scispace - formally typeset
Search or ask a question
Author

Michael Grätzel

Bio: Michael Grätzel is an academic researcher from École Polytechnique Fédérale de Lausanne. The author has contributed to research in topics: Dye-sensitized solar cell & Perovskite (structure). The author has an hindex of 248, co-authored 1423 publications receiving 303599 citations. Previous affiliations of Michael Grätzel include University of California, Berkeley & Siemens Energy Sector.


Papers
More filters
Journal ArticleDOI
TL;DR: The photoelectron spectroscopy studies indicate that the ligands of the ruthenium complex, containing thiophene groups, point out away from the surface of TiO(2) in comparison with the NCS group.
Abstract: The use of mixed self-assembled monolayers, combining hydrophobic co-adsorbents with the sensitizer, has been demonstrated to enhance the efficiency of dye-sensitized solar cells (DSCs). Herein, the influence of the anchoring groups of the co-adsorbents on the performance of the DSCs is carefully examined by selecting two model molecules: neohexyl phosphonic acid (NHOOP) and bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP). The effect of these co-adsorbents on the photovoltaic performance (J–V curves, incident photon-to-electron conversion efficiency) is investigated. Photoelectron spectroscopy and electrochemical impedance spectroscopy are performed to assess the spatial configuration of adsorbed dye and co-adsorbent molecules. The photoelectron spectroscopy studies indicate that the ligands of the ruthenium complex, containing thiophene groups, point out away from the surface of TiO2 in comparison with the NCS group.

27 citations

Journal ArticleDOI
TL;DR: The 3,4-ethylenedioxythiophene (EDOT) π-bridge is one of the most commonly used building blocks for sensitizers in dye-sensitized solar cells (DSSCs) as discussed by the authors.
Abstract: The 3,4-ethylenedioxythiophene (EDOT) π-bridge is one of the most commonly used building blocks for sensitizers in dye-sensitized solar cells (DSSCs). We investigated its influence on the molecular structure, the photophysical and electrochemical properties compared to a cyclopentadithiophene (CPDT) π-bridge in two pyrido[3,4-b]pyrazine featured D–A–π–A dyes SH3 (CPDT π-bridge) and SH4 (EDOT π-bridge). Surprisingly SH4 with EDOT as a π-bridge exhibited not only poor absorptivity but also inferior photovoltaic performance. On the contrary, SH3 achieved more than 5% power conversion efficiency under standard AM1.5G illumination at 100 mW cm−2 when employed in both solid state and liquid state DSSCs. Theoretical calculations suggested a significant twist in the molecular configuration between EDOT and carboxylic acid. We attributed it to the interaction between the O atom of EDOT and the H atom of alkene as well as the repulsion between the O atoms of EDOT and the carbonyl group of the carboxylic acid, which could retard the intramolecular charge transfer process. Consequently, this rotation in the molecule decreases the molar extinction coefficient and increases charge recombination. Electrochemical impedance spectroscopy results showed enhanced charge recombination in DSSC devices based on SH4, undermining the charge collection efficiency and the power conversion efficiency compared to SH3. Herein the detrimental effect of tilting the dye structure is isolated from the other characteristics of the dye, showing its importance as a general design strategy for new dyes.

27 citations

Journal ArticleDOI
TL;DR: In this article, a carboxyvinyl-pyrazolate sensitizer, TFRS-11TFRS-13, was proposed for dye-sensitized solar cells.
Abstract: A new class of thiocyanate-free Ru(II) sensitizers with 4,4-dicarboxyvinyl-2,2-bipyridine anchor and two trans-oriented pyrid-2-yl pyrazolate (or triazolate) functional chromophores is synthesized, characterized, and evaluated in dye-sensitized solar cells (DSCs). Despite their enhanced red response and absorptivity when compared to the parent sensitizer TFRS-2 that possesses standard 4,4-dicarboxyl-2,2-bipyridine anchor and shows the best conversion efficiency of = 9.82%, the newly synthesized carboxyvinyl-pyrazolate sensitizers, TFRS-11TFRS-13, exhibit inferior performance characteristics in terms of short-circuit current density (JSC), open-circuit voltage (VOC), and power conversion efficiency (), the latter being recorded to be in the range 5.607.62%. The reduction in device efficiencies is attributed to a combination of poor packing of these sensitizers on the TiO2 surface and less positive ground-state oxidation potentials, which, respectively, increase charge recombination with I3 in electrolytes and impede the regeneration of sensitizers by I anions. The latter obstacle can be circumvented in part by the replacement of the pyrazolates with triazolates, forming the TFRS-14 sensitizer, which exhibits an improved JSC, VOC, and of 16.4 mAcm2, 0.77 V, and 9.02%, respectively.

27 citations


Cited by
More filters
Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
24 Oct 1991-Nature
TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

26,457 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: The slow pace of hazardous waste remediation at military installations around the world is causing a serious delay in conversion of many of these facilities to civilian uses as discussed by the authors, which is a serious problem.
Abstract: The civilian, commercial, and defense sectors of most advanced industrialized nations are faced with a tremendous set of environmental problems related to the remediation of hazardous wastes, contaminated groundwaters, and the control of toxic air contaminants. For example, the slow pace of hazardous waste remediation at military installations around the world is causing a serious delay in conversion of many of these facilities to civilian uses. Over the last 10 years problems related to hazardous waste remediation have emerged as a high national and international priority.

17,188 citations