Browsing by Author "Yesil, T"

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    Perylene Diimide-Based Dimeric Electron Acceptors with Molecular Conformations for Perovskite Solar Cells
    Saltan, GM; Yesil, T; Ötken, AA; Zafer, C; Dincalp, H
    This paper reports five novel PDI dimer type electron transport materials (ETMs) employing o-indoloquinoxaline (o-Iq), m-indoloquinoxaline (m-Iq), and cibalackrot (Ci) groups as the core building blocks and presents the twisted structures of PDI dimers coded as PDI-NHR-o-Iq, PDI-o-Iq, PDI-NHR-m-Iq, PDI-m-Iq and PDI-NHR-Ci dyes (see Scheme 1 and 2). We have systematically compared their photophysical, electrochemical, and optoelectronic properties with respect to the reference dye (2PDI-NHR), which is directly connected of two PDI planes. Their calculated HOMO-LUMO energy levels are sufficient for charge transfer to the perovskite material so that structure-photovoltaic performance relationship of synthesized ETM dyes can be evaluated. When the binding position of indoloquinoxaline group between PDI rings are changed from o- to m- positions, most of the photophysical and electrochemical properties of PDI dimer are dramatically changed, finally improving the photovoltaic performances. Indoloquinoxaline and cibalackrot subunits covalently attached to perylene diimide dimers decorated with long-alkyl chains used as ETM are coated on the MAPbI2Br perovskite surface to manufacture solar cells. Attaching groups improve the charge transfer capability of the material depending on their molecular conformation, which plays important role in adjusting the energy level between the perovskite material and the ETL. image
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    Conformational control of morphology for perylene diimide dimer as electron transporting material at perovskite surface
    Ötken, AA; Saltan, GM; Yesil, T; Zafer, C; Dincalp, H
    Synthesis of core-twisted perylene diimide (PDI) dimers attached with thiophene linkers (PDI-NHR-Th(1-4)) and their electron transporting ability at perovskite surface were studied. Synthesized dyes showed a high-lying lowest unoccupied molecular orbital (LUMO) energy levels between -3.68 and -3.71 eV, which were compatible with the conduction band of CH3NH3PbI2Br (-3.60 eV). Herein, we have investigated the role of the different substituted positions of PDI monomers to thiophene linkage from its (2,5)-, (3,4)-, (2,4)-, or (2,3)-positions in modulating the morphology of PDI dimer, aggregation behavior for charge transfer properties, optical shifts in ground and excited states, and recombination resistances at the interfaces of p-i-n devices. Conformational changes of PDI dimers attaching to different positions of thiophene linkers are found to affect not only photo-pysical dynamics of excited states of the dyes, but also charge transport kinetics at the perovskite interfaces, changing the photovoltaic performance.
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    Highly conjugated isoindigo and quinoxaline dyes as sunlight photosensitizers for onium salt-photoinitiated cationic polymerization of epoxy resins
    Ercan, BT; Gultekin, SS; Yesil, T; Dincalp, H; Koyuncu, S; Yagci, Y; Zafer, C
    In this study, photoinitiated cationic polymerization of epoxy resins by photoinduced electron transfer reactions using four new chromophoric dyes, namely (3E)-1,1 '-bis(2-ethylhexyl)-6,6 '-dipyren-1-yl-3,3 '-biindole-2,2 '(1H,1 ' H)-dione (ISOIV), (3 ' E)-1,1 '''-diethyl-1 ',1 ''-bis(2-ethylhexyl)-1H,1 ''' H-5,6 ':3 ',3 '':6 '',5 '''-quaterindole-2 ',2 ''(1 ' H,1 '' H)-dione (ISOV), (3E)-6,6 '-bis(9-ethyl-9H-carbazole-3-yl)-1-[(2R)-2-ethylhexyl]-1 '-[(2S)-2-ethylhexyl]-3,3 '-biindole-2,2 '(1H,1 ' H)-dione (ISOVIII) and 3,3 '-(6-bromokinoksalin-2,3-diyl)bis(9-ethyl-9H-carbazole) (TPDC6), and diphenyliodonium hexafluorophosphate (Ph2I+PF6-; DPI) under sunlight is reported. Upon irradiation, photoexcited dye forms an exciplex with DPI. Electron transfer reactions within the exciplex result in the formation of ionic species capable of initiating ring-opening polymerization of an epoxy resin. It is shown that among the investigated dyes, ISOVIII and TPDC6 exhibited higher initiation efficiency in accordance with their stronger electron-donating nature due to the presence of carbazole groups. (c) 2021 Society of Industrial Chemistry.