Al-Foil on Encapsulant for the Interconnection of Al-Metalized Silicon Solar Cells

We demonstrate the interconnection of silicon solar cells with evaporated aluminum back contacts using an aluminum foil which is attached to a silicone encapsulant. The aluminum-based mechanical and electrical laser interconnection (AMELI) process forms laser weld spots using single laser pulses. These laser welds resist high mechanical stresses and have a low electrical contact resistivity. No solder, conductive adhesives, or Ag-pastes are required for interconnection. We find the electrical contact resistivity to be below ρc = 0.01 mΩ·cm². The contact resistance is constant under accelerated aging of 300 humidity-freeze cycles. With a tensile testing machine, we measure tear-off stresses in the perpendicular direction of up to 380 kPa for our laser weld spots. We present a proof-of-concept module which consists of five n-type back-junction back-contact solar cells with a conversion efficiency of 20.4%. The unchanged fill factor FF and open circuit voltage V_oc verify a damage- and loss-free interconnection which is supported by electroluminescence measurements.