What is an LED?
All About LED Technology from liwinchina group.
What is an LED?
LED (abbreviation LED – light emitting diodes) – a semiconductor device that converts electric current into light radiation. It is a pn-junction. It’s like a “brick” of semiconductor electronics, which consists of two pieces of semiconductor with different types of conductivity – n-type with an excess of electrons, p-type with an excess of holes. If the power source with plus is attached to p-transition, then current will go through. New development can create integrated circuits, including countless pn junctions on a single chip, for example, the processor Pentium-IV fits tens of millions.
Thus, the current went through the pn-junction. It is a moment when there is a redistribution of charge carriers – electrons and holes – when negatively charged electrons are attached to the positively charged ions of the crystal lattice of the semiconductor.
This redistribution may be radiative, that is, when connecting the hole and the electron energy is converted into radiation of a photon. If a transfer didn’t lead to radiation, the energy is converted into heat, and goes to heating the substance. In nature there is more than 5 types of radiative redistribution of carriers, including direct-band reallo- cation. The effectiveness of the LED at the beginning of their existence was measured in watts by increasing their efficiency, and is now determ- ined by a luminous flux (lm) or lumen lm/watt.
Luminous flux – is the density of the light rays that we see, a light output – this is the light intensity at 1 watt of power consumed. By light output energy-saving features of any lighting system can be judged. Accordingly, the more light output, the more energy-efficient lighting device may be considered.
For clarity, we give some figures: All approximate values.
Light output of HID lights – 2800-3500lumens/35-38 watts
Light output of Halogen lights – 700-2100 lumens/40-72 watts
Light output of incandescent bulbs – 15 lm/watt
Light output of fluorescent lamps – 60 lm/watt
Light output of metal halide lamps – 85 lm/watt
Continuous study of the properties of LEDs has led to efficient LEDs that provide light in different spectrals. For example, LEDs based on gallium aluminum phosphide, indium-(development of Hewlett Packard), produced a red-orange, yellow and yellow-green light. Their luminous efficiency was 30 lm/watt and external quantum efficiency up to 55%. Light-emitting diodes emit light in a narrow spectral line – of a width of 20-50 nm. For this indicator, they are somewhere in between the lasers (monochromatic light them, when the radiation comes from a strictly fixed wavelength) and lamps of various kinds, which give white light (a combination of different radiation spectra). Such a “narrow-band radiation” still referred to as “quasimonochromatic.”
LEDs for a long time are the best sources of “color” of light, and surpassed in this respect bulbs with filters.
LED Lights are commonly used in Emergency Vehicles, Police, Exploration, Medical and other industries.

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