ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

Displaying 1 - 2 of 2
Filtering by

Clear all filters

168575-Thumbnail Image.png

Metallization to Silicon Solar Cells: Improving Optothermal Performance of PERC and Developing New Systems for TOPCon and SHJ

Description
Metallization of solar cells is a critical process step in the manufacturing of silicon photovoltaics (PV) as it plays a large role in device performance and production cost. Improvements in device performance linked to metallization and reduction in material usage and processing costs will continue to drive next-generation silicon PV…

Metallization of solar cells is a critical process step in the manufacturing of silicon photovoltaics (PV) as it plays a large role in device performance and production cost. Improvements in device performance linked to metallization and reduction in material usage and processing costs will continue to drive next-generation silicon PV technology. Chapter 1 introduces the context for the contributions of this thesis by providing background information on silicon PV cell technology, solar cell device physics and characterization, and metallization performance for common silicon cell structures. Chapter 2 presents a thermal model that links sub-bandgap reflectance, an important metric at the rear metal interface, to outdoor module operating temperature. Chapter 3 implements this model experimentally with aluminum back-surface field (Al-BSF), passivated emitter and rear contact (PERC), and passivated emitter rear totally diffused (PERT) mini-modules, where the PERT cells were modified to include an optimized sub-bandgap reflector stack. The dedicated optical layer was a porous low-refractive index silica nanoparticle film and was deposited between the dielectric passivation and full area metallization. This created an appreciable boost in sub-bandgap reflectance over the PERC and Al-BSF cells, which directly lead to cooler operating temperature of the fielded module. Chapter 4 investigates low-temperature Ag metallization approaches to SiO2/polysilicon passivating contacts (TOPCon architecture). The low-temperature Ag sintering process does not damage TOPCon passivation for structures with 40-nm-thick poly-Si but shows higher contact resistivity than sputtered references. This disparity is investigated and the impact of Ag diffusion processes, microstructure changes, ambient gases, and interfacial chemical reactions are evaluated. Chapter 5 investigates sputtered Al metallization to silicon heterojunction contacts of both polarities. This In-free and Ag-free metallization process can achieve low contact resistivity and no passivation loss when annealed between 150-180 °C. The passivation degradation at higher temperatures was studied with high-resolution microscopy and elemental mapping, where the interdiffusion processes were identified. Lastly, Chapter 6 summarizes the contribution of this work.
ContributorsBryan, Jonathan Linden (Author) / Holman, Zachary C (Thesis advisor) / Bertoni, Mariana I (Committee member) / Bowden, Stuart G (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2022
171806-Thumbnail Image.png

Reliability and Degradation Characterization for PV Modules and Systems

Description
In-field characterization of photovoltaics is crucial to understanding performance and degradation mechanisms, subsequently improving overall reliability and lifespans. Current outdoor characterization is often limited by logistical difficulties, variable weather, and requirements to measure during peak production hours. It becomes a challenge to find a characterization technique that is affordable with…

In-field characterization of photovoltaics is crucial to understanding performance and degradation mechanisms, subsequently improving overall reliability and lifespans. Current outdoor characterization is often limited by logistical difficulties, variable weather, and requirements to measure during peak production hours. It becomes a challenge to find a characterization technique that is affordable with a low impact on system performance while still providing useful device parameters. For added complexity, this characterization technique must have the ability to scale for implementation in large powerplant applications. This dissertation addresses some of the challenges of outdoor characterization by expanding the knowledge of a well-known indoor technique referred to as Suns-VOC. Suns-VOC provides a pseudo current-voltage curve that is free of any effects from series resistance. Device parameters can be extracted from this pseudo I-V curve, allowing for subsequent degradation analysis. This work introduces how to use Suns-VOC outdoors while normalizing results based on the different effects of environmental conditions. This technique is validated on single-cells, modules, and small arrays with accuracies capable of measuring yearly degradation. An adaptation to Suns-VOC, referred to as Suns-Voltage-Resistor (Suns-VR), is also introduced to complement the results from Suns-VOC. This work can potentially be used to provide a diagnostic tool for outdoor characterization in various applications, including residential, commercial, and industrial PV systems.
ContributorsKillam, Alexander Cameron (Author) / Bowden, Stuart G (Thesis advisor) / Goryll, Michael (Committee member) / Augusto, Andre (Committee member) / Rand, James (Committee member) / Arizona State University (Publisher)
Created2022