Photonics / Fotonik

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

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Author: search.filters.author.Şahin, Çiğdem

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  • Article
    Citation - WoS: 28
    Citation - Scopus: 29
    Enhancing the Efficiency of Mixed Halide Mesoporous Perovskite Solar Cells by Introducing Amine Modified Graphene Oxide Buffer Layer
    (Elsevier, 2020) Şahin, Çiğdem; Diker, Halide; Sygkridou, Dimitra; Varlıklı, Canan; Stathatos, Elias
    In this study, graphene oxide (GO) was synthesized via Tour method and then modified with two different amine sources that contained different branched alkyl chains. The GO and modified GOs (mGOs) with dihexylamine (DHA) and 2-ethylhexylamine (2EHA) as amine sources were used respectively as buffer layers in mixed halide mesoporous perovskite solar cells (PSCs) in order to examine whether they could improve their performance. GO and mGO samples were characterized by several techniques such as X-Ray Diffraction, X-Ray photoelectron spectroscopy (XPS), Raman analysis and thermal gravimetric analysis (TGA). The preparation of the CH3NH3PbI3-xClx perovskite solution was performed using standard Schlenk techniques under argon atmosphere to attain a homogeneous coverage of the perovskite film. The solar cells with the additional layer of mGO derivatives between perovskite and hole transporting layer showed an improved overall performance compared to the reference devices which was attributed to the enhanced charge carrier transport via the mGOs. In particular, 10% increase to the overall performance of the solar cells was monitored in devices where 2-ethylhexylamine (2EHA) modified GO was used, compared to standard cell without buffer layer. (C) 2019 Elsevier Ltd. All rights reserved.
  • 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.