From Field to Failure: Detecting and Understanding Reliability Defects in Crystalline Silicon Photovoltaics

Severe pollution levels and the growing influence of climate change have shown that dirty energy sources need renewable and sustainable replacements. The field of photovoltaics (PV) has grown substantially over the years from a niche space solar market to a commodity in large part due to improvements in reliability. Reliability of all materials in a PV module must be considered. The industry has seen an explosion of innovation in cell interconnection technologies with significant market penetration in the past several years. These emerging, less mature technologies require more reliability information to guide improvements. Degradation studies of long-term outdoor exposure and accelerated stress testing provide the samples, but a comprehensive characterization suite is necessary for impactful results. The state of the art for characterization is highly valuable yet incomplete. This work presents a multiscale, multicomponent process that provides information on device physics, polymer performance, thermal signatures, chemical composition, and degradation mechanisms, as well as advancements in electrical performance and defect localization. A comprehensive characterization suite is proposed which expands upon conventional one-sun current-voltage (I-V) and high injection electroluminescence (EL) imaging to multi-irradiance I-V, suns-Voc, multi-injection EL imaging and analysis, IR thermography, and UV fluorescence imaging. A database of over 1000 I-V curve, high-injection EL image pairs is presented for public use. An analysis and measurement technique is developed using EL images at multiple injection levels to non-destructively extract dark I-V curves for each cell. These curves can be analyzed to extract device properties. A machine learning model is developed using annotated EL images for automated defect detection. The training set of 17,064 cell EL images is publicized for the industry\u27s benefit. While applicable to all module technologies, the focus of this work is on applying this expansion on characterization to studying interconnection and contact degradation. Several interconnection technologies are studied with varying results. Each technology is shown to have distinct advantages and disadvantages with respect to performance and reliability. Modules are studied that have undergone accelerated tests and outdoor exposure. It is shown that full interconnection separation influences degradation differently depending on location of failure, though requires many failures before significant performance losses are evident. In another study, a model is developed for the mechanism behind front contact corrosion in damp heat degraded modules. A coring process is developed to extract cell samples which allows materials characterization. Results demonstrate that the primary mechanism is based on Sn diffusion from interconnection ribbons via acetic acid and moisture. One study examines a system of modules exposed in Florida for 10 years showing rear interconnect corrosion at the Ag/solder interface. Intermetallic compound formation led to reduced carrier transport and contact embrittlement leading to fatigue failure susceptibility. Another study investigates four different interconnection technologies before, during, and after stages of different accelerated stress protocols. Five-busbar ribbon, shingled, soldered wire, and laminated wire technologies underwent mechanical loading, humidity freeze, damp heat, and thermal cycling tests. Laminated wire performed the best overall though showed some features in EL imaging that have not yet been published. In the final study presented, a system of heterojunction modules from a system in Florida after 10 years exposure show resistive degradation. Device and materials characterization shows recombination and resistive losses, with resistive losses due corrosion at the intrinsic a-Si/c-Si interface

Citizen Co-Learners: A Transgressive March toward Emancipatory Learning

Spanning continents and cultural borders, the writings of Paolo Freire, bell hooks, and Henry Giroux encompass post/decolonial and standpoint epistemologies focused on student-centered approaches. We seek to model peer learning and knowledge production bell hooks commands in Teaching to Transgress: “I have been most inspired by those teachers who have had the courage to transgress those boundaries that would confine each pupil to a rote, assembly-line approach to learning” (13).With these words in mind, we participate in a content analysis of literature and storytelling, creating sites of resistance at educational boundaries in order to increase accessibility to knowledge and scaffold various forms of meaning-making. We use this pedagogy as a springboard for inquiry into the nature of cultural borders within American Civil Rights and Racial Justice movements. Borders constructed by oppressors were locations in which the civil rights movement created moments of resistance, chronicled in the graphic novel March by John Lewis, Andrew Aydin, and Nate Powell. Claudia Rankine’s, Citizen: An American Lyric, along with her Situation videos, call into question the cultural borders and vernacular dictates which saturate modern Black American citizenry. Her work reflects the racial justices themes present in NPR StoryCorps animated short entitled Traffic Stop. Through analysis of these works, we seek to model content analysis as a form of border-crossing as co-learners in resistance and facilitators of learning as healing, breaking the boundaries between teacher and student, tending to the wounds created by borders between oppressor and oppressed

Opioid Crisis in Dayton: The Role of Facebook Comment Sections in Meaning-Making

This thesis provides a foundational understanding of the ways in which Facebook is being used as a location for meaning making around the opioid epidemic in Dayton, Ohio. A content analysis of the Dayton Daily News Facebook page analyzes four posts that were randomly selected from 2017 and their corresponding 1,336 comments. This work will identify and describe discursive civility and incivility. This work adds to the growing conversation about incivility in political discourse by bringing the focus to the opioid epidemic and Facebook as a location where understandings of drug use and prevention are co-constructed. This construction, along with understandings of what is civil or uncivil, can both perpetuate and subvert power structures. The implications of this pilot study provide a framework to consider opportunities to create more civil and subversive locations on Facebook for meaning making

Opioid Crisis in Dayton: The Role of Facebook Comment Sections in Meaning-Making

This thesis provides a foundational understanding of the ways in which Facebook is being used as a location for meaning making around the opioid epidemic in Dayton, Ohio. A content analysis of the Dayton Daily News Facebook page analyzes four posts that were randomly selected from 2017 and their corresponding 1,336 comments. This work will identify and describe discursive civility and incivility. This work adds to the growing conversation about incivility in political discourse by bringing the focus to the opioid epidemic and Facebook as a location where understandings of drug use and prevention are co-constructed. This construction, along with understandings of what is civil or uncivil, can both perpetuate and subvert power structures. The implications of this pilot study provide a framework to consider opportunities to create more civil and subversive locations on Facebook for meaning making

May We Do Work that Matters, Vale la Pena: Putting Community Coyolxauhqui Together and the Anzaldúa Seminar.

