There are three basic types of photovoltaic cells:
These cells are formed using thin slices of single crystal, this makes them most efficient and because of the manufacturing process these cells are the most expensive. The efficiency of monocrystalline panels are typically 15-20%.
To reduce the cost of the single cell manufacturing process, cells are often made from multi-crystalline material, this is called polycrystalline. Polycrystalline cells are made by pouring liquid silicon into molds and then slicing the molds once solidified into wafers. This process makes polycrystalline cells less expensive and less efficient then monocrystalline cells. The efficiency of polycrystalline panels are typically 13-16%.
Thin-film solar panels are made using extra thin layer of semiconducting material. These panels are a lot less expensive than silicon based panels, although they are a lot less efficient in converting sunlight into electricity as well. Thin-film cells are used in low voltage applications. They can also be used to create flexible building materials, when a solar panel is built into a structure, it is known as building integrated photovoltaics. There are four main types of thin-film cells:
- Cadmium telluride cells (CdTe)
- Copper Indium Gallium Diselenide (CIGS)
- Amorphous Silicon (a-Si)
- Thin-film Silicon (TF-Si)
Note that the type of crystal used determines efficiency of the cell.