How Does An LED Produce Light?
An LED uses what is called “solid-state lighting” technology, or SSL. Incandescent bulbs generate light by heating a thin strip of metal (tungsten) inside a vacuum, until it glows. Fluorescent bulbs generate ultraviolet light when the mercury vapor in the bulb is ionized. These ions then hit particles coated on the inside of the fluorescent bulb and make them fluoresce and give off visible light.
SSL technology emits light from a piece of solid matter. In the case of a traditional LED, that piece of matter is a semiconductor. An LED produces light when electrons move around within its semiconductor structure.
The semiconductor in LED lighting technology is comprised of layers of positively charged and negatively charged components. The positive layer has “holes” — openings for electrons; the negative layer has free electrons floating around in it. When an electric charge strikes the semiconductor, it activates the flow of electrons from the negative layer to the positive layer. When those excited electrons flow into the positively charged holes in the positive layer, they emit light.
This process of generating light from excited electrons in LED technology is much more efficient than both incandescent and fluorescent lighting because much less heat is generated in the process. The glowing tungsten filament in an incandescent bulb, for example, can emit 80% or more of its energy as heat, so that most of the electricity cost spent lighting the bulb is actually wasted.