298 research outputs found
An organic borate salt with superior pâdoping capability for organic semiconductors
Molecular doping allows enhancement and precise control of electrical properties of organic semiconductors, and is thus of central technological relevance for organic (optoâ) electronics. Beyond singleâcomponent molecular electron acceptors and donors, organic salts have recently emerged as a promising class of dopants. However, the pertinent fundamental understanding of doping mechanisms and doping capabilities is limited. Here, the unique capabilities of the salt consisting of a borinium cation (Mes2B+; Mes: mesitylene) and the tetrakis(pentaâfluorophenyl)borate anion [B(C6F5)4]â is demonstrated as pâtype dopant for polymer semiconductors. With a range of experimental methods, the doping mechanism is identified to comprise electron transfer from the polymer to Mes2B+, and the positive charge on the polymer is stabilized by [B(C6F5)4]â. Notably, the former salt cation leaves during processing and is not present in films. The anion [B(C6F5)4]â even enables the stabilization of polarons and bipolarons in poly(3âhexylthiophene), not yet achieved with other molecular dopants. From doping studies with high ionization energy polymer semiconductors, the effective electron affinity of Mes2B+[B(C6F5)4]â is estimated to be an impressive 5.9 eV. This significantly extends the parameter space for doping of polymer semiconductors
Lithium distribution across the membrane of motoneurons in the isolated frog spinal cord
Lithium sensitive microelectrodes were used to investigate the transmembrane distribution of lithium ions (Li+) in motoneurons of the isolated frog spinal cord. After addition of 5 mmol·lâ1 LiCl to the bathing solution the extracellular diffusion of Li+ was measured. At a depth of 500 m, about 60 min elapsed before the extracellular Li+ concentration approached that of the bathing solution. Intracellular measurements revealed that Li+ started to enter the cells soon after reaching the motoneuron pool and after up to 120 min superfusion, an intra â to extracellular concentration ratio of about 0.7 was obtained. The resting membrane potential and height of antidromically evoked action potentials were not altered by 5 mmol·lâ1 Li+
Elastic scattering and breakup of 17^F at 10 MeV/nucleon
Angular distributions of fluorine and oxygen produced from 170 MeV 17^F
incident on 208^Pb were measured. The elastic scattering data are in good
agreement with optical model calculations using a double-folding potential and
parameters similar to those obtained from 16^O+208^Pb. A large yield of oxygen
was observed near \theta_lab=36 deg. It is reproduced fairly well by a
calculation of the (17^F,16^O) breakup, which is dominated by one-proton
stripping reactions. The discrepancy between our previous coincidence
measurement and theoretical predictions was resolved by including core
absorption in the present calculation.Comment: 9 pages, 5 figure
An Organic Borate Salt with Superior pâDoping Capability for Organic Semiconductors
Molecular doping allows enhancement and precise control of electrical properties of organic semiconductors, and is thus of central technological relevance for organic (optoâ) electronics. Beyond singleâcomponent molecular electron acceptors and donors, organic salts have recently emerged as a promising class of dopants. However, the pertinent fundamental understanding of doping mechanisms and doping capabilities is limited. Here, the unique capabilities of the salt consisting of a borinium cation (Mes2B+; Mes: mesitylene) and the tetrakis(pentaâfluorophenyl)borate anion [B(C6F5)4]â is demonstrated as pâtype dopant for polymer semiconductors. With a range of experimental methods, the doping mechanism is identified to comprise electron transfer from the polymer to Mes2B+, and the positive charge on the polymer is stabilized by [B(C6F5)4]â. Notably, the former salt cation leaves during processing and is not present in films. The anion [B(C6F5)4]â even enables the stabilization of polarons and bipolarons in poly(3âhexylthiophene), not yet achieved with other molecular dopants. From doping studies with high ionization energy polymer semiconductors, the effective electron affinity of Mes2B+[B(C6F5)4]â is estimated to be an impressive 5.9 eV. This significantly extends the parameter space for doping of polymer semiconductors.Peer Reviewe
Breakup of F on Pb near the Coulomb barrier
Angular distributions of oxygen produced in the breakup of F incident
on a Pb target have been measured around the grazing angle at beam
energies of 98 and 120 MeV. The data are dominated by the proton stripping
mechanism and are well reproduced by dynamical calculations. The measured
breakup cross section is approximately a factor of 3 less than that of fusion
at 98 MeV. The influence of breakup on fusion is discussed.Comment: 7 pages, 8 figure
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
Energy level alignment at strongly coupled organic metal interfaces
Energy-level alignment at organicâmetal interfaces plays a crucial role for the performance of organic electronic devices. However, reliable models to predict energetics at strongly coupled interfaces are still lacking. We elucidate contact formation of 1,2,5,6,9,10-coronenehexone (COHON) to the (1â1â1)-surfaces of coinage metals by means of ultraviolet photoelectron spectroscopy, x-ray photoelectron spectroscopy, the x-ray standing wave technique, and density functional theory calculations. While for low COHON thicknesses, the work-functions of the systems vary considerably, for thicker organic films Fermi-level pinning leads to identical work functions of 5.2âeV for all COHON-covered metals irrespective of the pristine substrate work function and the interfacial interaction strength.Deutsche Forschungsgemeinschafthttps://doi.org/10.13039/501100001659Soochow University-Western University Joint Center for Synchrotron Radiation ResearchCollaborative Innovation Center of Suzhou Nano Science & Technology111 Project of the Chinese State Administration of Foreign Experts AffairsAustrian Science Fundhttps://doi.org/10.13039/501100002428National Key R&D Program of ChinaPeer Reviewe
Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells
Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61âV. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4âeV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control
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