How are crystalline silicon cells produced with Czochralski process?
Crystal seeds of silicon are in the so called Czochralski process put into melted polycrystalline silicon for further purification and processed with the puller into cylindrical silicon ingots (for monocrystaline cells) or with the dss furnace into quadratic silicon blocks (for polycrystalline cells).
These ingots are then – depending on the geometrical shape requirements with a wiresaw sliced into silicon wafers that are – depending on the production purpose – either monocrystalline or polycrstyalline cells.
Using a diffusion machine, boron and phosphorus are added. Now electrical contacts are placed to connect each solar cell to another as well as to the junction box.
The thinner the electrical contacts are the more sun can be absorbed by the cell so the contacts must be very thin.
Anti reflective coating
After this, tin-coated copper strips are placed between the cells. Since pure silicon is still to shiny and can reflect up to one third of the sunlight, anti-reflective coating of titanium dioxide or silicon oxide are put on the cell.