LEDs, or light–emitting diodes, are semiconductor devices that produce visible light when an electrical current is passed through them. LEDs are a type of Solid State Lighting (SSL), as are organic light–emitting diodes (OLEDs) and light–emitting polymers (LEPs).
A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction. This effect is a form of electro luminescence. LEDs are small extended sources with extra optics added to the chip, which emit a complex intensity spatial distribution. The color of the emitted light depends on the composition and condition of the semi conducting material used, and can be infrared, visible or near-ultraviolet. Rubin Braunstein of the Radio Corporation of America first reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955. Experimenters at Texas Instruments, Bob Biard and Gary Pittman, found in 1961 that gallium arsenide gave off infrared (invisible) light when electric current was applied. Biard and Pittman were able to establish the priority of their work and received the patent for the infrared light-emitting diode. Nick Holonyak Jr. of the General Electric Company developed the first practical visible-spectrum LED in 1962.