Showing papers by "Michael Grätzel published in 2003"
TL;DR: A DSC with unprecedented stable performance under both thermal stress and soaking with light, matching the durability criteria applied to silicon solar cells for outdoor applications is shown, fostering widespread practical application of dye-sensitized solar cells.
Abstract: Dye-sensitized nanocrystalline solar cells (DSC) have received considerable attention as a cost-effective alternative to conventional solar cells. One of the main factors that has hampered widespread practical use of DSC is the poor thermostability encountered so far with these devices. Here we show a DSC with unprecedented stable performance under both thermal stress and soaking with light, matching the durability criteria applied to silicon solar cells for outdoor applications. The cell uses the amphiphilic ruthenium sensitizer cis-RuLL'(SCN)(2) (L = 4,4'-dicarboxylic acid-2,2'-bipyridine, L' = 4,4'-dinonyl-2,2'-bipyridine) in conjunction with a quasi-solid-state polymer gel electrolyte, reaching an efficiency of >6% in full sunlight (air mass 1.5, 100 mW cm(-2)). A convenient and versatile new route is reported for the synthesis of the heteroleptic ruthenium complex, which plays a key role in achieving the high-temperature stability. Ultramicroelectrode voltammetric measurements show that the triiodide/iodide couple can perform charge transport freely in the polymer gel. The cell sustained heating for 1,000 h at 80 degrees C, maintaining 94% of its initial performance. The device also showed excellent stability under light soaking at 55 degrees C for 1,000 h in a solar simulator (100 mW cm(-2)) equipped with a ultraviolet filter. The present findings should foster widespread practical application of dye-sensitized solar cells.
1,541 citations
TL;DR: For the first time silica nanoparticles were used to solidify ionic liquids and these ionic liquid-based quasi-solid-state electrolytes were successfully employed for regenerative photoelectrochemical cells that yielded 7% efficiency at AM 1.5 sunlight.
Abstract: For the first time silica nanoparticles were used to solidify ionic liquids. These ionic liquid-based quasi-solid-state electrolytes were successfully employed for regenerative photoelectrochemical cells that yielded 7% efficiency at AM 1.5 sunlight in combination with an amphiphilic ruthenium polypyridyl photosensitizer.
948 citations
TL;DR: In this article, the interaction between N3, N719, and N712 sensitizers with nanocrystalline TiO2 film was investigated by ATR-FTIR spectroscopy.
Abstract: FTIR spectra of [Ru(dcbpyH2)2(NCS)2] (N3), (Bu4N)2[Ru(dcbpyH)2(NCS)2] (N719), and (Bu4N)4[Ru(dcbpy)2(NCS)2] (N712) complexes measured as solid samples in photoacoustic mode display fine resolution of IR bands and exhibit differences between the cis and the trans carboxylic acid groups. The interaction between N3, N719, and N712 sensitizers with nanocrystalline TiO2 film was investigated by ATR-FTIR spectroscopy. The data show that these complexes are being anchored onto the TiO2 surface in bridging coordination mode using two out of their four carboxylic acid groups, which are trans to the NCS ligand. The effect of protons on both the short circuit photocurrent and the open circuit photovoltage of dye-sensitized nanocrystalline solar cells was scrutinized. For the standard electrolyte formulation employed and TiCl4 treated mesoporous TiO2 films, the monoprotonated form of the N3 dye exhibited superior power conversion efficiency under AM 1.5 sun compared to the four, two, and zero proton sensitizers.
716 citations
TL;DR: In this paper, dye-sensitized solar cells have been fabricated based on nanocrystalline TiO2 film derivatized with an amphiphilic polypyridyl ruthenium complex, cis-RuLL(SCN)2 as light-harvester and hexadecylmalonic acid (HDMA) as coadsorbent.
Abstract: Dye-sensitized solar cells have been fabricated based on nanocrystalline TiO2 film derivatized with an amphiphilic polypyridyl ruthenium complex, cis-RuLL‘(SCN)2 (L = 4,4‘-dicarboxylic acid-2,2‘-bipyridine, L‘ = 4,4‘-dinonyl-2,2‘-bipyridine), as light-harvester and hexadecylmalonic acid (HDMA) as coadsorbent. The cells generated a short-circuit photocurrent of 15.2 mA cm-2, an open-circuit photovoltage of 764 mV, and a total power conversion efficiency of 7.8% under simulated full sunlight (air mass 1.5, 100 mW cm-2). Co-grafting enhanced the photocurrent, photovoltage, and overall conversion efficiency considerably with respect to cells containing no HDMA. Devices showed a good stability under light soaking at 55 °C.
