A Photovoltaic Cell is a device that converts light energy into electricity via the photovoltaic effect, where the photons trigger the release of electrons in a semi-conductor material. These devices are also known as Photoelectic or Solar cells, the latter based upon the usual source of light to power them.
In most cases PV cells are gathered into a large array to provide more power. Most PV cells are about 1cm square.
These cells are mounted on a light aluminum or flexible plastic backing with a transparent cover to protect the cells from incidental damage. This is sufficient for light weight consumer goods. For industrial use, the cells are mounted on a heavier backing and given a stronger (but more transparent) cover.
Usually discovered around TL–5, PV cells become commercially available at TL–6. Primitive PV cells are highly inefficient (1% or worse) usually because the semiconductor material is sensitive to a single or limited array of wavelengths. At TL–7 this efficiency has improved to 6%, 15% at TL–8, and, with the addition of multiple layer crystal systems, 40% at TL–9.
Photovoltaic cells are an especially well adapted power source for Space Stations which are orbiting near a star: the PV panels may face constantly the star and receive a constant light radiation, thus giving a constant power output. PV panels having very long lifetimes (up to 30 years at TL–9), they make an interesting power source for such isolated stations.