A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation {(C2H5)3NH}[Ru(H3tcterpy)(NCS)3] 1, {(C4H9)4N}2[Ru(H2tcterpy)(NCS)3] 2, {(C4H9)4N}3[Ru(Htcterpy)(NCS)3] 3, and {(C4H9)4N}4[Ru(tcterpy)(NCS)3] 4 (tcterpy = 4,4‘,4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine) have been synthesized and fully characterized by UV−vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a RuIIN6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properti...

Engineering of Efficient Panchromatic Sensitizers for Nanocrystalline TiO2-Based Solar Cells

Recent worldwide interest in building a decentralized, hydrogen-based energy economy has refocused attention on the solid oxide fuel cell (SOFC) as a potential source of efficient, environmentally friendly, fuel-versatile electric power. Due to its high operating temperature, the SOFC offers several potential advantages over polymer-based fuel cells, including reversible electrode reactions, low internal resistance, high tolerance to typical catalyst poisons, production of high-quality waste heat for (among other uses) reformation of hydrocarbon fuels, as well as the possibility of burning hydrocarbon fuels directly. Today, SOFCs are much closer to commercial reality than they were 20 years ago, due largely to technological advances in electrode material composition, microstructure control, thin-film ceramic fabrication, and stack and system design. These advances have led to dozens of active SOFC development programs in both stationary and mobile power and contributed to commercialization or development in a number of related technologies, including gas sensors,1 solid-state electrolysis devices,2 and iontransport membranes for gas separation and partial oxidation.3 Many reviews are available which summarize the technological advances made in SOFCs over the last 15-35 yearssreaders who are primarily interested in knowing the state-of-the art in materials, design, and fabrication (including the electrodes) are encouraged to consult these reviews.4-12 This review focuses on the factors governing SOFC cathode performancesadvances we have made over † Dedicated to Brian Steele, 1929-2003. Researcher, Entrepreneur, Consensus Seeker. 4791 Chem. Rev. 2004, 104, 4791−4843

Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes

Progress in material selection for solid oxide fuel cell technology: A review

The ruthenium complexes [Ru(dcbpyH2)2(Cl)2] (1), [Ru(dcbpyH2)2(NCS)2] (2), (Bu4N)4[Ru(dcbpy)2(NCS)2] (3), and (Bu4N)2[Ru(dcbpyH)2(NCS)2] (4) were synthesized and characterized by cyclic voltammetry, UV−vis absorption, and emission, IR, Raman, and NMR spectroscopy. The absorption and emission maxima of these complexes red shifted with decreasing pH, and showed pH-dependent excited-state lifetimes. The ground-state pKa values were determined by spectrophotometeric methods, and the dissociation of protons was found to occur in two steps (pKa = 3 and 1.5). The Ru(II)/(III) couple in the complex (Bu4N)4[Ru(dcbpy)2(NCS)2] is shifted ca. 290 mV negatively with regard to that of the complex [Ru(dcbpyH2)2(NCS)2] due to the replacement of H+ by tetrabutylammonium cation. The negative shift for the dcbpy-based reduction potential is even larger, i.e., about 600 mV compared to that of the complex [Ru(dcbpyH2)2(NCS)2]. The effect of deprotonation on the performance of these complexes as photosensitizers for nanocrysta...

Acid-Base Equilibria of (2,2'-Bipyridyl-4,4'-dicarboxylic acid)ruthenium(II) Complexes and the Effect of Protonation on Charge-Transfer Sensitization of Nanocrystalline Titania.

Arylamine organic dyes with donor (D), π-bridge (π) and acceptor (A) moieties for dye-sensitized solar cells (DSCs) have received great attention in the last decade because of their high molar absorption coefficient, low cost and structural variety. In the early stages, the efficiency of DSCs with arylamine organic dyes with D–π–A character was far behind that of DSCs with ruthenium(II) complexes partly due to the lack of information about the relationship between the chemical structures and the photovoltaic performance. However, exciting progress has been recently made, and power conversion efficiencies over 10% were obtained for DSCs with arylamine organic dyes. It is thus that the recent research and development in the field of arylamine organic dyes employing an iodide/triiodide redox couple or polypyridyl cobalt redox shuttles as the electrolytes for either DSCs or solid-state DSCs has been summarized. The cell performance of the arylamine organic dyes are compared, providing a comprehensive overview of arylamine organic dyes, demonstrating the advantages/disadvantages of each class, and pointing out the field that needs to reinforce the research direction in the further application of DSCs.

