Multi-Crystalline Silicon Solar Cells Laser Edge Isolation: A Comparison of Process Results Achieved With State-of-the-Art Tripled ND:YAG and Fiber Lasers

Laser Edge Isolation is the main laser application in photovoltaic applications. This laser process is necessary to remove parasitic emitter diffusion wrapping around the wafer edge, in order to avoid very low fill factors. We have investigated in detail, and compared the results thus obtained, the cell surface scribing realized with State of the Art Pulsed Fiber Laser (emitting at about 1070 nm) and tripled ND:YAG (emitting at 355 nm). Using the LBIC technique, outstanding isolation efficiency was detected in case of Fiber Laser scribing. Measured LBIC signal ratio > 97% on wide parameters range, and >99% in best cases, are the fingerprint of nearly ideal isolation process. Extremely high isolation efficiency was as well detected in case of UV Laser process; LBIC signal ratio > 92% was routinely obtained on wide parameters range, and >98% in best cases.