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Institution

École Polytechnique Fédérale de Lausanne

FacilityLausanne, Switzerland
About: École Polytechnique Fédérale de Lausanne is a facility organization based out in Lausanne, Switzerland. It is known for research contribution in the topics: Population & Catalysis. The organization has 44041 authors who have published 98296 publications receiving 4372092 citations. The organization is also known as: EPFL & ETHL.


Papers
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Journal ArticleDOI
28 Jul 2014-ACS Nano
TL;DR: The fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties are reported, finding that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency.
Abstract: We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room temperature on/off current ratio of similar to 10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as similar to 140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices.

615 citations

Journal ArticleDOI
TL;DR: PPS nanoparticles of 20-45nm have the potential for immunotherapeutic applications that specifically target DCs in lymph nodes, and an increase in nanoparticle-containing DCs (and other APCs) was seen at 96h vs. 24h, suggesting an infiltration of these cells to lymph nodes.

613 citations

Journal ArticleDOI
TL;DR: The IBM SU-8 resist as discussed by the authors is an epoxy-based resist designed specifically for ultrathick, high-aspect-ratio MEMS-type applications and it has been shown that with single-layer coatings, thicknesses of more than 500 μm can be achieved reproducibly.
Abstract: Detailed investigations of the limits of a new negative-tone near-UV resist (IBM SU-8) have been performed. SU-8 is an epoxy-based resist designed specifically for ultrathick, high-aspect-ratio MEMS-type applications. We have demonstrated that with single-layer coatings, thicknesses of more than 500 μm can be achieved reproducibly. Thicker resist layers can be made by applying multiple coatings, and we have achieved exposures in 1200 μm thick, double-coated SU-8 resist layers. We have found that the aspect ratio for near-UV (400 nm) exposed and developed structures can be greater than 18 and remains constant in the thickness range between 80 and 1200 μm. Vertical sidewall profiles result in good dimensional control over the entire resist thickness. To our knowledge, this is the highest aspect ratio reported for near-UV exposures and the given range of resist thicknesses. These results will open up new possibilities for low-cost LIGA-type processes for MEMS applications. The application potential of SU-8 is demonstrated by several examples of devices and structures fabricated by electroplating and photoplastic techniques. The latter is especially interesting as SU-8 has attractive mechanical properties.

613 citations

Journal ArticleDOI
TL;DR: A side- and back-wall concept to enforce chirality transfer onto the central metal atom is introduced and Cp(x) derivatives hold promise as powerful steering ligands for further transition-metals used in asymmetric catalysis.
Abstract: ConspectusTransition-metal catalyzed C–H functionalizations became a complementary and efficient bond-forming strategy over the past decade. In this respect, Cp*Rh(III) complexes have emerged as powerful catalysts for a broad spectrum of reactions giving access to synthetically versatile building blocks. Despite their high potential, the corresponding catalytic enantioselective transformations largely lag behind. The targeted transformations require all the remaining three coordination sites of the central rhodium atom of the catalyst. In consequence, the chiral information on a competent catalyst can only by stored in the cyclopentadienyl unit. The lack of suitable enabling chiral cyclopentadienyl (Cpx) ligands is the key hurdle preventing the development of such asymmetric versions. In this respect, an efficient set of chiral Cpx ligands useable with a broad variety of different transition-metals can unlock substantial application potential. This Account provides a description of our developments of two...

613 citations

Journal ArticleDOI
TL;DR: Key optoelectronic properties for donor and acceptor organic semiconductors are identified to obtain organic solar cells with reduced open-circuit voltage losses and high power conversion efficiencies.
Abstract: The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps Energy losses during charge separation at the donor–acceptor interface and non-radiative recombination are among the main causes of such voltage losses Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend Following these rules, we present a range of existing and new donor–acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 003%, leading to non-radiative voltage losses as small as 021 V This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells Key optoelectronic properties for donor and acceptor organic semiconductors are identified to obtain organic solar cells with reduced open-circuit voltage losses and high power conversion efficiencies

613 citations


Authors

Showing all 44420 results

NameH-indexPapersCitations
Michael Grätzel2481423303599
Ruedi Aebersold182879141881
Eliezer Masliah170982127818
Richard H. Friend1691182140032
G. A. Cowan1592353172594
Ian A. Wilson15897198221
Johan Auwerx15865395779
Menachem Elimelech15754795285
A. Artamonov1501858119791
Melody A. Swartz1481304103753
Henry J. Snaith146511123155
Kurt Wüthrich143739103253
Richard S. J. Frackowiak142309100726
Jean-Paul Kneib13880589287
Kevin J. Tracey13856182791
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023234
2022704
20215,247
20205,644
20195,432
20185,094