Electricity Produced from Light
Electricity may be produced (or controlled) by using light as a source of energy. This occurs because materials like potassium, sodium, germanium, cadmium, cesium, selenium, and silicon release electrons when excited by light under the right conditions. This release of electrons is called the photoelectric effect.
The photoelectric effect is used in three ways. Light causes pho-toemission; the incident beam of light causes a surface to emit electrons that are collected to form an electric current. Light causes a change in how well a material conducts electricity. This is called the photoconductive effect. The third effect is the photovoltaic effect; the energy from the incident beam of light is converted directly into a flow of electrons. Although the photoconductive and photoemissive effects are very useful, particularly in electronic systems, the only source for significant amounts of electricity from light involves the principle of the photovoltaic effect. The solar cells that are used to power space vehicles and satellites are of this type. Let's take a look at how the photovoltaic cell is made and how it works.