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What is an LED?

Basic principle of an LED (light emitting diode)


Basic components of an LED

A light emitting diode consists of multiple layers of semi-conducting material. When current passes through a diode, light is produced in its active layer. The light produced is decoupled directly or by reflections. In contrast to incandescent reflector lamps, which emit a continuous spectrum, an LED emits light in a particular color. The light’s color depends on the semiconductor material used. Two material systems are mainly used to produce LEDs with a high degree of brightness in all wide range of colors from red to green to blue and amber. With the help of an additional yellowish fluorescent layer, blue LEDs can also produce white light (luminescence conversion). Another method of producing white light consists in mixing red, green and blue light-emitting diodes (RGB). This is used particularly where the priority is not general white lighting but rather decorative effects with various rich colors.

With RGB, thousands of color tones can be mixed by varying the proportions of the individual colors. LED lighting can establish just the right experience wherever they are used.

LED cross section


LED cross-section

LEDs come in a wide variety of white light colors as well. They range from very warm white 2700 Kelvin through neutral white 4000 Kelvin right through to cold white 6500 Kelvin similar to daylight. The color rendering index (CRI) within the various white tones reaches values ranging from 70 to well above 90. Luminous efficiencies of more than 130 lumens per watt are now possible with the currently available components.