Showing papers by "Michael Grätzel published in 2001"
Journal Article•
TL;DR: In this paper, the authors look into the historical background, and present status and development prospects for photoelectrochemical cells, based on nanocrystalline materials and conducting polymer films.
Abstract: Until now, photovoltaics - the conversion of sunlight to electrical power - has been dominated by solid-state junction devices, often made of silicon. But this dominance is now being challenged by the emergence of a new generation of photovoltaic cells, based, for example, on nanocrystalline materials and conducting polymer films. These offer the prospect of cheap fabrication together with other attractive features, such as flexibility. The phenomenal recent progress in fabricating and characterizing nanocrystalline materials has opened up whole new vistas of opportunity. Contrary to expectation, some of the new devices have strikingly high conversion efficiencies, which compete with those of conventional devices. Here I look into the historical background, and present status and development prospects for this new generation of photoelectrochemical cells.
8,305 citations
TL;DR: The black dye, when anchored to nanocrystalline TiO(2) films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE).
Abstract: 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...
2,477 citations
TL;DR: In this paper, the performance of dye-sensitized solar cells based on spiro-MeOTAD was improved by controlling charge recombination across the interface of the heterojunction.
Abstract: The performance of solid-state dye-sensitized solar cells based on spiro-MeOTAD was considerably improved by controlling charge recombination across the interface of the heterojunction. This was achieved by blending the hole conductor matrix with a combination of 4-tert-butylpyridine (tBP) and Li[CF3SO2]2N. Open circuit voltages Uoc over 900 mV and short circuit currents Isc up to 5.1 mA were obtained, yielding an overall efficiency of 2.56% at AM1.5 illumination. These values have been fully confirmed at the National Renewable Energy Laboratories for a device with an active area of 1.07 cm2, signifying a dramatic improvement compared to previously reported values for a similar device.
485 citations
TL;DR: In this paper, transient absorption spectroscopy was employed to study charge transfer dynamics in dye-sensitized nanocrystalline solar cells (DSSC) containing a new one-electron redox mediator, cobalt(II)-bis[2,6-bis(1‘)-butylbenzimidazol-2‘-yl)pyridine] Photovoltaic cells incorporating this relay have yielded light-toelectricity power conversion efficiencies of up to 52%
Abstract: Transient absorption spectroscopy was employed to study charge-transfer dynamics in dye-sensitized nanocrystalline solar cells (DSSC) containing a new one-electron redox mediator, cobalt(II)-bis[2,6-bis(1‘-butylbenzimidazol-2‘-yl)pyridine] Photovoltaic cells incorporating this relay have yielded light-to-electricity power conversion efficiencies of up to 52% This rivals the performance of the tri-iodide/iodide couple that is currently almost exclusively used in DSSC Interception of the dye oxidized state by electron transfer from the Co(II) complex in diluted electrolyte was found to follow a first-order kinetics with a rate constant of km = 5 × 105 s-1 Above a threshold of 10-2 M, under which the cationic relay is essentially adsorbed onto the negatively charged particle surface, larger concentrations of the reduced mediator resulted in a linear increase of the apparent rate, yielding a second-order rate constant of km‘‘ = 29 × 106 M-1 s-1 Dynamics of the recombination reaction between injected co
404 citations
TL;DR: In this article, the onset wavelengths of the surface photovoltage (SPV) in dye-sensitized solar cells (DSSCs) with different mesoporous, wideband gap electron conductor anode materials, viz., TiO2 (anatase), Nb2O5 (amorphous and crystalline), and SrTiO3, using the same Ru bis-bipyridyl dye for all experiments, are different.
Abstract: The onset wavelengths of the surface photovoltage (SPV) in dye-sensitized solar cells (DSSCs) with different mesoporous, wide-band gap electron conductor anode materials, viz., TiO2 (anatase), Nb2O5 (amorphous and crystalline), and SrTiO3, using the same Ru bis-bipyridyl dye for all experiments, are different. We find a clear dependence of these onset wavelengths on the conduction band edge energies (ECB) of these oxides. This is manifested in a blue-shift for cells with Nb2O5 and SrTiO3 compared to those with TiO2. The ECB levels of Nb2O5 and SrTiO3 are known to be some 200−250 meV closer to the vacuum level than that of our anatase films, while there is no significant difference between the optical absorption spectra of the dye on the various films. We, therefore, suggest that the blue shift is due to electron injection from excited-state dye levels above the LUMO into Nb2O5 and SrTiO3. Such injection comes about because, in contrast to what is the case for anatase, the LUMO of the adsorbed dye in the s...
329 citations
TL;DR: Materials that change their colour as a result of a simple electric potential could be key to a new generation of flat-screen displays, but the speed at which they undergo this change of hue has held them back, until now.
Abstract: Materials that change their colour as a result of a simple electric potential could be key to a new generation of flat-screen displays. But the speed at which they undergo this change of hue has held them back, until now.
280 citations
TL;DR: The dye-sensitized nanocrystalline solar cells (DYSC) as discussed by the authors are a promising alternative 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 semiconductor.
