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Stability and Decomposition Kinetics of Alloyed Perovskite Semiconductors for Next-Generation Photovoltaics
Get PDFThesis (Ph.D.)--University of Washington, 2025Organic-inorganic metal halide perovskite semiconductors have captured the attention of the global scientific community for the past decade plus due to their excellent optoelectronic characteristics and ease of fabrication. These characteristics make them promising for application in low-cost, high efficiency solar cells. Despite their many favorable characteristics, the inherent instability of halide perovskites remains a significant hurdle that presently inhibits their commercialization. Although much work has been done to gain insight into stability of the most promising perovskite compositions, a comprehensive understanding of the chemical reaction landscape that governs decomposition has not been fully elucidated. The work presented here is focused on measuring and modeling decomposition reactions and, where appropriate, linking them to declines in relevant physical properties. First, I study the decomposition of FA0.8Cs0.2Pb(I0.83Br0.17)3, a promising composition for application in perovskite-on-silicon tandem solar cells, under combined light and heat stress. These conditions represent the limiting case of a well encapsulated solar cell, and thus, such tests probe the most basic hurdles that a viable absorber layer material must pass for photovoltaic applications. Through combined structural and optical characterization, we find that films degrade rapidly under illumination in an inert N2 environment, with notable generation of reduced lead species. Using in situ measurements of ambipolar diffusion length and photoluminescence, I show that film optoelectronic degradation is altered when oxygen is present in the ambient at sufficient concentrations. I then measure the kinetics of reduced lead species formation with in situ sub bandgap absorption measurements and model the observed kinetics. Next, I extend the kinetic studies of FA0.8Cs0.2Pb(I0.83Br0.17)3 thin films to the photooxidation regime. Under ambient conditions in which the partial pressure of oxygen is >3 kPa, photooxidation decomposition dominates. In situ above bandgap absorbance measurements reveal two dominant modes of photooxidation: dry-photooxidation and water-accelerated photooxidation. Interestingly, the presence of water vapor in the ambient is found to increase the rate (posited and modeled to be via water-accelerated photooxidation) at lower temperatures but decreases the rate (posited and modeled to be the result of hydrate formation) at higher temperatures compared to dry conditions. I then derive a rate expression and fit relevant parameters for the three processes assumed to be at play: dry-photooxidation, water-accelerated photooxidation, and hydrate formation. The derived model fits the data well across a range of conditions (<15% median error). Finally, I consider the effects that varied bromide X-site concentration has on stability, an important lever for tuning the bandgap of halide perovskites. I find that, under combined light and heat stress, the rate of increase of sub bandgap absorption, an indicator of reduced lead species formation, is faster in compositions with greater X-site bromine concentration. This finding is correlated with in situ measurements of ambipolar diffusion length during light heat stress. I also test the stability of the films in the presence of I2 vapor, a known byproduct of light induced decomposition and photooxidation, finding that the inverse is true: higher bromide fractions impart greater stability. Collectively, the work included in this dissertation demonstrates significant progress toward the understanding of the full decomposition landscape of alloyed lead halide perovskites
Impact of the Island Mass Effect on Zooplankton Community Composition Around the NAM-2 Coral Atoll in the Western Pacific Ocean
Get PDFPhytoplankton acts as the base of the marine food web, providing energy to higher tropic
levels such as zooplankton. Zooplankton are an intermediate part of the food chain that can
provide evidence of an area with high productivity. The focus of this study was to investigate the
Island Mass Effect (IME) and its impact on zooplankton communities around the NAM-2 Atoll
located to the southeast of Guam. Data was collected on the TN440 research cruise on the R/V
Thomas G. Thompson from December 29th, 2024, to January 11th, 2025. Zooplankton nets were
deployed at five stations around the unmapped atoll, NAM-2, (09º08’40’’N, 148º07’50’’ E), and
three stations on the 149ºE WOCE line in the open ocean, specifically at latitudes 5ºN, 9ºN, and
15ºN. Zooplankton metrics of abundance and diversity, current direction, temperature, nutrients,
and bathymetry were measured around the NAM-2 Atoll and the open ocean to observe the
biological productivity of the IME. The highest abundance of zooplankton throughout all of the
sites were the calanoid copepods, followed by the cyclopoid copepods, and then the
chaetognaths. There was a statistically significant relationship between copepods and their
predator, chaetognaths. There was no statistical significance between zooplankton abundance
and diversity between the atoll and open ocean sites and among the variables of temperature,
nutrients, current direction, and bathymetry. These factors likely still impacted the abundance
and diversity of zooplankton. These factors, along with the predator-prey relationship between
copepods and chaetognath, may still indicate NAM-2 as a biologically productive area,
according to the IME. Also, the varying current directions may bring different compositions of
zooplankton to the study stations. Further research is needed to discover the complete picture of
this location, which could eventually lead to contributions to Guam’s fishing economy
Bridging the Gap: Developing Trauma Informed Training for Correctional Staff to Support Successful Reintegration and Reduce Recidivism
