How do LEDs make light from electricity?
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I’ll give this a try. I think a good ELI5 way to think about it is actually to look at regular light bulbs first (what are referred to as “incandescent” lightbulbs). Incandescent work by sending electricity through a material, usually tungsten, that gets hot – REALLY HOT – but not hot enough to melt or break anything. You can think of this piece of hot metal like when you heat up a stove or oven and the heating elements get “red-hot” and thus radiates energy at a high enough level to produce both light and heat.
An LED is completely different, and the real mechanics of how LEDs work on the finite scale is complex and has to do with complex properties of special electromechanical materials called semiconductors. I can’t ELI5 on those because I never fully grasped those mechanics in engineering school.
Ignoring a lot of the physical things going on, we can basically think of LEDs as a bulb that takes a small amount of energy and almost fully turns that energy into light by bouncing the electricity around inside the bulb in a clever pattern. Meaning, the LED doesn’t get very hot, and most of the energy input put into the LED comes out as light and not heat.
To create different LED colors, we spray the inside of the LED bulb with a special material called a phosphor, which is sorta-kind of like a fancy crystal coating that allows some colors through but not others.
Imagine being in a room with a floor with a single step. All the floor is covered in marbles.
You start taking marbles from below the step and bring them on top of it. What will happen is that now many marbles will start to fall from the step and, in doing that, they’ll lose potential energy and will make noise. Each single marble makes its own tiny noise, all combined make a continuous, loud noise.
LEDs are made from two materials, one next to the other. When we apply a voltage, electrons flow from one material to the other. Like the marbles.
When an electron is on an atom of the first material, it has some potential energy, like a marble on top of the step.
When the electron is pushed to the other material, it loses some potential energy, like the marble falling. And, in doing so, that energy has to go somewhere: it’s released as a photon, “an element of light”, just like the marble transforms the energy from the fall into noise.
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