Solar panels are devices that convert sunlight into electricity. They are called solar because they use one of the most abundant and renewable energy resources on Earth: sunlight. Solar panels are made up of many smaller units called solar cells. When photons from the sun hit a solar cell, they knock electrons loose from their atoms. These free-flowing electrons generate electricity.
There are three types of solar panels: monocrystalline, polycrystalline, and thin film.
Monocrystalline solar panels are made out of a single large crystal of silicon, resulting in a panel with very high efficiency (about 15-20%). These panels also tend to be more expensive than other types.
Polycrystalline solar panels are made out of multiple small crystals of silicon fused together. They have lower efficiency than monocrystalline panels (about 10-15%), but they are also less expensive to manufacture.
Thin film solar panels are made by depositing layers of photovoltaic material on a substrate (usually glass or metal). The most common type is cadmium telluride (CdTe), which has an efficiency of about 5-10%. Thin film solar cells can be manufactured very cheaply, but their low efficiency means that more area is required to produce the same amount of power as other types of solar cells.