LED, WHAT IS IT?

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Light Emitting Diode (LED) is a semiconductor light-producing unit.  When an electrical current passes through the unique materials, there is a recombination of positive and negative charges resulting in the emission of photons, as light energy.  This action is called electroluminescence.  The color of the light is determined by the energy gap of semiconductor and the material used within the diode.

The LED is a chip of semi conducting material, coated with impurities to create a P-N junction.  Current flows from the anode (P-side) to the cathode (N-side), but not in the reverse direction.  Electrically-charged electrons flow into the junction and meets in a hole falling into a lower energy level, releasing energy in the form of protons.  The wavelength of the light-emitted color, depends on the band gap energy of the materials forming the P-N junction.

LEDs are usually built on an N-type substrate with an electrode attached to the P-type layer deposited on its surface.  The ideal shape of a semiconductor with maximum light output, would be a microsphere with photon emission occurring at the exact center.

Many LED semiconductor chips are potted in clear or colored, molded plastic shells.  The plastic shell allows: 1) Mounting of the semiconductor chip in the devices to be accomplished more efficiently and easier, 2) The fragile electrical wires to be supported and protected, and 3)  The plastic to act as a refractive intermediary between the relatively high-index semiconductor and low-index of open air (#32).

LED lighting requires very constant low voltages.  These voltages are transformed from our standard 120 or 277 volts, by what are called drivers.  The drivers and LEDs form an assembly.  Remember OHMS Law.  These low voltages produce heat and heat must be dealt with.  The driver and lamp assembly must be designed into a fixture that must be appealing visually, in order to market it, but at the same time, have the ability to dispense heat.

Now, let’s talk about the advantages and disadvantages of LED (See Article #3, “LEDs-Pros and Cons”).