Femtosecond laser patterning of Mo thin film on flexible substrate for CIGS solar cells

Finding ways to scribe Mo back conductor plays an important role in the fabrication and assembly of CIGS thin film solar cells. Using a femtosecond (fs) laser, we selectively removed the Mo thin films of 800 ∼850 nm thick on flexible Polyamide (PI) substrates. In particular, we studied the effect of laser fluence and laser scanning speed on the ablation quality. The single pulse ablation thresholds at various pulse durations were determined. Clean removal of the Mo layer was observed when laser fluence was above the threshold of 0.08-0.1 J/cm². Furthermore, the morphologies and structure of the grooves were characterized using scanning electron microscope (SEM) and KLA Tencor P-16 Profiler. The femtosecond laser provides a unique scheme to ablate the metal layer on flexible substrates for the fabrication of thin film solar cells.