Showing papers by "Michael Grätzel published in 2004"
TL;DR: The dye-sensitized solar cell (DSC) as mentioned in this paper provides a technically and economically credible alternative concept to present day p-n junction photovoltaic devices, where light is absorbed by a sensitizer, which is anchored to the surface of a wide band gap oxide semiconductor.
Abstract: The dye-sensitized solar cell (DSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. In contrast to the conventional silicon systems, where the semiconductor assumes both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band gap oxide semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The use of sensitizers having a broad absorption band in conjunction with oxide films of nanocrystalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photon into electric current is achieved over a large spectral range extending from the UV to the near IR region. Overall solar (standard AM 1.5) to current conversion efficiencies of 10.6% have been reached. New electrolytes based on ionic liquids have been developed that show excellent stability both under prolonged light soaking and high temperature stress. There are good prospects to produce these cells at lower cost than conventional devices. Here we present the current state of the field, and discuss the importance of mastering the interface of the mesoporous films by assisting the self-assembly of the sensitizer at the surface of the oxide nanocrystals.
2,148 citations
TL;DR: In this article, the first ≥7% power conversion efficiencies under AM 1.5 sunlight have been achieved for photovoltaic devices with a binary ionic liquid electrolyte composed of 1-propyl-3methylimidazolium iodide and 1-ethyl-3-methyloride thiocyanate.
Abstract: For the first time ≥7% power conversion efficiencies under AM 1.5 sunlight have been acheived for photovoltaic devices with a binary ionic liquid electrolyte composed of 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium thiocyanate.
354 citations
TL;DR: A solvent-free ionic liquid electrolyte based on the SeCN-/(SeCN)3- redox couple has been employed for high-efficiency dye-sensitized nanocrystalline solar cells for the first time.
Abstract: A solvent-free ionic liquid electrolyte based on the SeCN-/(SeCN)3- redox couple has been employed for high-efficiency dye-sensitized nanocrystalline solar cells. For the first time an alternative ...
351 citations
TL;DR: In this paper, a new heteroleptic polypyridyl ruthenium complex with a high molar extinction coefficient has been synthesized and demonstrated to be a highly efficient, stable sensitizer for nanocrystalline dye-sensitized solar cells.
Abstract: A new heteroleptic polypyridyl ruthenium complex (see Figure) with a high molar extinction coefficient has been synthesized The complex is demonstrated to be a highly efficient, stable sensitizer for nanocrystalline dye-sensitized solar cells For a newly developed dye, the achievement of 102 % power conversion efficiency is very encouraging
323 citations
TL;DR: It is concluded that the primary factor controlling the charge recombination dynamics in dye-sensitized, nanocrystalline TiO2 films is the spatial separation of the dye cation from the electrode surface.
Abstract: In this paper we address the dependence of the charge recombination dynamics in dye-sensitized, nanocrystalline TiO2 films upon the properties of the sensitizer dye employed. In particular we focus upon dependence of the charge recombination kinetics upon the dye oxidation potential E0(D+/D), determined electrochemically, and the spatial separation r of the dye cation HOMO orbital from the metal oxide surface, determined by semiempirical calculations. Our studies employed a series of ruthenium bipyridyl dyes in addition to porphyrin and phthalocyanine dyes. A strong correlation is observed between the recombination dynamics and the spatial separation r, with variation in r by 3 A resulting in a more than 10-fold change in the recombination half-time t50%. This correlation is found to be in agreement with electron tunneling theory, t50% ∝ exp(−βr) with β = 0.95 ± 0.2 A-1. In contrast, the recombination dynamics were found to be relatively insensitive to variations in E0(D+/D), indicative of the recombinati...
322 citations
TL;DR: This poster presents a probabilistic procedure to characterize the response of the immune system to chemotherapy-like injuries to treat central giant cell granuloma.
Abstract: Reference LPI-ARTICLE-2004-029doi:10.1021/la0496082View record in Web of Science Record created on 2006-02-21, modified on 2016-08-08
278 citations
TL;DR: A [Ru(dcbpy)(2)(NCS)(2)] dye has been chemically modified by the addition of a secondary electron donor moiety, N,N-(di-p-anisylamino)phenoxymethyl, showing a remarkably long-lived charge- separated state.
Abstract: Reference LPI-ARTICLE-2004-002View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
212 citations
TL;DR: In this article, the adsorption of formate and acetate from aqueous solutions at pH 3−9 onto the TiO2 rutile (110) surface was studied by ATR-FTIR spectroscopy.
Abstract: The adsorption of formate and acetate from aqueous solutions at pH 3−9 onto the TiO2 rutile (110) surface was studied by ATR-FTIR spectroscopy. The spectra indicated that there was only one type of adsorbed species, and that formate and acetate were adsorbed in a similar manner. On the basis of the measured νas(COO) − νs(COO) splitting (Δνas-s) of 191 and 87 cm-1, for formate and acetate, respectively, the monodentate (ester type) binding mode could be excluded. Ab initio calculations at the Hartree−Fock level showed that for pentacoordinated TiIV, present in the (110) surface, the chelating bidentate binding mode is unstable with respect to the rearrangement to the monodentate or the bridging bidentate mode. The computed vibrational frequencies of formate and acetate adsorbed in a bridging bidentate mode onto Ti clusters with 2−5 Ti centers, representing the (110) surface, agreed with experiment and thus showed that this methodology can be used for the determination of the structures of adsorbates on, fo...