Get PDFMaster of Social Work (MSW)In the United States, the incarceration rate is reported to have increased by 700%, with the incarceration rate reportedly being sevenfold higher than in any other developed Western country (Ferguson et al., 2016). Incarceration disproportionately affects people of color living in low-income and poverty-stricken communities. There is a higher prevalence of mental illness taking place in prisons versus non-incarcerated settings; incarcerated individuals are not receiving adequate mental health services, leading to recidivism. People of color with substance use disorder and mental illness are overrepresented in the criminal justice system, with 16 percent of men and 31 percent of women in jails and prisons having a mental illness, compared to 5 percent of the general population (Cloud et al., 2014). As we examine the causes and consequences of rising recidivism rates, we aim to increase awareness of inadequate mental health services in both community and carceral settings. To reduce recidivism, increase access and utilization of mental health services, and increase successful reintegration into society for released inmates, we have developed a pilot intervention aimed at engaging the correctional staff in prisons and jails. The long-term goal of this pilot program is to create a holistic support program that trains correctional staff in empathetic and trauma-informed approaches to engage incarcerated individuals to bridge a connection between prison and communities, resulting in a reduction in recidivism rates. This program will shift the prison culture starting with the staff in these facilities
Direct and indirect ecosystem responses to vehicle compaction of intertidal flats
Get PDFThis paper was published: https://doi.org/10.1016/j.marenvres.2025.107746. Data are archived on Dryad: DOI: 10.5061/dryad.fbg79cp8pChange in an ecological community after a disturbance may be a direct impact or may be indirectly mediated through the response of a highly influential species. In northeastern Pacific tidal flats, a native bioturbator, ghost shrimp Neotrypaea californiensis, engineers soft-sediment habitat and interacts antagonistically with bivalve shellfish. Vehicle compaction has been used in pest control of ghost shrimp, but this disturbance lacks quantitative evidence of its efficacy and environmental impacts. Through three large (~10 ha) experiments in Grays Harbor, Washington, USA, we tested the direct and indirect impacts of compaction by a tracked vehicle (MarshMaster) on ghost shrimp density, sediment conditions, and infauna. We also examined how oyster survival and waterbird usage of tidal flats responded post-compaction. Compaction pushed <20% of ghost shrimp to the surface, where they were vulnerable to predation and damage, yet did not significantly reduce subsurface densities within 1-2 days. Rather, declines in shrimp density and shifts to smaller size classes appeared at later sample timepoints and were more pronounced with more compaction passes. All compaction experiments resulted in firmer sediment for at least a year, even in the experiment where shrimp densities were unaffected by a single compaction pass. Where compaction briefly reduced shrimp densities below 50 m-2, sediment increased in mud and organic content and infauna increased in abundance, suggesting that these changes were mediated through reduced bioturbation rather than a direct impact of compaction. Similarly, multivariate responses of infauna appeared only in the experiments where compaction reduced shrimp densities. Habitat use by waterbirds was more influenced by tidal stage than by compaction; statistically, only dunlin (Calidris alpina) foraged more on compacted than on reference beds. Finally, although survival of outplanted oyster seed improved with compaction at one site, it remained too low (~34-40% yr-1) for viable farming. This implementation of vehicle compaction, with disturbance from as many as five passes or spaced at annual intervals, provided insufficient pest control. Nevertheless, reduced densities of ghost shrimp were associated with follow-on effects on sediment content and the infaunal community
Corporate Social Responsibility in Peru: Financial Performance of Social Responsible Companies
Get PDFThe purpose of this paper is twofold: it aims first at reviewing Corporate Social Responsibility (CSR) in Peruvian corporations. Second, it analyzes the Corporate Financial Performance (CFP) of Peruvian companies that are regarded as socially responsible and have been recognized for their efforts with CSR awards
Mapping Disparities in Medication Access, Utilization, and Spending across the United States
No full textThesis (Ph.D.)--University of Washington, 2025Achieving equitable access to medicines requires measuring disparities in pharmaceutical utilization and spending and understanding the mechanisms that drive them. Yet in the United States, disparities in medication access, use, and spending—by race, geography, and disease—remain inadequately measured and insufficiently addressed. This dissertation develops new tools and applies them at scale to quantify these inequities, leveraging large-scale spending, prevalence, and geospatial data to examine underlying mechanisms and support targeted health policy action. Chapter 2 introduces a novel probabilistic framework to map prescription drugs to likely health conditions in retail pharmaceutical claims data, addressing a major limitation of existing administrative datasets. Unlike approaches based on US Food and Drug Administration–approved indications or clinical guidelines, it captures real-world prescribing practices, enabling measurement of both on- and off-label use. The resulting drug-condition map supports national, state, and county-level estimates of condition-specific utilization and spending across the US. Chapter 3 applies this drug-condition map to generate state-level estimates of pharmaceutical utilization and spending by race and ethnicity, producing the most comprehensive geographic mapping of medication inequities to date, covering 143 conditions, four payer types, and all 50 states and DC. Findings reveal persistent underutilization among Black populations relative to need, and substantial variation across states and conditions. Decomposition analyses highlight the relative contributions of disease prevalence, prescribing intensity, spending per prescription. Chapter 4 evaluates the role of physical access to community pharmacies in shaping these disparities over a ten-year period across the US. Using over a decade of geolocated pharmacy data, I develop a metric incorporating both driving and walking proximity to assess access across urban and rural census block groups nationwide. I then examine how access relates to medication use, using a disparity index building on findings from Chapter 3. I find that inadequate pharmacy access is associated with wider racial disparities in medication use across health conditions. Together, these chapters offer a data-rich framework for understanding and addressing inequities in access, use, and spending on prescribed medicines across the United States
