Differences in Printed Contacts Lead to Susceptibility of Silicon Cells to Series Resistance Degradation

In this case study, we investigate a degradation mode occurring at the cell level in fielded multi-Si modules. The modules exhibit a mix of affected and unaffected cells. Affected cells show a progressive, series-resistance-related power degradation as shown via module- and cell-level IV curves, alo...

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Bibliographic Details
Published in:IEEE journal of photovoltaics 2022-05, Vol.12 (3), p.690-695
Main Authors: Gaulding, E. Ashley, Mangum, John S., Johnston, Steve, Jiang, Chun-Sheng, Moutinho, Helio, Reed, Mason, Rand, Jim, Flottemesch, Robert, Silverman, Timothy, Deceglie, Michael
Format: Article
Language:English
Subjects:
Acetic acid
Composition
Degradation
Electroluminescence
Imaging
Modules
oxide
photovoltaic
Photovoltaic systems
Resistance
Screen printing
series resistance
Silicon
Silver
silver paste
SOLAR ENERGY
Zinc
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Summary:In this case study, we investigate a degradation mode occurring at the cell level in fielded multi-Si modules. The modules exhibit a mix of affected and unaffected cells. Affected cells show a progressive, series-resistance-related power degradation as shown via module- and cell-level IV curves, along with electroluminescence (EL) and PL imaging at the module, cell, and cell core sample scales. Scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal a difference in the oxides in the silver paste used in screen printing of the gridline contacts. The paste in the affected cells is lead rich, whereas the paste in the unaffected cells is zinc rich. This suggests that the cells were screen printed with different silver paste compositions and possibly firing conditions, and that the different composition correlates with the susceptibility to degradation. Our results indicate degradation of the contact at the oxide-silver interface, causing a severe increase in series resistance across the cell that continues to progress over time.
ISSN:2156-3381
2156-3403
DOI:10.1109/JPHOTOV.2022.3150727