Browsing by Author "Saltan G.M."
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Item Impact of the different electron-releasing subunits on the dye-sensitized solar cell performance of new triphenylamine-benzimidazole based molecules(Elsevier, 2015) Dinçalp H.; Saltan G.M.; Aykut D.; Zafer C.New triphenylamine-benzimidazole type small molecules with different electron-releasing groups were designed and synthesized to investigate their photovoltaic performances in dye sensitized solar cells (DSSCs). Their good visible absorptions covering the 400-535 nm in addition to suitable lowest unoccupied molecular orbital (LUMO) energy levels between -3.03 and -3.11 eV make good candidates them for DSSC devices. Fluorescence quenching studies of the dyes with pristine titania support the good electron injection to conduction band of TiO2. Time resolved measurements of the dyes in solutions indicate the occurence of charge generation during the excited state. One of the used dyes in DSSC devices, TPA5a, carrying a methoxy group in triphenylamine part of the structure, gave much higher power conversion efficiency (PCE) value of 4.31% as compared to the other derivatives. Device fabricated from TPA5a dye gives good external quantum efficiency (EQE) value above 70% at 460 nm. Also, electron impedance spectroscopy (EIS) analysis of the devices gives a good explanation of the understanding of the cell performances. © 2015 Elsevier B.V.Item Novel organic dyes based on phenyl-substituted benzimidazole for dye sensitized solar cells(Elsevier Ltd, 2015) Saltan G.M.; Dinçalp H.; Kiran M.; Zafer C.; Erbaş S.Ç.Two new sensitizers derived from benzimidazole core for dye-sensitized solar cell (DSSC) applications were designed and synthesized as D-π-A structures, in which two phenyl-substituted benzimidazole group, a phenyl ring and a cyanoacrylic acid were used as the electron donor, π-conjugated linkage and the electron acceptor, respectively. Effect of methoxy- and N,N-dimetylamino- moieties attached to the phenyl groups of benzimidazole were investigated by means of optical and photovoltaic measurements. The compounds exhibit broad absorption maximum at 387 nm with the tail extending up to 500 nm on TiO2-coated thin film. The longer wavelength absorption band around 360 nm and the much longer decay components could be attributed to the existence of charge transfer state of the dyes in solutions. DSSC device fabricated by using methoxy substituted dye (BI5a) as a sensitizer shows much better incident photon-to-current conversion efficiency (IPCE) of 64% giving cell efficiency of 2.68%. © 2015 Elsevier B.V. All rights reserved.Item Comparison of the Optoelectronic Performance of Neutral and Cationic Forms of Riboflavin(Springer New York LLC, 2017) Saltan G.M.; Kıymaz D.A.; Zafer C.; Dinçalp H.The riboflavin dye 2,3,4,5-tetra-O-acetyl-1-[3-(6-bromohexyl)-7,8-dimethyl-2,4-dioxo-3,4-dihydrobenzo[g]pteridin-10(2H)-yl]-1-deoxypentitol and its pyridinium salt were synthesized, and studied by absorption and fluorescence spectroscopy in solutions and on thin film states. The first absorption band of riboflavin-pyridinium salt derivative is red-shifted by 10 nm compared to neutral one on film. Cationic riboflavin derivative shows significant wavelength changes on its fluorescence emission spectrum in the excited state depending on the solvent polarity and the electronic environment. The fluorescence quantum yields of cationic riboflavin gave much higher values as compared to that of its neutral form. The fluorescence lifetimes were found to be in the range of 5.5–6.6 ns with mono − exponential behavior. These dyes possess low-lying HOMO energy levels which are suitable to be able to inject holes to donor polymers so that they can be used as acceptor component in the active layer of bulk heterojunction solar cells (BHJ-SCs). Photovoltaic responses are reported for P3HT:riboflavin active layer wherein the synthesized dyes are used as acceptor component. Also, neutral riboflavin shows greater electron mobility value of 1.3 × 10−3 cm2/V∙s compared to its cationic derivative. © 2017, Springer Science+Business Media, LLC.Item Synthesis and photophysical characterization of isoindigo building blocks as molecular acceptors for organic photovoltaics(Elsevier B.V., 2018) Dinçalp H.; Saltan G.M.; Zafer C.; Mutlu A.Five isoindigo-based donor-acceptor-donor (D-A-D) type small molecules have been synthesized in order to investigate their intramolecular charge transfer characteristics. UV–vis absorption of these dyes exhibits a wide absorption band ranging from 300 to 650 nm with two distinct bands, giving the narrow bandgaps between 1.72 and 1.85 eV. Taking into account their HOMO-LUMO energy levels and bandgaps, isoindigo dyes have been used in the active layer of organic solar cell (OSC) devices. When these small molecule semiconductors were used as acceptors with the donor poly(3-hexylthiophene-2,5-diyl (P3HT) polymer