681 citations
TL;DR: In this article, an ionic liquid electrolyte composed of 1-methyl-3-propylimidazolium iodide, 1-ethyl-3]-dimethyl-polypyridyl ruthenium dicyanamide, and lithium iodide (LiI) was combined with an amphiphilic polypyrinyl-rushenium sensitizer to obtain a solar cell based on a solvent-free electrolyte that had an efficiency of 6.6% at an irradiance of air mass 1.5 and >7.1
Abstract: An ionic liquid electrolyte composed of 1-methyl-3-propylimidazolium iodide, 1-methyl-3-ethylimidazolium dicyanamide, and lithium iodide (LiI) was combined with an amphiphilic polypyridyl ruthenium sensitizer to obtain a solar cell based on a solvent-free electrolyte that had an efficiency of 6.6% at an irradiance of air mass 1.5 (AM 1.5, 100 mW cm -2 ) and >7.1% at lower light intensities. This is the first time such a high efficiency was obtained for dye-sensitized solar cells with pure ionic liquid electrolytes. A thin-layer electrochemical cell was used to determine the redox potential of sensitizers anchored on TiO 2 nanocrystalline film by square-wave voltammetry. Laser transient absorbance measurements revealed that a significant enhancement of the device efficiency, after adding LiI to the ionic liquid electrolyte, could be ascribed to an increase in the electron injection yield and dye regeneration rate.
617 citations
TL;DR: In this article, the authors studied the hole transport phase in a solid-state dye-sensitized solar cells employing spiro-MeOTAD [2,2‘7,7‘-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9‘ -spirobifluorene] as a hole-transportation phase.
Abstract: Solid-state dye-sensitized solar cells employing spiro-MeOTAD [2,2‘7,7‘-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9‘-spirobifluorene] as a hole transport phase were studied by intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy (IMVS) over a wide range of illumination intensity. The IMPS and IMVS responses provide information about charge transport and electron−hole recombination, respectively. For the range of light intensities investigated, the dynamic photocurrent response appears to be limited by the transport of electrons in the nanocrystalline TiO2 film rather than by the transport of holes in the spiro-MeOTAD. The diffusion length of electrons in the TiO2 was found to be 4.4 × 10-4 cm. This value was almost independent of light intensity as a consequence of the fact that the electron diffusion coefficient and the rate constant for electron−hole recombination both increase in the same way with light intensity (proportional to I00.64).
352 citations
TL;DR: A series of new cobalt complexes synthesized and evaluated as redox mediators for dye-sensitized nanocrystalline TiO(2) solar cells yielded incident photon-to-current conversion efficiencies (IPCE) of up to 80% and the one-electron-transfer redoxmediator performed best among the compounds investigated.
Abstract: A series of new cobalt complexes [Co(LLL)(2)X(2)] were synthesized and evaluated as redox mediators for dye-sensitized nanocrystalline TiO(2) solar cells. The structure of the ligand and the nature of the counterions were found to influence the photovoltaic performance. The one-electron-transfer redox mediator [Co(dbbip)(2)](ClO(4))(2) (dbbip = 2,6-bis(1'-butylbenzimidazol-2'-yl)pyridine) performed best among the compounds investigated. Photovoltaic cells incorporating this redox mediator yielded incident photon-to-current conversion efficiencies (IPCE) of up to 80%. The overall yield of light-to-electric power conversion reached 8 % under simulated AM1.5 sunlight at 100 W m(-2) intensity and more than 4% at 1000 W m(-2). Photoelectrodes coated with a 2 microm thick nanoporous layer and a 4 microm thick light-scattering layer, sensitized with a hydrophobic ruthenium dye, gave the best results.
314 citations
270 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-2003-015.
Abstract: Reference LPI-ARTICLE-2003-015doi:10.1149/1.1581262View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
262 citations
TL;DR: In this paper, a nanocomposite organic/inorganic gel electrolyte made by the sol−gel method was used to construct a TiO2 dye-sensitized quasi-solid-state solar cells.
Abstract: TiO2 dye-sensitized quasi-solid-state solar cells have been constructed by employing a nanocomposite organic/inorganic gel electrolyte made by the sol−gel method. The nanocomposite gel is based on silica while its organic subphase is a mixture of a surfactant (Triton X-100), an organic solvent (propylene carbonate), iodine, and 1-methyl-3-propylimidazoliumiodide, which is an ionic liquid (molten salt). The last two components produce a I3-/I- redox couple. Improved results were obtained by also adding N-methylbenzimidazole. Time-resolved luminescence quenching analysis, dark dc conductivity measurements, and cell efficiency measurements were used to determine the optimal composition of the gel for maximum cell efficiency, which in the present case was 5.4%.
