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.

Pyridyl- and Picolinic Acid Substituted Zinc(II) Phthalocyanines for Dye-Sensitized Solar Cells.

Abstract: A series of tri-tert-butyl zinc(II) phthalocyanines (Pcs) substituted with pyridyl, carboxyl, or picolinic acid anchoring groups on the periphery were prepared. Photovoltaic (PV) studies on these dyes were carried out revealing some interesting features. In the case of the pyridyl-substituted Pcs, the PV properties were found to depend strongly on the the pyridyl substitution pattern (meta or para) and the number of pyridyl units at the macrocycle's periphery (one or two). For these four pyridyl-substituted Pcs, higher photovoltaic efficiencies were obtained for 1) the para- versus the meta-substituted Pcs, and 2) the mono- versus the bis-functionalized dyes. In order to improve the poor adsorption of the pyridyl-substituted Pcs onto TiO2 , a new dye was tested bearing a picolinic acid unit. This moiety combines a carboxylic acid function, as a strong anchoring group for binding to TiO2 , with an electron-withdrawing nitrogen atom for better electron injection into the semiconductor's conduction band. For this latter system, an improvement in the PV efficiency up to 2.1 % was obtained.

Efficient and Stable Large Bandgap MAPbBr3 Perovskite Solar Cell Attaining an Open Circuit Voltage of 1.65 V

Abstract: We report on the preparation of MAPbBr3 perovskite films of high electronic quality by applying a methylamine (MA) vapor treatment and mitigating surface defects using the amphiphilic molecular passivator, neopentylammonium chloride (NPACl). We find that post-treatment of MAPbBr3 with methylamine (MA) vapor effectively smooths the surface of the perovskite, eliminating unwanted corrugations and producing phase-pure pinhole free films. The subsequent coating of MAPbBr3 with NPACl eliminates deleterious surface states that act as electron–hole recombination centers while enhancing the resilience of the perovskite solar cell (PSC) against heat stress and ambient moisture, with solid state NMR demonstrating their atomic-scale interaction. As a result, we achieve an unprecedented Voc of 1.65 V which is a record level for mesoporous single junction PSCs together with a power conversion efficiency (PCE) of over 10% in standard AM 1.5 sunlight. The PSC also retains 91.3% of its initial performance after 1100 h of light soaking under full sunlight and at 60 °C while maintaining the device at maximum power point. In contrast, the pristine PSC maintained only 34% of its initial efficiency under the same aging conditions.

New Insights into the Interface of Electrochemical Flow Cells for Carbon Dioxide Reduction to Ethylene

Abstract: The implementation of an electrochemical flow cell has enabled improved efficiency for CO2 reduction. However, in situ spectroscopic insights into the interface are still lacking. Here, we investigate a series of copper layers with different thicknesses on gas diffusion electrodes as a benchmark, with the best-performing one showing a Faradaic efficiency of 59.5% and a partial current density of -170 mA cm-2 for ethylene formation in 1 M KOH at -0.70 V against a reversible hydrogen electrode. By comparing the geometric as well as specific current density for ethylene on four Cu catalysts with different thicknesses, we illustrate the effects of bulk pH, local pH, and diffusion of CO2 on C-C coupling. We also reveal that the flexible rotation of the Cu-C bond of the *CO intermediate adsorbed on Cu, as shown by in situ Raman spectroscopy, is likely to be the key factor for efficient C-C coupling in a flow cell.

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.