Teaching Gloria Anzaldúa provides pedagogical application of Anzaldúa\u27s noted theories including, la facultad, the path of conocimiento, and autohistoria among others. This text provides examples, lesson plans, and activities for scholars, professors, teachers, and community members in various disciplines including, history, composition, literature, speech and debate and more for those interested in teaching the theories of Gloria Anzaldúa Gloria Evangelina Anzaldúa--theorist, Chicana, feminist--famously called on scholars to do work that matters. This pronouncement was a rallying call, inspiring scholars across disciplines to become scholar-activists and to channel their intellectual energy and labor toward the betterment of society. Scholars and activists alike have encountered and expanded on these pathbreaking theories and concepts first introduced by Anzaldúa in Borderlands/La frontera and other texts. Teaching Gloria E. Anzaldúa is a pragmatic and inspiring offering of how to apply Anzaldúa\u27s ideas to the classroom and in the community rather than simply discussing them as theory. The book gathers nineteen essays by scholars, activists, teachers, and professors who share how their first-hand use of Anzaldúa\u27s theories in their classrooms and community environments. The collection is divided into three main parts, according to the ways the text has been used: Curriculum Design, Pedagogy and Praxis, and Decolonizing Pedagogies. As a pedagogical text, Teaching Gloria E. Anzaldúa also offers practical advice in the form of lesson plans, activities, and other suggested resources for the classroom. This volume offers practical and inspiring ways to deploy Anzaldúa\u27s transformative theories with real and meaningful action

May We Do Work that Matters, Vale la Pena: Putting Community Coyolxauhqui Together and the Anzaldúa Seminar.

Teaching Gloria Anzaldúa provides pedagogical application of Anzaldúa\u27s noted theories including, la facultad, the path of conocimiento, and autohistoria among others. This text provides examples, lesson plans, and activities for scholars, professors, teachers, and community members in various disciplines including, history, composition, literature, speech and debate and more for those interested in teaching the theories of Gloria Anzaldúa Gloria Evangelina Anzaldúa--theorist, Chicana, feminist--famously called on scholars to do work that matters. This pronouncement was a rallying call, inspiring scholars across disciplines to become scholar-activists and to channel their intellectual energy and labor toward the betterment of society. Scholars and activists alike have encountered and expanded on these pathbreaking theories and concepts first introduced by Anzaldúa in Borderlands/La frontera and other texts. Teaching Gloria E. Anzaldúa is a pragmatic and inspiring offering of how to apply Anzaldúa\u27s ideas to the classroom and in the community rather than simply discussing them as theory. The book gathers nineteen essays by scholars, activists, teachers, and professors who share how their first-hand use of Anzaldúa\u27s theories in their classrooms and community environments. The collection is divided into three main parts, according to the ways the text has been used: Curriculum Design, Pedagogy and Praxis, and Decolonizing Pedagogies. As a pedagogical text, Teaching Gloria E. Anzaldúa also offers practical advice in the form of lesson plans, activities, and other suggested resources for the classroom. This volume offers practical and inspiring ways to deploy Anzaldúa\u27s transformative theories with real and meaningful action

Solder Bond Degradation Of Fielded Pv Modules: Correlation Between Performance, Series Resistance And Electroluminescence Imaging

One of the most dominant degradation modes affecting the degradation rate and lifetime of field deployed modules is the degradation of interconnect-metallization system. The effect of solder bond degradation on the performance of three 10-year-old modules installed at a Florida site has been quantified through the cell series resistance (Rs) acquired from dark current-voltage (I-V) curves, which has been correlated with performance loss and electroluminescence (EL) intensity. The regions of poor solder joints are identified in EL image through high luminescence spots at interconnect ribbons because of current crowding. Each individual cell of the tested modules was accessed by cutting off a small segment of backsheet and soldering at cell interconnect. A spatial distribution of Rs in the modules is mapped, which demonstrated a good correlation with fill factor and output power as identified by two parallel trendlines. This implies that the performance loss of these fielded modules is significantly dictated by the solder bond degradation. Further, the ultraviolet fluorescence images showed an identical encapsulant browning pattern over the cells, indicating considerable current loss in all cells of the module

Black Women\u27s Lives Matter

Students from Dr. Judith Ezekiel\u27s Spring 2015 Women\u27s Studies courses, Feminist Activism and Women, Gender, and Black Freedom Movements, collaborated to create a booklet that presents the lives of a dozen black women who were killed by the police or who died while in police custody, in order to argue for the inclusion of black women in the Black Lives Matter movement, not merely as originators and supporters of the cause but as a group that is protected and remembered within the movement in the same capacity as black men

DataSheet1_Field studies of PERC and Al-BSF PV module performance loss using power and I-V timeseries.PDF

We have studied the degradation of both full-sized modules and minimodules with PERC and Al-BSF cell variations in fields while considering packaging strategies. We demonstrate the implementations of data-driven tools to analyze large numbers of modules and volumes of timeseries data to obtain the performance loss and degradation pathways. This data analysis pipeline enables quantitative comparison and ranking of module variations, as well as mapping and deeper understanding of degradation mechanisms. The best performing module is a half-cell PERC, which shows a performance loss rate (PLR) of −0.27 ± 0.12% per annum (%/a) after initial losses have stabilized. Minimodule studies showed inconsistent performance rankings due to significant power loss contributions via series resistance, however, recombination losses remained stable. Overall, PERC cell variations outperform or are not distinguishable from Al-BSF cell variations.</p