How does an LED bulb make so much light from so little power?

Hook

Why and how does an LED bulb make so much light from so little power? An old incandescent bulb wastes most of its energy as heat. An LED uses a completely different trick, built into a tiny chip.

Old

An incandescent bulb runs electricity through a thin wire filament until it glows white hot. Most of the energy comes out as heat, not visible light.

Chip

An LED, or light emitting diode, is a tiny semiconductor chip. It's made of two layers. One has extra electrons. The other has gaps, called holes, where electrons are missing.

Junction

When current flows, electrons cross the boundary between the layers and drop into those holes. Each time one falls in, it releases its extra energy as a tiny packet of light, called a photon.

Color

The color depends on the material. Different semiconductors release different amounts of energy, which means different colors. Red LEDs came first. Bright blue ones took decades, and earned a Nobel Prize in 2014.

White

Most white LED bulbs are actually blue LEDs coated with a yellow phosphor. Blue plus yellow light looks white to your eyes.

Save

Because far less energy is wasted as heat, LED bulbs use at least seventy five percent less energy than incandescent bulbs, and can last up to twenty five times longer, according to the US Department of Energy.

Close

So an LED makes light when electrons drop into holes inside a chip, releasing energy as light instead of heat. ThatsWhyHow.