209 citations
TL;DR: Doping the molecular plastic crystal of succinonitrile with solid N-methyl-N-butylpyrrolidinium iodide salt and iodine has produced a highly conductive solid iodide/triiodide conductor that was employed for a highly efficient, all-solid-state dye-sensitized solar cell.
Abstract: Doping the molecular plastic crystal of succinonitrile with solid N-methyl-N-butylpyrrolidinium iodide salt and iodine has produced a highly conductive solid iodide/triiodide conductor. Furthermore, it was employed for a highly efficient, all-solid-state dye-sensitized solar cell.
195 citations
TL;DR: In this paper, the electrochemical properties of the redox mediator Co(III)/Co(II) in a mixed acetonitrile/ethylene carbonate solvent have been studied by a range of techniques in order to determine the rate constants for electron transfer and the diffusion coefficients of the Co(II/Co(III) species.
192 citations
TL;DR: The method is based upon an aluminum isopropoxide treatment of the monosensitized film prior to deposition of a second sensitizer, resulting in a suppression of interfacial charge recombination and a significantly improved photovoltaic device performance relative to single-layer co-sensitization devices.
Abstract: We report a method for achieving multilayer co-sensitization of nanocrystalline TiO2 films. The method is based upon an aluminum isopropoxide treatment of the monosensitized film prior to deposition of a second sensitizer. Appropriate selection of sensitizer dyes allows vectorial, multistep, electron transfer processes, resulting in a suppression of interfacial charge recombination and a significantly improved photovoltaic device performance relative to single-layer co-sensitization devices.
TL;DR: All the ligands and the complexes were characterized by analytical, spectroscopic, and electrochemical techniques and the performance of these complexes as charge-transfer photosensitizers in nanocrystalline TiO(2)-based solar cells was studied.
Abstract: Amphiphilic ligands 4,4'-bis(1-adamantyl-aminocarbonyl)-2,2'-bipyridine (L(1)), 4,4'-bis[5-[N-[2-(3beta-cholest-5-en-3-ylcarbamate-N-yl)ethyl]aminocarbonyl]]-2,2'-bipyridine (L(2)), 4,4'-bis[5-[N-[2-(3beta-cholest-5-en-3-ylcarbamate-N-yl)propyl]aminocarbonyl]]-2,2'-bipyridine (L(3)), and 4,4'-bis(dodecan-12-ol)-2,2'-bipyridine (L(4)) and their heteroleptic ruthenium(II) complexes of the type [Ru(II)LL(1)(NCS)(2)] (5), [Ru(II)LL(2)(NCS)(2)] (6), [Ru(II)LL(3)(NCS)(2)] (7), and [Ru(II)LL(4)(NCS)(2)] (8) (where L = 4,4'-bis(carboxylic acid)-2,2'-bipyridine) have been synthesized starting from dichloro(p-cymene)ruthenium(II) dimer. All the ligands and the complexes were characterized by analytical, spectroscopic, and electrochemical techniques. The performance of these complexes as charge-transfer photosensitizers in nanocrystalline TiO(2)-based solar cells was studied. When complexes 5-8 anchored onto a 12 + 4 microm thick nanocrystalline TiO(2) films, very efficient sensitization was achieved (85 +/- 5% incident photon-to-current efficiencies in the visible region, using an electrolyte consisting of 0.6 M butylmethylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butyl pyridine in 1:1 acetonitrile + valeronitrile). Under standard AM 1.5 sunlight, the complex 8 yielded a short-circuit photocurrent density of 17 +/- 0.5 mA/cm(2), the open-circuit voltage was 720 +/- 50 mV, and the fill factor was 0.72 +/- 0.05, corresponding to an overall conversion efficiency of 8.8 +/- 0.5%.
TL;DR: In this article, the authors demonstrate the usefulness of certain DBS derivatives as efficient gelators to form thermoreversible gels in electrolyte solutions which are of particular interest for solar cell applications.
Abstract: 1,3:2,4-Di-O-benzylidene-D-sorbitol (DBS) and its derivatives are efficient gelators to solidify organic solvents over a wide range of polarity. In this paper we demonstrate the usefulness of certain DBS derivatives as efficient gelators to form thermoreversible gels in electrolyte solutions which are of particular interest for solar cell applications. The adjustable, high sol–gel phase transition temperature of 1,3:2,4-di-O-dimethylbenzylidene-D-sorbitol (DMDBS) with a 3-methoxypropionitrile-based electrolyte made this particular organic gelator very attractive in dye sensitized solar cells. For example, with an amphiphilic ruthenium dye and a quasi-solid-state gel electrolyte system based on 1,3:2,4-di-O-dimethylbenzylidene-D-sorbitol/3-methoxypropionitrile, a stable overall solar energy conversion efficiency of 6.1% was achieved at AM 1.5 sunlight illumination (99.8 mW cm−2).
