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Understanding the Role Thin Film Interfaces Play in Solar Cell Performance and Stability
Get PDFAs more efficient and cost-effective photovoltaic (PV) architectures are developed, solar becomes an ever more competitive and viable replacement for fossil fuels. Full grid electrification necessitates the development of efficient, reliable, cost-effective technologies - and there is room for many different kinds of PV in this expanding market. The practical challenges and constraints of terawatt PV production have brought scalability and durability into sharp scientific focus. From a materials perspective, there are commonalities in the materials questions and challenges across different PV technologies. Whereas most PV technology is referred to by the absorber layer - e.g. silicon, or perovskite solar cells, other layers in the device are equally important to performance and durability. These layers are often composed of metal oxides, and are common across device technologies - for example, interfacial layers (such as charge transport layers, CTLs), and transparent conducting oxides (TCOs) used as electrodes.This work addresses materials oxide characterization and its relationship to materials and device performance and degradation across PV technologies.
Among the most promising PVs to date are two technologies with different levels of thin film incorporation: silicon heterojunction (SHJ) and perovskite PV. SHJ cells are part of the industrial Si PV portfolio, and perovskite cells are starting to be commercially produced after a decade of intensive research. However, there are well-known stability and cost limitations associated with each technology. Understanding the thin film materials science in these devices, and using that understanding to enhance device performance and stability is key to more reliable and cost effective electricity production.
Under practical aging conditions, careful materials-level characterization is required to understand the degradation mechanisms of these materials and the complex effects of aging on the multilayer system. This work details the effects of practical degradation challenges such as damp heat (DH) exposure and encapsulation degradation on the stability of inorganic metal oxides in both the SHJ and perovskite thin film photovoltaic architectures. For perovskite devices, MAPbI3 films were deposited by spin coating onto a range of substrates and CTLs; substrates of glass and indium tin oxide (ITO) were paired with metal oxides (MOs) including MoOX, NiOX, and ZnO. SE and SEM were used to characterize the surface and bulk properties of the perovskite films. Results demonstrate that the underlying layers affect the rate of absorber degradation when exposed to heat and moisture.
Unencapsulated SHJ cells (a subset of which were exposed to low concentrations of acetic acid under an applied voltage) were aged under DH 85°C/85% relative humidity conditions. The contact-ITO interface was examined via optical profilometry (OP), spectroscopic ellipsometry (SE), and scanning electron microscopy (SEM). SHJ cells have interfaces unique to their architecture, namely the c-Si/a-Si:H and a-Si:H/ITO interfaces at the top of the device. Examining the degradation of unencapsulated SHJ cells and comparing those results to historical degradation profiles of encapsulated SHJ cells in addition to the simulated effects of acetic acid exposure will help to decouple the effects of encapsulation on ITO stability in this architecture. It is well known that ethylene vinyl acetate (EVA) encapsulation degrades and produces acetic acid upon exposure to heat and humidity. When under an applied voltage, even small concentrations of acetic acid can quickly corrode the contact-ITO interface, leading to decreases in efficiency and increases in series resistance of the cell. Here, XPS was used to monitor the changes in the front contact of the SHJ cells during DH and acetic acid exposure. Changes to the materials will be correlated to changes in device performance under the same aging conditions
The Status of Women\u27s and Gender Centers at Public Research Universities
Get PDFThis research examined women’s and gender centers at land-grant universities classified as Carnegie R1 institutions in the United States that were also APLU and AAU member institutions. The purpose of the inquiry was to understand how descriptive information about commonalities and standard practices among existing women’s and gender centers at these types of higher education institutions could be compiled from publicly available information and analyzed for use towards establishing support for new centers. Sixteen data points were collected from a final sample consisting of 12 centers that met the research criteria. These women’s and gender centers provided programs, services, referrals, and resources for students, faculty, and staff. All but one of the centers included all genders, half addressed the inclusion of individuals from all races, ethnicities, and the majority engaged with other multi-cultural organizations. The centers were primarily managed by the divisions of Student Affairs, and Diversity, Equity, and Inclusion. All of the centers were separate entities from the universities’ Title IX offices. Common practices maintained by the centers included having dedicated space on campus, providing annual reports, employing professional and student staff, and publicizing programming, resources
