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 ©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 (MAPbI₃) 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>–<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 organic–inorganic hybrid material methylammonium cadmium iodide, (CH₃NH₃)₂CdI₄. 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 film’s 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

MAPbI₃ 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 organic–inorganic hybrid materials. In this work, we investigate the optoelectronic quality of RIR-MAPLE-deposited CH₃NH₃PbI₃ (MAPbI₃) 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