Photonics / Fotonik

Permanent URI for this collectionhttps://hdl.handle.net/11147/2590

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Author: search.filters.author.Yeşil, Fatih

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Contribution of O-2 Plasma Treatment and Amine Modified Gos on Film Properties of Conductive Pedot:pss: Application in Indium Tin Oxide Free Solution Processed Blue Oled
    (Elsevier, 2019) Diker, Halide; Yeşil, Fatih; Varlıklı, Canan
    Primary (n-propyl amine, n-PRYLA), secondary (dipropyl amine, DPRYLA) and alcohol (propanol amine, PRPOHA) amine derivatives were used as amine sources in graphene oxide (GO) modification and obtained samples were named as nPRYLA-GO, DPRYLA-GO and PRPOHA-GO, respectively. Modified graphene oxide (mGO) derivatives were doped in poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PH1000) and O-2 plasma treatment (70W, 3 min) was applied on the spin casted films. PH1000:mGO films presented high optical transparency values (> 90%) and low resistivity (177-183 Q/sq). The roughness values were increased especially when the hydrophobic alkyl chain containing DPRYLA-GO and nPRYLA-GO were doped in PH1000. Prepared films were utilized as anode in solution processed blue organic light emitting diode. PH1000:PRPOHA-GO anode presented more than 30 nm of decrement in full with at half maximum and 1.6, 1.5 and 1.9 fold enhancements in current, power and external quantum efficiency values, compared to those of ITO anode, respectively.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Synthesis, Photophysical and Electrochemical Properties of Novel Carbazole-Triazine Based High Triplet Energy, Solution-Processable Materials
    (Elsevier, 2018) Öner, Saliha; Aydemir, Murat; Yeşil, Fatih; Şahin, Çiğdem; Varlıklı, Canan
    A series of molecules; tBuCz1SiTrz, tBuCz2SiTrz and tBuCz3SiTrz, which contain carbazole unit as hole-transporting group (donor-D) and triazine unit as electron transporting group (acceptor-A) were synthesized and characterized as high-triplet energy (>2.9 eV), solution-processable bipolar emitting materials. The conjugation between the D-A groups was interrupted by using bulky tetraphenylsilane groups as spacer aiming to obtain large bandgap and high-triplet energy. The photophysical behaviors of the molecules were investigated by UV-Vis absorption, photoluminescence, phosphorescence, photoluminescence quantum yield and lifetime measurements. Solvent polarity effects were investigated on the intramolecular charge transfer (ICT) behaviour and large solvatochromic effect was observed with the increasing solvent polarity. Electrochemical properties were determined by cyclic voltammetry. All molecules showed oxidation bands arise from the carbazole groups. Reduction bands were originated from the triazine groups and the intramolecular charge transfer between D-A groups. Photophysical, electrochemical and computational characterizations addressed that tBuCz2SiTrz has the weakest ICT character, highest photoluminescence quantum yield (PLQY) and charge balance.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 20
    Controlling the Distribution of Oxygen Functionalities on Go and Utilization of Pedot:pss-Go Composite as Hole Injection Layer of a Solution Processed Blue Oled
    (Elsevier Ltd., 2017) Diker, Halide; Durmaz, Gamze Belkis; Bozkurt, Hakan; Yeşil, Fatih; Varlıklı, Canan
    Graphene oxide (GO) was synthesis by Tour method. Particle size distribution effects of raw graphite on the resulting structural, morphological, optical and electrical properties of GO samples and their poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites are studied for the graphite particle distributions of <150, 45–75 and 25–45 μm. It is determined that particle size of raw graphite have an impact on oxidation degree, the chemical nature of oxygen functional groups on GO and it also affects the lateral size of obtained GO. PEDOT:PSS-GO composites are utilized as hole injection layer (HIL) in a solution process blue organic light emitting diode. Presence of GO caused negative differential resistance (NDR) and NDR intensity was decreased with the decrease in lateral size of GO, increase in the graphite particle size and carboxyl% of obtained GO. All PEDOT:PSS-GO composite based devices presented better performance than the bare PEDOT:PSS based reference device. The maximum luminous and external quantum efficiency values of the device that contain HIL of PEDOT:PSS-GO(150) were more than 40% and 50% higher than that of the reference, respectively. Two folds of increase in these performance values were able to be reached with the concentration optimization of GO/150 in PEDOT:PSS.