Product Briefing Outline: BASF and Schmid have together developed a new, contact-free laser transfer printing (LTP) process for metallizing the front and back of solar cells. At present, it is mainly the screen printing process that is used for metallization. The printer and paste system now developed by BASF and Schmid is based on a contact-free laser process and not only offers customers advantages with regard to handling, but also increases the efficiency of cell production.
Problem: There is a need to reduce cracking rates in ultra-thin solar cell production, while boosting performance and simplify handling.
Solution: The LTP PV 1500 laser transfer printer was developed by the Schmid Group to completely replace the existing screen printing process. It can be used for coating both the backs of solar cells with aluminum and aluminum/silver and the fronts with silver. The system can be integrated into existing production lines and is suitable for all types and sizes of cells. There are plans for technical interlinking for combined printing of fronts and backs. The LTP printer achieves a throughput of 1500 wafers per hour and works without actual contact to prevent any mechanical stress on the wafers. A wafer is held in place on a vacuum conveyor and then passed through under the laser. The laser beam separates the metallization paste from the carrier film and transfers the paste to the wafer. The paste on the film is constantly replaced in a cycle. An integrated ink supply with viscosity control ensures that pastes with different compositions can be used. Because the printing is done digitally, any patterns can be printed and serialization of the individual printed wafers is possible.
Applications: Front and backside solar cell metallization.
Platform: BASF will be offering customized metallization pastes for mono- and multicrystalline solar cells that are designed specifically for the new LTP process and can also be used in conventional screen printing. The portfolio will comprise both silver pastes for front side printing and aluminum-based pastes for printing of back sides.
Availability: Market launch planned for early 2010.