in the inverted OSC devices, the highest power conversion efficiency (PCE) was obtained as 0.10% for pyrene-substituted isoindigo derivative. © 2018 Elsevier B.V.Item Indigo-Based Acceptor Type Small Molecules: Synthesis, Electrochemical and Optoelectronic Characterizations(Springer New York LLC, 2018) Saltan G.M.; Kıymaz D.A.; Zafer C.; Dinçalp H.In this paper, we report design and synthesis of novel low bandgap small molecules, indigo-benzimidazole (Tyr-3) and indigo-schiff base (Tyr-4) type acceptors. In these structures, tert-butoxycarbonyl (t-BOC) group has been attached to indigo nitrogen atom in order to increase the solubility. UV-vis absorption spectra of Tyr-3 and Tyr-4 dyes exhibit wide absorption bands ranging from 350 to 600 nm, indicating the relatively low bandgap giving around 2.07 eV for each. Excitation of both Tyr-3 and Tyr-4 dyes at 485 nm displays characteristic emission features of indigo moiety and also intramolecular charge transfer complex (ICT) related with their subunits. Besides increasing fluorescence quantum yields as compared to model compound, biexponential decay times for fluorescence life times were also obtained for Tyr-3 and Tyr-4 dyes. Their appropriate energy levels along with low HOMO levels are desired for light harvesting acceptors for organic solar cells when blended with poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole] (PCDTBT) as donor polymer. Photovoltaic behavior of the synthesized dyes were examined in bulk heterojunction concept and achieved photovoltaic conversion efficiencies were discussed. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.Item Bromo-substituted cibalackrot backbone, a versatile donor or acceptor main core for organic optoelectronic devices(Elsevier B.V., 2018) Dinçalp H.; Saltan G.M.; Zafer C.; Kıymaz D.A.Cibalackrot (Ci-I), one of the latest highly conjugated compound possessing bis-lactam structure, was investigated with respect to their brominated derivatives in order to determine their suitable substitution points for the syntheses of new class of small molecules for optoelectronic devices. 7,14-Bis(4-bromophenyl) (Ci-II) and 3,10-dibromo (Ci-III) derivatives of cibalackrot possess moderately narrow band gaps of 2.15 and 2.09 eV, respectively. Notably, Ci-III dye exhibits more red-shifted ultraviolet–visible (UV–vis) absorption and fluorescence emission spectra as compared to that of Ci-II dye because Ci-III shows more prominent intramolecular charge transfer (ICT) complex than that of Ci-II dye. Electron mobilities of the order of 7.0 × 10−4 cm2/V and 3.1 × 10−4 cm2/V were measured using Ci-II and Ci-III as active layer, respectively. Charge transfer properties of the molecules were investigated in bulk heterojunction device configuration wherein Ci-III showed p-type behavior against n-type PCBM in photovoltaic device. Photovoltaic performance of Ci-III dye which was used as donor component is 20 times higher than that of the device in which this dye was used as acceptor. © 2018 Elsevier B.V.Item Small biomolecule dopant retinals: Electron blocking layer in P3HT:PCBM type organic solar cells(Elsevier Ltd, 2018) Kırmacı E.; Dinçalp H.; Saltan G.M.; Kıran M.; Zafer C.We present a comparative study of the photophysics and electron/hole properties of all-trans retinal-benzimidazole type molecules decorated with different electronic moieties (such as –OCH3, –N(CH3)2, –F, –CF3) in organic photovoltaic (OPV) devices in solution and on solid thin films. Steady-state spectra of synthesized dyes give large Stokes shifts (6887–13152 cm−1) in studied solvents. Decay times of these dyes were found to be substituent dependent giving a bi-exponential decay for fluorine containing retinals. Trans to cis photoisomerization rate constants of synthesized dyes were found to be about 3.3–16.4 × 10−6 s−1. Using a cyclic voltammetry measurements, HOMO and LUMO energy levels of fluorine-substituted dyes shift to lower values as compared to that of unfluorinated derivatives. We compared unusual electron blocking behavior of methoxy- and N,N-dimethylamino-substituted derivatives (Ret-I and Ret-II, respectively) in bulk heterojunction solar cells (BHJ-SCs) incorporating an active layer of P3HT:PCBM doped with Ret derivatives at various weight ratios. Hole mobility values for fluorine containing retinals were found to be about 1.0 × 10−4 and 7.1 × 10−4 cm2/V s for Ret-III and Ret-IV dyes, respectively. © 2017 Elsevier B.V.Item Optoelectronic performance comparison of new thiophene linked benzimidazole conjugates with diverse substitution patterns(Elsevier B.V., 2018) Saltan G.M.; Dinçalp H.; Kırmacı E.; Kıran M.; Zafer C.In an approach to develop efficient organic optoelectronic devices to be used in light-driven systems, a series of three thiophene linked benzimidazole conjugates were synthesized and characterized. The combination of two thiophene rings to a benzimidazole core decorated with different