmed by atomic force microscopy and scanning electron microscopy studies.
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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.