Failure mechanisms for solar cells with laser doped selective emitter and plated Ni-Cu metal contacts

Al-BSF solar cells with a laser doped selective emitter and plated Ni-Cu contacts are an attractive approach for industrial fabrication. Yet the contact adhesion of the plated Ni-Cu contacts due to diffusion barriers in the contact area and electrical stability against tempering induced non-ohmic Ni shunts are two main challenges for this cell concept. This work presents failure mechanisms of laser doped solar cells. Microscopic characterization analyzes process induced defects separately, which result in poor contact adhesion and non-ohmic shunting. A process route is presented, which yields in solar cells with pseudo fill factors above 80 % and a sufficient contact adhesion of 1 N/mm.