Browsing by Author "Kiran, M"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Small biomolecule dopant retinals: Electron blocking layer in P3HT:PCBM type organic solar cells
    Kirmaci, E; Dinçalp, H; Saltan, GM; Kiran, 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 end 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 photo-isomerization rate constants of synthesized dyes were found to be about 3.3-16.4 x 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 x 10(-4) and 7.1 x 10(-4) cm(2)/V s for Retail and Ret-IV dyes, respectively.
  • No Thumbnail Available
    Item
    Optoelectronic performance comparison of new thiophene linked benzimidazole conjugates with diverse substitution patterns
    Saltan, GM; Dinçalp, H; Kirmaci, E; Kiran, 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. (C) 2017 Elsevier B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Novel organic dyes based on phenyl-substituted benzimidazole for dye sensitized solar cells
    Saltan, GM; Dinçalp, H; Kiran, M; Zafer, C; Erbas, SÇ
    Two new sensitizers derived from benzimidazole core for dye-sensitized solar cell (DSSC) applications were designed and synthesized as D-pi-A structures, in which two phenyl-substituted benzimidazole group, a phenyl ring and a cyanoacrylic acid were used as the electron donor, pi-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%. (C) 2015 Elsevier B.V. All rights reserved.