eli5: if a wire burns in a normal bulb, what “burns” inside an LED (what makes the light)?

143 views

eli5: if a wire burns in a normal bulb, what “burns” inside an LED (what makes the light)?

In: Physics

This is what i remember from high school. An LED is made up of semi conductors (p-type and n-type). P type semi conductors are electron donors. While N type semi conductors are electron acceptors.

When current is passed through an LED, atoms in the p-type semiconductor get excited and release high energy electrons, which are then accepted by the n-type. The n-type semiconductor half can’t directly accept these excited electrons. They have to drop some of the energy before joining and usually, that energy is emitted as light.

P.S. I don’t know if electron excitation is ELI5 acceptable.

A wafer of silicon. This is the yellow rectangle you will see when the light is off.

This wafer is a diode, the D in LED. A diode is a thing in which energy may only travel one direction.

Its kind of a different mechanism: in an old light bulb, the wire heats up, and the heat causes it to create light through what we call “black body radiation”. It basically means the atoms of the wire jiggle very fast, and this motion creates the light we see.

For LEDs, light is created using a different mechanism: we use electricity to move electrons across a barrier, and once they are over, they return to their normal state, releasing light. Kind of like pushing a rock over a hill.

This is why it’s almost impossible to make wire bulbs with light that isn’t orange/yellow, since it requires insane temperatures that are unsafe for the materials or people around them. With LEDs, since you don’t need to heat up anything, you just need to find the right kind of material with the right “height” of the mountain such that the light is in the color you want.