Screen printed, large area bifacial selective emitter N-PERT cells using single-step implantation through laser patterned dielectric layer

In this paper, we demonstrate the formation of a boron selective emitter using single-step B implantation through laser patterned dielectric layer. Optimized dielectric thickness, implantation dose and annealing results in a high sheet resistance of ~170 ohm/D was formed in the oxide mask area and low sheet resistance of~60 ohm/D in the laser ablated regions. Screen printed metal grid lines were aligned inside the laser exposed p++ highly doped region to complete the fabrication of large area, screen printed n-type bifacial selective emitter cells. The samples with laser patterned grid lines gave cell efficiency of 20.75% compared to 20.5% cells without laser pattering. Detailed cell analysis showed that the performance of 20.75% efficiency cell is limited by the recombination in metallized homogeneous phosphorus BSF. Application of this technology for the formation of phosphorus selective BSF, optimization of the laser ablation conditions to reduce laser damage, and reducing in the width of selective region can give much higher cell efficiency.