functional groups (such as –OCH3, –N(CH3)2, –CF3) resulted in donor-acceptor type molecular scaffold. The effect of the electronic behavior of the substituents on the optical, electrochemical, morphological and electron/hole transporting properties of the dyes were systematically investigated. DTBI2 dye exhibited distinct absorption properties among the other studied dyes because N,N-dimethylamino group initiated intramolecular charge transfer (ICT) process in the studied solvents. In solid state, the dyes exhibit peaks extending up to 600 nm. Depending on the solvent polarities, dyes show significant wavelength changes on their fluorescence emission spectra in the excited states. Morphological parameters of the thin films spin-coated from CHCl3 solution were investigated by using AFM instrument; furthermore photovoltaic responses are reported, even though photovoltaic performances of the fabricated solar cells with different configurations are quite low. © 2017 Elsevier B.V.Item Synthesis of a new adsorbent poly(allylisothiocyanate-co-hydroxyethylmethacrylate-co-vinylimidazole) via photopolymerization: Characterization and investigation of heavy metal adsorption capacity(John Wiley and Sons Inc, 2022) Saltan F.; Saltan G.M.We report the copolymerization synthesis of novel poly(allylisothiocyanate-co-hydroxyethylmethacrylate-co-vinylimidazole) (PAHV) adsorbents for potential applications in the heavy metal removals. In the present study, the copolymerization reaction was introduced by photopolymerization using benzophenone as the photoinitiator. The chemical structure in the PAHV adsorbents was monitored and evaluated by Fourier transform infrared spectroscopy, 1H-nuclear magnetic resonance, andX-ray photoelectron spectroscopy measurements. Surface analysis and molecular weight distribution of PAHV adsorbents were performed by scanning electron microscopy and gel permeation chromatography analysis, respectively. The adsorption method, which is one of the most effective techniques, was used for the elimination of heavy metal ions from aqueous solutions in this study. In order to understand the adsorption capacity and removal efficiency of heavy metal ions by PAHV, the effects of pH value and monomer ratio in the adsorbents were investigated. Inductively coupled plasma mass spectrometry device was used for these analyses. The optimum pH values for adsorption capacity and removal efficiency of heavy metal ions have been 6–8. The removal efficiency of heavy metal ions by the various PAHV adsorbents decreased in the order: Cd2+ > Pb2+ > Co3+ > Cr3+ > Ni2+ > Cu2+. © 2022 Wiley Periodicals LLC.Item Conformational control of morphology for perylene diimide dimer as electron transporting material at perovskite surface(Elsevier B.V., 2023) Ötken A.A.; Saltan G.M.; Yeşil T.; Zafer C.; Dinçalp 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 photopysical dynamics of excited states of the dyes, but also charge transport kinetics at the perovskite interfaces, changing the photovoltaic performance. © 2023 Elsevier B.V.Item Perylene Diimide-Based Dimeric Electron Acceptors with Molecular Conformations for Perovskite Solar Cells(John Wiley and Sons Inc, 2024) Saltan G.M.; Yeşil T.; Ötken A.A.; Zafer C.; Dinçalp 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. © 2024 Wiley-VCH GmbH.Item Photopolymerization and characterization of vinyl imidazole based allyl derivative polymers; Cr3+ and Cd2+ metal adsorption and antibacterial studies(John Wiley and Sons Inc, 2024) Saltan F.; Saltan G.M.; İlktaç R.; Özdokur K.V.A new type polymeric adsorbent, poly(allylphenol-co-hydroxyethyl methacrylate-co-vinyl imidazole) (PAHV), is synthesized in this study. 2-Hydroxyethyl methacrylate is used as complementary monomers along with 1-vinyl imidazole and allylphenol monomers. The photopolymerization method is preferred as a synthesis method and benzophenone is used as the photoinitiator. The effectiveness of the PAHV against bacterial species such as Escherichia coli and Staphylococcus aureus is investigated by the Clinical and Laboratory Standards Institute (CLSI) disk diffusion method. The inhibition areas of PA1H1V3 and PA1H1V1 derivatives against E. coli and S. aureus are measured as 25 mm ± 0.25 mm and 7 mm ± 0.1 mm; 20 mm ± 0.25 mm, and 5 mm ± 0.1 mm, respectively. Sorption efficiencies (%) at pH = 6 (selected optimum pH) for 100 μg/L Cd and Cr of the PA1H1V1, PA1H3V1, and PA1H1V3 derivatives are found to be 69.0 ± 2.7 and 58.3 ± 6.7, 66.8 ± 6.2 and 75.8 ± 5.5, and 97.2 ± 3.7 and 97.7 ± 3.2 (n = 3), respectively. Adsorption studies revealed that the PA1H1V3 polymer can be used as an alternative for the sorption of cadmium and chromium. The pseudo-second-order model and Langmuir isotherm model fits for both adsorption processes. The adsorption capacities obtained from the Langmuir isotherm model for chromium and cadmium sorption are 52.63 and 68.49 μg g−1, respectively. © 2024 Wiley Periodicals LLC.