When photovoltaic cells are hit by sunlight, photons are absorbed, electrons are released and capturing those free electrons causes an electric current. Photovoltaic cells create a direct current (DC), which must be transformed into an alternating current (AC) for industry and home use. Photovoltaic systems rely on an inverter to accomplish this conversion.
The majority of photovoltaic cells are made from monocrystalline or polycrystalline silicon. Monocrystalline photovoltaic panels are more expensive and laborious to make than polycrystalline, as they are made by growing a large, pure crystal in a furnace, and then cutting the crystal into individual squares. However, they do run more efficiently than polycrystalline panels. Roughly, 35 percent of the world's photovoltaic production is made from monocrystalline silicon, according to About.com.
Polycrystalline panels are made by molding molten silicon in blocks, which is quicker and more cost-effective. However, the result is a photovoltaic cell that is less efficient than a monocrystalline one. Approximately 45 percent of the world's photovoltaic production is made from polycrystalline silicon, according to About.com.
Thin film is another type of photovoltaic module, which involves embedding photovoltaic cells on a thin, pliant material like plastic, glass or heavy tin foil. Thin film photovoltaics are commonly used to power small devices for camping or military purposes.