Solar cells must comprise differently doped zones that perform different functions, e.g. the p-n junction or high-low junctions. A range of methods is available at Fraunhofer ISE to achieve such doping either across the entire surface or in specific areas. These include the established tube furnace diffusion method as well as a variety of other options:
- Diffusion from deposited/printed coatings, patterned if necessary, in tube furnace and continuous through-feed processes
- Laser diffusion from deposited/printed coatings or liquid phase, as well as laser transfer doping
- Ion implantation incl. annealing
This development work aims to achieve ideal, tailored solutions for creating doped zones in the many different solar cell types. The specific challenges here lie in generating a physically perfect doping profile (metal semiconductor contact, minimized recombination, structure size, etc.) and in using methods that are both inexpensive and viable at the throughput rate required for production.