You may know, what is the earliest illumination from? It is the use of natural light sources. The earliest use of the sun to illuminate, you can use bonfires, torches. All of these are natural products that are illuminated with natural light sources. It was not until the 19th century that it was the first time that humans had the incandescent lamps we saw today in 1878. Illumination entered the “electrical age” and it was truly possible to achieve illumination in a completely controllable way.
Today's incandescent lamps have improved over the past, but because of physical limitations, its luminous efficiency is still difficult to break through the 15% recognized limits. Later, with the advancement of technology, mercury lamps were invented. Mercury lamps are not the same as the lighting mechanism of incandescent lamps. The mercury lamp is an excitation gas, which is a glow discharge and a gas discharge. It is more efficient than incandescent lamps, but its efficiency is also limited by today's point of view. With the advancement of technology, on the one hand, humans hope to improve the efficiency of lighting, and on the other hand, we also hope to develop all-solid lamps. It is very durable and it will generally last a long time. At this time, with the development of semiconductor technology, LEDs came into being. When Xiamen hosted the BRICS meeting, the entire city of Xiamen was also very beautifully decorated, and the main electric light source for decorating it was LED.
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From mobile phones to spaceships, why can't modern art be separated from it? From LED, especially from LED to large-scale production and application, today, after three generations, they are often called first-generation LED. Second-generation LED, third-generation LED.
The first generation of LED are familiar to everyone, the most typical is silicon. More than 90% of the various semiconductor devices we use today are made of silicon. The characteristics of silicon, the first is that the process is very mature, the technology is very mature; the second is that it is relatively cheap, its raw material is silicon dioxide, all kinds of sand can be used to extract silicon. But from the perspective of physicists, this material also has its limitations, that is, silicon is difficult to emit light, its luminous efficiency is very low, it is difficult to let it emit the light we need. So the first generation of LED can't usually be used as a light-emitting device.
The second generation of LED, which we also called compound LED in the early days, are mainly LED such as gallium arsenide and indium phosphide. What is the difference between the second generation of LED and silicon? The second generation of LED, because of its energy spacing, is a little wider than the first generation of LED, making it a variety of combinations. Therefore, with the second generation of LED through different combinations, it is possible to achieve higher energy conversion efficiency than the large-area photovoltaic cells we have seen so far. The solar panels that we are now seeing in large areas are generally 20%, good to 22%, and can be used more than 40% with compound LED. Nowadays, these materials from China, whether it is a spaceship or our space station, such as enamel, jade rabbit, lunar rover, etc., use solar panels to be made of compound LED. This technology Xiamen University has also made a very big contribution, and now 70% of the devices are supplied by Xiamen University and partner units. The main contributor to this technology is Professor Kang Junyong of Xiamen University, who also participated in our activities today. The above is my second generation semiconductor. What kind of material is the third-generation semiconductor we are talking about now? The most typical representative of the third-generation semiconductor is nitride semiconductor, especially gallium nitride, and its related aluminum nitride and indium nitride. Group III nitride LED are the most typical third-generation LED. With this nitride semiconductor, we can develop blue LEDs, develop green LEDs, and develop white LEDs through a combination. Most of the colorful displays we see today are actually LCD screens, and the light source behind them is LED. It is precisely because of the LED technology, especially the technology of the third-generation semiconductor-driven LED that can emit a variety of colors of light, we have today's colorful world, we can see the radiant architectural lighting, Only to see such a beautiful city view.
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200 billion degrees! With it, it can save so much electricity in one year. The development process of LED is on the one hand to seek electric light source, called "lighting revolution", and seek breakthrough in lighting technology. But in fact, another important feature is that solid-state lighting technology has become a very good energy-saving and emission-reduction technology, and LED has become a low-carbon light source. General Secretary Xi Jinping pointed out: "We must accelerate energy conservation and emission reduction and pollution prevention, leaving a beautiful home for the future generations of sky blue, green land and water. LED technology is precisely to improve our environment and reduce energy consumption. Our ecological civilization construction contributes. What is the effect of LED energy conservation? Very bad. In 2017, we promoted LEDs and saved nearly 200 billion kWh in China. This figure is close to the national electricity consumption in Australia in 2014. So this is a great achievement.
Source: Central Commission for Discipline Inspection, National Supervision and Reform Commission website