60 research outputs found
Predicting the location of polar cusp in the Lyon-Fedder-Mobarry global magnetosphere simulation
In this paper we compare observations of the high-latitude cusp from DMSP data to simulations conducted using the Lyon-Fedder-Mobarry (LFM) global magnetosphere simulation. The LFM simulation is run for the 31 August 2005 to 02 September 2005 moderate storm, from which the solar wind data exhibits a wide range of conditions that enable a statistical representation of the cusp to be obtained. The location of the cusp is identified using traditional magnetic depression and plasma density enhancement at high altitude. A new diagnostic using the parallel ion number flux is also tested for cusp identification. The correlation of the cusp latitude and various solar wind interplanetary magnetic field (IMF) coupling functions is explored using the three different cusp identification methods. The analysis shows (1) the three methods give approximately the same location and size of the simulated cusp at high altitude and (2) the variations of the simulated cusp are remarkably consistent with the observed statistical variations of the low-altitude cusp. In agreement with observations, a higher correlation is obtained using other solar wind coupling functions such as the Kan-Lee electric field. The magnetic local time (MLT) position of the simulated cusp is found to depend upon the IMF B y component, with a lower linear correlation. The width of the simulated cusp in both latitude and MLT is also examined. The size of the cusp is found to increase with the solar wind dynamic pressure with saturation seen when the dynamic pressure is greater than 3 nPa. Key Points Parallel ion number flux is used in the simulation for cusp identification The simulated cusp variations are consistent with observations The size of the cusp saturates when solar wind pressure > 3 nPa ĆĀ©2013. American Geophysical Union. All Rights Reserved.Link_to_subscribed_fulltex
Effects of Cd Diffusion and Doping in High-Performance Perovskite Solar Cells Using CdS as Electron Transport Layer
Perovskite
solar cells with stabilized power conversion efficiency
exceeding 15% have been achieved, using a methylammonium lead iodide
(MAPbI<sub>3</sub>) absorber and CdS as the electron transport layer.
X-ray photoelectron spectroscopy reveals a small presence of Cd at the surface of most
perovskite films fabricated on CdS. Perovskite films were deliberately
doped with Cd to understand the possible impacts of Cd diffusion into
the perovskite absorber layer. Doping substantially increases the
grain size of the perovskite films but also reduces device performance
through the formation of an electrical barrier, as inferred by the
S-shape of their <i>J</i>ā<i>V</i> curves.
Time-resolved photoluminescence measurements of the doped films do
not indicate substantial nonradiative recombination due to bulk defects,
but a secondary phase is evident in these films, which experiments
have revealed to be the organicāinorganic hybrid material methylammonium
cadmium iodide, (CH<sub>3</sub>NH<sub>3</sub>)<sub>2</sub>CdI<sub>4</sub>. It is further demonstrated that this compound can form via
the reaction of CdS with methylammonium iodide and may form as a competing
phase during deposition of the perovskite. Buildup of this insulating
compound may act as an electrical barrier at perovskite interfaces,
accounting for the drop in device performance
Examining the Effects of Homochirality for Electron Transfer in Protein Assemblies
Protein voltammetry
studies of cytochrome c, immobilized
on chiral tripeptide monolayer films, reveal the importance of the
electron spin and the filmās homochirality on electron transfer
kinetics. Magnetic film electrodes are used to examine how an asymmetry
in the standard heterogeneous electron transfer rate constant arises
from changes in the electron spin direction and the enantiomer composition
of the tripeptide monolayer; rate constant asymmetries as large as
60% are observed. These findings are rationalized in terms of the
chiral induced spin selectivity effect and spin-dependent changes
in electronic coupling. Lastly, marked differences in the average
rate constant are shown between homochiral ensembles, in which the
peptide and protein possess the same enantiomeric form, compared to
heterochiral ensembles, where the handedness of the peptide layer
is opposite to that of the protein or itself comprises heterochiral
building blocks. These data demonstrate a compelling rationale for
why nature is homochiral; namely, spin alignment in homochiral systems
enables more efficient energy transduction
A Comparative Study on the Mode of Action of Dihydrotachysterol and Vitamin D on the Calcium Metabolism
MAPbI<sub>3</sub> Solar Cells with Absorber Deposited by Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation
Resonant
infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) is
a gentle thin-film deposition technique that combines the facile chemical
control of solution processing with the growth control of vapor-phase
deposition, yet one that has not been widely applied to crystalline
organicāinorganic hybrid materials. In this work, we investigate
the optoelectronic quality of RIR-MAPLE-deposited CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPbI<sub>3</sub>) perovskite films and report
on the fabrication of perovskite solar cells in which the absorber
is deposited by RIR-MAPLE. We find the composition, morphology, and
optical properties of these perovskite films to be comparable to those
produced by more conventional methods, such as spin coating. The champion
device reaches a stabilized power conversion efficiency of over 12%,
a high value for perovskite solar cells deposited by a laser ablation
process, highlighting the ability of this new technique to produce
device-quality films
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