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What is LED?
LED (Light Emitting Diode) is an electronic light source based on the semiconductor diode. A diode is a device that allows current to flow in only one direction. Light is emitted when the diode is forward biased (switched on). This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. Early commercial LEDs were commonly used as indicators. As the LED materials technology became more advanced, the light output was increased, the invention and development of the high power white light LED are making LED illumination more possible. LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.
LED Physics
LED consists of a chip of semiconducting material with impurities to create a p-n junction. 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 wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction.
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