Yazar "Kus, Mahmut" seçeneğine göre listele

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    Aggregation-induced red-shift emission from self-assembled planar naphthalene diimide dye: Interlayer in a Schottky-type photodiode and DFT studies
    (Elsevier, 2024) Karsili, Pelin; Abourajab, Arwa; Dinleyici, Meltem; Altinisik, Sinem; Koyuncu, Sermet; Dolek, Gamze; Kus, Mahmut
    In this study, a planar, soluble, thin film-forming and self-assembled small naphthalene diimide (3) molecule with a subtle moiety at the imide-nitrogen was synthesized, and applied for the first time in literature as an interfacial layer between Al and p-Si layers in a Schottky-type photodiode. The morphology of the compound was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thin film structure and morphology affected the optical and electrical properties. The energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of 3 were calculated as -6.14 eV and -4.02 eV, corresponding to the band gap of 2.12 eV consistent with density functional theory (DFT) results. Differential scanning calorimetry (DSC) studies revealed a relatively high Tg value at 208 degrees C, indicating high-temperature applicability of the crystalline structure. The I-V measurements of Al/3/p-Si heterostructure were performed under dark and various light power intensities. The current steadily rose with each incremental 20 mW increase in light intensity. The reverse current increased almost 10-fold at 100 mW/cm2 illumination compared to dark measurement. The photodiode's responsivity, photosensitivity, and detectivity factors were elucidated. The photodiode's characteristic values, such as Io, n, phi b, and Rs, were obtained as 3.50 x 10-6 A, 8.24, 0.588 eV and 2.266 k Omega, respectively. The fabricated Schottky-type diode showed promising results for the optoelectronic field. The compound's perfect solubilities in a wide range of solvents, processability, excellent chemical and photochemical stabilities, and exciting optical, thermal and electrochemical properties make it an ideal candidate for thin film and molecular electronics applications.
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    Electrochemical and optical properties of novel donor-acceptor thiophene-perylene-thiophene polymers
    (Wiley, 2008) Koyuncu, Sermet; Kus, Mahmut; Demic, Serafettin; Kaya, İsmet; Ozdemir, Eyup; Icli, Siddik
    In this study, donor-acceptor type thiophene-perylene-thiophene monomers were synthesized and polymerized by both oxidative polymerization using FeCl3 as catalyst and the electrochemical process. UV-vis, FTIR, H-1 NMR, and elemental analysis techniques were used for structural characterization. Thermal behaviors of these compounds were determined by using TGA system. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and electrochemical and optical band gap values were calculated by using the results of cyclic voltammetry and UV-vis measurements, respectively. The number-average molecular weight (M-n), weight-average molecular weight (M-n), and polydispersity index (PDI) values of synthesized polymers were determined by size exclusion chromatography. Conductivity measurements of these polymers were carried out by electrometer by using a four-point probe technique. The conductivity was observed to be increased by iodine doping. (C) 2008 Wiley Periodicals, Inc.
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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.
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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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    Thiol-ene-clickable and emissive carbazole-based polymer networks with tunable colors
    (Elsevier Science Bv, 2016) Doyranli, Ceylan; Buyukcelebi, Sumeyra; Koyuncu, Sermet; Usluer, Ozlem; Kus, Mahmut; Koyuncu, Fatma Baycan
    Band gap tuning and processability of organic materials are significant topics for both scientific research and commercial applications. In this study, we synthesized a series of main chain cross-linkable polymers by thiol-ene click chemistry from N-allyl carbazole and different heterocycles via conventional Suzuki coupling polymerization reaction. The emission color of polymers could be successfully tuned from blue to red by attaching different benzazole-acceptor moieties to the carbazole donor unit. We also investigated the effects of cross-linking with respect to the amount of pentaerythritol tetrakis(3-mercaptopropionate) cross-linker on the optical, electrochemical, and surface morphological properties of the polymer films. The results showed that these polymers can be used as emissive active layers in solution-processable multilayer organic light-emitting diodes. (C) 2016 Published by Elsevier B.V.