Yazar "Varal, Nurhan Mehmet" seçeneğine göre listele

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    Fabrication of quaternary Cu2FeSnS4 (CFTS) nanocrystalline fibers through electrospinning technique
    (SPRINGER, 2015) Ozel, Faruk; Kus, Mahmut; Yar, Adem; Arkan, Emre; Can, Mustafa; Aljabour, Abdalaziz; Varal, Nurhan Mehmet
    Copper-based quaternary chalcogenide Cu2FeSnS4 (CFTS) is an important material due to its indium-free nature and presence of earth-abundant elements. Herein, CFTS nanofibers have been first fabricated via a facile two-step approach using a simple and inexpensive electrospinning technique. X-ray diffraction and scanning electron microscopy techniques were used to determine structural, morphological, and compositional features of the obtained films. Nanofibers annealed at 500 degrees C for 1 h were characterized by (112), (200), (220), (312) preferred orientations via X-ray diffraction method. Nanofibers showed well crystallization and tetragonal phase. The average diameters of obtained fibers were found to be 100 +/- 50 nm. Cyclic voltammograms showed that CFTS fibers showed p-type behavior.
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    Improvement of photovoltaic performance and stability of AnE-PV:PCBM based organic solar cells using solution processed inverted geometry
    (PERGAMON-ELSEVIER SCIENCE LTD, 2015) Yuksel, Sureyya Aydin; Ongul, Fatih; Bozar, Sinem; Varal, Nurhan Mehmet; Kus, Mahmut; Cakmak, Gulbeden; Guney, Hasan Yuksel
    Organic bulk heterojunction and inverted type solar cells were fabricated using AnE-PVstat:PCBM blends as photoactive layers. The device was inverted using thin films of TiO2 as hole blocking and electron conducting layers. The power conversion efficiency (PCE) of organic bulk heterojunction solar cells increased from 1.70% to 2.59% when inverted device configuration was used instead of regular organic bulk heterojunction solar cell configuration. Stability studies reveal that the inverted type devices are more stable than the herein investigated regular organic bulk heterojunction solar cells fabricated using AnE-PVstat:PCBM blends as photoactive layers. (C) 2015 Elsevier Ltd. All rights reserved.
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    İnorganik nanoparçacık temelli polimer hibrit led'lerde yük taşıyıcılarının mobilite ölçümleri
    (Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2013-12-30) Varal, Nurhan Mehmet; Kuş, mahmut
    Bu çalışmada, MEHPPV kırmızı emisyon yapan polimer içerisine katkılanan Fe3O4 manyetik nano-parçacıklarının boşluk yük taşıyıcısı mobilitesi üzerine olan etkisi incelenmiş ve organik ışık yayan diyot uygulaması yapılmıştır. Yük taşıyıcısının mobilitesini hesaplayabilmek için, admitans spektroskopisi (kpasitans/frekans taramaları) ve FET mobilitesi yöntemi kullanılmıştır. Elde edilen veriler ışığında organik ışık yayan diyot uygulaması ile Fe3O4 nano-parçacıklarının cihaz performansına olan etkisi incelenmiş ve değerlendirmeler yapılmıştır.