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Viewing upcoming talks containing the keyword: 3
Shaping the density of states in organic hole conductors with switchable traps (Joint EaStCHEM/Physics Colloquium)
Speaker: Klaus Meerholz (Cologne)
 R. Shallcross, P. Körner, E. Maibach, A. Köhnen, K. Meerholz, Adv. Mater. 2013, 25, 4807 -4813.
Shaping the density of states in organic hole conductors with switchable traps
Despite the success of organic materials in applications such as OLED, a fundamental understanding of charge transport is far from being complete. Partly this is due to the difficulty of probing the density of states (DOS) in organic semiconductors directly. Thus, it is a challenge to differentiate between intrinsic limitations of the material under investigation and “extrinsic” effects like structural or electronic defects, traps stemming from impurities during synthesis or device operation. To better understand the influence of traps on the charge transport properties of organic semiconductors our strategy is to design the DOS of the transport layer on purpose. We synthesized a number of crosslinkable hole transport molecules with identical core structure and varying side groups to tune the ionization potential (IP, “HOMO energy”) between 5.1 eV and 5.8 eV. Devices were prepared by mixing variable amounts of a molecule with low IP (trap) into a host molecule with high IP. This approach allows to deliberately change th e depth of the trap and shape of the combined DOS more or less freely.
The analysis of current -voltage characteristics and impedance spectroscopy allows to identify the crossover from space -charge limited to trap limited transport and to test charge trans port models. Although, intentional mixing of traps serves it purpose, the device in its trap -free state cannot be recovered. To broaden the scope of charge transport investigations we show that the use of switchable traps has some interesting benefits. We present a unique hole trap, dithienlyethene (DTE), which can be photochemically switched . DTE features two stable isomers that differ in HOMO energy. In a hole -conducting matrix with a certain HOMO energy, one DTE isomer acts as a hole trap, while the other isomer has a negligible influence on charge transport. The energetic trap depth is varied by blending DTE with various TPD -type hole conductors featuring different HOMO levels. In this way the amount of traps can be controlled and the initial, native , state of the device can be restored. Download PDF
On: October 13, 2017 From: 10h00 To: 11h00View talk
History of Mathematics
Speaker: Evelyn Fox Keller (Massachusetts Institute of Technology)
The Fauvel Lecture, supported by the British Society for the History of Mathematics
Free, but booking essentialÂ
Evelyn Fox Keller is one of the most internationally respected historians of science. A physicist, author and feminist, she is currently Professor Emerita of the History & Philosophy of Science at MIT. Beginning her career in theoretical physics, she moved on to work in molecular biology before becoming renowned for her work as a feminist critic of science. Her books include Keywords in Evolutionary Biology (1998), The Century of the Gene (2000) and Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines (2002). The latter has a particular focus on mathematical biology and in her lecture she will discuss the legacy of Dâ€™Arcy Thompsonâ€™s work.
This free public lecture is associated with the 3-day conference celebrating the centenary of D'Arcy Thompson's On Growth and Form. Full programme and registration
On: October 14, 2017 From: 18h30 To: 19h30View talk
Speaker: Scott Cockroft (Edinburgh)
DISSECTING INTERACTI ONS IN SOLUTION Scott L. COCKROFT EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, UK. firstname.lastname@example.org , http://homepages.ed.ac.uk/scockrof/ research .php
The study of non -covalent interactions is often complicated by their fundamentally weak nature and the role of solvent effects. This talk will illustrate how synthetic molecular torsion balances -- and supramolecular complexes  can be used to quantify difficult -to-study interactions includi ng van der Waals dispersion forces,  aromatic stacking,  hydrogen -bonding cooperativity,  solvent ,- and solvophobic effects.  I will show how the information gleaned from such studies can be used to develop our theoretical understanding of molecular recognition phenomenon.
