{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/119344"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/119344","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Root cause defect identification in multicrystalline silicon for improved photovoltaic module reliability","abstract":"To meet climate targets by 2030, manufacturing capacity for photovoltaic (PV) modules must be scaled at 22-25% annual growth rate while maintaining high performance and low selling price. The most suitable material substrate to enable this scale-up is cast multicrystalline silicon (mc-Si) due to its low operating cost and capital requirements compared to other technologies. However, a new form of light-induced degradation was discovered when transitioning mc-Si to the latest high efficiency device architecture. Light- and elevated temperature-induced degradation (LeTID) causes performance to decrease by about 10% (relative) under field-relevant conditions within only four months. In this work, the root cause of LeTID is investigated in three parts: (1) Candidate hypotheses are developed for LeTID; (2) Targeted experiments are carried out toward developing a defect-based description of LeTID; and (3) The basis for a predictive model of LeTID is proposed. Techniques including minority carrier lifetime spectroscopy, synchrotron-based X-ray fluorescence, intentional contamination, and process simulation are employed to probe the defect causing LeTID. The results indicate that LeTID is caused by at least two reactants-hydrogen and one or more reactants that can be modified by high-temperature processing-and that the defect at the point of maximum degradation has recombination characteristics similar to a deep-level donor in silicon. By providing the basis for a predictive model, this work enables both identification of the root cause of LeTID and de-risking of novel solar cell architectures based on mc-Si, allowing assessment of the impact of LeTID on the future of the PV industry. This work also enables development of mitigating strategies for LeTID.","abstract_html":"To meet climate targets by 2030, manufacturing capacity for photovoltaic (PV) modules must be scaled at 22-25% annual growth rate while maintaining high performance and low selling price. The most suitable material substrate to enable this scale-up is cast multicrystalline silicon (mc-Si) due to its low operating cost and capital requirements compared to other technologies. However, a new form of light-induced degradation was discovered when transitioning mc-Si to the latest high efficiency device architecture. Light- and elevated temperature-induced degradation (LeTID) causes performance to decrease by about 10% (relative) under field-relevant conditions within only four months. In this work, the root cause of LeTID is investigated in three parts: (1) Candidate hypotheses are developed for LeTID; (2) Targeted experiments are carried out toward developing a defect-based description of LeTID; and (3) The basis for a predictive model of LeTID is proposed. Techniques including minority carrier lifetime spectroscopy, synchrotron-based X-ray fluorescence, intentional contamination, and process simulation are employed to probe the defect causing LeTID. The results indicate that LeTID is caused by at least two reactants-hydrogen and one or more reactants that can be modified by high-temperature processing-and that the defect at the point of maximum degradation has recombination characteristics similar to a deep-level donor in silicon. By providing the basis for a predictive model, this work enables both identification of the root cause of LeTID and de-risking of novel solar cell architectures based on mc-Si, allowing assessment of the impact of LeTID on the future of the PV industry. This work also enables development of mitigating strategies for LeTID.","abstract_has_math":false,"creators":["Jensen, Mallory Ann"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Mechanical Engineering.","school":null,"contributors":[],"advisors":["Tonio Buonassisi."],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018","date_published":"2018","updated_at":"2026-07-22T22:22:27Z","subjects":["Mechanical Engineering."],"languages":["eng"],"rights":["MIT theses are protected by copyright. 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The most suitable material substrate to enable this scale-up is cast multicrystalline silicon (mc-Si) due to its low operating cost and capital requirements compared to other technologies. However, a new form of light-induced degradation was discovered when transitioning mc-Si to the latest high efficiency device architecture. Light- and elevated temperature-induced degradation (LeTID) causes performance to decrease by about 10% (relative) under field-relevant conditions within only four months. In this work, the root cause of LeTID is investigated in three parts: (1) Candidate hypotheses are developed for LeTID; (2) Targeted experiments are carried out toward developing a defect-based description of LeTID; and (3) The basis for a predictive model of LeTID is proposed. Techniques including minority carrier lifetime spectroscopy, synchrotron-based X-ray fluorescence, intentional contamination, and process simulation are employed to probe the defect causing LeTID. The results indicate that LeTID is caused by at least two reactants-hydrogen and one or more reactants that can be modified by high-temperature processing-and that the defect at the point of maximum degradation has recombination characteristics similar to a deep-level donor in silicon. By providing the basis for a predictive model, this work enables both identification of the root cause of LeTID and de-risking of novel solar cell architectures based on mc-Si, allowing assessment of the impact of LeTID on the future of the PV industry. This work also enables development of mitigating strategies for LeTID."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:title","label":"Title","values":["Root cause defect identification in multicrystalline silicon for improved photovoltaic module reliability"]}]}],"canonical_facts":{"dc:contributor.advisor":["Tonio Buonassisi."],"dc:contributor.department":["Massachusetts Institute of Technology. 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However, a new form of light-induced degradation was discovered when transitioning mc-Si to the latest high efficiency device architecture. Light- and elevated temperature-induced degradation (LeTID) causes performance to decrease by about 10% (relative) under field-relevant conditions within only four months. In this work, the root cause of LeTID is investigated in three parts: (1) Candidate hypotheses are developed for LeTID; (2) Targeted experiments are carried out toward developing a defect-based description of LeTID; and (3) The basis for a predictive model of LeTID is proposed. Techniques including minority carrier lifetime spectroscopy, synchrotron-based X-ray fluorescence, intentional contamination, and process simulation are employed to probe the defect causing LeTID. 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They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Mechanical Engineering."],"dc:title":["Root cause defect identification in multicrystalline silicon for improved photovoltaic module reliability"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:22:27Z"}