Arylamine organic dyes for dye-sensitized solar cells

The relationship between overpotential and the three phase boundary length

The absorption coefficient of the dye used in dye-sensitized solar cells is a major factor in the total energy efficiency of the cell. In this work, we increased the absorption coefficient of the dye cis-(NCS)2 bis(2,2‘-bipyridyl-4,4‘-dicarboxylate)ruthenium(II) used in such cells by having the dye adsorbed on silver islands. We studied the effect of the surface area of silver (per surface area of substrate) and the effect of dye concentration on this enhancement. This technique significantly enhanced the absorption coefficient of the Ru-dye for the metal−ligand charge-transfer transition, which generates electrons and holes in dye-sensitized solar cells. The enhancement ratio of the absorption was controlled by the amount of Ru-dye directly adsorbed on the silver islands. The absorption was enhanced by a factor of 149, which was achieved for a dye concentration of 3 × 10-10 mol/cm2 and an average surface area of silver island of 0.63 cm2/cm2 of substrate. Such enhancement is expected to be useful in impr...

Enhancement of the Absorption Coefficient of cis-(NCS)2 Bis(2,2‘-bipyridyl-4,4‘-dicarboxylate)ruthenium(II) Dye in Dye-Sensitized Solar Cells by a Silver Island Film

A triphenylamine (TPA) dye with two hexyl groups at the opposable 3,3′-positions of a bithiophene linker (1a) was prepared and compared to a dye with a regio regular 4,3′-dihexylbithiophene unit (1b). The absorption spectrum of 1a showed a blue shift in comparison to 1b, suggesting the structure of 1a was twisted in comparison to 1b. The twisted structure agreed with the structure optimized by DFT calculations. By replacing one thiophene unit of 1a and 1b with a pyridine ring (2a and 2b, respectively), a further blue shift was observed. Dye-sensitized solar cells (DSSCs) were prepared from these dyes and a conventional Ru dye (N719). Under one sun conditions, DSSCs/2a showed comparable or higher open-circuit voltage (Voc) than did DSSCs/N719. The high Voc was attributed solely to long electron lifetime in the DSSCs/2a. A previous study has suggested that TPA dyes with long π-conjugation unit suffer from larger dispersion forces between the dyes and acceptors, I3− and/or I2, causing short electron lifetime...

Molecular Design of Organic Dye toward Retardation of Charge Recombination at Semiconductor/Dye/Electrolyte Interface: Introduction of Twisted π-Linker

Photoelectric conversion efficiency (Eff) of a dye-sensitized solar cell (DSSC) was improved by localized surface plasmon on silver (Ag) nanoparticles modified with polyacrylate-based comb-shaped block copolymer. The polymer-modified Ag nanoparticles were inserted into pores of a TiO2 film in a DSSC. Then, the characteristics of this photoabsorption enhanced DSSC (PE-DSSC) with the Ag nanoparticles were evaluated. To clarify the effect of Ag nanoparticles on the characteristics, the thickness of the TiO2 film in the DSSC was 2 μm, thinner than that for a typical DSSC (10 μm). A PE-DSSC showed an improved Eff of 2.5%, compared with about 1.5% for a DSSC with no Ag nanoparticles.

Manabu Ihara

Papers

The relationship between overpotential and the three phase boundary length

Enhancement of the Absorption Coefficient of cis-(NCS)2 Bis(2,2‘-bipyridyl-4,4‘-dicarboxylate)ruthenium(II) Dye in Dye-Sensitized Solar Cells by a Silver Island Film

Molecular Design of Organic Dye toward Retardation of Charge Recombination at Semiconductor/Dye/Electrolyte Interface: Introduction of Twisted π-Linker

Photoabsorption-enhanced dye-sensitized solar cell by using localized surface plasmon of silver nanoparticles modified with polymer

Cathodic reaction mechanism for dense Sr-doped lanthanum manganite electrodes