Root cause defect identification in multicrystalline silicon for improved photovoltaic module reliability
Name
1065537939-MIT.pdf
Description
Full printable version
Size
21.49 MB
Format
Adobe PDF
Checksum (MD5)
b288a4738d44557e2c2fed5809396253
Author(s)
Jensen, Mallory Ann
Advisor(s)
Tonio Buonassisi.
Date Issued
2018
Publisher
Massachusetts Institute of Technology
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.
Description
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-145).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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