Living Apart After Adoption or Guardianship: Perspectives of Adoptive Parents and Guardians
No full textBackground: For children who are not reunified with their biological family members, the child welfare system promotes legal permanence through adoption or guardianship. The intent of adoption and guardianship is a safe home where children develop familial relationships that last a lifetime. However, issues may arise that result in children or youth living apart (LA) from their families after adoption or guardianship. In this study, LA is defined as a youth living outside the home after adoption or guardianship for two weeks or longer because the youth was receiving treatment in a residential or hospital setting, in a juvenile justice setting, or became homeless or ran away from home. Objective: Using caregiver survey data, this study examined the following questions: (1) What is the prevalence of LA? (2) What are the risk and protective factors at child and family levels that are associated with LA? (3) What is the nature of the relationships between family members among those who have experienced LA? Participants and Setting: This study re-purposed data from surveys of adoptive parents and guardians of children formerly in foster care in four states (n = 2473). Methods: Data were collected concurrently, and analyzed through an explanatory sequential mixed methods design began with determining prevalence rates and logistic regression to explore risk and protective factors for LA. This was followed by an examination of survey responses from a subsample of children who experienced LA to provide a deeper understanding of family relationships. Results: 8% of respondents experienced LA. Regression findings: kinship (OR = 0.57), higher family income (OR = 0.89), and engagement in extracurricular activities (OR = 0.37) served as protective factors for LA. Two elements of relationships were identified: Reciprocal, nurturing connections, which enhanced familial relationships and unfulfilled, unsupported connections that strained familial relationships. Conclusions: This study expands our understanding of the challenges faced by adoptive and guardianship families. Key findings include the importance of extracurricular school-related involvement, biological family support, and adoption or guardianship specific services
Piece‐By‐Piece Shape‐Morphing: Engineering Compatible Auxetic and Non‐Auxetic Lattices to Improve Soft Robot Performance in Confined Spaces
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Teaching Spatial Data Analysis: A Case Study with Recommendations
Get PDFLearning from data is a valuable skill for nonprofit professionals and researchers. Often, data have a spatial component, and data relevant to the nonprofit sector are no exception. Understanding spatial aspects of the nonprofit sector may provide immense value to social entrepreneurs, funders, and policy makers, by guiding programmatic decisions, facilitating resource allocation, and development policy. As a result, spatial thinking has become an essential component of critical thinking and decision making among nonprofit professionals. The goal of this case study is to support and encourage instruction of spatial data analysis and spatial thinking in nonprofit studies. The case study presents a local nonprofit data set, along with open data and code, to assist the instructors teaching spatial aspects of the nonprofit sector. Pedagogical approaches are discussed
A Novel Approach to Legacy Donations with Long-Term Benefits Supported by Mathematical Analysis
Get PDFA novel approach to legacy donations, called the “Master Fund Strategy,” is proposed. Potential long-term financial benefits for both donor and nonprofit organizations (NPOs) when compared to a “Traditional Fund Strategy” are established through mathematical analysis and computer simulations, providing nonprofit marketing and fundraising professionals an alternative way to lock in bequest funding. In particular, formulas are developed for computing relevant financial quantities associated with the two strategies. Conditions are presented under which the Master Fund Strategy is better than the Traditional Fund Strategy, in the sense that there is a point in time when the net present value of the distributions to the NPO under the Master Fund Strategy exceeds that of a Traditional Fund Strategy and continues to do so beyond that point. These analytical results are obtained under the assumption that the investment rates of return and the fund payouts rates are known constants; however, formulas for relaxing these restrictions are also developed and the consequences are examined with Monte Carlo simulations
