Technology
How does an LED work?
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.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how an LED works.
Step by step
- 1It is a diode — current flows one way — made of a semiconductor with two differently 'doped' regions.
- 2When electrons cross the junction, they drop to a lower energy level and emit the difference as a photon of light.
- 3The semiconductor's makeup sets each photon's energy, which decides the color.
- 4Almost all the energy becomes light rather than heat, so LEDs are highly efficient and long-lasting.
- 5White LEDs usually pair a blue LED with a coating that converts some of the light to other colors.
Frequently asked questions
- 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.