The Science Behind LEDs – Part 1: What is an LED? And What Makes it So Energy Efficient?

What is LED? And what makes it so great?

A light-emitting diode (LED) is a semiconductor light source. A diode is a two-terminal electronic component that conducts electric current in only one direction. LEDs produce 10X more light per watt than incandescent bulbs. Their efficiency is not affected by shape and size unlike Fluorescent light bulbs or tubes. LEDs can have a relatively long productive life. Reports estimate 35,000 to 50,000 hours of useful life, though time to complete failure may be longer. Also, LEDs being solid state components are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.

The Science Behind LEDs

Like a normal diode, the LED consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.

The Layman Definition

Incandescent lights work by using electricity to heat a filament until it glows. The high heat produced explains why they are relatively inefficient sources of light. LEDs work on principles of subatomic physics — but don’t get scared off, it’s quite simple:

Electrons orbit around the nucleus of an atom at various levels, some of which have higher energy states, others have lower. When an electron “drops” from a higher energy state to a lower energy state, it gives off some of its energy in the form of a photon, which is a unit of light.