Evidence of PbI2-Containing Debris Upon P2 Nanosecond Laser Patterning of Perovskite Solar Cells

Laser-based patterning for monolithic serial interconnection of metal halide perovskite (MHP) solar cells is a key process for industrial manufacturing of large-scale MHP solar panels. It requires reliable patterning process parameters to achieve low interconnection losses and, thus, high efficiencies. Here, P2 laser patterning of the perovskite layer was obtained by laser ablation using conventional nanosecond laser pulses at systematically varied laser fluences. The correlation of the laser impact to the morphology, composition, and electrical functionality was analyzed in detail by several surface-analytical techniques. The occurrence of laser-induced periodic surface structures and microdroplets at the bottom of the trenches indicates that material removal via stress-assisted ablation is strongly influenced by thermal processes. The formation of PbI2-containing residuals was evidenced, possibly causing contact resistance losses through the P2 interconnect. These results contribute to the identification of loss factors in laser-based serial interconnection of perovskite solar cells and to further process optimization for upscaling to industrial module sizes.