Toward Effective Gettering in Boron-Implanted Silicon Solar Cells

Boron-implantation is a pathway to high-quality, low-cost emitters required to the industry standard BBr3 diffusion, B-implant requires no edge isolation or boron rich layer (BRL) removal, which reduces manufacturing complexity and cost. B-implant also offers easy control of the dopant profile, which can translate to lower emitter saturation current density (j(0e)) and thus higher cell efficiencies. In addition to low emitter saturation current density, an important property of the emitter is its gettering efficiency, or its ability to reduce recombination active bulk defects that degrade bulk minority charge carrier diffusion length. Here, we perform a controlled experiment to map the potential of high-quality (j(0e) <50 fA/cm(2)) B-implanted emitters to reduce bulk iron point defects. We show that the point defect concentration can be reduced by more than 99.9 %. We describe efforts to generalize our results and elucidate the underlying gettering mechanisms via predictive modeling.