Laser Micromachining for Cutting Photovoltaic Module Cores and Isolating Cell Regions

Ultra-short pulse (USP) laser micromachining provides capabilities to accurately cut the variety of materials found in a photovoltaic module. During reliability studies, it is often desirable to extract a fragment of the cell from within the module packaging. Our USP laser-based approach uses a femtosecond pulse laser to first cut through the backsheet and encapsulation. These layers are optionally peeled off first, and then the laser is used to cut a circle through the silicon solar cell. Alternatively, the laser can cut a circle through the back polymer layers and cell together. A metal stub is glued to either the cell or the backsheet, and the circular cell piece is removed using torque applied by a wrench. The resulting circular cell piece has smooth edges, and this increased strength helps prevent crack formation and propagation during extraction. Laser scribing can also isolate regions of a cell for localized electrical measurements. The laser can remove an area of backsheet and rear encapsulation for probing or soldering a tab to a busbar wire.