Solid-state lighting (SSL) is a technology in which light-emitting diodes (LEDs) replace conventional incandescent and fluorescent lamps for general lighting purposes. An SSL device produces visible light by means of electroluminescence, a phenomenon in which electric current passing through a specially formulated semiconductor diode causes the semiconductor material to glow.
Originally, LEDs were used as indicator lamps in electronic devices such as radio transmitters, and in some home appliances such as clock radios and television sets. Later, as brighter LEDs were developed, SSL lamps found applications in traffic lighting, electronic billboards, and headlamps for motor vehicles. Today, we find them in flashlights, searchlights, cameras, indoor and outdoor lighting arrangements, and many other situations.
The principal advantage of SSL lamps over incandescent and fluorescent lamps lies in their superior energy conversion efficiency. For example, a typical incandescent bulb, intended for home use, converts about 10 percent of the supplied electrical energy into visible light; the rest comes off as infrared (IR) radiation ("heat"), which is invisible. An SSL device, in contrast, converts about 90 percent of the supplied energy into visible light, and only 10 percent into IR. Another advantage of SSL technology lies in the long lifespans of SSL devices. A typical SSL lamp lasts 35,000 to 50,000 hours, more than 20 times the average life of an incandescent bulb, and roughly six times the life of a compact fluorescent light bulb (CFL).
Solid-state lamps do not contain hazardous substances (as CFLs do) and they don't shatter when dropped (as all other common types of lamps do). A typical SSL lamp is fully dimmable like an incandescent bulb, but unlike a fluorescent lamp or CFL. In addition, SSL lamps do not emit ultraviolet (UV) radiation, which can cause problems ranging from insect attraction to wallpaper and artwork fading. A high-quality SSL device can function at a lower temperature than a typical CFL. The manufacturers of SSL lamps offer color shades ranging from "cool blue" to "warm yellow" to suit all preferences.
On the downside, SSL lamps cost considerably more than incandescent lamps and somewhat more than CFLs. However, when the long lifespan of the SSL lamp is taken into account, and the long-term reduction in energy consumption is factored in, consumers may actually save money by using SSL lamps in as many situations as possible.
Continue reading about solid-state lighting:
The Green Atom offers a primer on SSL.
The International Energy Agency (IEA) maintains a Web site devoted to SSL.
Rensselaer Polytechnic Institute offers an SSL engineering program.