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.

Cationic Iridium(III) Complexes with Two Carbene-Based Cyclometalating Ligands: Cis Versus Trans Isomers

Abstract: A series of cationic iridium(III) complexes with two carbene-based cyclometalating ligands and five different N^N bipyridine and 1,10-phenanthroline ancillary ligands is presented. For the first time—in the frame of a rarely studied class of bis(heteroleptic) iridium complexes with two carbene-based cyclometalating ligands—a pair of cis and trans isomers has been isolated. All complexes (trans-1–5 and cis-3) were characterized by 1H NMR, 13C NMR, 31P NMR, and HRMS (ESI-TOF); in addition, crystal structures of cis-3 and trans-4 are reported and discussed. Cyclic voltammetric studies show that the whole series exhibits highly reversible oxidation and reduction processes, suggesting promising potential for optoelectronic applications. Ground-state DFT and TD-DFT calculations nicely predict the blue shift experimentally observed in the room-temperature absorption and emission spectra of cis-3, compared to the trans complexes. In CH3CN, cis-3 displays a 4-fold increase in photoluminescence quantum yield (PLQY)...

Computational Characterization of the Dependence of Halide Perovskite Effective Masses on Chemical Composition and Structure

Abstract: Effective masses are calculated for a large variety of perovskites of the form ABX3 differing in chemical composition (A= Na, Li, Cs; B = Pb, Sn; X= Cl, Br, I) and crystal structure. In addition, the effects of some defects and dopants are assessed. We show that the effective masses are highly correlated with the energies of the valence-band maximum, conduction-band minimum, and band gap. Using the k·p theory for the bottom of the conduction band and a tight-binding model for the top of the valence band, this trend can be rationalized in terms of the orbital overlap between halide and metal (B cation). Most of the compounds studied in this work are good charge-carrier transporters, where the effective masses of the Pb compounds (0 < mh* < me* < 1) are systematically larger than those of the Sn-based compounds (0 < mh* ≈ me* < 0.5). The effective masses show anisotropies depending on the crystal symmetry of the perovskite, whether orthorhombic, tetragonal, or cubic, with the highest anisotropy for the tetr...

In situ growth of graphene on both sides of a Cu–Ni alloy electrode for perovskite solar cells with improved stability

Abstract: The instability of rear electrodes undermines the long-term operational durability of efficient perovskite solar cells. Here, a composite electrode of copper–nickel (Cu–Ni) alloy stabilized by in situ grown bifacial graphene is designed. The alloying makes the work function of Cu suitable for regular perovskite solar cells. Cu–Ni is the ideal substrate for preparing high-quality graphene via chemical vapour deposition, which simultaneously protects the device from oxygen, water and reactions between internal components. To rivet the composite electrode with the semi-device, a thermoplastic copolymer is applied as an adhesive layer through hot pressing. The resulting devices achieve power conversion efficiencies of 24.34% and 20.76% (certified 20.86%) with aperture areas of 0.09 and 1.02 cm2, respectively. The devices show improved stability: 97% of their initial efficiency is retained after 1,440 hours of a damp-heat test at 85 °C with a relative humidity of 85%; 95% of their initial efficiency is retained after 5,000 hours at maximum power point tracking under continuous 1 sun illumination. The instability of contact layers for perovskite solar cells under operating conditions limits the deployment of the technology. Now, Lin et al. develop a Cu–Ni electrode sandwiched between in situ-grown graphene protective layers, enabling solar cells with improved stability under light, humidity and high temperature.

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.