Photovoltaic production process - production of solar cells

There is a number of well-established processes to produce the raw material for solar cells. Silicon (Si) is the base material used in most of the production processes. (exception: thin-film solar cells). 

 

    • Bridgeman method
    • EFG method
    • Czochralski method

 

Silicon is the second most frequent chemical element in the Earth's crust. Silicon as a tetravalent metalliod has the ability to form covalent bonds with neighbor atoms forming hard and brittle crystals - silicates or silica (SiO2) - with a solid diamond-like structure.

 

For the production of solar cells, the purity requirements of the silicon used for the solar cells are almost as high as for the production of semiconductors. While the semiconductor industry requires a purity of 99.9999999%, a 100 to 1,000 fold lower grade is sufficient for solar silicon.

 

During this early production Step p-type doping takes place by adding an impurity of valence-three elements - boron - to a valence-four silicon semiconductor in order to increase the number of free charge carriers.