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Local nm-Scale Imaging of Electrical Contact for Series Resistance Degradation of Silicon Solar Cells

Conference ·

We report on an electrical conduction mechanism for series resistance (Rs) degradation observed in a utility scale solar farm by nm-scale imaging of the local resistance at the Ag/Si interface of c-Si front metallization. Scanning spreading resistance microscopy imaging revealed that the number of point or small area electrical contacts decreased in a degraded cell compared to an unaffected cell, demonstrating the direct root cause of the Rs degradation. The degraded cell shows both a morphological and chemical difference in the screen-printed finger contact compared to the unaffected cell, which likely caused the degradation during the long-term field service. The reduction in electrical contact is likely caused by a structural change: The Ag particles in contact with the Si cell aggregate into bulk Ag, and a highly resistive ceramic oxide is formed in a "belt" shape at the Ag/Si interface. This resistive belt with a thickness of ~1 um blocks the current conduction from cell emitter to the Ag grid. Our results demonstrate an example of the multi-scale characterization approach for understanding degradation mechanisms in photovoltaics.

Research Organization:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
DOE Contract Number:
AC36-08GO28308
OSTI ID:
1913953
Report Number(s):
NREL/CP-5K00-85047; MainId:85820; UUID:d0c47f98-f38a-4e11-9a71-7ed908aeb577; MainAdminID:68497
Resource Relation:
Conference: Presented at the 2022 IEEE 49th Photovoltaics Specialists Conference (PVSC), 5-10 June 2022, Philadelphia, Pennsylvania; Related Information: 83107
Country of Publication:
United States
Language:
English

References (6)

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Scanning spreading resistance microscopy and spectroscopy for routine and quantitative two-dimensional carrier profiling
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Differences in Printed Contacts Lead to Susceptibility of Silicon Cells to Series Resistance Degradation journal May 2022