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Title:
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In-situ doping and local overcompensation of high performance LPCVD polysilicon passivated contacts as approach to industrial IBC cells
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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10-8-2016
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ECN report number:
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Document type:
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ECN-W--16-024
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Article (scientific)
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Number of pages:
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7
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Published in: Energy Procedia (Elsevier), , 2016, Vol.92, p.427-433.
Abstract:
In this work, we investigate polysilicon passivation contacts, to be used for high performance IBC cells. We demonstrate an LPCVD process for in-situ p-type doped polysilicon. The p-type polysilicon can be locally overcompensated to n-type polysilicon using phosphorous implantation or POCl3 diffusion. Both contacts show excellent surface passivation, with recombination current (Jo) of 12 fA/cm2 for p-poly on a polished Si surface, and less than 10 fA/cm2 for compensated n-poly both on textured and polished surfaces. These polysilicon layers are implemented in the fabrication of n-PERT cells with front and rear polysilicon contacts. The resulting textured half-fabricated cells have an implied Voc of 701 mV after hydrogenation via PECVD deposition of SiNx:H. Different metallization processes, relevant for IBC cells, are applied. A Voc of 685 mV is obtained for the best cell metallized with low-temperature metallization (ITO/low-temperature Ag paste), and 678 mV is obtained for the best cell with industrial screen-printed firing-through contacts. In these n-PERT cells the same thin oxide layer is used for p-type and n-type polysilicon contacts.
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