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How does an LED work?

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Quick answer

An LED (light-emitting diode) works by passing electricity through a semiconductor so that electrons release their energy as particles of light. Because it turns electricity almost directly into light, it wastes far less energy as heat than an old-style bulb.

Step by step

  1. It is a diode — current flows one way — made of a semiconductor with two differently 'doped' regions.
  2. When electrons cross the junction, they drop to a lower energy level and emit the difference as a photon of light.
  3. The semiconductor's makeup sets each photon's energy, which decides the color.
  4. Almost all the energy becomes light rather than heat, so LEDs are highly efficient and long-lasting.
  5. White LEDs usually pair a blue LED with a coating that converts some of the light to other colors.

People also ask

Why are LEDs so energy-efficient?
They convert electricity almost directly into light at the atomic level, wasting little as heat — unlike incandescent bulbs that glow only by getting hot.
What decides an LED's color?
The semiconductor material sets the energy of each emitted photon, and that energy determines the color of the light.
How do LEDs make white light?
Most combine a blue LED with a phosphor coating that converts part of the blue into yellow and red, which together look white.