Abstract: The dye sensitized solar cells (DYSC) provides a technically and economically credible alternative concept to present day p-n junction photovoltaic devices. In contrast to the conventional 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 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 present concepts evolved in the context of research on mesoporous oxide semiconductor films prepared via a sol-gel process. The use of transition metal complexes having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photons into electric current is achieved over a large spectral range extending over the whole visible region. Overall solar (standard AM 1.5) to electric conversion efficiencies over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. The lecture will present the current state of the field. We shall discuss new concepts of the dye-sensitized nanocrystalline solar cell (DYSC) including solid heterojunction variants and analyze the perspectives for the future development of the technology into the next millennium.
251 citations
TL;DR: In this article, a photo-voltaic cell based on molecular light absorbers and mesoporous electrodes was developed, and the certified overall power conversion efficiency of the new solar cell for standard air mass 1.5 solar radiation stands presently between 10 and 11.
Abstract: Learning from the concepts used by green plants, we have developed a photo- voltaic cell based on molecular light absorbers and mesoporous electrodes. The sensitized nanocrystalline injection solar cell employs organic dyes or transition-metal complexes for spectral sensitization of oxide semiconductors, such as TiO 2, ZnO, SnO2, and Nb2O5. Mesoporous films of these materials are contacted with redox electrolytes, amorphous organ- ic hole conductors, or conducting polymers, as well as inorganic semiconductors. Light har- vesting occurs efficiently over the whole visible and near-IR range due to the very large inter- nal surface area of the films. Judicious molecular engineering allows the photoinduced charge separation to occur quantitatively within femtoseconds. The certified overall power conversion efficiency of the new solar cell for standard air mass 1.5 solar radiation stands presently between 10 and 11. The lecture will highlight recent progress in the development of solar cells for practical use. Advancement in the understanding of the factors that govern photovoltaic performance, as well as improvement of cell components to increase further its conversion efficiency will be discussed.
138 citations
TL;DR: In this article, thin layer electrodes of highly organized nanotextured anatase were prepared by hydrolysis of TiCl4 in the presence of poly(alkylene oxide) block copolymer, Pluronic P-123, acting as a structure-directing agent.
104 citations
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-2001-007.
87 citations
TL;DR: The Web of Science Record was created on 2006-02-21, modified on 2017-05-12 as discussed by the authors, and is used for the Web of Medicine Record (WORR).
Abstract: Reference LPI-ARTICLE-2001-006doi:10.1016/S1010-6030(01)00572-XView record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
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-2001-017.
Abstract: Reference LPI-ARTICLE-2001-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
TL;DR: In this article, a series of quaterpyridines as functionalized tetradentate ligands is described, allowing different solubilities, π-systems or grafting modes.
Patent•
29 Jul 2001
TL;DR: In this paper, the photocatalytic film of semiconducting iron oxide (Fe 2 O 3 ) was used for the direct cleavage of water with visible light into hydrogen and oxygen.
Abstract: The Photocatalytic film of semiconducting iron oxide (Fe 2 O 3 ), contains an n-dopant, or a mixture of n-dopants, or a p-dopant or a mixture of p-dopants. Electrode consists of a substrate, with one or more films or photocatalytic arrangements of film of semiconducting n-doped or p-doped iron oxide (Fe 2 O 3 ) e.g. on the surface of one side of the substrate or on the surface of different sides. The photoelectrochemical cell comprises electrodes with a film or with films of the n-doped or p-doped semiconducting iron oxide (Fe 2 O 3 ). The semiconducting iron oxide (Fe 2 O 3 ) film can be manufactured with a spray pyrolysis process or a sol gel process. The system for the direct cleavage of water with visible light, into hydrogen and oxygen the system comprises one or more of the photoelectrochemical cells with photocatalytic films. The system can be a tandem cell system, comprising the photoelectrochemical cell with the doped iron oxide (Fe 2 O 3 ) film.
Patent•
29 Jul 2001
TL;DR: In this article, the photocatalytic film of semiconducting iron oxide (Fe2O3) was used for the direct cleavage of water with visible light into hydrogen and oxygen.
Abstract: The Photocatalytic film of semiconducting iron oxide (Fe2O3), contains an n-dopant, or a mixture of n-dopants, or a p-dopant or a mixture of p-dopants. Electrode consists of a substrate, with one or more films or photocatalytic arrangements of film of semiconducting n-doped or p-doped iron oxide (Fe2O3) e.g. on the surface of one side of the substrate or on the surface of different sides. The photoelectrochemical cell comprises electrodes with a film or with films of the n-doped or p-doped semiconducting iron oxide (Fe2O3). The semiconducting iron oxide (Fe2O3) film can be manufactured with a spray pyrolysis process or a sol gel process. The system for the direct cleavage of water with visible light, into hydrogen and oxygen the system comprises one or more of the photoelectrochemical cells with photocatalytic films. The system can be a tandem cell system, comprising the photoelectrochemical cell with the doped iron oxide (Fe2O3) film.
TL;DR: Reference LPI-CHAPTER-2002-008View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12 as discussed by the authors, created on 2007-06-21
Abstract: Reference LPI-CHAPTER-2002-008View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12