Local Corrosion of Silicon as Root Cause for Potential‐Induced Degradation at the Rear Side of Bifacial PERC Solar Cells

Industrial bifacial PERC solar cells are exposed to a high‐voltage stress at the rear side. The tested cells show a potential‐induced degradation (PID) in Voc and Isc. From a front side current–voltage measurement, a power loss of about 12%rel is observed, however, without a significant change in th...

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Bibliographic Details
Published in:Physica status solidi. PSS-RRL. Rapid research letters 2019-09, Vol.13 (9), p.n/a
Main Authors: Sporleder, Kai, Naumann, Volker, Bauer, Jan, Richter, Susanne, Hähnel, Angelika, Großer, Stephan, Turek, Marko, Hagendorf, Christian
Format: Article
Language:English
Subjects:
bifacial PERC
Corrosion
crystalline silicon
Damage localization
Degradation
Electrical measurement
Energy dispersive X ray spectroscopy
Energy transmission
Ion beams
Ion recombination
Photovoltaic cells
potential-induced degradation
Power loss
silicon corrosion
Silicon dioxide
Solar cells
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Summary:Industrial bifacial PERC solar cells are exposed to a high‐voltage stress at the rear side. The tested cells show a potential‐induced degradation (PID) in Voc and Isc. From a front side current–voltage measurement, a power loss of about 12%rel is observed, however, without a significant change in the fill factor. The degradation is traced back to micron‐sized hole‐shaped damages of the rear surface, which correlate with localized regions of increased recombination. A focused ion beam (FIB) cross‐section through a hole‐shaped damage is performed for subsequent transmission electron microscopy (TEM) and energy‐dispersive X‐ray spectroscopy (EDXS). EDXS shows an accumulation of Na, K, and Ca impurities in the cavity. Thus, it is assumed that corrosion of the Si surface occurs beneath the AlOx/SiNy passivation layer stack and is accompanied by the formation of a SiO2 layer. Industrial bifacial PERC solar cells show a new type of potential‐induced degradation (PID) at the rear side. After the PID stress, cells exhibit power losses of about 12%rel. The origin of the losses is traced back to a local silicon corrosion, forming hole‐shaped damages within the passivation layers at the rear side.
ISSN:1862-6254
1862-6270
DOI:10.1002/pssr.201900163