The objective of this work is to develop and optimize the new dye-sensitized solar cell technology. In view of the infancy of rutile material development for solar cells, the PV response of the dye-sensitized rutile-based solar cell is remarkably close to that of the anatase-based cell.

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Comparison of Dye-Sensitized Rutile- and Anatase-Based TiO2 Solar Cells

Highly photocatalytically active silver-modified ZnO has been prepared and the effect of silver modification was studied. The structural and optical properties were characterized by X-ray diffraction, Fourier transform IR, differential scanning calorimetry, BET surface area, Raman, UV−vis, and photoluminescence spectroscopy. The photocatalytic activity of these materials was studied by analyzing the degradation of an organic dye, rhodamine 6G (R6G), and it is found that 3 mol % silver-modified ZnO at 400 °C shows approximately four times higher rate of degradation than that of unmodified ZnO and a three times higher rate than that of commercial TiO2 photocatalyst Degussa P-25. It was also noted that the photocatalytic activity for the modified ZnO sample was five times higher than the unmodified sample using sunlight. The effect of silver in enhancing the photocatalytic activity has been studied by analyzing the emission properties of both ZnO and silver-modified ZnO in the presence (emission increases) a...

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A Highly Efficient Ag-ZnO Photocatalyst: Synthesis, Properties, and Mechanism

During the last years, ZnO thin films have been studied extensively due to their potential applications in e.g. piezoelectric and optoelectronic devices or photovoltaic cells. Ordered c-axis orientation of ZnO crystallites is desirable for applications where crystallographic anisotropy is a prerequisite such as for short-wavelength semiconductor diode lasers (SDLs), and piezoelectric surface acoustic wave or acousto-optic devices. Many works were dedicated to c-axis oriented ZnO thin films elaboration and the study of their properties, including physical and chemical methods. For instance, sol–gel processes are particularly well adapted to produce ZnO films in a simple, low-cost and highly controlled way. This review summarizes the main chemical routes used in the sol–gel synthesis of undoped ZnO thin films and highlights the chemical and physical parameters influencing their structural properties. In this process, the ZnO films synthesis includes three principal steps: (i) solution preparation, (ii) coating and (iii) heat treatment. For the first step, the particle formation is discussed including nucleation and growth, particle size, morphology and colloids stability. These three steps involve several parameters such as: (i) nature and concentration of precursor, solvent and additive, and solution aging time, for the chemical system, (ii) coating method, thickness and substrate for the coating step, and (iii) pre-and post-heat treatment for the last step. The influence of these steps and synthesis parameters on ZnO thin films orientation is discussed.

Sol–gel-deposited ZnO thin films: A review

The incessant demand for energy forces us to seek it from sustainable resources; and concerns on environment demands that resources should be clean as well. Metal oxide semiconductors, which are stable and environment friendly materials, are used in photovoltaics either as photoelectrode in dye solar cells (DSCs) or to build metal oxide p–n junctions. Progress made in utilization of metal oxides for photoelectrode in DSC is reviewed in this article. Basic operational principle and factors that control the photoconversion efficiency of DSC are briefly outlined. The d-block binary metal oxides viz. TiO2, ZnO, and Nb2O5 are the best candidates as photoelectrode due to the dissimilarity in orbitals constituting their conduction band and valence band. This dissimilarity decreases the probability of charge recombination and enhances the carrier lifetime in these materials. Ternary metal oxide such as Zn2SnO4 could also be a promising material for photovoltaic application. Various morphologies such as nanoparticles, nanowires, nanotubes, and nanofibers have been explored to enhance the energy conversion efficiency of DSCs. The TiO2 served as a model system to study the properties and factors that control the photoconversion efficiency of DSCs; therefore, such discussion is limited to TiO2 in this article. The electron transport occurs through nanocrystalline TiO2 through trapping and detrapping events; however, exact nature of these trap states are not thoroughly quantified. Research efforts are required not only to quantify the trap states in mesoporous metal oxides but new mesoporous architectures also to increase the conversion efficiency of metal oxide-based photovoltaics.

Metal Oxides for Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) belong to the group of thin-film solar cells which have been under extensive research for more than two decades due to their low cost, simple preparation methodology, low toxicity and ease of production. Still, there is lot of scope for the replacement of current DSSC materials due to their high cost, less abundance, and long-term stability. The efficiency of existing DSSCs reaches up to 12%, using Ru(II) dyes by optimizing material and structural properties which is still less than the efficiency offered by first- and second-generation solar cells, i.e., other thin-film solar cells and Si-based solar cells which offer ~ 20–30% efficiency. This article provides an in-depth review on DSSC construction, operating principle, key problems (low efficiency, low scalability, and low stability), prospective efficient materials, and finally a brief insight to commercialization.

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Dye-Sensitized Solar Cells: Fundamentals and Current Status

Nine new transition-metal di-thiocarbamates involving ferrocene (Fc), namely, [M(FcCH2Bzdtc)2] (M = NiII(1), Cu II (2), CdII (3), HgII (4), PdII (5), PtII (6) and PbII (7); Bzdtc = N-benzyl dithiocarbamate) and [M(FcCH2BZdtc)3] (M = CoII (8) and UO2 (9)), have been synthesised and characterised by micro analyses, IR spectroscopy, 1H and 13C NMR spec-troscopy, and in three cases by single-crystal X-ray analysis. The peak broad-ening in the 1H spectrum of the copper complex indicates the paramagnetic be-haviour of this compound. A square-planar geometry around the nickel and copper complexes and distorted linear geometry around the mercury complex have been found. The latter geometry is attributed to the bulkiness of the methylferrocenyl and benzyl groups. The observed single quasi-reversible cyclic voltammograms for complexes 2, 8 and 9 indicate the stabilisation of a metal centre other than Fe in their characteristic oxidation state. These complexes have been used as a photo-sensitiser in dye-sensitised solar cells. 2010 Wiley-VCH Verlag GmbH Co. KGaA dithiocarbamates, fer-rocene, heterometallic complexes, solar cells, transition metals.

