The LED light revolution has only just begun

   How LEDs dethroned the incandescent bulb, and how they can expand their empire of light     

 Why was it so hard to change a light bulb? The incandescent lamp had a couple big things going for it: It was simple and cheap. It works by passing an electric current through a filament in a vacuum bulb, causing the filament to heat and glow.

The LED, invented by Nick Holonyak Jr. in 1962, is a bit more complicated. It lights up when an electric current passes through a semiconductor diode. A diode is essentially a check valve or one-way lane for an electric current. A light-emitting diode uses a specialized semiconductor material that emits light as electrons flow through it.

These specialized materials raised the cost of early LEDs and limited their performance compared to incandescents. LEDs also don’t produce white light on their own. A white LED requires blending several different LED colors or it needs a material called a phosphor that absorbs light at one wavelength and emits it in another. LEDs often need a driver, a device that converts high-voltage alternating current from a wall outlet into a direct current at a lower, more usable voltage.

However, because LEDs produce light without producing much heat, they have an inherent advantage over incandescents. Only about 10 percent of the electricity used in incandescent bulbs is converted into light. The rest is wasted as heat.