Silicon solar cells using aluminum foil as rear side metallization reaching 21.0 % efficiency

In this contribution we present the latest results of our experiments regarding the use of aluminum foil as rear side metallization for solar cells with dielectric passivation and laser fired contacts (LFC). In this approach the foil is fixed during the contacting process onto the wafer by local alloying of an IR laser. The proof of that concept was already shown at the 22nd EUPVSEC conference in Milan. Meanwhile, we have optimized the overall cell process by using aluminum oxide Al2O3 since it is a more appropriate passivation material for this approach. Furthermore, we investigated the laser process and compared different laser parameters regarding the resistance of the contacts and the adhesion properties of the foil. Finally, we show that the efficiency potential of the foil metallization is on the same level compared to the originally metallization concept for LFC cells based on physical vapor deposition (PVD) by achieving efficiencies of 21.0 %.