LED is an abbreviation of English Light Emitting Diode, which is a semiconductor solid-state light-emitting device. A solid semiconductor chip is used as a light-emitting material, and in the semiconductor, excess energy is recombined by carriers to cause photon emission, and red, orange, yellow, green, cyan, blue, purple, and white light is directly emitted. LED products are high-tech products that use LEDs as light sources.
LED history
The earliest application of the LED light source made by the principle of semiconductor PN junction light was introduced in the early 1960s. The material used at that time was GaAsP, which emitted red light (λp=650 nm). When the driving current was 20 mA, the luminous flux was only a few thousandths of lumens, and the corresponding luminous efficiency was about 0.1 lm/W.
In the mid-1970s, the elements In and N were introduced to produce green light (λp = 555 nm), yellow light (λp = 590 nm) and orange light (λp = 610 nm), and the luminous efficiency was also increased to 1 lm/W.
By the early 1980s, the LED light source of GaAlAs appeared, making the red LED's luminous efficiency reach 10 lumens per watt.
In the early 1990s, the development of two new materials, GaAlInP, which emits red light and yellow light, and GaInN, which emits green and blue light, have greatly improved the light efficiency of LEDs. In 2000, the former made LEDs in the red and orange regions (λp = 615 nm) with a luminous efficacy of 100 lm/W, while the latter made LEDs with a luminous efficacy of 50 lumens in the green region (λp = 530 nm). watt.
LED advantages
1. Luminous (energy conversion) efficiency is high, that is, it is more energy efficient than traditional light bulbs.
2. The reaction (switching) time is fast and can reach a very high flicker frequency.
3, long service life, up to 35,000 ~ 50,000 hours. Fluorescent lamps are 10,000 to 15,000 hours, and incandescent lamps are 1,000 to 2,000 hours.
4, shock resistance and other mechanical impact. Because it is a solid-state component, it can withstand greater shocks than fluorescent lamps, incandescent lamps, and the like.
5, small size. Its volume can be made very small (less than 2mm). 6, easy to focus. Due to the small size of the illuminating light, it is easy to achieve the desired degree of dispersion by means of a lens or the like. By changing the shape of the package, the directionality can be achieved by scattering from a large angle to focusing on a fine angle.
7, a variety of colors. It can provide a variety of different colors without a filter, and has a strong monochromaticity.
8, rich color gamut. The LED coverage color gamut is wider than other light sources.
LED defects
1, heat dissipation problem, if the heat is not good will greatly shorten the life.
2. The power saving of the low-end LED lamp is still lower than that of the energy-saving lamp (cold cathode tube, CCFL).
3. The initial purchase cost is higher.
4, due to the strong directionality of the LED light source, the design of the luminaire needs to consider the special optical characteristics of the LED.
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