Solar Cells

What is a solar cell?

Solar cells are small, square-shaped panel semiconductors made from silicon and other conductive materials, manufactured in thin film layers. When sunlight strikes a solar cell, chemical reactions release electrons, generating electric current. Solar cells are also called photovoltaic cells or “PV cells” and can be found on many small appliances such as calculators.

How a solar cell works.

Photovoltaic’s (PV) are solid-state semiconductor devices that convert light directly into electricity. They are usually made of silicon with traces of other elements and are first cousins to transistors, liquid electronic devices (LEDs), computer chips and other electronic devices.

A photovoltaic device (generally called a solar cell) consists of layers of semiconductor materials with different electronic properties. In a typical crystalline silicon 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.

Photons and solar cells

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 atoms in the cell and into an external circuit as energy. As they flow through the external circuit they give up their energy as useful work (turning motors, charging batteries, for example.) 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. During a typical sunny day, an array of solar cells one meter square exposed to the sun at noon will receive approximately 1 kilowatt (kW) of power.