For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?

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Peibst, R.; Kruse, C.; Schäfer, S.; Mertens, V.; Bordihn, S. et al.: For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?. In: Progress in Photovoltaics: Research and Applications 28 (2020), Nr. 6, S. 503-516. DOI:

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We present a systematic study on the benefit of the implementation of poly-Si on oxide (POLO) or related junctions into p-type industrial Si solar cells as compared with the benchmark of Passivated Emitter and Rear Cell (PERC). We assess three aspects: (a) the simulated efficiency potential of representative structures with POLO junctions for none (=PERC+), one, and for two polarities; (b) possible lean process flows for their fabrication; and (c) experimental results on major building blocks. Synergistic efficiency gain analysis reveals that the exclusive suppression of the contact recombination for one polarity by POLO only yields moderate efficiency improvements between 0.23%abs and 0.41%abs as compared with PERC+ because of the remaining recombination paths. This problem is solved in a structure that includes POLO junctions for both polarities (POLO2), for whose realization we propose a lean process flow, and for which we experimentally demonstrate the most important building blocks. However, two experimental challenges—alignment tolerances and screen-print metallization of p+ poly-Si—are unsolved so far and reduced the efficiency of the “real” POLO2 cell as compared with an idealized scenario. As an intermediate step, we therefore work on a POLO IBC cell with POLO junctions for one polarity. It avoids the abovementioned challenges of the POLO2 structure, can be realized within a lean process flow, and has an efficiency benefit of 1.59%abs as compared with PERC—because not only contact recombination is suppressed but also the entire phosphorus emitter is replaced by an n+ POLO junction.
License of this version: CC BY-NC 4.0 Unported
Document Type: Article
Publishing status: publishedVersion
Issue Date: 2019-11-05
Appears in Collections:Fakultät für Elektrotechnik und Informatik
Fakultät für Mathematik und Physik

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1 image of flag of United States United States 21 36.84%
2 image of flag of Germany Germany 19 33.33%
3 image of flag of China China 9 15.79%
4 image of flag of Turkey Turkey 3 5.26%
5 image of flag of Taiwan Taiwan 1 1.75%
6 image of flag of Russian Federation Russian Federation 1 1.75%
7 image of flag of Peru Peru 1 1.75%
8 image of flag of France France 1 1.75%
9 image of flag of Austria Austria 1 1.75%

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