Silicon is a chemical element with the symbol SI. It is a metalloid, thus a material with metallic and non-metallic characteristics. After oxygen, it is the direct secondary most frequent element on earth. In the form of dioxides it exists in form of many minerals, begun from sand, quartz up to half jewels.

Silicon is grey-black in the color and has mostly a metallic gloss. For the processing to solar cells silicon must be cleaned several times so that the purity is more than 99,999%, in order to be able to use it effectively.