Analysis of laser-induced damage during laser ablation process using picosecond pulse width laser to fabricate highly efficient PERC cells

A highly efficient passivated emitter and rear cell(PERC) was fabricated using a picosecond (ps) pulse width laser ablation system. To evaluate the applicability of the laser ablation process to remove dielectric layers, the laser-induced damage was thoroughly analyzed using TEM and Raman spectroscopy. At the optimized laser intensity, passivation layers such as SiNx and Al₂O₃ were well ablated and laser damage was suppressed. In this case, only a thin layer of amorphous silicon of 30 Å in thickness was formed but recrystallized domains or dislocations were not observed underneath the processed region. At excessive irradiation powers, the dislocation density significantly increased under the ablated spot. As a result, as the laser irradiation energy increased from 3.2W to 9.6W, the cell efficiency linearly decreased from 19.35% to 19.04%.