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 3.2 W to 9.6 W, the cell efficiency linearly decreased from 19.35% to 19.04%.