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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
Carrier Mobility In Methylammonium Lead Iodide Perovskite Solar Cells: Mobility Versus Composition In Spin Coated And Vapor Deposited Samples, Max A. Zinman, James Heyman
Carrier Mobility In Methylammonium Lead Iodide Perovskite Solar Cells: Mobility Versus Composition In Spin Coated And Vapor Deposited Samples, Max A. Zinman, James Heyman
Macalester Journal of Physics and Astronomy
We performed research on a set methylammonium lead iodide (MaPI) perovskite solar cell samples, including samples produced both by vapor deposition and spin coating. We used time resolved THz spectroscopy to measure carrier mobility in the samples and excitation of vibrational modes in the THz and IR spectra to gauge relative sample compositions (ratio of PbI to Ma). Plotting carrier mobilities against composition ratios, we found a peaked distribution of carrier mobilities suggesting an ideal ratio of lead iodide to methylammonium to maximize mobility. We also observed that the spin coated samples had considerably less variance in their composition ratios …
Effects Of Post-Deposition Annealing On Room Temperature Deposited Zinc Oxide, Ishan Rayen
Effects Of Post-Deposition Annealing On Room Temperature Deposited Zinc Oxide, Ishan Rayen
Macalester Journal of Physics and Astronomy
This study focuses on thin film deposition of ZnO onto a glass slide using magnetron sputtering. The focus of the study is to understand the effects of post-deposition annealing temperatures. The goal is to optimize crystal quality, conductivity, and transparency. The results attempt to answer the effects of room temperature deposition and changes in film properties once annealed. Annealing temperatures ranged from 100°C to 400°C with an annealing time of 30 minutes. This found an ideal temperature of 250°C for post-deposition annealing, resulting in approximately 3.86 times more conductivity with little to no decrease in transparency. However crystal quality did …
Probing Charge Recombination In Organic Solar Cells, Ally C. Hurd, Awwad Alotaibi, Acacia Patterson, Obaid Alqahtani, James Doyle, Brian Akira Collins
Probing Charge Recombination In Organic Solar Cells, Ally C. Hurd, Awwad Alotaibi, Acacia Patterson, Obaid Alqahtani, James Doyle, Brian Akira Collins
Macalester Journal of Physics and Astronomy
Printable and flexible organic solar panels are promising sources of inexpensive, large-scale renewable energy, where panels can be manufactured by printing from polymer inks. There are some limitations to these types of solar cells, however. First, toxic halogenated solvents have historically been necessary to dissolve polymers to make the ink. In addition, organic solar cells typically have high rates of recombination, which limits their efficiency. Here, we use a transient photovoltage (TPV) technique to measure charge lifetimes in cells made from two different organic solvents. The first solvent is toxic, halogenated dichlorobenzene (DCB) which is typically used to make organic …
Investigation Of Tantalum Sodium Lead Borate Glass Using Laser Ionization Time Of Flight Mass Spectrometry (Litof-Ms), Siri Erickson-Green
Investigation Of Tantalum Sodium Lead Borate Glass Using Laser Ionization Time Of Flight Mass Spectrometry (Litof-Ms), Siri Erickson-Green
Macalester Journal of Physics and Astronomy
Laser ionization time of flight mass spectrometry (LITOF-MS) is a spectrometry method which can measure, with exceptional accuracy, the composition of ions within a glass system. Additionally, unlike other spectroscopy and spectrometry methods, this technique allows insight into the abundance of each kind of ion within a given glass system. This specific project tackled the topic of tantalum-doped sodium and lead borate glasses, as sodium and lead borate glasses doped with a transition metal is a topic which has not been thoroughly explored. Our group synthesized such a glass and was able to use LITOF-MS to gain insights into how …
Strain Methods For Changing Local Electric Field Gradient In Bafe2as2, Caleb Williams
Strain Methods For Changing Local Electric Field Gradient In Bafe2as2, Caleb Williams
Macalester Journal of Physics and Astronomy
In this study, we introduce a novel approach aimed at advancing the investigation of local nematicity in BaFe2As2 via dynamically pulsed strain fields. Our research is motivated by the pursuit of a more sensitive alternative to existing static strain methods. Employing nuclear magnetic resonance techniques, we measure the nuclear quadrupolar energy splittings, utilizing them as a sensitive indicator of the electric field gradient (EFG) that couples strongly to the orbital occupations of the 75As p-orbitals. In the new method, we discern an EFG response through changes in the phase acquired by the nuclear magnetization while time-evolving in the strain field, …
