Foil metallization process for PERC solar cells towards industrial feasibility

Aluminium foil in combination with laser fired contacts (FolMet) as rear side electrode for highly efficient passivated emitter and rear cells (PERC) has proven a high efficiency potential of up to 21.3 % using an optimized and simplified cell process. Two objectives towards industrialization are the acceleration of the laser process and the feasibility of module assembly. An ultrafast polygon scanning system and comprehensive simulations enabled process times tpro < 0.8 s for 156x156 mm² wafers, which corresponds to an acceleration of processing speed by a factor of 20. An easy-to-apply possibility to realize the electrical interconnection between foil metallized cells, is the single-side coating of the aluminium foil using a special treatment. This process could be carried out before the foil attachment to the solar cell, which allows the usage of a fast and cheap role to role production tool. The created soldering pads are compatible with conventional interconnection techniques and modules assembled with this technique passed the humidity-freeze (HF10) and temperature-cycle (TC200) test successfully.