Chemical Definition: This type of Silicon contains several regions of crystalline Silicon kept together through covalent bonding and separated by ‘grain boundaries.’
What-that-means: This type of silicon goes through a lower number of cycles of the energy intensive filtration and separation processes that monocrystalline cells do and therefore are a less expensive material for manufacturers to use.
Interesting point: These cells are usually grown in a square shape. This is because the molten liquid in the (square) ingots does not to be extruded or go through another process to produce the big block of silicon out of which the little cells are cut. (Grain boundaries can have an interesting effect on efficiency and this shall be covered in a later article)