LED

From Architect Wiki

LED stands for light-emitting diode, which is a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. LED is a fairly new concept to lighting, but it is becoming more popular as it is a low-cost energy source, more durable, last longer than a traditional light bulb, and emits almost no heat.