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Emitter performance improvement of multicrystalline Si solar cell by controlling the n++ layer
Komatsu, Y.; Anker, J.; Geerman, H.; Venema, P.; Stassen, A.F.
Gepubliceerd door: Publicatie datum:
ECN Zonne-energie 5-9-2011
ECN publicatienummer: Publicatie type:
ECN-M--11-012 Conferentiebijdrage
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The phosphorus concentration in the n++ layer (top layer of a phosphorus emitter) was lowered by either thinning or thickening the phosphosilicate glass (PSG) film as the dopant source. Reducing the concentration by thickening the PSG combined with oxidation led to the improvement of the solar cell performance. Thinning the PSG by lowering the process temperature hardly showed positive effect. Reducing the sheet resistance from 66 ohm/square to 51-56 ohm/square by deepening the emitter depth itself and lowering the phosphorus concentration in the n++ layer resulted in a maximum efficiency gain of 0.3%abs for a uniform emitter structure. A selective emitter was fabricated through a process flow including two separate POCl3 diffusion steps. Significant increase of Voc by 18 mV was obtained resulting in an average efficiency gain of 0.5%abs and the largest of 0.7%abs for the best cell. Our 2 ├Ś POCl3 selective emitter process for multicrystalline silicon demonstrated the highest gain in efficiency and Voc, compared with to previously reported selective emitter approaches.

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