213 citations
TL;DR: For the first time highest power conversion efficiencies are obtained for dye sensitized solar cells using a swift self-assembled procedure.
TL;DR: In this article, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12, with the purpose of improving the quality of the record.
Abstract: Reference LPI-ARTICLE-2003-026doi:10.1021/la034466hView record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
TL;DR: A new device, moving away from the traditional silicon design, shows promise and could revolutionise the way that electricity is produced from sunlight.
Abstract: The idea of producing electricity from sunlight is attractive, but in practice the technology to do so is expensive. A new device, moving away from the traditional silicon design, shows promise.
TL;DR: In this article, the resonant behavior of anatase (101) and (001) surfaces has been investigated using synchrotron photoemission spectroscopy, and the results show good general agreement with bulk band-structure calculations.
Abstract: The resonant behavior of anatase ${\mathrm{TiO}}_{2}$ (101) and (001) surfaces has been investigated using synchrotron photoemission spectroscopy. The data are compared with earlier photoemission work from rutile ${\mathrm{TiO}}_{2}(110)$ and calculations for bulk anatase in order to elucidate the degree of Ti-O hybridization in the valence band. The results for the (101) surface show good general agreement with bulk band-structure calculations. Deviations from the bulk band structure in the case of the (001) surface are attributed to the reconstruction of this surface. A small peak is observed at around 1 eV binding energy (relative to the Fermi energy) for both surfaces following the creation of surface defects (O vacancies), which is thought to arise from surface ${\mathrm{Ti}}^{3+}.$ The attenuation of this peak by gentle heating in ${\mathrm{O}}_{2}$ is attributed to healing of the surface O vacancies.
TL;DR: In this article, photoinduced electron injection from eosin Y into the conduction band of titanium dioxide was further scrutinized, as previous studies on the charge injection from xanthene dyes have led to diverging conclusions.
Abstract: Photoinduced electron injection from eosin Y into the conduction band of titanium dioxide was further scrutinized, as previous studies on the charge injection from xanthene dyes have led to diverging conclusions. Eosin-sensitized TiO2 constitutes in many aspects a model system for studying the dynamics of charge injection: Adsorption of the sensitizer onto the oxide surface through electrostatic interaction and hydrogen bonding make this system exemplary of the weak electronic coupling case. The formation of dimeric eosin on the surface of metal oxide nanoparticles in an aqueous suspension was inferred from the study of the deactivation of the dye's singlet excited state on insulating particles, such as ZrO2 and Al2O3, and of the formation of the resulting radical ion pair, using femtosecond stimulated emission and transient absorption. It was found that dimers undergo ultrafast dismutation with a time constant of 500 fs. The same process occurs also on TiO2 particles and results in a competition between...
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-2003-013.
TL;DR: This poster presents a probabilistic simulation of the response of the immune system to laser-spot assisted, 3D image recognition technology and its applications in wound healing and sports medicine.
Abstract: Reference LPI-ARTICLE-2003-027doi:10.1126/science.1085119View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
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, with the purpose of improving the quality of the record.
Abstract: Reference LPI-ARTICLE-2003-027doi:10.1126/science.1085119View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
01 Jan 2003
08 Dec 2003
TL;DR: In this paper, a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs is given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions.
Abstract: The electron transfer (ET) from organic dye molecules to semiconductor-colloidal systems is characterized by a special energetic situation with a charge transfer reaction from a system of discrete donor levels to a continuum of acceptor states. If these systems show a strong electronic coupling they are amongst the fastest known ET systems with transfer times of less than 10 fs. In the first part a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs will be given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions. In a second part we will try to give a simple picture for the scenario of such superfast ET reactions and one main focus will be the discussion of electronic dephasing and its consequences for the ET reaction. We show that the actual ET process can be understood as a kind of dispersion process of the initially located electron into the colloid representing a real motion of charge density from the alizarin to the colloid.
01 Jan 2003
TL;DR: In this article, a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs is given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions.
Abstract: The electron transfer (ET) from organic dye molecules to semiconductor-colloidal systems is characterized by a special energetic situation with a charge transfer reaction from a system of discrete donor levels to a continuum of acceptor states. If these systems show a strong electronic coupling they are amongst the fastest known ET systems with transfer times of less than 10 fs. In the first part a detailed discussion of the direct observation of an ET reaction with a time constant of about 6 fs will be given, with an accompanying argumentation concerning possible artifacts or other interfering signal contributions. In a second part we will try to give a simple picture for the scenario of such superfast ET reactions and one main focus will be the discussion of electronic dephasing and its consequences for the ET reaction. We show that the actual ET process can be understood as a kind of dispersion process of the initially located electron into the colloid representing a real motion of charge density from the alizarin to the colloid.