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dc.contributor.advisorAgarwal, Sumit
dc.contributor.advisorStradins, Paul
dc.contributor.authorKale, Abhijit S.
dc.contributor.committeememberWu, Ning
dc.contributor.committeememberCarreon, Moises A.
dc.contributor.committeememberPylypenko, Svitlana
dc.date.accessioned2019-10-03T21:27:49Z
dc.date.available2019-10-03T21:27:49Z
dc.date.submitted2019
dc.descriptionIncludes bibliographical references.
dc.description2019 Summer
dc.description.abstractGlobal energy demands have been increasing and the ability of fossil fuels to meet these demands is limited. Due to the associated climate change concerns, most of the current new energy installations have been based on renewable energy resources such as wind and solar. However, to further develop solar energy as a renewable energy resource, improvements in silicon-based solar cells, which represent more than 90% of the current photovoltaics market, is critical. In this thesis work we explore strategies for more efficient and cheaper solar cells. Efficiency improvements are enabled via passivated contacts, which serve both as a contact layer and a passivation layer for the crystalline silicon (c-Si) surface, and are a potential candidate for next-generation industrial c Si solar cells. In this thesis work, we identify a few salient features of passivated contacts comprising of a polycrystalline Si (poly-Si) deposited on top of ultrathin, 1.5–2.2 nm thick SiOx layers forming a metal/poly-Si/SiOx/c-Si contact stack. Poly-Si/SiOx contact passivation and conduction depends on both the SiOx thickness and contact annealing temperature. Depending on the processing conditions, two different scenarios for conduction through the SiOx layer are observed: uniform tunneling conduction or locally enhanced conduction. The locally enhanced conduction occurs through 10s of nanometer size regions with either no SiOx layer, or a thinned-down tunneling SiOx layer. The performance of the poly-Si/SiOx contacts on a pyramidal textured Si surface, which is critical for light-trapping, is also studied. The poorer passivation on a textured surface is related to the surface morphology: both the pyramidal morphology and nanoscale roughness over the pyramidal shape, causing SiOx related nonuniformities. Both the pyramidal morphology and nanoscale roughness can be modified using wet-chemical etching via HF:HNO3 solution. Such a morphological change improves surface passivation, but deteriorates the light trapping properties of the Si surface. We also explored strategies to replace current solar cell metallization processes based on the expensive Ag metal with a cheaper Cu metal, which necessitates a conductive Cu diffusion barrier interlayer between Cu and Si. The superior Cu diffusion barrier properties and thermal stability of a Cu/NiSi/Si stack over a Cu/Ni/Si stack is demonstrated.
dc.identifierKale_mines_0052E_11802.pdf
dc.identifierT 8789
dc.identifier.urihttps://hdl.handle.net/11124/173273
dc.languageEnglish
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.rightsCopyright of the original work is retained by the author.
dc.subjectPassivated contact
dc.subjectSilicon oxide
dc.subjectTunneling
dc.subjectPassivation
dc.subjectElectron beam induced current
dc.subjectSilicon solar cell
dc.titlePassivated contacts for high efficiency monocrystalline silicon solar cells
dc.typeThesis
thesis.degree.disciplineChemical and Biological Engineering
thesis.degree.grantorColorado School of Mines
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (Ph.D.)


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