Electricity can be produced by solar cells whose principal component consists of a semiconductor that is typically made of silicon. A semiconductor consists of a material that cannot be classified as an isolator or a conductor and whose electrical properties can be influenced by adding foreign substances (doping). The solar cells comprise two adjoining semiconductor layers that are equipped with separate metal contacts and have each been doped, thus creating an “n” layer (n = negative) with a surplus of electrons and below that, a “p” layer (p = positive) with an electron deficiency. Due to the difference in concentration, the electrons flow from n into the p area, thus creating an electrical field, or “space charge zone”, inside the semiconductor structure.

The upper “n” layer in a solar cell is so thin that the photons from sunlight can penetrate it and can only discharge their energy to an electron once they are in the space charge zone. The electron that is activated in this manner follows the internal electrical field and thus travels outside of the space charge zone and reaches the metal contacts of the “p” layer. When an electrical load is connected, the power circuit is closed: the electrons flow across the electrical load to the solar cell’s rear contact and then back to the space charge zone. This effect is called the “photovoltaic effect” (derived from ‘‘Phos’’, the Greek word for light and the name of the physicist Alessandro Volta). An inverter, the “heart” of the system, converts the direct current (DC) produced by the solar cells into alternating current (AC).