|
What's a LED?
Light Emitting Diodes or LEDs are found in a
wide variety of everyday electronic devices. From the on/off indicator
light on your computer to remote controls, flashlights, traffic lights,
digital clocks and more. LEDs are ubiquitous in modern society.
LEDs have several advantages
over traditional incandescent bulbs: 1) LEDs last much longer since they
have no filaments to burn out. 2) Since they have no filament to heat up
they emit much less heat than incandescent bulbs and thus work more
efficiently. 3) Their small size makes them ideal for today's ever
shrinking electronic circuits.
To understand how LEDs produce
light we need to take a closer look at the diode. A diode is a simple
semiconductor device. A semiconductor is a material with a varying ability
to conduct an electric current. A diode is made up of two semiconductor
material layers bonded together with wires on each end.
One layer called the N-type
material comprises an excess of negatively charge particles (electrons),
while the other P-type layer has a depletion of electrons or positively
charged “holes” where free electrons from the N-type material can move in
and occupy. When enough voltage (from a battery for example) is applied
across the diode, the electrons from the N-type material are forced to
move into the P-type material occupying vacant positively charged holes.
The movement of electrons across the junction between the two materials
produces an electric current and the production of visible light. To
understand where the light comes from we need to take a closer look at the
atom.
In an atom electrons orbit the nucleus. Electrons furtherest from the
nucleus contain more energy than those in orbits closer to the nucleus.
When an electron drops from a higher orbit to a lower orbit energy is
released in the form of a photon (the basic unit of light). The frequency
of the vibrating released photons determines the color light we see. In
the range of the visible light spectrum red is emitted from the lowest
frequency photons and violet from the highest. Larger electron orbital
drops produce higher energy photons with higher frequencies. The diode
material itself determines the frequency of the photons when electrons
move from the N-type to P-type material and thus the light color. To
direct the light the diode is housed in a small plastic bulb which
functions to concentrate the light outward through the center of the bulb. |
