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

Conference ·
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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 Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
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
Country of Publication:
United States
Language:
English

References (6)

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High-resolution characterization of ultrashallow junctions by measuring in vacuum with scanning spreading resistance microscopy journal May 2007
Differences in Printed Contacts Lead to Susceptibility of Silicon Cells to Series Resistance Degradation journal May 2022
Investigation of Acetic Acid Corrosion Impact on Printed Solar Cell Contacts journal May 2015
Scanning spreading resistance microscopy and spectroscopy for routine and quantitative two-dimensional carrier profiling
  • Eyben, P.; Xu, M.; Duhayon, N.
  • Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, Vol. 20, Issue 1 https://doi.org/10.1116/1.1424280
journal January 2002
Multiscale Characterization of Photovoltaic Modules—Case Studies of Contact and Interconnect Degradation journal January 2022

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Related Subjects

SOLAR ENERGY
c-Si solar cell
front metallization
nm-scale imaging
scanning spreading resistance microscopy (SSRM)
series resistance degradation