What is LED lampa?
LED - a semiconductor device that converts electricity directly into light radiation. By the way, in English called the LED light emitting diode, or LED. LED (diode) lamps LED - a new generation of lamps in lighting engineering, LED lamps are the most effective instruments of artificial lighting on the market of environmentally friendly light sources.
From what is LED lampa?
Of a semiconductor crystal on a substrate, the housing with the terminals and the optical system. Modern LED lampor bear little resemblance to the first hull LEDs were used for display. The design of a powerful series of LED lampor Luxeon, manufactured by Lumileds, is shown schematically in Fig.
How does the LED lampa?
Luminescence occurs when the electron-hole recombination in the pn-junction. So, first of all need a pn-junction, then there is contact between two semiconductors with different types of conductivity. To do this, the contact layer of a semiconductor crystal doped by different impurities: on one side of the acceptor, on the other - donor. But not all the pn-junction emits light. Why? First, the bandgap in the active region of LEDs should be close to the energy of photons in the visible range. Secondly, the probability of radiation during the recombination of electron-hole pairs must be high, for which a semiconductor crystal must contain few defects, due to which recombination occurs without radiation. These conditions are more or less contradict each other.Really, to comply with both conditions, a single p-n junction in the crystal is not enough, and you have to make multi-layered semiconductor structures, the so-called heterostructure for the study of which the Russian physicist ZhoresAlferov was awarded the Nobel Prize in 2000.
What good is LED lampa?
In the LED lampa, as opposed to incandescent or fluorescent lamps, electric current is converted directly into thermal radiation, and theoretically it can be done almost without loss. Indeed, the LED lampa (with proper heat sink) is not very hot, which makes it ideal for certain applications. Further, the LED lampa emits in a narrow part of the spectrum, the color is pure, that is especially appreciated by designers, and UV and IR radiation, as a rule, are absent. LED mechanically strong and extremely reliable, its service life can reach 100 thousand hours, which is almost 100 times more than incandescent bulbs, and a 5 - 10 times greater than that of fluorescent lamps. Finally, LED lampa - low-voltage electrical device, and therefore, safe.
