system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How do LEDs work?
gpt
Electron goes in, photon comes out. You can't explain that!

More seriously, you know how there's glow-in-the-dark stuff? It works because electrons in the glow-in-the-dark powder can absorb photons from sunlight and go into high-energy states (they absorb and store energy) and sooner or later they go back to their low-energy states, releasing photons again.

LEDs are kinda the same thing but instead of using light to put electrons in high-energy states, electricity is used. We put electrons into one material where their normal state is relatively high energy, then they cross over a junction into another material where the normal state is lower, and they fall down into it releasing photons. To complete the circuit, a power source is needed to suck the electrons out of the second material and put them into the first.