Now, we can see the "shadow" of LEDs (light-emitting diodes) everywhere: it flashes in front of our computer; reveals its brilliant smile in the neon lights of the city; it is a beam of light in the new flashlight in the dark; it also forms a square The central video wall... The brilliance of the city and the world comes from the efforts of scientists.
According to the Nobel official website, Japanese scientists Akasaka, Amano and Japanese-American scientist Nakamura Shuji won the 2014 Nobel Prize in Physics for inventing the "High Brightness Blue LED". The Nobel Prize Selection Committee said in a statement. The three winners made a significant contribution to the invention of a new high-efficiency, environmentally friendly light source, the blue LED. By borrowing blue LEDs, white light can be created in new ways. With LED lights, we can have more durable and efficient lighting instead of the original light source, which not only saves a lot of energy for humans, but also illuminates more places around the world.
Blue LED, late arrival
In 1907, the British engineer Henry Joseph Lauder, who worked at Marconi Electronics in the UK, observed electroluminescence for the first time in a piece of silicon carbide crystal. He applied a voltage between the two contacts of a silicon carbide crystal and found that at low voltages, yellow light can be seen; at high voltages, more colors of light can be seen. The phenomenon of luminescence also laid the physical foundation for the invention of LEDs.
In 1962, Nick Helenak, a 34-year-old general researcher at General Electric, invented an LED that emits red visible light. His name is also red with the red light of the LED. Since Helenak's invention was widely used, he was generally called "the father of LEDs". In 1972, George Crawford, a student of Helenak, stood on the shoulders of giants and invented the first orange-yellow LED, which is 10 times brighter than the previous red LED, which indicates that LEDs improve luminous efficiency. The first step in the direction.
By the end of the 1970s, LEDs had appeared in red, orange, yellow, green, green and other colors, and were used as display lights for machine instruments, but still no blue LEDs. Since the three primary colors of light contain red, green, and blue, and the blue light source is missing, the white light source of illumination is always unavailable. The market value of blue LED is huge, and it was also a worldwide problem at that time, attracting countless scientific heroes to compete.
In 1973, Akasaki, who was at the Tokyo Research Institute of Matsushita Electric Co., Ltd., first started research on blue LED. Later, Akasaka and Amano co-founded the basic research and development of blue LED in Nagoya University. In 1989, the blue LED was successfully developed.
In 1993, Nakamura Shuji, a 39-year-old working at Nichia Corpora TIon, finally invented a commercial-use blue LED based on gallium nitride and indium gallium nitride, which led to a new revolution in lighting technology. With this invention, he won the 2006 Millennium Technology Award, which is equivalent to Nobel in the scientific community! Soon after, people added yellow phosphors to the blue LEDs to get white LEDs. Using this phosphor technology, LEDs of any color (such as purple light and pink light) can be produced. The emergence of blue and white LEDs has broadened the field of application of LEDs, making applications such as full-color LED display and LED lighting possible.
Young and promising
At present, lighting technology is undergoing an unprecedented revolution, from light bulbs and fluorescent lamps to LEDs. In 1879, the American inventor Thomas Edison invented the light bulb. In the early spring of 1882, the first practical incandescent lamps finally came out. It brought light and joy to thousands of families. The incandescent lamp is Edison’s most brilliant contribution to mankind. one. But the incandescent lamp invented by Edison also has the disadvantage that its efficiency is very low, about 16 lumens per watt, which is equivalent to converting only 4% of electrical energy into light energy. In 1900, Peter Cooper-Hewitt invented fluorescent lamps with an efficiency of up to 70 lm/W. The current white LEDs exceed 300 lumens per watt.
White LEDs used for illumination are often based on high-brightness blue LEDs that excite a fluorescent phosphor such that blue light is converted to white light. These high-quality LEDs have a lifespan of up to 100,000 hours, compared to one-tenth of the life of fluorescent lamps, which is one percent longer. The cost of white LEDs is gradually decreasing, and the market is also rapidly expanding. In the near future, tri-color LEDs may replace the combination of blue LEDs and phosphorous phosphors for high-brightness illumination, a technology that will allow us to dynamically control color composition. Now, we can see a variety of novel colors in the LED market, such as light green and pink.
In addition, since lighting accounts for 20%-30% of the world's total power consumption, and new white LEDs consume only one-tenth the energy of ordinary light bulbs, the use of white LEDs can save a lot of energy for humans. At the same time, LEDs help save material consumption due to the long life of LEDs of up to 100,000 hours, compared to 1,000 hours for incandescent bulbs and 10,000 hours for fluorescent lamps.
Today, GaN-based LEDs have become a key technology for backlit LCDs for many mobile phones, tablets, computer monitors, and TV screens. Gallium-emitting diode lasers that emit blue and ultraviolet light are also used in high-density DVDs, greatly facilitating the development of music, picture and film storage technologies. In the future, people may use ultraviolet-emitting gallium nitride aluminum/gallium nitride LEDs to purify water because it kills bacteria, viruses, and microbial DNA. In addition, the world's lack of power grid population will exceed 1.5 billion, the emergence of LED lights give them hope, because of the low power consumption of LEDs, some local cheap solar energy is enough to power them.
Despite being only 20 years old, the blue LED has brought great benefits to mankind, and it has also fulfilled the wish of the Nobel Prize-winning founder Alfred Nobel for the benefit of mankind. The award is truly deserved. The Nobel Prize Selection Committee stated in its statement on the achievements of the award: "The incandescent lamps illuminate the 20th century, and the 21st century will be illuminated by LED lights."
It is not known how far LEDs can develop. Maybe one day you can develop an LED that emits X-rays. Early LEDs could only be used in lights, calculator displays, and digital watches, but are now beginning to appear in the field of ultra-brightness. High-power LED devices are currently emerging LED products, mainly used in lighting, but this technology is still not very mature, mainly because high-power LEDs, although high in brightness, have a large amount of heat, "worth is expensive."
From the introduction of the semiconductor PN junction luminescence theory in 1907, to the ubiquity of LED technology today, during the course of more than a century, countless scientists including Akasaki, Amano, and Nakamura Shuji have made tremendous efforts for the development of LED. The economic and social benefits brought by LED will be incomparable.
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