Light-emitting diode, abbreviated LED, is a tiny device that gives off light in response to an electric current. Many modern electronic devices make use of LED’s. For example, huge displays in baseball stadiums and roadside billboards use thousands of LED’s to produce images. Traffic lights, street lamps, and even car headlights shine with LED’s. Some LED’s—such as those used on remote controls—emit invisible infrared light rather than visible light.
A light-emitting diode typically consists of a semiconductor, such as gallium arsenide. A semiconductor is a material that conducts electric current better than an insulator (nonconductor) but not as well as a conductor. Gallium arsenide and other compounds used in LED’s give off light when electrons flow into them. In large LED displays, individual LED’s glow with red, green, or blue light. Viewed from a distance, the individual lights combine and can appear as any desired color, depending on the relative brightness of each color of LED.
LED’s use electric power much more efficiently than do traditional incandescent lights. When electric current flows through an incandescent light bulb, most of it is transformed into heat. But in an LED, almost all of the electric current results in light.
Organic light-emitting diodes (OLED’s) are composed of extremely thin films made chiefly of carbon, rather than semiconductors. The films—a thousand times thinner than human hairs—emit light when current is applied. OLED’s are used in extremely thin mobile phone and television displays.
See also Electric light (Light-emitting diodes (LED’s)) ; Electronics (Light-emitting devices) ; Light (Light and energy efficiency) .
