Efficiency gain in plated bifacial n-type PERT cells by means of a selective emitter approach using selective epitaxy

This work evaluates the potential of selective epitaxy to mitigate the recombination losses at the p-type contact regions of plated bifacial n-type PERT cells. Following the growth of a 500 nm, 2.5 1019 cm−3 boron doped epitaxial layer at the emitter contact regions defined by laser ablation of the passivating dielectrics, both an increase in Voc (+6 mV) and FF (+1% absolute) are measured in the final cells compared to the reference with a homogeneous diffused emitter. These results come with an average efficiency gain of 0.3 and 0.5% absolute for front and rear side illumination, respectively. If the diffused, blanket emitter in the passivated regions is replaced by a thicker, lowly doped epitaxial profile (3 μm, 5 1018 cm−3) to further reduce recombination, an additional rise in implied Voc after metallization of 10 mV is estimated. This increase would be the result of a reduction in J0,pass, emitter (down to 6 fA/cm2) and J0,plated, emitter (down to 1967 fA/cm2).