Showing papers by "Michael Grätzel published in 1997"
TL;DR: In this article, a charge recombination between dye-sensitized nanocrystalline TiO2 electrodes and the I3/I-couple in nonaqueous solution is described.
Abstract: Charge recombination between dye-sensitized nanocrystalline TiO2 electrodes and the I3-/I- couple in nonaqueous solution is described. The sensitizer was [RuL2(NCS)2] (L = 2,2‘-bipyridyl-4,4‘-dicarboxylic acid). An apparent inequality between the dark current and the recombination current is ascribed to a voltage shift caused by a potential drop at the SnO2/TiO2 interface, ohmic losses in the SnO2 and TiO2, and an overpotential for the redox reaction at the Pt counter electrode. Treating the dye-coated TiO2 electrodes with pyridine derivatives (4-tert-butylpyridine, 2-vinylpyridine, or poly(2-vinylpyridine)) improves significantly both the open-circuit photovoltage Voc (from 0.57 to 0.73 V) and the cell conversion efficiency (from 5.8 to 7.5%) at a radiant power of 100 mW/cm2 (AM 1.5) with respect to the untreated electrode. An analytical expression relating Voc to the interfacial recombination kinetics is derived, and its limitations are discussed. Analysis of Voc vs radiant power data with this expressi...
906 citations
TL;DR: In this paper, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12.Reference LPI-ARTICLE-1997-026
Abstract: Reference LPI-ARTICLE-1997-026View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
752 citations
TL;DR: In this paper, a black trithiocyanato-ruthenium(II) terpyridylII complex was used to enhance the sensitization of nanocrystalline TiOI to solar cells.
498 citations
TL;DR: The mixed-ligand complex [Ru(HP-terpy)(Me(2)bpy)(NCS)] based on X-ray diffraction study is reported and appears to be a promising candidate as a photosensitizer in dye-sensitized photoelectrochemical cells based on nanocrystalline films of TiO(2).
Abstract: We report the results of an investigation on the preparation, spectral, and photoelectrochemical properties of Ru(II)−polypyridyl complexes containing a new phosphonated terpyridine (P-terpy) ligand: [Ru(H2P-terpy)2] and [Ru(HP-terpy)(Me2bpy)(NCS)]. Resonance Raman spectral and luminescence studies allow probing into the nature of the low-energy MLCT transitions observed in these complexes. The crystal and molecular structure of the mixed-ligand complex [Ru(HP-terpy)(Me2bpy)(NCS)] based on X-ray diffraction study is reported. This complex appears to be a promising candidate as a photosensitizer in dye-sensitized photoelectrochemical cells based on nanocrystalline films of TiO2.
228 citations
TL;DR: In this article, the surface area of sensitizer for different types of anchoring is estimated on the basis of single-crystal X-ray diffraction studies of the esterified form of the complex.
Abstract: Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray powder diffraction (XRD) studies on nanocrystalline TiO2 powders and thin films are presented The size, shape (mostly exposed faces), and ordering of the TiO2 anatase particles in the nanocrystalline films are discussed The use of the topochemical approach, which considers the properties of (nanocrystalline) solids in terms of crystallographic features of (nano)crystals is suggested The surface area of sensitizer [bis(4,4‘-dicarboxy-2,2‘-bipyridine)bis(thiocyanato)]ruthenium(II) [abbreviated as (cis-Ru(dcbpy)2(NCS)2] on the semiconductor surface for the different types of anchoring is estimated on the basis of single-crystal X-ray diffraction studies of the esterified form of the complex
225 citations
TL;DR: Reference LPI-ARTICLE-1997-007View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12 as mentioned in this paper, created on 2016
Abstract: Reference LPI-ARTICLE-1997-007View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
172 citations
TL;DR: In this paper, a 2 V rocking chair lithium battery with nano-crystalline TiO2 (anatase) as the negative and LiNi0.5Co 0.5O2 as the positive electrode with LiN(CF3SO2)2 + ethylene carbonate/dimethoxyethane electrolyte was studied.
92 citations
TL;DR: A series of new ruthenium(II) complexes were synthesized for the application in photoelectrochemical solar cells based on dye-sensitised nanocrystalline titanium dioxide.
