Annealing, Passivation and Contacting of Ion Implanted Phosphorus Emitter Solar Cells

Abstract Recently, ion implantation doping technique has shown potential to improve silicon solar cell efficiency while reducing the number of process steps. In this context, we developed and studied a p-type silicon solar cells fabrication process with a phosphorus implanted emitter. The process is similar to the POCl3 homogeneous diffusion process however replaces the high temperature gaseous diffusion and associated steps by an implantation step followed by an annealing to activate phosphorus dopants. We employed simulation results and advanced characterization to optimize the annealing temperature. The influence of this annealing temperature on the activated dopant profiles and on the crystal damage was highlighted. By adding an O2 flow during the annealing step, a SiO2 layer was grown and an optimum SiO2/SiNx stack was used to improve passivation. Its benefits were quantified by comparison with the standard SiNx passivation. The influence of the implantation dopant density on the passivation quality was also studied. By using an adapted front screen-printed silver paste to contact this new implanted emitter profile we demonstrated an 18,73% certified solar cell efficiency on industrial 156x156 mm2 pseudo square substrate.