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ECN publication
Efficiency Gain For Bi-Facial Multi-Crystalline Solar Cell With Uncapped Al2O3 And Local Firing-Through Al-BSF
Cesar, I.; Manshanden, P.; Janssen, G.J.M.; Granneman, E.; Siarheyeva, O.; Weeber, A.W.
Published by: Publication date:
ECN Solar Energy 16-6-2013
ECN report number: Document type:
ECN-M--13-013 Conference Paper
Number of pages: Full text:
6 Download PDF  

The p-type bi-facial cell concept, p-PASHA (Passivated on all sides H- pattern), is developed at ECN and employs an uncapped AlOx passivation layer on the rear through which a screen printed H-pattern of aluminium contacts is fired. Here we report a net gain in cell efficiency of 0.2% absolute for the p-PASHA cell vs. industrial reference with the addition of a clean and an ALD step. Even higher gains up to 0.5% abs. are expected after optimization of the cell design and process. Apart from the efficiency gain, the bi-facial cell concept allows for 50-80% reduction in Al paste consumption, the use of thinner wafers, and consists of less processing steps compared to prevalent PERC concepts. The Al2O3 dielectric layer is deposited in the Levitrack, an industrial-type system for high-throughput Atomic Layer Deposition (ALD) developed by Levitech. The efficiency gain is obtained on multi-crystalline wafers, at a rear metal fraction of 40%. Localized IQE mapping, cross-sectional SEM investigation, resistance measurements and 2D simulation relate the efficiency improvement compared to our conventional process to better eutectic and BSF formation at the Al contact edges.

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