Aluminum-Based Mechanical and Electrical Laser Interconnection Process for Module Integration of Silicon Solar Cells

In this paper, an interconnection method for the module integration of silicon solar cells by laser microwelding of the Al-metalized rear side of the solar cell to a metalized substrate is introduced. This laser microwelding process forms a direct mechanical and electrical connection between two Al-layers without the need for any soldering, conductive adhesives, or Ag-pastes. With a tensile tester, we measure tear-off stresses of up to 303 kPa for our laser weld spots. Furthermore, carrier lifetime measurements show that no defects are induced into the Si-crystal by the laser process over a wide range of laser pulse energies and number of laser pulses. In order to demonstrate the applicability of this laser-based interconnection method, we present a proof-of-concept module consisting of five n-type back-junction back-contact solar cells with a conversion efficiency of 20.0%.