A photovoltaic panel consists of a series of photovoltaic cells made from two layers of a semiconductor material, one with a positive charge (P) and the other with a negative charge (N). This is called a PN junction. When an electron breaks free, a "hole" is formed, which behaves like a positive charge.
The electron and the hole break away on either side of the PN junction (the electrons towards N and the holes towards P), creating a difference in potential (which is measured in volts). A photovoltaic cell thus produces a continuous electric current.
There are different types of cells and production processes. The most commonly used semiconductor is silicon. Performance is measured first by output: the percentage of sunlight effectively transformed into electricity. Amongst panels sold commercially, are available from the least to the most expensive:
A monocrystalline silicon photovoltaic solar panel. © Public domain