Fundamental consideration of junction formation strategies for phosphorus-doped emitters with J_0e < 10 fA/cm²

This work shows the potential of further optimization of phosphorus-doped emitters in p-type silicon solar cells. We investigate the impact of different combinations of phosphorus doping profiles and surface passivation qualities on the saturation current density J_0e by considering boundary conditions based on published experimental data. Our simulation study shows that there are two possible ways to achieve J_0e values below 10 fA/cm². One is the reduction of the electrically active phosphorus concentration n_surf at the surface beneath 2×10¹⁹ cm^-3 and simultaneously reducing the surface recombination velocity S_p to below 10³ cm/s. The other contrarily increases n_surf to values of up to 1×10²¹ cm^-3 while ensuring full activation of all phosphorus dopants. In the latter case, J_0e values below 10 fA/cm² seem possible, even for S_p = 10⁷ cm/s which is equal to the thermal velocity.