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.

A New Heteroleptic Ruthenium Sensitizer for Transparent Dye-Sensitized Solar Cells

Abstract: A new heteroleptic ruthenium complex, coded CYC-B19, incorporating an ancillary ligand endowed with hexylthio-bithiophene segments and a conjugated anchoring ligand with vinyl groups was prepared. This new sensitizer exhibits a lower energy MLCT band centred at 562 nm with a remarkably high molar absorption coefficient of 2.97 x 104 M-1 cm-1. DFT-TDDFT theoretical calculation revealed that insertion a vinyl group in the anchoring ligand pushes the LUMO electron locating more on the anchoring ligand. This will benefit the electron transfer from dye to TiO2 when the dye molecules were excited by light. Physicochemical measurements and the optimization of electrolyte were done to investigate the potential of CYC-B19 in TiO2 scattering-layer free dye-sensitized solar cells. Not only is a good photovoltaic efficiency of 8.4% reached, but the transparent device sensitized by CYC-B19 also presents a superior spectral response to its predecessor CYC-B11.

Cyclopentadithiophene-Based Hole-Transporting Material for Highly Stable Perovskite Solar Cells with Stabilized Efficiencies Approaching 21%

Abstract: There is an urge to develop new hole-transporting materials (HTMs) for perovskite solar cells (PSCs), which can yield comparable power conversion efficiencies (PCEs) yet mitigate the issue of stability associated with the state-of-the-art HTM Spiro-MeOTAD Herein, we designed and prepared C-2v-symmetric spiro-configured HTM-1 comprising a central acridine-cyclopentadithiophene core unit flanked with triarylamine moieties PSCs containing a 40 nm thin HTM-1 layer for hole extraction yielded a stabilized PCE approaching 21% under standard illumination Owing to its higher hole mobility (mu(h)) at low electric field, an impressive short-circuit current density (J(SC)) of 247 mA cm(-2) and a high fill factor (FF) of 077 have been achieved More importantly, HTM-1-based PSCs presented an excellent long-term operational stability under continuous illumination for 400 h and thermal stability at 80 degrees C, which can be ascribed to its high glass transition temperature of 168 degrees C and superior moisture tolerance Arguably, the confluence of high performance and remarkable stability will lead to the development of technologically interesting new, stable, and efficient PSCs

Peripherally and Axially Carboxylic Acid Substituted Subphthalocyanines for Dye-Sensitized Solar Cells

Abstract: A series of subphthalocyanines (SubPcs) bearing a carboxylic acid group either at the peripheral or axial position have been designed and synthesized to investigate the influence of the COOH group positions on the dye-sensitized solar cell (DSSC) performance. The DSSC devices based on SubPcs with axially substituted carboxylic acid groups showed low photovoltaic performance, whereas peripherally substituted one exhibited higher power conversion efficiency owing to improved injection from LUMO of SubPcs to the TiO2 conduction band.

Influence of cations of the electrolyte on the performance and stability of dye sensitized solar cells

Abstract: The electrolyte is one of the key components for DSC and its properties have great influence on the photo-conversion efficiency and stability of the devices. Five new low volatile electrolytes containing 3-methoxypropionitrile (MPN) as solvent were prepared with different cationic structures of the iodide source to evaluate their photovoltaic performance in dye-sensitized solar cells. We are interested in studying the role of cations in the device performance and selected the cations of iodide salts such as 1,3-dimethylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1-ethyl-1-methylpyrrolidinium, tetrabutylammonium and 1-propylpyridinium for comparison. These electrolytes are characterized by measuring the triiodide diffusion coefficients using both electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. In combination with the Ruthenium C106 dye these newly developed electrolytes show an initial power conversion efficiency between 8 and 9% under full sunlight at AM1.5G conditions. The DSC devices prepared with these electrolytes subjected to prolonged aging under full sunlight at 60 °C showed excellent stability. EIS has been employed to characterize the photovoltaic parameter variations observed during the durability tests.

Effect of bulky groups in ruthenium heteroleptic sensitizers on dye sensitized solar cell performance

Abstract: Two novel heteroleptic ruthenium sensitizers, TT204 and TT205, containing bulky substituents at the 4,4-positions of the ancillary 2,2-bipyridine ligand, were synthesized and characterized. They exhibit absorption maxima in the visible region at 520–530 nm due to metal-to-ligand charge transfer (MLCT) transitions. The EHOMO and ELUMO values indicate sufficient driving force for efficient dye regeneration by the iodide/tri-iodide redox electrolyte and efficient electron injection into the TiO2 conduction band following photoexcitation, respectively. The performance of these heteroleptic sensitizers in dye sensitized solar cells was investigated where TiO2 sensitization was carried out both in the presence and absence of chenodeoxycholic acid. The best efficiency among these sensitizers was recorded in the presence of chenodeoxycholic acid which generated a high short circuit current of 18.7 mA cm−2, an open circuit potential of 0.72 V and a fill factor of 73% with a resulting total power conversion efficiency of 9.81% under AM 1.5G 1 sun illumination. Comparison with the reference dye C101 indicates that though bulky groups can prevent aggregation resulting in high photocurrents even in the absence of chenodeoxycholic acid, they can also lead to lower cell voltages due to inefficient dye packing on the TiO2 surface.

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.