75 citations
TL;DR: In this paper, the lowest energy metal-to-ligand charge transfer transitions in these complexes could be tuned from 500 to 590 nm by choice of appropriate ligands and the highest occupied molecular orbital varied over 400 mV.
Abstract: Ruthenium(II) complexes of the type [Ru(dmbip)(Hdcbpy)X], [Ru(dmbip)(Hdcbiq)X] and [Ru(dhbip)(Hdcbpy)X], where dmbip = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine, dhbip = 2,6-bis(1-hexadecylbenzimidazol-2-yl)pyridine, H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, H2dcbiq = 4,4′-dicarboxy-2,2′-biquinoline and X = Cl–, NCS–, CN– or H2O, have been synthesized and spectroscopically characterized. They act as efficient charge-transfer sensitizers, when anchored onto nanocrystalline TiO2 films. The lowest-energy metal-to-ligand charge-transfer transitions in these complexes could be tuned from 500 to 590 nm by choice of appropriate ligands and the highest occupied molecular orbital varied over 400 mV. Some of the complexes reported are emissive at room temperature. The ground- and excited-state pKa values of dcbpy complexes were measured by spectrophotometric and spectrofluorimetric titration. Resonance-Raman spectra show bands characteristic of the dmbip and dcbpy ligand for excitation at 468 nm, while excitation at 568 nm gave predominantly bands associated with the dcbpy ligand. The excited-state pKa values and the resonance-Raman data indicate that the lowest excited state is a metal to dcbpy or dcbiq ligand charge-transfer state.
64 citations
TL;DR: In this article, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12.Reference LPI-ARTICLE-1997-022
Abstract: Reference LPI-ARTICLE-1997-022View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
56 citations
TL;DR: In this paper, the forward biasing of a mesoporous TiO2 (anatase) film whose surface is derivatized with a monolayer of the phosphonated ruthenium bipyridyl complex RuL2L with L = 4,7-diphenyl-1,10-phenanthroline an
Abstract: Forward biasing of a mesoporous TiO2 (anatase) film whose surface is derivatized with a monolayer of the phosphonated ruthenium bipyridyl complex RuL2L‘ with L = 4,7-diphenyl-1,10-phenanthroline an...
TL;DR: Light excitation results in photodissolution of the iron oxide cluster with concomitant formation of Fe(II) with novel findings concerning the photocatalytic activity of ferritin with its inherent biological implications.
Abstract: Under excitation by visible light the iron storage protein ferritin catalyses the reduction of cytochrome c and viologens as well as the oxidation of carboxylic acids, thiol compounds, and sulfite. The photochemically active element of ferritin is its mineral ferrihydrite semiconductor core. Band-gap excitation of these microcrystals leads to generation of electron-hole pairs that are sufficiently long-lived and reactive to engage in redox reactions with components of the medium. Photoreduction of cytochrome c and viologens occurs due to electron transfer from the conduction band of the iron oxide cluster through the protein shell surrounding the ferritin core. Laser photolysis coupled with time-resolved kinetics spectroscopy showed the electron transfer to propylviologen sulfonate to proceed in the microsecond time range. In the absence of electron acceptor at pH < 7, light excitation results in photodissolution of the iron oxide cluster with concomitant formation of Fe(II). These novel findings concerning the photocatalytic activity of ferritin with its inherent biological implications are discussed.
TL;DR: Reference LPI-CHAPTER-1997-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12 as mentioned in this paper, created on 2007-06-21.
Abstract: Reference LPI-CHAPTER-1997-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
TL;DR: In this paper, the authors review the principles and performance features of very efficient solar cells that are being developed in our laboratories based on the concept of dye-sensitization of wide bandgap semiconductors used in the form of mesoporous nanocrystalline membrane type films.
