One of the most important factors for the performance and service life of an LED is the temperature in the junction - the so-called junction temperature Tj. As the temperature rises, the luminous efficacy and service life of an LED decrease. Thermal management therefore plays a central role.

When considering the service life of an LED, a distinction is made between parametric faults, i.e. a reduction in luminous flux (degradation) and total failure, which is independent of this. For technological reasons, the luminous flux of LEDs decreases over time until it falls below an acceptable threshold value for the respective area of application. The reduction in luminous flux of LED luminaires must be taken into account when planning the lighting system. The average rated service life Lx is generally used as a guide, where "L" indicates the number of operating hours within which the luminous flux is expected to fall to a predetermined minimum percentage value of "x". In the case of high-quality LED luminaires, the total failure is negligible within the time frame of the service life, meaning that it is irrelevant in planning.

Despite the enormous efficiency of LEDs, which convert around 60% of the electrical energy supplied into visible light, the heat generated by the remaining 40% of electrical losses still places high demands on reliable thermal management. The heat generated in the almost point-like small volume of the LED crystal must be dissipated continuously and reliably so that no heat build-up occurs even in continuous operation and the service life of the thermally sensitive semiconductor is not impaired. The adequate design of the construction and precise production processes are therefore basic prerequisites for being able to offer a high-quality product.

If you compare the light from different light sources, you will notice major differences. Candlelight is perceived as warm light, while the light from a fluorescent tube appears colder. Both light sources are so-called white light sources and emit a broad spectrum of different wavelengths. The ratio of the different spectral components determines the perceived light color, warm white with increased red components and cool white with increased blue components.

The light emitted by a light-emitting diode is not the small, visible portion of its temperature radiation, as is the case with an incandescent lamp - it is instead generated by the recombination of positive and negative charge carriers in the junction layer of the semiconductor. A large proportion of the energy released is emitted as electromagnetic radiation in the visible range - i.e. as light. The efficiency of the LED exceeds that of an incandescent lamp many times over. Around 60 % of the electrical energy used is converted into light by a light-emitting diode.

At first sight an LED assembly consists of a series of simple components. The central element is the actual LED (light emitting diode), a specially doped semiconductor that transforms the electrical energy into visible light. This process takes place in a very narrow area in the centre of the semiconductor, the so-called junction area or junction. The LED itself features two electrical connections and can be fixed onto a thermally conducting carrier material to dissipate the heat occurring during operation. These components are protected by a robust housing that is covered above, i.e. in the radiation direction, by a primary optical system (usually a small lens).

If the spectral composition of the light from various light sources is compared then major differences are seen. Candlelight for example contains an above average red component and is perceived as warm light, whereas the light from a fluorescent tube has a higher blue component and appears cooler. As most natural light sources emit a wide spectrum of various wavelengths, specification of a single wavelength is not suitable for characterising white light. More decisive is the ratio of the various spectral components. These specify the colour temperature with white light or the colour of coloured light.

The light emitted from a diode is not the by-product of a thermal process as with incandescent lamps but is generated as part of an electrical reaction within the diode, with recombination of positive and negative charge carriers in the junction area of the semiconductor. The energy released is emitted as electromagnetic radiation in the visible range, meaning in the form of light. The efficiency of LEDs exceeds that of an incandescent lamp many times over. Around 50 % of electrical energy input is transformed by LEDs into light.