Yazar "Havare, Ali Kemal" 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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    Functionalized organic semiconductor molecules to enhance charge carrier injection in electroluminescent cell
    (ELSEVIER SCIENCE BV, 2017) Yalcin, Eyyup; Kara, Duygu Akin; Karakaya, Caner; Yigit, Mesude Zeliha; Havare, Ali Kemal; Can, Mustafa; Tozlu, Cem
    Organic semiconductor (OSC) materials as a charge carrier interface play an important role to improve the device performance of organic electroluminescent cells. In this study, 4,4"-bis(diphenyl amino)-1,1':3',1"-terphenyl-5'-carboxylic acid (TPA) and 4,4"-di-9H-carbazol-9-yl-1,1':3',1"-terphenyl-5'-carboxylic acid (CAR) has been designed and synthesized to modify indium tin oxide (ITO) layer as interface. Bare ITO and PEDOT:PSS coated on ITO was used as reference anode electrodes for comparison. Furthermore, PEDOT:PSS coated over CAR/ITO and TPA/ITO to observe stability of OSC molecules and to completely cover the ITO surface. Electrical, optical and surface characterizations were performed for each device. Almost all modified devices showed around 36% decrease at the turn on voltage with respect to bare ITO. The current density of bare ITO, ITO/CAR and ITO/TPA were measured as 288, 1525 and 1869 A/m(2), respectively. By increasing current density, luminance of modified devices showed much better performance with respect to unmodified devices. (C) 2017 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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    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.