From traffic lights to Christmas lights and even home lighting, light-emitting diode lamps are an energy-efficient alternative to traditional incandescent or fluorescent bulbs and are used in an increasing number of applications. Introduced in 1962, LEDs are semiconductors that emit light when electrons recombine with electron holes -- the vacancies created when those electrons are excited to higher states by variations in electrical current. This interaction releases energy in the form of particles called photons -- which are the basic components of light -- in a process called electroluminescence.
Physical Properties Determine LED Colors
The difference in the colour of LEDs -- red, green, blue, white and amber -- is determined by the energy gap of the materials that form the p-n junction of the diode. A diode consists of a section of N-type material (negatively charged) bonded to a section of P-type material (positively charged), with electrodes on each end. The p-n junction is where these two types of material are joined. Different N- and P-type materials result in different energy gaps that can be measured in the wavelengths that correspond to different colours of the spectrum of visible light.
LEDs Conserve Energy
Traditional incandescent bulbs are known for their energy inefficiency; almost 90 per cent of the energy they consume is lost to the heat they generate. (See References 5) LEDs, on the other hand, use at least 75 per cent less energy than incandescents and only produce 3.4 BTUs per hour, compared to 85 BTUs for incandescent bulbs. (See References 4)
LEDs Reduce Energy Costs
LEDs use only 2 to 10 watts of electricity, which is approximately one-third to one-thirtieth of that used by incandescent bulbs or compact fluorescent lamps. LED lights last 35 to 50 times longer than incandescent bulbs, and approximately 2 to 5 times longer than fluorescents. The U.S. Department of Energy estimates the widespread adoption of LED lighting in the next 20 years will save about £172 billion, prevent the need for constructing 40 new power plants and reduce the electricity demand of lighting by 33 per cent.
LEDs Require No Warm-up Time
LEDs are "instant-on," which means they achieve their optimal brightness immediately upon being powered on. This makes them especially useful in applications such as automotive and aircraft instrumentation illumination, emergency lighting and flashlights.
LEDs Have Many Home Lighting Uses.
Small LED lights can be clustered together and equipped with diffuser lenses to generate wider beams of light. Also, researchers at Purdue University developed a process that uses inexpensive silicon wafers instead of costlier sapphire-based technology. These advancements make LED lighting solutions comparable to traditional incandescent bulbs or CFLs.