Optimized scribing of TCO layers on glass by selective femtosecond laser ablation

Narrow trenches have been scribed into transparent conductive oxide (TCO) films on glass by laser ablation using nano- and femtosecond pulses of ~ 1 μm wavelength. A detailed analysis of the obtained ablation craters and trenches shows that this processing, known as P1 scribes in the production of thin film solar cells, can be considerably optimized utilizing “cold” ablation: using femtosecond pulses, the P1-scribe can be done with almost rectangular cross-section profiles achieving the required electrical separation already at widths below 10 μm, without thermal and mechanical stresses in the substrate or adjacent material. Analogous preliminary results for P2-scribes indicate that this technique allows reducing the total scribe region (optically-inactive zone) to widths below 50 μm.