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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
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Journal ArticleDOI
TL;DR: In this paper, the first comprehensive comparative synthetic, structural, electrochemical, and spectroscopic study of an extended series of fluorocarbon-modified iridium(III) complexes is presented.

43 citations

Journal ArticleDOI
TL;DR: It is shown that a non-exponential dependence of capacitance, transport resistance, and recombination resistance on photovoltage can be interpreted as evidence for partial unpinning of the TiO2 energy levels, and the nature of the sensitizing dye determines the predominant recombination route.
Abstract: Dye-sensitized solar cells (DSCs) employing the [Co(bpy)3]3+/2+ redox mediator have recently attained efficiencies in excess of 12%, increasing the attractiveness of DSCs as an alternative to conventional photovoltaics. Heterogeneous electron transfer from dye-sensitized nanocrystalline TiO2 to [Co(bpy)3]3+ ions in solution, a process known as recombination in the context of DSC operation, is an important loss mechanism in these solar cells. Here, we employ impedance spectroscopy over a range of temperatures to characterize electron storage, transport, and recombination in efficient DSCs based on the [Co(bpy)3]3+/2+ redox mediator, with either the amphiphillic ruthenium sensitizer Z907 or the state-of-the-art organic sensitizer Y123. The temperature dependence of the electron-transport resistance indicates that transport occurs via states at energies lower than commonly assumed for the TiO2 conduction band edge. We show that a non-exponential dependence of capacitance, transport resistance, and recombinat...

43 citations

Journal ArticleDOI
TL;DR: In this paper, an ionic liquid electrolyte formulation using sulfolane as a plasticizer for eutectic melts is proposed to realize highly stable and efficiently performing dye-sensitized solar cells (DSCs) in hot climate conditions.
Abstract: Ionic liquid electrolytes are prepared using sulfolane as a plasticizer for eutectic melts to realize highly stable and efficiently performing dye-sensitized solar cells (DSCs) in hot climate conditions. Variations in the viscosity of the formulations with sulfolane content are measured and performance in DSCs is investigated using the ruthenium dye C106 as a sensitizer. A power conversion efficiency (PCE) of 8.2% is achieved under standard reporting conditions. Apart from lowering the viscosity, the addition of sulfolane induces a negative shift of the TiO2 conduction band edge. Strikingly the device performance increases to 8.4% at 50 degrees C due to higher short circuit photocurrent and fill factor, over-compensating the loss in open circuit voltage with increasing temperature. The PCE increases also upon decreasing the light intensity of the solar simulator, reaching up to 9% at 50 mW cm(-2). Devices based on these new electrolyte formulations show excellent stability during light soaking for 2320 h under full sunlight at 60 degrees C and also during a 1065 h long heat stress at 80 degrees C in the dark. A detailed investigation provides important information about the factors affecting the principal photovoltaic parameters during the aging process and the first results from a series of outdoor measurements are reported.

43 citations

Journal ArticleDOI
TL;DR: This work introduces thermal annealing as a powerful tool to generate a well-controlled excess of PbI2 in the perovskite formulation and shows that this benefits the photovoltaic performance.
Abstract: Despite the rapid increase in the performance of perovskite solar cells (PSC), they still suffer from low lab-to-lab or people-to-people reproducibility. Aiming for a universal condition to high-performance devices, we investigated the morphology evolution of a composite perovskite by tuning annealing temperature and precursor concentration of the perovskite film. Here, we introduce thermal annealing as a powerful tool to generate a well-controlled excess of PbI2 in the perovskite formulation and show that this benefits the photovoltaic performance. We demonstrated the correlation between the film microstructure and electronic property and device performance. An optimized average grain size/thickness aspect ratio of the perovskite crystallite is identified, which brings about a highly reproducible power conversion efficiency (PCE) of 19.5 %, with a certified value of 19.08 %. Negligible hysteresis and outstanding morphology stability are observed with these devices. These findings lay the foundation for further boosting the PCE of PSC and can be very instructive for fabrication of high-quality perovskite films for a variety of applications, such as light-emitting diodes, field-effect transistors, and photodetectors.

43 citations


Cited by
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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