Rear-side picosecond laser ablation of indium tin oxide micro-grooves

• Picosecond laser ablation of indium tin oxide (ITO) micro-grooves using 1064 nm radiation is studied.
• A detailed comparative study of rear-side and front-side ablation is presented.
• Formation mechanism of micro-cracks on grooves rims in rear-side ablation is analyzed.
• High quality grooves are obtained in rear-side ablation after the optimization of scan speed.

A comparative study of the fabrication of micro-grooves in indium tin oxide films by picosecond laser ablation for application in thin film solar cells is presented, evaluating the variation of different process parameters. Compared with traditional front-side ablation, rear-side ablation results in thinner grooves with varying laser power at a certain scan speed. In particular, and in contrast to front-side ablation, the width of the micro-grooves remains unchanged when the scan speed was changed. Thus, the micro-groove quality can be optimized by adjusting the scan speed while the groove width would not be affected. Furthermore, high-quality micro-grooves with ripple free surfaces and steep sidewalls could only be achieved when applying rear-side ablation. Finally, the formation mechanism of micro-cracks on the groove rims during rear-side ablation is analyzed and the cracks can be almost entirely eliminated by an optimization of the scan speed.