Self-beliefs, Transactive Memory Systems, and Collective Identification in Teams: Articulating the Socio-Cognitive Underpinnings of COHUMAIN
Get PDFSocio-cognitive theory conceptualizes individual contributors as both enactors of cognitive processes and targets of a social context\u27s determinative influences. The present research investigates how contributors’ metacognition or self-beliefs, combine with others’ views of themselves to inform collective team states related to learning about other agents (i.e., transactive memory systems) and forming social attachments with other agents (i.e., collective team identification), both important teamwork states that have implications for team collective intelligence. We test the predictions in a longitudinal study with 78 teams. Additionally, we provide interview data from industry experts in human–artificial intelligence teams. Our findings contribute to an emerging socio-cognitive architecture for COllective HUman-MAchine INtelligence (i.e., COHUMAIN) by articulating its underpinnings in individual and collective cognition and metacognition. Our resulting model has implications for the critical inputs necessary to design and enable a higher level of integration of human and machine teammates
Spatiotemporal Walking Gait Kinematics of Semi-Arboreal Red Pandas (Ailurus fulgens)
No full textSemi-arboreal mammals must routinely cope with the differing biomechanical challenges of terrestrial versus arboreal locomotion; however, it is not clear to what extent semi-arboreal mammals adjust footfall patterns when moving on different substrates. We opportunistically filmed quadrupedal locomotion (n = 132 walking strides) of semi-arboreal red pandas (Ailurus fulgens; n = 3) housed at Cleveland Metroparks Zoo and examined the effects of substrate type on spatiotemporal gait kinematic variables using linear mixed models. We further investigated the effects of substrate diameter and orientation on arboreal gait kinematics. Red pandas exclusively used lateral sequence (LS) gaits and most frequently utilized LS lateral couplet gaits across terrestrial and arboreal substrates. Red pandas moved significantly slower (p \u3c 0.001), and controlling for speed, had significantly greater relative stride length (p \u3c 0.001), mean stride duration (p = 0.002), mean duty factor (p \u3c 0.001), and mean number of supporting limbs (p \u3c 0.001) during arboreal locomotion. Arboreal strides on inclined substrates were characterized by significantly faster relative speeds and increased limb phase values compared with those horizontal and declined substrates. These kinematics adjustments help to reduce substrate oscillations thereby promoting stability on potentially precarious arboreal substrates. Red panda limb phase values are similar to those of (primarily terrestrial) Carnivora examined to date. Despite the similarity in footfall patterns during arboreal and terrestrial locomotion, flexibility in other kinematic variables is important for semi-arboreal red pandas that must navigate disparate biomechanical challenges inherent to arboreal versus terrestrial locomotion
Thirty-Day Mortality Rates Among Young Adult Stroke Patients and Their Characteristics at Kiruddu and Mulago Hospitals in Uganda: A Prospective Observational Cohort Study
No full textStroke outcomes among young adults in Uganda are unclear. This study therefore determined the clinical characteristics and 30-day outcome among young adults with an acute stroke. In a prospective observational cohort study, 61 young adults with confirmed stroke were followed up for 30 days. Socio-demographic and clinical characteristics were collected using a study questionnaire. Kaplan–Meier curves, and modified Poisson regression were performed for factors associated with the 30-day mortality outcome. A third of the screened stroke survivors, (61/195) were young adults aged between 18 and 50 years. About two-thirds were male. More than half were diagnosed with ischaemic strokes while 42.6% had a haemorrhagic stroke. Nearly half (29/61) were known hypertensives, 43% (26/61) had a history of alcohol consumption with 95% classified as dependent on CAGE assessment. Ten percent had a prior smoking history while 29% of the female gender had a prior history of oral contraception use. Twenty-three percent (14/61) of the young stroke patients died within 30 days of stroke onset (95% CI: 0.01, 0. 901). A history of smoking (adjusted prevalence ratio: aPR;5. 094, 95% CI: 3.712, 6. 990) and stroke severity National Institutes of Health Stroke score (NIHSS) \u3e16; Prevalence ratio (PR) -3. 301, 95%CI: 1. 395, 7. 808) and not drinking alcohol (aPR (adjusted prevalence ratio) -7. 247, 95% CI: 4. 491, 11.696) were associated with 30- day mortality. A third of all stroke survivors were young adults. About 23. 3% died within 30 days of stroke onset. Stroke severity and a history of smoking were associated with mortality. Identifying high risk patients and early outpatient follow up may help reduce the 30-day mortality in our settings
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