Linking The Population Of Binary Black Holes With The Stochastic Gravitational-Wave Background, Olivia X. Laske
Linking The Population Of Binary Black Holes With The Stochastic Gravitational-Wave Background, Olivia X. Laske
Macalester Journal of Physics and Astronomy
The astrophysical stochastic gravitational-wave background (SGWB) is the product of overlapping waveforms that create a single unresolvable background. While current LIGO sensitivity is insufficient to uncover the SGWB, future space-based detectors and Third Generation (3G) experiments are expected to probe deep enough for detection. Predictions of the SGWB can constrain future searches as well as provide insight into star formation, merger history, and mass distribution. Here, three primary methods are used to calculate a theoretical SGWB. The first method integrates over a precomputed mass distribution probability grid, while the second and third employ Monte Carlo integration with simulated data. After …
Simulation Of Polymerization On Surfaces: Implications For Abiogenesis, Sylvia Greene
Simulation Of Polymerization On Surfaces: Implications For Abiogenesis, Sylvia Greene
Macalester Journal of Physics and Astronomy
How did life arise from the prebiotic conditions of the early earth? This problem has vexed scientists for decades with no consensus on its solution. Significant spontaneous formation of biopolymers such as proteins and nucleic acids in the aqueous phase appears to be improbable due to thermodynamic constraints. It has been proposed that mineral surfaces could have served as a catalyst for the initial formation of biopolymers. However, the feasibility of this mechanism has not been thoroughly studied. In this study, a particle simulation of polypeptide formation on surfaces is developed to assess the feasibility of this mechanism. Elementary processes …
The Hodgkin-Huxley Model For Neuron Action Potentials: A Computational Study, Uditi Chandrashekhar
The Hodgkin-Huxley Model For Neuron Action Potentials: A Computational Study, Uditi Chandrashekhar
Macalester Journal of Physics and Astronomy
Neurons are the fundamental units of the nervous system that receive stimuli as signals and pass on this information to other cells in different parts of the body. An action potential refers to the transmission of the electrical nerve impulse along the neuron. In their seminal work published in 1952, Alan L. Hodgkin and Andrew Huxley proposed a mathematical model of neuronal membrane action potentials based on a series of experiments they conducted using the giant squid neuron. This thesis is a study of the nature of the action potential used to transfer signals along the neuron based on the …
Variability Of High-Degree Modes Over Multiple Solar Cycles Using Local Helioseismic Data From Gong, Nicholas Cebula, Sushanta Tripathy, Kiran Jain, John M. Cannon
Variability Of High-Degree Modes Over Multiple Solar Cycles Using Local Helioseismic Data From Gong, Nicholas Cebula, Sushanta Tripathy, Kiran Jain, John M. Cannon
Macalester Journal of Physics and Astronomy
In this investigation we use the local helioseismic technique of ring diagrams to study the power, energy, and damping rates of high degree solar acoustic modes. Our data covers the period from the maximum phase of solar cycle 23 to the ascending phase of cycle 25. The goal is to examine the variations in the mode parameters with solar activity as well as the differences between different cycles. For this, we use different proxies of solar activity. We use 10.7 cm radio flux measurements and a measure of magnetic flux known as magnetic activity index from magnetograms.
Ammonia Emission In The Milky Way Galactic Bar Dust Lanes, Charles G. Burton
Ammonia Emission In The Milky Way Galactic Bar Dust Lanes, Charles G. Burton
Macalester Journal of Physics and Astronomy
The Central Molecular Zone (CMZ) of the Milky Way is a region of molecular gas within the inner few hundred parsecs of the Galaxy. This inner region of the Milky Way is hotter and more turbulent when compared with the disk of the Milky Way. Gas is thought to be funneled into the CMZ through dense gaseous dust lanes that are associated with the Galactic Bar. I studied two regions of one of these dust lanes using the NH3 inversion transitions of (J,K) = (1,1), (2,2), (3,3), and (4,4). Data has been obtained from the Green Bank Telescope targeting these …