İlkay Şişman

One-step anion-assisted electrodeposition of ZnO nanofibrous networks as photoanodes for dye-sensitized solar cells

A highly efficient ZnO photoanode consisting of three-dimensional (3D) nanofibrous-like networks (NFs) for dye-sensitized solar cells (DSSCs) was synthesized using a one-step and seed-layer-free electrodeposition on an indium-tin-oxide (ITO) substrate at 75 °C in a solution containing Zn(NO3)2, KCl, NaCH3COO, and Na3C6H5O7. In this solution, KCl as the supporting electrolyte promotes the reduction of NO3− and the diffusion of Zn2+, whereas CH3COO− and C6H5O73− anions act as the capping agents to selectively inhibit ZnO growth along the c-axis. The photoelectrochemical results reveal that the DSSC based on ZnO NFs has the highest power conversion efficiency (3.78%) in comparison with those of DSSCs based on nanosheets (1.36%), nanorods (2.18%), and microplates (2.55%). This can be attributed to the large dye adsorption amount, efficient light scattering and direct electron transfer networks, which lead to a significant improvement in solar cell performance. Therefore, the ZnO NFs structure can be considered as a promising and efficient photoanode for DSSCs.

Surfactant-assisted polyol preparation of nickel powders with different morphologies

Sub-micrometer nickel powders of controlled size and morphology were produced by a surfactant-assisted polyol method, using ethylene glycol (EG) as solvent and reductant in the presence of sodium dodecyl sulfate (SDS) surfactant and NaOH. The resultant Ni powders were characterized by XRD, SEM, EDS, and FTIR. Spherical, hexagonal, and triangular fcc Ni powders from 0.30 to 0.60 μm were obtained in the presence of SDS; irregular spherical fcc Ni powders were obtained in its absence. The concentrations of SDS, NaOH and Ni(CH3COO)2·4H2O greatly influence the product morphology and size.

Thiochalcone substituted phthalocyanines for dye-sensitized solar cells: Relation of optical and electrochemical properties for cell performance

Abstract The new peripherally tetra-substituted metallophthalocyanines (MPcs, M=Zn, Co, Ni) bearing the chalcone, (E)-3-(4-hydroxyphenyl)-1-(thiophen-2-yl)prop-2-en-1-one, for dye-sensitized solar cells (DSSCs) were synthesized. FT-IR, 1H NMR, 13C NMR, and UV–Vis spectroscopy techniques were utilized for characterization of all the MPcs. Electrochemical, optical and photovoltaic properties of all the MPcs as sensitizers were examined. Electrochemical studies reveal that while the ZnPc (4) and NiPc (6) give only Pc ring-based redox reactions, the CoPc (5) shows redox reactions based on both the central metal and the ring due to the metal 3d orbitals lying between the Pc HOMO and LUMO. The DSSC based on 5 gave the lowest power conversion efficiency (0.51%), perhaps due to the presence of a redox active central metal ion in the core of the complex, which results in a decrease electron transfer in the device. However, cells based on the other complexes including redox inactive central metal ions, which cannot reduce electron transfer, showed reasonable power conversion efficiencies of 1.27% and 1.11% for 4 and 6, respectively. The slight difference between the efficiencies can be attributed to higher molar extinction coefficient and narrower band gap of 4 than 6, which ensure a higher photocurrent and broader light absorption in the visible region.

Comparative studies of photophysical and electrochemical properties of sulfur-containing substituted metal-free and metallophthalocyanines

The synthesis, photophysical and electrochemical properties of soluble sulfur-containing 4-(methylthio) benzenethiol substituted, non-peripherally metal-free and metallo (Zn, Ga, Co, and Mn) phthalocyanine complexes (2–6) are reported for the first time. The new phthalocyanines have been characterized by FT-IR spectroscopy, 1H-NMR, 13C-NMR, mass and UV–Vis spectroscopy techniques. Spectroscopic properties of these compounds were investigated in different solvents. Spectral and photophysical (fluorescence quantum yield) properties of metal free (2), zinc(II) (3), and gallium(III) phthalocyanines (4) were reported in different solvents toluene, tetrahydrofuran, and dimethyl sulfoxide. These results suggest that the solvents play role on the fluorescence quantum yields ΦF of the synthesized complexes (2–4). The electrochemical studies exhibit that while complexes (3) and (4) give only Pc ring-based redox processes, complexes (5) and (6) give both metal and ring-based redox reactions due to the energy level of metal in the Pc core lie between the HOMO and the LUMO of the ring.