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Blue light source opens a new era of lighting technology
Akasaki was born in Japan in 1929 and was awarded a doctorate in Nagoya University in Japan in 1964. He is currently a professor at the University of Japan and a Distinguished Professor at the University of Nagoya, Japan. Amano is a Japanese national, born in Hamamatsu, Japan in 1960. He received his Ph.D. from Nagoya University, Japan in 1989 and is currently a professor at Nagoya University, Japan. Nakamura Shuji is a US citizen and was born in Ifang-cho, Japan in 1954. In 1994, he received his Ph.D. from Tokushima University, Japan. He is currently a professor at the University of California, Santa Barbara. Blue Light Emitting Diodes (LEDs) Red and green light emitting diodes have been with us for more than half a century, but only after the complete use of the three primary colors of red, green and blue can we produce a white light source. However, the technical challenge of producing a blue light source lasted for more than 30 years. At that time, Akasaka and Amano worked at Nagoya University in Japan, while Nakamura Shuji worked at a small company called Nichia Chemical in Tokushima City on Shikoku Island. When they produced a blue light source through semiconductors, the door to the lighting technology revolution opened. Incandescent lamps illuminate the entire 20th century, and the 21st century will be the era of LED lights. 1 Efficacy: Electrical energy is directly converted into photon. The luminous efficiency is more than four times that of fluorescent lamps. One LED is composed of several layers of semiconductor materials. In LED lights, electrical energy is directly converted into photons, which greatly enhances the performance of the light. In other luminaire technologies, electrical energy is first converted to heat, and only a small portion is converted to light. In incandescent lamps, current is used to heat a filament to illuminate. The gas is discharged in the fluorescent tube, and simultaneously heats up and emits light during the process. The new LED lamps consume much less energy, and the technology is still being improved, and its luminous efficiency is constantly improving. The latest record has exceeded 300 lumens / watt, while the average bulb is 16 and the fluorescent lamp is 70. Considering that about 1/4 of the world's electricity is currently used for lighting purposes, high-efficiency LED lighting technology is globally energy efficient. has great significance. 2 Principle: When electrons meet positive electric holes, the wavelength of illuminating light depends on the nature of semiconductors. LED technology is the same engineering technology as mobile phones, computers, and all other modern technologies based on the principle of quantum phenomena. A light-emitting diode consists of several layers: the n-layer has extra negative charge, and the p-layer has insufficient electron count. You can also understand it as there are excess positively charged holes or positive holes. Between them is a layer of active layer that, when a voltage is applied to the semiconductor, drives the interaction between the negatively charged electron layer and the positive hole layer. When an electron meets a positive hole, the two combine and produce light. The wavelength at which this process produces light depends entirely on the nature of the semiconductor. The wavelength of the blue light is very short, and only certain materials can produce light of this wavelength. For half a century, many laboratories have worked hard for this, but in the end they all ended in failure. 3 Materials: Most of the experiments in which the inventors chose thousands of gallium nitrides failed. Most of the Nobel Prize winners decided to challenge this problem. They have worked hard and taken great risks. They built the equipment they needed, did thousands of experiments, and most of the time they failed, but that didn't make them lose confidence. Gallium nitride is the material chosen by Chisaki, Amano and Nakamura to repair, although most people at the time thought zinc selenide was more promising. The difficulties they face in real work are enormous: no one has ever been able to obtain a sufficiently high quality light source from a gallium nitride crystal. In addition, there is almost no way to arrange the desired p-layer structure in this material. 4 Breakthrough: Blue Light Diode was born in 1992. Nakamura Shuji found a smarter way. In 1986, Akasaki and Amano made high-quality gallium nitride crystals for the first time. The method they used was to apply a layer on the sapphire substrate. An aluminum nitride material is grown on top of the gallium nitride crystal. A few years later, they made a breakthrough in the creation of the p-layer. The electron flow generated by the scanning electron microscope can improve the efficiency of the p-layer. In 1992, they finally made the first blue-emitting diode. Nakamura Shuji began developing his blue LED in 1988. Two years later, he also succeeded in producing high quality gallium nitride crystals. He found a clever way to make high-quality crystals by first growing a thin layer of gallium nitride crystals at low temperatures and then continuing the crystal culture at a slightly higher temperature. Nakamura Shuji uses a simpler, smarter and cheaper way to create a p-layer: heating the material. In this way he succeeded in producing a p-layer with perfect functions in 1992. Therefore, it can be seen that the technical scheme adopted by Nakamura Shuji is different from that of Akasaki and Amano. The technological revolution of extending Blu-ray discs, laser printers, LED screens, etc. continues in the 1990s. Both research groups have made great progress in the continuous improvement of LED technology, making the technology more perfect. The structure of LEDs has also become more complex and sophisticated. Akasaki, Amano and Nakamura also invented a blue laser. Unlike a typical LED that emits divergent light, a blue laser emits a sharp focused beam. Since the wavelength of blue light is very short, it can be compressed to a higher density, and blue light can store four times more information than infrared light. This technology quickly led to the development of more powerful Blu-ray discs and higher quality laser printer equipment. LED technology is also used in many household appliances. For example, LED screens for TVs, computers, and mobile phones, as well as countless fixtures and camera flashes. LED lights are very flexible light sources, from which millions of different colors of light have been derived, and can also mimic natural light sources, so that our biological clock can better adapt. The emergence of LED lighting technology is also expected to send light to as many as 1.5 billion people worldwide. Due to poverty and lack of grid facilities, these people are not able to enjoy the convenience of lighting equipment, but with the low energy consumption of LED lights, these people will be expected to use the electricity generated by small solar power stations to achieve lighting in the future. In addition, contaminated water bodies can be sterilized using ultraviolet LED lamps. LED technology only appeared just 20 years ago, but it creates well-being for the entire human society.