ECN publication
Investigation of new ready to use solar crucible for crystallisation of multicrystalline silicon ingots
Kvande, R.; Arnberg, L.; Coletti, G.; Martin, C.; Ndzogha, C.; Rancoule, G.
Published by: Publication date:
ECN Solar Energy 28-8-2007
ECN report number: Document type:
ECN-M--07-074 Conference Paper
Number of pages: Full text:
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Presented at: 22nd European Photovoltaic Solar Energy Conference and Exhibition, Milan, Italy, 3-7 september 2007.

A new crucible concept has been investigated where silica crucibles used for directional solidification of multicrystalline silicon are coated with a high purity silicon oxide layer on top of the standard silicon nitride coating. The purpose is to create a mechanical resistant coating interface which will dissolve in the melt. Two solidification experiments using this Ready-to-Use (RTU) crucible have been conducted in addition to a reference experiment using a crucible coated with only silicon nitride. A onsiderable increase in scratch resistance was observed for the RTU crucibles in addition to excellent releasing properties and no contact areas between crucible and ingot. Higher oxygen levels were found in the ingots solidified in RTU crucibles due to dissolution of silica coating into the melt. The minority carrier lifetime was satisfactory but seemed to be lower than in the reference material. The efficient diffusion length was highest close to the bottom of the ingots and decreased towards the top. This trend can not be explained by the oxygen, indicating that other factors must influence the solar cell performance. Further investigations are needed to determine the optimal thickness of the silica layer to obtain a mechanical resistant coating combined with low oxygen levels in the solidified ingots.

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