A light-emitting diode or luminescent diode (LED) is a semiconductor component of optoelectronics that emits light according to the principle of electroluminescence. The electroluminescent diode converts energy supplied by electric current directly into light. This is understood to be the ability of semiconductors to displace electrons with simultaneous emission of photons. This occurs through an electron or quantum jump from one shell of the Bohr atomic model to another. A quantum jump always occurs with absorption or emission of the energy difference.
During the quantum leap and the associated transition from a higher to a lower energy level, energy is released in the form of a photon. The process of reciprocal absorption of energy and subsequent return to the original state with emission of light (photons) is called luminescence.(GaP) or arsenides like gallium arsenide (GaAs) or indium arsenide (InAs). These semiconductors or combinations of them determine the color of the light emission. yellow results in white. The color temperature is about 5,600 Kelvin. There are also light emitting diode arrays with adjustable color temperature that can produce daylight of 6,500 Kelvin.
LED applications: Optical transmission technology, status displays, displays and printers, automotive and lighting technology.Like laser diodes, light-emitting diodes are used in communications as a light source for transmission in optical media, and also as status indicators, in LED displays, in lighting technology and in automotive technology. Important characteristic values of light emitting diodes are the luminous flux as well as the characteristic values for color and brightness perception summarized in the bin code. Further characteristic values are the luminousefficacy, the efficiency and the LED service life. radiation area lies between 50 µm and 100 µm and above. They are therefore primarily used in multimode fibers. Since the radiation is larger than the core glass area, LED launch is referred to as overfilled launch (OFL). LEDs have some inertia in optical signal generation due to their switching hysteresis. They can be used at data rates up to 100 Mbit/s. They are not suitable for high bit rate applications such as those found in 10 Gigabit Ethernet. Corresponding data rates are covered by VCSEL lasers.
Characteristics and applications of LEDsLEDs based on the semiconductor gallium arsenide (GaAs) radiate at a wavelength of 850 nm. However, they are also available in other dopants for wavelengths at 1,300 nm and 1,500 nm. Typical output powers are 1 mW, coupling losses are -17 dB. Gbit/s.
Energy efficiency and color rendering of LEDsLight-emitting diodes are also being developed for the backlighting of LCD displays and are increasingly being used as power LEDs for the LED lighting of living spaces, shops, halls and automotive technology in the form of LED lights, LED spots and LED headlights. The high-intensity light-emitting diodes already available have an illumination efficiency of over 150 lumens per watt and a luminous efficacy of up to 8,000 cd/m2. In terms of brightness, these values are already in the range of a 20 W halogen lamp; in addition, the color rendering index (CRI) is 95 and higher, making them ideally suited for residential lighting. Depending on the cooling system, their life is between 50,000 and 100,000 hours, by which is meant the period after which the brightness has fallen to 70 % or 50 % (depending on the manufacturer) of the initial brightness.
Further developments include Organic Light Emitting Diodes (OLED), polymer LEDs (PLED), UV LEDs, which are used in UV surface treatment, and AC LEDs for room lighting, which can be connected directly to the mains. Infrared LEDs (IR LEDs), from which visible light LEDs have evolved, should also be mentioned in this context. In addition to the monochromatic light-emitting diodes, there are also two-colour and three-colour LEDs, bi-colour LEDs and tri-colour LEDs.