Research Software Systems: Exploration and Infrastructure in Observational Cosmology
Get PDFThesis (Ph.D.)--University of Washington, 2025In the last 20 years software has become an increasingly problematic object in the sciences. While it has become integral to research in many fields, scientific communities have struggled with problems of reproducibility, reuse, and the validity of findings produced by complex software systems. This has been attributed in part to the unplannable and unpredictable nature of scientific work itself, which makes it difficult to test research software or to define its requirements ahead of time. In this dissertation I draw on ethnographic work with a research group in the field of reionization cosmology in order to develop an understanding of how researchers develop novel software instrumentation in these contexts of uncertainty. I elaborate the notion of exploratory programming as a central process in scientific work that is distinct from software production, and I further develop the concept of the research software system as a system of heterogeneous software processes that is organized to reconcile the need for rigidity and flexibility in research infrastructures. This contribution reconceptualizes how software is used in scientific work as well as the process by which software engineering methods might be integrated into that work, and it provides new conceptual handles with which to support both activities
Buckle Up for Buckling: Poacher Fish Scale Behavior Under Compression
Get PDFPoacher fishes (Agonidae) are a family defined by their bony armor. Unlike the
flexible scales possessed by many fishes, poachers are encased in rigid plates that overlap
in rows. Uniquely, when viewed in the hoop direction, rows appear as distinct geometric
rings which can be dissected out both digitally and physically. These rings vary across
species in both number and arrangement of plates, forming octagons, hexagons, and
squares. The diversity in row count and overlap across species implies different ring
designs may be specialized for different functions. To test this, we 3D-printed models of
poacher armor rings as regular polygons with flexible joints at either the center or
corners, varying the number sides to match the diversity seen in nature. We used a
material testing system to compress the models to a locking position, recording force
displacement curves for each model. We found that, across most shapes, models with
central joints, which most closely match poacher scale morphology, require more force to
reach a locked position than models with joints in the corners. This means the models that
closely resemble fish, despite being contradictory to conventional engineering design,
resist compression better. Poachers are not fast swimmers and thus hide under rocks,
compressing themselves, but due to their scales’ resistance, they can prevent damage to
their soft internal structures
"The crown is heavy": A textual analysis of masculine ritual aggression in the Kendrick v. Drake Hip Hop beef
Get PDFThesis (Master's)--University of Washington, 2025Using a textual analysis to examine the Kendrick Lamar - Drake beef as a case study of ritualized aggression in Hip Hop, this essay analyzes how artists perform, negotiate, and challenge racialized and socially privileged masculine forms. This research analyzes diss tracks, media discourse, and audience interactions to make meaning of the racial and gender politics present in the Kendrick v. Drake rivalry. The study interprets Kendrick's performance of Black masculinity as adhering to hegemonic expressions typical in Hip Hop, emphasizing cultural authority and lyrical dominance. Kendrick's approach contrasts against Drake's hybrid forms of masculinity that subvert established aesthetics, while strategically incorporating machismo displays. Ultimately, this essay advances that ritual aggression through Hip Hop beef – as seen in the case of Kendrick v. Drake – is a practice whereby audiences validate performances of contemporary Black masculinities, privileging select identifying portrayals over others
Imaging Future Reciprocal Human–AI Encounters Through Interactive Exhibition: Designing Wander Poet AI
Get PDFThesis (Master's)--University of Washington, 2025This thesis presents Wander Poet AI, a playful anddiegetic prototype introducing unique interactions
such as ritualistic awakening, refusing utilitarian tasks,
requiring creative collaboration, and actively
managing memories through manual curation by
participants, limiting memory storage capacity to
encourage thoughtful interactions in an interactive
exhibition. The Wander Poet AI embraces ludic,
speculative, and intentionally counterfunctional
interactions, inviting participants to explore more
profound and meaningful relationships with an AIembedded
entity. The main research question of the
thesis is: How can experimental AI art installations
function as diegetic prototypes for alternative
sociotechnical imaginaries that counter dominant AI
narratives? Ultimately, this work aims to diversify
and challenge dominant narratives about Artificial
Intelligence, encouraging people to think more
critically and creatively about meaningful interactions
between humans and AI