How a Solar System Works

A photovoltaic device (generally called a solar cell) consists of layers of semiconductor materials with different electronic properties. In a typical BP Solar crystalline cell the bulk of the material is silicon doped with a small quantity of boron to give it a positive or p-type character. A thin layer on the front of the cell is doped with phosphorous to give it a negative or n-type character. The interface between these two layers contains an electric field and is called a junction.

Light consists of particles called photons. When light hits the solar cell, some of the photons are absorbed in the region of the junction, freeing electrons in the silicon crystal. If the photons have enough energy the electrons will be able to overcome the electric field at the junction and are free to move through the silicon and into an external circuit. As they flow through the external circuit they give up their energy as useful work (turning motors, lighting lamps, etc.) and return to the solar cell.

The photovoltaic process is completely solid state and self-contained. There are no moving parts and no materials are consumed or emitted.