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Excellent average diffusion lenghts of 600 µm of n-Type multicrystalline silicon wafers after the full solar cell process including boron diffusion

: Michl, B.; Benick, J.; Richter, A.; Bivour, M.; Yong, J.; Steeman, R.; Schubert, M.; Glunz, S.W.

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Energy Procedia 33 (2013), pp.41-49
ISSN: 1876-6102
PV Asia Pacific Conference (PVAP) <2012, Singapore>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Herstellung und Analyse von hocheffizienten Solarzellen; Charakterisierung; Zellen und Module

In this paper we investigate the material quality of n- and p-type multicrystalline silicon wafers after different high- temperature steps, as applied during cell processing. Both materials start with a high initial bulk diffusion length of around 440 μm (harmonic mean of the whole wafer) which is further improved by the solar cell process. A diffusion length of 510 μm was measured after phosphorus and boron diffusion and firing in the n-type material. The p-type wafers showed diffusion lengths of 540 μm after phosphorus diffusion and firing. These diffusion lengths were measured at a generation rate of 1/20 sun close to maximum power point injection conditions of a solar cell. At higher injection levels both materials reach 600 μm diffusion length. The high material quality of n-type material maintained after the high temperature boron diffusion is remarkable. An efficiency analysis shows that these excellent diffusion lengths allow for high efficiency devices exceeding 20% efficiency.