What is LED?
Throughout man’s history, there has always been a need for light. Mankind’s mastery of fire provided not only him with much needed warmth but protection from the nocturnal predators that might try to eat him. Though the move from caves to more permanent structures and the advent of electricity may have obviated the protection that fire once provided, we still have the need for light and the different type of warmth it provides.
There are many ways we can use electricity to produce light and in the home, two main types can be found: incandescent light bulbs and fluorescent lamps.
Incandescent light bulbs produce light by passing a current through a thin metal filament. This heats the wire until it glows and emits visible light.
Fluorescent lamps produce light by passing an electrical current through a mercury vapor, exciting it to emit ultraviolet or UV light. This UV light is then absorbed by phosphors that coat the lamp to emit light in the visible region in a process called fluorescence.
Despite their widespread use, these two methods suffer from significant disadvantages that have lead to some countries to move away from and even ban their use. Incandescent light bulbs are highly inefficient, converting a mere 3% of electricity into visible light and wasting the rest as heat. While fluorescent lamps are more efficient, converting about 85% of the electrical energy into light, the mercury contained inside the bulbs are very toxic and needs to be disposed of properly.
Light Emitting Diodes
A light-emitting diode or LED is a semiconductor electronics component.Semiconductors are materials whose electrical conductivity lies somewhere in between a conductor and an insulator. Unlike the majority of electrical components that are made of silicon, LEDs are typically made from gallium, another type of semiconducting material.
By doping or adding impurities to the gallium crystal, p-type and n-type regions, areas in the crystal where there is an abundance of either positive or negative charge carriers. In the p-type region, there is an abundance of positive charge carriers or holes and in the n-type region, there is an abundance of negative charge carriers or electrons. When a voltage is applied across the terminals of a LED, the charge carriers move with the electrons moving into the p-type region and the holes moving into the n-type region. When an electron meets a hole, it releases energy in the form of a photon or light.
This process in which a LED converts electricity into light is known as electroluminesence where a material emits light in response to a current or electrical field. The advantage of this method over others is the efficiency at which energy is converted into light. Unlike fluorescent light bulbs, its efficiency is not affected by its shape or size.
Compared to the other methods for generating light in the home, the use of LEDs can lead to considerable savings in energy use. As gallium is considered to be non-toxic, a “dead” LED can safely and easily be disposed in the trash. The mercury found in fluorescent lamps is a dangerous neurotoxin and must be taken to an appropriate center that will either dispose or recycle them properly. The use of LED provides home owners with the options of a lighting source that is economical, efficient and environmentally friendly.
Figure SEQ “Figure” \*Arabic 1: Holes move from the p-type region into the n-type region. Electrons also move from the n-type region to the p-type region. The combination of electrons and holes result in light emission.