Atomic electrons have many energy levels. When electrons transition from high energy level to low energy level, the energy of electrons is reduced, and the reduced energy is converted into photon emission. A lot of these photons are lasers.
The LED principle is similar. However, the difference is that the LED does not emit light through the internal electron transition of the atom, but by adding a voltage across the PN junction of the LED, the PN junction itself forms an energy level (actually, a series of energy Level), then the electrons jump at this level and produce photons to illuminate.
The new LED display device has the advantages of low power consumption, high brightness, long life and small size. This article starts with a brief history of LED display devices, and discusses LEDs for surface mount LEDs, LEDs for automotive applications and LEDs for lighting. The development trend has certain reference value for Chinese engineers engaged in the development of display devices. The world's first commercially available light-emitting diode (LED) was made from tantalum in 1965 and is priced at $45.
In 1968, breakthroughs were made in the development of LEDs, which used a nitrogen-doping process to achieve GaAsP devices with an efficiency of 1 lm/W and emit red, orange and yellow light. By 1971, the industry has introduced GaP green die LEDs with the same efficiency. A small number of LED displays were used in 1972 for watches and calculators. The world's first LED-based watch was originally sold in an expensive jewelry store, priced at $2,100. Almost at the same time, HP and Texas Instruments also introduced a calculator with a 7-segment red LED display. By the 1970s, the price of LEDs plummeted due to the large number of applications of LED devices in home and office equipment. In fact, LED is the digital and text display technology of that era. However, in many commercial devices, LED displays are also increasingly subject to fierce competition from other display technologies, such as liquid crystal, plasma and vacuum fluorescent tube displays.
This competitive incentive for LED manufacturers to further expand their product offerings and actively seek out applications where LEDs have a clear competitive advantage. The LEDs are then applied to text dot matrix displays, light grids for background patterns, and bar graph arrays. The size and complexity of digital displays continues to grow, from 2-digit to 3-bit or even 4-bit, from 7-segment numbers to 14- or 16-segment arrays that display complex combinations of text and patterns. By 1980, manufacturers began to provide intelligent dot matrix LED displays. This technological advancement enables LEDs to be used in outdoor sports information distribution as well as in automotive central high-level installation stop light (CHMSL) equipment. The invention of the bright blue LED enables the realization of a true color advertising display that can display true color, full motion video images.
The advent of blue LEDs has enabled people to partially convert higher energy blue light into other colors using reverse converted phosphorescent materials. Now all LEDs can be used to completely cover all saturated colors in the CIE chromaticity curve, and the organic integration of various color LEDs with phosphorus can produce virtually any color without limitation. In terms of reliability, the half-life of the LED (that is, the time when the light output is reduced to half of the initial value) is about 10,000 to 100,000 hours. In contrast, the half-life of a small indicator incandescent lamp (where half-life refers to the time when half of the lamps fail) is typically between 100,000 and thousands of hours, depending on the rated operating current of the lamp.
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