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.

Temperature-Dependent Ordering Phenomena of a Polyiodide System in a Redox-Active Ionic Liquid

Abstract: Iodine added to iodide-based ionic liquids leads to dramatic changes of their physical properties which may have implications for technological applications. Here we study the phase diagram of 1-methyl-3-propylimidazolium iodide, the temperature versus iodine (I2) concentration. Above a threshold I2 concentration of 3.9 M, polyiodides are found to be the major determinant of the thermodynamic properties, where nucleation occurs at reduced temperatures leading to a crystalline phase followed by a nematic phase. At the highest concentrations and for increasing temperatures a phonon mode develops which gives indication of mesophases with both improved orientational order of the polyiodide chains and a degree of positional order close to melting. These novel results are important for the fundamental understanding of the physical properties in molten salts and for applications where ionic liquids are used as charge-transporting media such as in batteries and dye-sensitized solar cells.

Organometal halide perovskite photovoltaics: a diamond in the rough

Abstract: The sun finds a diamond in the rough, which is the organo-metal halide perovskite. Thanks to exceptional optoelectronic characteristics, solar cells employing perovskite demonstrated first a power conversion efficiency (PCE) of 9.7% in the middle of 2012, which rose steeply to an amazing 16% at the end of 2013. Perovskite-based photovoltaics have several advantages over conventional semiconductor p-n junction devices because high efficiency can be achieved from sub-micrometer-thick very cheap perovskite layers that can be formed by solution processing at temperatures below 150°C, rendering the perovskite solar cell versatile in its application. If photo- and thermal stability as well as tolerance to humidity can be achieved, commercial application on the large scale appear to be feasible.

High‐Surface‐Area Porous Platinum Electrodes for Enhanced Charge Transfer

Abstract: Cobalt-based electrolytes are highly tunable and have pushed the limits of dye-sensitized solar cells, enabling higher open-circuit voltages and new record efficiencies. However, the performance of these electrolytes and a range of other electrolytes suffer from slow electron transfer at platinum counter electrodes. High surface area platinum would enhance catalysis, but pure platinum structures are too expensive in practice. Here, a material-efficient host-guest architecture is developed that uses an ultrathin layer of platinum deposited upon an electrically conductive scaffold, niobium-doped tin oxide (NTO). This nanostructured composite enhances the counter electrode performance of dye-sensitized solar cells (DSCs) using a (CoBPY3)-B-(II/III) electrolyte with an increased fill factor and power conversion efficiency (11.26%), compared to analogous flat films. The modular strategy is elaborated by integrating a light scattering layer onto the counter electrode to reflect unabsorbed light back to the photoanode to improve the short-circuit current density and power conversion efficiency.

Nondestructive Probing of Perovskite Silicon Tandem Solar Cells Using Multiwavelength Photoluminescence Mapping

Abstract: In this paper, spatially resolved photoluminescence (PL) spectroscopy with various excitation wavelengths is presented as a nondestructive and versatile technique providing access to the individual subcells of multijunction solar cells. This method is demonstrated on a state-of-the-art monolithic tandem solar cell composed of a planar perovskite solar cell and a silicon heterojunction solar cell. It is shown that the lateral distribution of inhomogeneities can be attributed unambiguously to the individual cells and be related to the manufacturing process. The approach of depth-selective probing of the silicon bottom cell is verified by comparison to reflection maps and by comparison to measurements of the silicon cell after removing the perovskite top cell. Analyzing subcells integrated into a monolithic tandem solar cell is challenging though crucial in order to identify performance limiting loss mechanisms. This method can be used to improve the study of the mutual influence of adjacent subcells in the fully fabricated device, which has been an unfeasible task up to now.

Process for manufacturing an electrode for an electrochemical device

Abstract: The present invention aims at improving the catalytic activity of the metallic platinum deposited on the substrate of the counterelectrode (i.e. the cathode), so as to obtain a high value of the catalytic activity on the reduction reaction of triiodide to iodide essentially independant of the nature of the solvent used in the electrolyte. To that effect, the manufacturing process according to the invention is characterized in that said metallic platinum is deposited in the form of a plurality of spheroidal microcrystallite clusters each having a size of less than about 100 nanometers, dispersed over the surface of said substrate, and in that said deposited metallic platinum is submitted to a thermal treatment, carried out at a temperature in the range of about 375 to 400 °C, so as to enhance the catalytic properties of the platinum on the oxido-reduction reaction of iodine and triiodide 3I2 + 2e- ⇐∊ 2I?3?- in the redox system iodine/iodide.

I and i

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 …

Fast parallel algorithms for short-range molecular dynamics

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.

A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films

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.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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。

Environmental Applications of Semiconductor Photocatalysis

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.