How LED Works

Jon Bryan Uncategorized

People in Ontario are really beginning to explore LED (Light Emitting Diode) lighting for business and home, and that’s a good thing.  Good for the environment, good for the wallet.  But I’m often asked ‘how do LEDs work?’  I think that’s a good starting point for my first blog post.

First a little history, and for that we go all the way back to the last century – the 1900s.  LEDs really aren’t a brand new technology that has just sprung up.  In the early 1900s a process, later to be called electroluminescence, was discovered when a researcher noticed how applying a current to a specific type of crystal diode created a faint light, and the material was not heating up.

This phenomenon sat idle until it was applied to the creation of the first LED lights in the 1950s.  At that time they were called semiconductor radiant diodes.  From there, over the next 60 years, scientists and engineers have learned to harness this light and we’ve arrived at the LED lighting technology of today.

Basically LEDs are small semiconductor chips.  They are made of two layers, each treated with different materials to give each their own property.  One layer contains a lot of high-energy electrons that it wants to give away, this is called the n-type layer.  The other layer has spaces for these electrons that it really wants to fill at a lower energy level, this is the p-type layer.  The combination of these two layers creates what is called a pn-junction.  These two layers form a diode, from the Greek di (two) and ode (way, or path).

….this junction creates a waterfall like effect: they can flow one way but can’t go back up the other way. 

To the electrons, this junction creates a waterfall like effect: they can flow one way but can’t go back up the other way.  When the negative end of a circuit is applied to the n-type layer, the electrons flow between the two layers easily.  If you apply the negative end of the circuit to the p-type layer the flow is blocked.  So, like a waterfall the flow can only travel one way and not another.

Unlike a waterfall, which creates noise, the electrons flowing across the pn-junction of an LED release light.  As the electrons flow from the n-layer to the p-layer the energy levels of the electrons falls. This creates the release of energy in the form of photons, which we see as light.

So photons sounds very sci-fi, doesn’t it?  Well, it really isn’t, all light is made of photons, which are tiny particles of light that are too small to see individually.

How much light this creates depends on the difference of the energy levels of the two layers.  This is called the band gap.  By learning to control the band gap engineers figured out new ways to make LEDs and create light across the spectrum.

Now, we have LEDs that consume less than 20% of the energy of traditional incandescent and halogen bulbs.  Because there is no heated filament or unusual gasses required these LED lights last far longer.

The result is we’ve now moved to an extremely energy efficient method of producing light.  Now, we have LEDs that consume less than 20% of the energy of traditional incandescent and halogen bulbs.  Because there is no heated filament or unusual gasses required these LED lights last far longer.  LEDs do break down over time, but this takes a very long time.  We’re now seeing commercial LED luminaries with 50,000 hour and even 100,000 hours life expectancies.

The future looks bright (all puns intended) for LED lighting and if you’d like to explore this environmentally friendly, cost saving technology for your business or organization email me at jonb@swantech.ca I’d love to help you lower your carbon footprint and reduce your hydro bill while providing you with better light.

About the Author

Jon Bryan

Jon Bryan is an energy efficiency specialist serving clients across Ontario. An expert in LED lighting and lighting design for all types of businesses, Jon also provides full energy audits & feasibility studies, LEED certification & building commissioning, and provides saveONenergy rebate applicant representative services. Jon can be reached at jonb@swantech.ca