Solar cells are combined into solar panels which can be mounted on roofs, open fields, or other locations. Most solar cells are made of polycrystalline or monocrystalline silicon. Silicon is the most common metalloid. It is also the eighth most common element in the universe by mass. It has very good semiconductor characteristics and is, therefore, widely used.
Silicon solar cells are made from silicon wafers. A silicon wafer is a thin slice of silicon crystal that is produced in several steps of a microfabrication process. For protection the slice has to be covered with a glass sheet. A silicon solar cell is usually put in a square form as photovoltaic cell.
Solar cells. Source: SolarWorld AG
Polycrystalline Solar Cells
Polycrystalline solar cells are most common as the relation of price and efficiency is quite good. Other types of solar cells might be more effective, but more expensive. Polycrystalline solar cells have an efficiency of 11-14%.
Monocrystalline Solar Cells
Monocrystalline solar cells have higher efficiency rates than their polycrystalline counterparts. The production is more complex and makes monocrystalline solar cells more expensive than others.
Thin Film Solar Cells
Thin film solar cells, used in thin film solar panels, are also more expensive but have some significant advantages to other solar cells. They´re made out of lighter materials and are better suited for roofs which cannot carry a heavy roof load. Another advantage is a high efficiency rate in diffuse sunlight. Thin film solar, therefore, is better suited for areas with less direct sunlight or roofs that do not face south.
There are some emerging photovoltaic technologies where different materials are tested like organic solar cells, also known as plastic solar cells. This technology is still not fully developed and organic solar cells still have a low efficiency rate.
When several solar cells are interconnected they form a photovoltaic/solar panel system, which can be mounted on a field or on house roofs.