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ECN publication
Response of n-type mc-Si to large variations of gettering and hydrogenation
Published by: Publication date:
ECN Solar Energy 29-1-2007
ECN report number: Document type:
ECN-M--07-012 Conference Paper
Number of pages: Full text:
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Presented at: 17th Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, Vail CO, USA, 5-8 augustus 2007.

The minority charge carrier recombination behaviour of n-type multicrystalline silicon wafers was systematically studied through microwave detected photoconductance decay, on as-grown samples, on samples submitted to phosphorus diffusion step and on samples after gettering and hydrogenation processes. First, we show that extreme gettering parameters (high temperature, high phosphorous-dosing of the wafer surface, long process) result in a significantly better cleaning of the edge zone of ingots, compared to typical phosphorous emitter diffusion. On the other hand, it results in less cleaning of the bulk silicon matrix, and somewhat more decoration of extended crystal defects. Second, we show that there is much improvement possible by enhanced hydrogenation of the wafer. This improvement applies to extended crystal defects but especially to bulk silicon matrix. Bulk silicon lifetime (in low defect crystals) continues to improve with increasing hydrogenation, in the wafers that we investigated e.g. from values around 150 µs after typical industrial hydrogenation, to 270 µs after the highest hydrogenation dose which we investigated.

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