Abstract: The direct conversion of sunlight to electricity via photoelectrochemical solar cells is an attractive option that has been pursued for nearly two decades in several laboratories. In this paper, we review the principles and performance features of very efficient solar cells that are being developed in our laboratories. These are based on the concept of dye-sensitization of wide bandgap semiconductors used in the form of mesoporous nanocrystalline membrane-type films. The key feature is charge injection from the excited state of an anchored dye to the conduction band of an oxide semiconductor such as TiO2. In the use of the semiconductor in the form of high surface area, highly porous film offers several unique advantages: monomeric distribution of a large quantity of the dye in a compact (few micron thick) film, efficient charge collection and drastic inhibition of charge recombination (‘capture of charge carriers by oxidized dye’). Near quantitative efficiency for charge collection for monochromatic light excitation gives rise to sunlight conversion efficiency in the range of 8–10% This has led to fruitful collaboration with several industrial partners. Possible applications and commercialization of these solar cells and also other practical applications of nanosized films are briefly outlined.
TL;DR: In this article, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12, for the LPI-ARTICLE-1997-034.
TL;DR: In this article, the work functions of solid layers of various thicknesses of Dithioketopyrrolopyrrole (DTPP), evaporated on SnO2:F, were measured by the Kelvin probe technique.
Abstract: The work functions of solid layers of various thicknesses of dithioketopyrrolopyrrole (DTPP), evaporated on SnO2:F, were measured by the Kelvin probe technique. Surface photovoltage (SPV) measurements confirm the p-conductivity type. By front and back side illumination of the thick DTPP layers, two space-charge layers are distinguished, allocated to the air/DTPP and DTPP/SnO2:F interface, respectively. The SPV of thinner layers is a superposition of the front side signal and back side signal, modulated by a filter effect through the organic layer. This permitted the construction of the energy diagram of the DTPP/SnO2:F junction.
Journal Article•
TL;DR: In this paper, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12 for the LPI-ARTICLE-1997-019.
Abstract: Reference LPI-ARTICLE-1997-019View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
TL;DR: In this paper, a photochemical probe was used to determine the rate constant for a solubilizate molecule to escape from its parent micelle, where the quencher molecules for the excited probe are located exclusively outside of the micelle.
Abstract: A photochemical probe was used to determine the rate constant for a solubilizate molecule to escape from its parent micelle, where the quencher molecules for the excited probe are located exclusively outside of the micelle. Stern–Volmer kinetics of the solubilizates, naphthalene and pyrene, in dodecylammonium trifluoroacetate micelles were analyzed at 35°C in order to determine their exit (k-) and entry rate constants (k+) from and to the micelle. The ion Ag+, with the same charge as the micelle, was used as the quencher for the excited probes. The values of k- (k+) were determined to be 6.11×106 s-1 (2.25×1012 d mol-1 s-1) and 1.39×106 s-1 (1.51×1013 d mol-1 s-1) for naphthalene and pyrene, respectively, from analysis of the Stern–Volmer quenching ratio vs. the quencher concentration in micellar solutions. Analysis using the initial slope of the curve led to slightly lower values for the rate constants. The spontaneous decay rate constants for the excited probes in the aqueous bulk and solubilized in the micelles and the quenching rates of excited probes by the quencher were also determined from this analysis. The same experiments were also conducted with anthracene, but the final kinetic results were not discussed as they could not be readily explained.
TL;DR: In this paper, the electron transfer kinetics in dye-sensitized TiO2 films used in commercial photovoltaic devices were studied and the electron injection in these dye sensitized films occurs on an ultrafast time scale with two components, 150 fs and 1·2 ps.
Abstract: Sub-picosecond transient absorption study has been employed to study the electron transfer kinetics in the dye-sensitized TiO2 films used in commercial photovoltaic devices. The electron injection in these dye sensitized films occurs on an ultrafast time scale with two components, 150 fs and 1·2 ps.
01 Jan 1997
Patent•
13 Mar 1997
TL;DR: Dispositif electrochromes and photo-electrochromes as discussed by the authors utilisent des electrodes de semi-conducteur nanocristallin de haute surface specifique a la surface desquelles sont absorbees des molecules.
Abstract: Dispositif electrochromes et photoelectrochromes qui utilisent des electrodes de semi-conducteur nanocristallin de haute surface specifique a la surface desquelles sont absorbees des molecules electrochromes.