Yazar "Demic, Serafettin" seçeneğine göre listele

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    Charge transfer through amino groups-small molecules interface improving the performance of electroluminescent devices
    (ELSEVIER SCIENCE BV, 2016) Havare, Ali Kemal; Can, Mustafa; Tozlu, Cem; Kus, Mahmut; Okur, Salih; Demic, Serafettin; Demirak, Kadir
    A carboxylic group functioned charge transporting was synthesized and self-assembled on an indium tin oxide (ITO) anode. A typical electroluminescent device [modified ITO/TPD (50 nm)/Alq(3) (60 nm)/LiF (2 nm)/(120 nm)] was fabricated to investigate the effect of the amino groups-small molecules interface on the characteristics of the device. The increase in the surface work function of ITO is expected to facilitate the hole injection from the ITO anode to the Hole Transport Layer (HTL) in electroluminescence. The modified electroluminescent device could endure a higher current and showed a much higher luminance than the nonmodified one. For the produced electroluminescent devices, the I-V characteristics, optical characterization and quantum yields were performed. The external quantum efficiency of the modified electroluminescent device is improved as the result of the presence of the amino groups-small molecules interface. (C) 2016 Elsevier B.V. All rights reserved.
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    Modification of ITO surface using aromatic small molecules with carboxylic acid groups for OLED applications
    (ELSEVIER SCIENCE SA, 2011) Havare, Ali Kemal; Can, Mustafa; Demic, Serafettin; Okur, Salih; Kus, Mahmut; Aydin, Hasan; Yagmurcukardes, Nesli
    4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) was synthesized in order to facilitate the hole-injection in Organic Light Emitting Diodes (OLED). MPPBA was applied to form self-assembled monolayer (SAM) on indium tin oxide (ITO) anode to align energy-level at the interface between organic semiconductor material (TPD) and inorganic anode (ITO) in OLED devices. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). KPFM was used to measure the surface potential and work function between the tip and the ITO surface modified by SAM technique using MPPBA. The OLED devices (ITO/MPPBA/TPD/Alq(3)/Al) fabricated with SAM-modified ITO substrates showed lower turn-on voltages and enhanced diode current compare to the OLED devices fabricated with bare ITO substrates. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
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    Optical and electrochemical properties of polyether derivatives of perylenediimides adsorbed on nanocrystalline metal oxide films
    (ELSEVIER SCIENCE BV, 2008) Kus, Mahmut; Hakli, Oezguel; Zafer, Ceylan; Varlikli, Canan; Demic, Serafettin; Ozcelik, Serdar; Ieli, Siddik
    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 (Phi(f)) of PDIs with end amino substituents in chloroform solutions are over 0.95, while the quantum yield of triethoxyphenyl substituted PDI Phi(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. (C) 2008 Elsevier B.V. All rights reserved.
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    The performance of OLEDs based on sorbitol doped PEDOT:PSS
    (ELSEVIER SCIENCE SA, 2012) Havare, Ali Kemal; Can, Mustafa; Demic, Serafettin; Kus, Mahmut; Icli, Siddik
    We report the performance of OLED devices with a configuration of FTO/sorbitol-PEDOT:PSS (60 nm)/TPD (50 nm)/Alq(3) (40 nm)/Al (120 nm) and FrO/plain-PEDOT:PSS (60 nm)/TPD (50 nm)/Alq(3) (40 nm)/Al (120 nm) prepared from poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) undoped (plain-PEDOT:PSS) and doped by a constant concentration 5% of sorbitol, respectively. The OLED devices were tested in terms of electrical and optical characteristics in order to investigate the effect of sorbitol doping and thermal annealing on PEDOT:PSS thin film on FTO. The device fabricated from sorbitol-PEDOT:PSS with thermal annealing showed the maximum luminance of 130 (cd m(-2)). The devices with sorbitol doping showed a lowering of the operating voltage from 6.5 down to 3 V. A constant luminous efficiency higher than 1.8 cd A(-1) was obtained in the range of current of 4-7 (mA/cm(2)) with doped sorbitol. Published by Elsevier B.V.
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    White organic light emitting diodes based on fluorene-carbazole dendrimers
    (ELSEVIER SCIENCE BV, 2014) Usluer, Ozlem; Demic, Serafettin; Kus, Mahmut; Ozel, Faruk; Sariciftci, Niyazi Serdar
    In this paper, we report on the Prod. Type: FTP fabrication and characterization of blue and white light emitting devices based on two fluorene-carbazole containing dendrimers and para-sexiphenyl (6P) oligomers. Blue light emitting diodes were fabricated using 9',9 ''-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis-9' H-9,3':6',9 ''-tercarbazole (OFC-G2) and 9',9 ''-(9,9'-spirobi[fluorene]-2,7-diyl)bis-9'H-9,3':6',9 ''-tercarbazole (SBFC-G2) dendrimers as a hole transport and emissive layer (EML) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer. White light emitting diodes were fabricated using 6P and these two dendrimers as an EML OLED device with the structure of ITO/PEDOT:PSS (50 nm)/OFC-G2 (40 nm)/6P (20 nm)/LiF:Al (0.5:100 nm) shows maximum luminance of nearly 1400 cd/m(2) and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.30) at 12 V. (C) 2013 Elsevier B.V. All rights reserved.