Synthesis, Structure and Light-Harvesting Properties of Some New Transition-Metal Dithiocarbamates Involving Ferrocene

Four natural pigments, extracted from the leaves of teak (Tectona grandis), tamarind (Tamarindus indica), eucalyptus (Eucalyptus globulus), and the flower of crimson bottle brush (Callistemon citrinus), were used as sensitizers for TiO2 based dye-sensitized solar cells (DSSCs). The dyes have shown absorption in broad range of the visible region (400–700 nm) of the solar spectrum and appreciable adsorption onto the semiconductor (TiO2) surface. The DSSCs made using the extracted dyes have shown that the open circuit voltages () varied from 0.430 to 0.610 V and the short circuit photocurrent densities () ranged from 0.11 to 0.29 mA cm−2. The incident photon-to-current conversion efficiencies (IPCE) varied from 12–37%. Among the four dyes studied, the extract obtained from teak has shown the best photosensitization effects in terms of the cell output.

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Natural Pigments from Plants Used as Sensitizers for TiO2 Based Dye-Sensitized Solar Cells

Dye-sensitized solar cell using extract from petals of male flowers Luffa cylindrica L. as a natural sensitizer

Biferrocene bearing planar metal dithiocarbamates, namely, [M(FcCH2dtc)2] (dtc = furan-2-ylmethyldithiocarbamate, M = Cu(II) 1, Ni(II) 4; dtc = benzo[d][1,3]dioxol-5-ylmethyl dithiocarbamate, M = Cu(II) 2, Ni(II) 5; dtc = pyridin-2-ylmethyldithiocarbamate, M = Cu(II) 3, Ni(II) 6; Fc = ferrocenyl; Fe(η5-C5H5)(η5-C5H4–)), have been synthesized and characterized by microanalysis, magnetic susceptibility and cyclic voltammetry. Structures of 1, 2 and 4 have been obtained by single crystal X-ray diffraction. These complexes with pyridyl, piperonyl and furfuryl as heteroaromatic groups in the dithiocarbamate ligands have been exploited as sensitizers in dye sensitized TiO2 solar cells for converting sunlight into electrical energy. Light-to-electrical energy conversion efficiencies achieved using these sensitizers are considerably greater than those obtained with analogous compounds previously reported by us. The overall conversion efficiency (η) is found to be dependent upon the nature of the heteroaromatic conjugated linkers and increases in the order η (ferrocenylfurfuryl) > η (ferrocenylpiperonyl) > η (ferrocenylpyridyl) all values being lower than that obtained in the reference Ru dye N719 under similar experimental conditions. The conversion efficiencies also vary with the metal being higher for Ni (4, 5 and 6) than for Cu complexes (1, 2 and 3). The X-ray structural analyses reveal the existence of rare M⋯H–C intermolecular anagostic interactions involving the metal atom in chain motifs in 1 and 4, which are retained in solution as evidenced by 1H NMR spectroscopy.

Photosensitizing activity of ferrocenyl bearing Ni(II) and Cu(II) dithiocarbamates in dye sensitized TiO2 solar cells

Two new heterobimetallic phenylmercury(II) dithiocarbamate complexes incorporating the ferrocenyl moiety (C5H5)Fe(C5H4) (Fc), namely PhHgS2CN(CH2Fc)CH2C5H4N, (1) and PhHgS2CN(CH2Fc)CH2C4H3O, (2) have been prepared and characterized by elemental analysis, UV-Vis, IR, 1H and 13C NMR spectroscopies. The crystal structures of 1 and 2 showed a linear core at the Hg(II) centre of the molecule, bound by the sulfur atom of the dithiocarbamate ligand and carbon atom of the aromatic ring. Weak intermolecular Hg⋯S interactions form “head-to-tail” dimers in the cases of 1 and 2. The observed quasi-reversible cyclic voltammograms of the complexes have been corroborated by calculating gross natural electron population and gross natural electron spin population at each atom for the neutral as well its oxidized species obtained at density functional level (DFT) of theory, which suggests that the delocalization of electron spin population can affect the magnitude of ΔEp. The electronic absorption bands of both the complexes were assigned with the help of time dependent density functional theory (TD-DFT) calculations. The light harvesting properties of both 1 and 2 in conjunction with our previously reported compound PhHgS2CN(CH2Fc)CH2C6H5 (3) have been reported.

Lal Bahadur

Papers

Synthesis, Structure and Light-Harvesting Properties of Some New Transition-Metal Dithiocarbamates Involving Ferrocene

Natural Pigments from Plants Used as Sensitizers for TiO2 Based Dye-Sensitized Solar Cells

Dye-sensitized solar cell using extract from petals of male flowers Luffa cylindrica L. as a natural sensitizer

Photosensitizing activity of ferrocenyl bearing Ni(II) and Cu(II) dithiocarbamates in dye sensitized TiO2 solar cells

Efficient phenylmercury(II) methylferrocenyldithiocarbamate functionalized dye-sensitized solar cells