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ECN publication
PASHA: a new industrial process technology enabling high efficiencies on thin and large mc-Si wafers
Published by: Publication date:
ECN Solar Energy 31-8-2007
ECN report number: Document type:
ECN-M--07-092 Conference Paper
Number of pages: Full text:
5 Download PDF  

Presented at: 33rd IEEE Photovoltaic Specialists Conference, San Diego, USA, 11-16 mei 2008.

To maintain high efficiencies for solar cells and reduce the cell bowing, the full Al rear surface of thin conventional solar cells has to be replaced by a more suitable passivating rear surface layer. In our new PASHA-cell (Passivated on All Sides H-patterned cell) we apply a single silicon-nitride (SiNx:H) layer for rear surface passivation in combination with an open, firing through aluminum metallization. This improved processing results in a gain in efficiency of almost 1% absolute compared to full Al BSF, achieving 16.4% on 156 cm2, 200 µm thick mc Si solar cells. Besides this efficiency gain, due to lower consumption of aluminum, there will be a reduction in the costs of cell fabrication. Furthermore, the severe bowing of wafers thinner than 200 µm has been reduced to zero. To test the industrial stability, the processing was applied on a batch of large (243 cm2) and thin (160 µm) wafers which yielded an average cell efficiency of 15.5% with a maximum of 16.1%. This is 0.5% absolute better than the full Al rear reference, even though the rear metallization pattern has not been optimized yet.

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