Stuttgart, Germany – At LASYS I renewed the acquaintance of Berthold Richerzhagen, CEO of Synova S.A., who I had first met when he introduced his laser water jet system for hole drilling at the Laser Munich show years ago. I had spotted this system as an innovation that could find a solid niche in industrial laser material processing. It took a few years – new technology innovations usually do – but Synova has had recent successes that have established the laser water jet as a viable processing tool.
The company’s newest technology, patented by the Fraunhofer Institute for Solar Energy System and Synova, is a laser chemical doping system used to increase the efficiency of solar cells by locality diffusing dopant underneath the front contacts, the so-called emitters. The laser beam grooves the passivation layers, and a chemical jet, through which the laser beam is guided (the original system concept), simultaneously introduces local doping at the surface of the silicon wafers. In this manner, thin selective emitters can be produced with a laser-based industrial process.
A manually loaded laser chemical doping system is now available that offers increases in efficiency to 20.4% in a fast and simple process for selective emitter formation. The AR layer opening and groove doping are accomplished in one step.
The process is compatible for P-type back-side doping. Doping is possible before and after SiNx deposition.
Other advantages are reduced contact resistance and the elimination of separate etch, diffusion, and anneal steps. In addition, selective emitters are sufficiently doped for screen printing and electroplating. Line widths are greatly reduced (down to 20 micron) in combination with Ni plating.
As the technology evolves, other steps such as seeding can be added.
Interested parties are encouraged to contact Synova.
– David A. Belforte