Optimisation of p+ doping level of n+-p-p+ bifacial b.s.f. solar cells by ion implantation

High-low junctions of n+-p-p+ bifacial back surface field solar cells have been fabricated by B11+ implantation. After an isothermal annealing step at 900°C for 10 min, an optimum surface concentration of 5 × 1019 cm¿3 is observed. Its origin is found to lie in the partial electrical activation of the implanted impurities.