TL;DR: A new amphiphilic polypyridyl ruthenium complex, cis-Ru(dpbpy),dnbpy)(NCS)2, was synthesized and demonstrated as an efficient sensitizer as mentioned in this paper.
Abstract: A new amphiphilic polypyridyl ruthenium complex, cis-Ru(dpbpy)(dnbpy)(NCS)2 (dpbpy = 4,4‘-diphosphonic acid-2,2‘-bipyridine; dnbpy = 4,4‘-dinonyl-2,2‘-bipyridine), was synthesized and demonstrated as an efficient sensitizer. The sensitizer was characterized by NMR, voltammetry, ATR-FTIR, resonance Raman, as well as electronic absorption and emission spectra. Nanocrystalline dye-sensitized solar cells (DSCs) with this new sensitizer generated ≥8.0% power conversion efficiencies under illumination with simulated air mass 1.5 sunlight. This is the first time such a high solar-to-electricity power conversion efficiency for DSCs has been reached by a sensitizer bearing non-carboxylic acid anchoring groups. Additionally, the devices exhibited excellent stability under light soaking at 55 to 60 °C. Time-resolved nanosecond laser experiments revealed that the dye regeneration rate of this new sensitizer seems to be quite similar but the charge recombination is significantly slower in comparison to the analogues c...
TL;DR: In this article, a quasi-solid state electrolyte was used for regenerative phtoelectrochemical cells that yielded about 6.7% efficiency under simulated full sunlight (air mass 1.5, 100mW cm−2) in combination with an amphiphilic ruthenium polypyridyl photosensitizer.
TL;DR: In this paper, a novel family of room temperature ionic liquids, N,N-diethyl, N′,N′-dipropyl-N′′-hexyl-n′-methylguanidinium iodide (SGI) and SGTM were designed and synthesized.
Abstract: A novel family of room temperature ionic liquids, N,N-diethyl-N′,N′-dipropyl-N′′-hexyl-N′′-methylguanidinium iodide (SGI) and N,N,N′,N′-tetramethyl-N′′,N′′-dipentylguanidinium tricyanomethanide (SGTM) were designed and synthesized. Due to the strong charge delocalization on the tricyanomethanide anion and, thus, weaker ion-pairing, SGTM has a lower viscosity than SGI salt that has iodide as an anion. SGI was successfully used as an iodide resource for dye-sensitized nanocrystalline solar cells. The device with a solvent-free, SGI-based electrolyte achieved a 5.9% power conversion efficiency under an air mass 1.5 incident light of 9.47 mW/cm2.
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-2004-016.
Abstract: Reference LPI-ARTICLE-2004-016View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
TL;DR: In this paper, two heteroleptic polypyridyl ruthenium complexes [Ru(dcbpy)(L)(NCS)2] have been synthesized and characterized by elemental analysis, voltammetry, 1H NMR, UV−vis, ATR-FTIR, and resonance Raman spectroscopies.
Abstract: Two heteroleptic polypyridyl ruthenium complexes [Ru(dcbpy)(L)(NCS)2, where dcbpy is 4,4‘-dicarboxylic acid-2,2‘-bipyridine and L is N,N-di(2-pyridyl)-dodecylamine or N,N-di(2-pyridyl)-tetradecylamine] have been synthesized and characterized by elemental analysis, voltammetry, 1H NMR, UV−vis, ATR-FTIR, and resonance Raman spectroscopies. Resonance Raman studies have revealed that the lowest unoccupied molecular orbital (LUMO) of the two sensitizers is localized on the dcbpy-ligand-bearing anchoring group. Nanosecond laser transient measurements have shown that dye regeneration by iodide in the electrolyte can efficiently compete with the recombination reaction of injected electrons trapped in the nanocrystalline TiO2 film with dye molecules in the oxidized state. Furthermore, these amphiphilic ruthenium complexes were successfully used as sensitizers for nanocrystalline dye-sensitized solar cells with efficiencies of 8.2% at the 100 mW cm-2 irradiance of air mass 1.5 solar light and ≥8.7% at lower light i...
01 Jan 2004
TL;DR: In this paper, dye-sensitized solar cells (nc-DSC) have been explored in the field of new concepts and materials, fabrication protocols for TiO2 and scatterlayers, metal oxide blocking layers and low temperature processes of platinum deposition.
Abstract: Several areas are explored for dye-sensitized solar cells (nc-DSC) in the field of new concepts and materials, fabrication protocols for TiO2 and scatterlayers, metal oxide blocking layers and low temperature processes of platinum deposition. The combined efforts have led to maximum power conversion efficiencies under full sunlight of 11 % for areas 1 cm 2 .
TL;DR: Reference LPI-CONF-2005-033View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12 as discussed by the authors, created on 2016-06-12
Abstract: Reference LPI-CONF-2005-033View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12