References :  I. K. Mati, S. L. Cockroft , Chem. Soc. Rev., 2010 , 39, 4195 -205 .  L. Yang, C. Adam, G. S. Nichol s, S. L. Cockroft , Nature Chem ., 2013 , 5(12),1006 -10.  C. Adam, L. Yang , S. L. Cockroft , Angew. Chem. Int. Ed., 2015 , 54(4), 1164 -7.  L. Yang, J. Brazier, T. Hubbard, D. M. Rogers & S. L. Cockroft , Angew. Chem. Int. Ed ., 2016 , 55(3), 912 -6.  N. Dominelli -Whiteley, J. J. Brown, K. B. Muchowska, I. K. Mati, C. Adam, T. A. Hubbard, A. Elmi, A. J. Brown, I. A. W. Bell, S. L. Co ckroft , Angew. Chem. Int. Ed., 2017 , DOI: 10.1002/anie.201703757 .  K. B. Muchowska, C. Adam, I. K. Mati , S. L. Cockroft , J. Am. Chem. Soc ., 2013 , 135, 9976 -79 .  I. K. Mati, C. Adam , S. L. Cockroft , Chem. Sci. , 2013 , 4, 3965 -72 .  L. Yang, C. Adam , S. L. Cockroft , J. Am. Chem. Soc. , 2015 , 137(32), 10084 -7. Download PDF
On: October 18, 2017 From: 15h30 To: 16h30View talk
Cond Mat Seminars
Speaker: Federico Mazzola (University of St Andrews)
The ability to manipulate the surface and interface properties of correlated electron systems underpins the burgeoning field of “designer” quantum matter. Over the last few years there has been enormous interest in using surfaces and interfaces to tune the interacting electronic states in perovskite-based transition-metal oxides 1 but it is important to expand the search of materials systems which may be tuned to host new surface and interface phases. Here, we study the “ABO2” delafossite oxides,2 a particularly promising material class both because of its naturally layered structure, as well as the potential to drastically alter its physical properties by changing the A- and B- site cations. MCoO2 [M=Pt,Pd] are non-magnetic metals with simple single-band Fermi surfaces. In bulk, they stand apart as the most conductive of all known normal-state oxides.3,4 The polar nature of their surfaces,5-6 however, opens the potential to stabilise local electronic environments and phases different to those of the bulk. Using angle-resolved photoemission spectroscopy we show how this drives an intrinsic Stoner-instability towards itinerant ferromagnetism at the Pd-terminated surface of both PdCoO2, and of its sister compound PdCrO2, a bulk antiferromagnet. Our measurements also reveal a large mass enhancement from electron-magnon coupling of the surface electrons. This work, altogether, could open potential routes for the creation, control and manipulation of collective phases in oxide surfaces and heterointerfaces.
References: 1Mannhart & Schlom, Science 327, 1607 (2010); 2 Mackenzie, Rep. Prog. Phys. 80, 32501 (2017); 3 Hicks et al., Phys. Rev. Lett. 109, 116401 (2012); 4 Kushwaha et al., Science Adv. 1, e1500692 (2015); 5 Sunko et al., Nature, 549, 492-496 (2017); 6 Kim et al., Phys. Rev. B., 80, 035116 (2009).
On: October 18, 2017 From: 12h00 To: 13h00View talk
RSC Award Lectures
Speaker: Manfred Bochmann (East Anglia)
Putting Organometallic Chemistry to Work
The talk will briefly review contributions to unravelling the mechanism and principles of homogeneously catalysed olefin polymerisation catalysis and the applications of this chemistry to carbocationic polymerisations for more sustainable industrial processes, before concentrating on recent advances in the chemistry of coinage metals, from gold(III) anti -cancer compounds to new approaches to the molecular design of highly efficient photoemitters for orga nic light -emitting diodes. Download PDF
On: October 19, 2017 From: 16h00 To: 17h00View talk
Physics and Astronomy Colloquia
Speaker: Jane Luu (MIT)
The Kuiper Belt, a population of icy bodies beyond Neptune, consists of material left over from the planet formation process. Its architecture records its interaction with the giant planets, and it still supplies a variety of small bodies to the inner solar system, including comets. The Kuiper Belt appears to be a universal phenomenon, its analog having been found in several extrasolar planetary systems. This talk will give a brief summary of the Kuiper Belt’s most important features.
On: October 20, 2017 From: 10h00 To: 11h00View talk