WHAT IS AN LED/ BASIC WORKING PRINCIPLE
A light-emitting diode (LED) is a special type of semiconductor device that emits visible light when an electric current passes through it. It has two sides – one with an abundance of electrons called “n-type semiconductor” & the other with bunch of holes that need to be filled by electrons known as “p-type semiconductor “. With the help of these p-n junctions, these semiconductors can control the direction of the flow of electricity. The LED works on the principle that when electrons lose energy, they move from a higher orbit to a lower orbit. The energy lost is in the form of light photons. The color of the light emitted depends upon the frequency of the light photon released. The higher the frequency, the greater is the energy release. Gallium nitride is the light emitting ingredient in LEDs. It is used in the sapphire-based blue and green LEDs. Its practical application is in traffic signals & in lasers in high-definition DVD players.
LED HISTORY
H. J. Round of Marconi Labs discovered Electroluminescence as a phenomenon in 1907. Later in 1955, Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor. Nick Holonyak can be called the “father of the light-emitting diode”. He developed the first practical visible-spectrum (red) LED in 1962, while working at General Electric Company.
LED ADVANTAGES
LED APPLICATIONS
CHALLENGES – Some of the electricity in an LED becomes heat rather than light. If that heat is not removed, the LEDs run at high temperatures, which not only lowers their efficiency, but also makes the LED more dangerous and less reliable. Thus, thermal management of high power LEDs is a crucial area of research and development.
TYPES OF LEDs
Different color LEDs require different forward voltages to operate. Red LEDs require the least voltage, while blue requires higher voltage. Typically, a red LED requires about 2 volts, while blue LEDs require around 4 volts. Based on the color of LED, it can be divided into:
LED COST
LEDs are created on a substrate of sapphire & hence are expensive. However, a technique is developed to create LEDs on low-cost, metal-coated silicon wafers. The sapphire-based technology, however, is currently too expensive for widespread domestic-lighting use, costing at least 20 times more than conventional incandescent and compact fluorescent light bulbs. China with its low production cost & labor cost has made the manufacturing of LEDs very cheap & affordable.There are LED bulbs on the market which can replace the regular CFLs,the cost has fallen rapidly to around $20.With major Chinese makers getting into the manufacture of the sapphire substrates and wafres,it is expected that the general lighting market will be completely taken over by LEDs.