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2011
Conference Paper
Titel
18.7% Emitter Wrap-Through Silicon Solar Cells With Screen-Printed Silver Contacts Acting as a Barrier for Evaporated Aluminium Metallization
Abstract
Since earlier EWT cells with an evaporated aluminium metallization suffered from an inability of providing annealing, a screen-printed silver finger is used to contact the emitter. This silver finger hinders the evaporated aluminium layer, which is used for the laser-fired contacts, from reducing the pseudo fill factor in a final annealing step. The pseudo fill factor is thereby increased up to over 80% leading to conversion efficiencies up to 18.2% on FZ silicon using an emitter with a sheet resistance of 60 /sq. Front and rear side are passivated in a short oxidation step. This reduces the phosphorus concentration at the surface while simultaneously increasing the conductivity of the emitter. Furthermore it is shown, that a single side polishing step after the laser damage removal and texturization process approves to be beneficial for the open-circuit voltage. By using a standard POCl3 diffusion process conversion efficiencies up to 18.7% are achieved on FZ silicon.
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