What is a photovoltaic cell and how does it work?

Photovoltaic or PV cells are semiconductor devices that convert sunlight directly into electricity. A typical cell comprises a wafer of silicon which is manufactured with a "p-n junction" within it. This junction is the boundary between "n type" silicon on one side of the wafer (silicon with an excess of free electrons) and "p type" on the other (silicon with a deficit of free electrons). The energy in light frees electrons within the silicon cell - these are captured by the electric field of the p-n junction. Metal contacts on the front and the rear of the cell are used to draw off the electric current produced by this flow of electrons.