Photovoltaics

Photovoltaics is the direct conversion of light into electrical energy through the generation of electric current in illuminated materials. Its most common devices are semiconductor solar cells.

Photovoltaic effect: The generation of voltage or electric current in a material when it absorbs light. This is the physical effect that enables photovoltaic cells to produce electricity.
Photoelectric effect: The emission of electrons from a material after it absorbs light of sufficient frequency. Unlike photovoltaic conversion, the classic effect ejects electrons from a surface into an external space.
Solar panel: An assembly of interconnected photovoltaic cells packaged to produce electrical power. Panels combine cells into practical units with useful voltage and power.
Solar thermal energy: The capture of sunlight as heat for direct use or for producing electricity. It collects solar energy as heat instead of converting light directly into electricity.
Semiconductor: A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled by doping or other means. Semiconductor properties let photovoltaic cells control light-generated charge carriers.
Band gap: The energy range separating a semiconductor's valence band from its conduction band, where electronic states are unavailable. A cell's band gap determines which photons it can absorb and how much energy carriers can deliver.
Photovoltaic system: An installation that uses photovoltaic modules and associated equipment to supply electrical power. Systems combine panels with inverters, wiring, and controls to deliver usable electricity.
Concentrated solar power: Electricity generation that concentrates sunlight to heat a working fluid and drive a heat engine. It uses concentrated heat and a thermodynamic cycle rather than photovoltaic cells.
P–n junction: A boundary between p-type and n-type semiconductor regions, where carrier diffusion creates an internal electric field. Its internal field separates light-generated electrons and holes in many solar cells.
Doping (semiconductor): The intentional addition of impurities to a semiconductor to change its carrier concentration and electrical properties. Doping creates the p-type and n-type regions used to form many photovoltaic junctions.

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