Cases Study

LED: Technology for energy-efficient, flexible lighting solutions

Basic principle of a LED (light emitting diode) A light emitting diode consists of multiple layers of semi-conducting material. When the diode is being used with direct current, light is produced in the 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, in order to produce LEDs with a high degree of brightness in all colors from blue to red and, by means of luminescence conversion, also in white. Different voltages are necessary, to operate the diode in forward bias. LEDs are semiconductor crystals. Depending on the composition of the crystal compounds, they emit light in the colors of red, green, yellow or blue, when current flows through them. With the help of an additional yellowish fluorescent layer, blue LEDs 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 the three RGB colors, any number of color tones may be mixed by varying the proportions of the individual colors. In this way, the LED lighting can create fascinating worlds of experience.