High quality LED lighting should have the characteristics of low color temperature, high color rendering index, high light efficiency, safety and comfort for human eyes, etc. Technically speaking, there are two ways to achieve high-quality LED lighting. One is to synthesize full spectrum white light with multi-color and high-efficiency LEDs (such as red, yellow, green, blue light), and the other is to excite multi-color phosphors (such as red, yellow, green and blue light) with monochromatic LEDs to obtain white light.
The first approach is physically the most suitable one, which is the next generation of semiconductor lighting technology. Firstly, there is no energy loss caused by LED excited phosphor. Secondly, the spectrum can be adjusted in a large range through the independent control of multi-color led, which provides light source support for intelligent lighting and human body rhythm regulation. The main problem of this technology is that the electro-optic conversion efficiency of green LED and yellow LED is obviously low, that is, "green gap". Therefore, the technical route needs to greatly improve the efficiency of yellow, green LED (especially yellow light), and further improve the efficiency of red, blue and blue LED. In recent years, the silicon-based yellow light and green light technologies with independent intellectual property rights in China have made some progress. In 2018, the electro-optical conversion power efficiency of silicon-based yellow light (565nm @ 20A / cm2) reached 24.3%, and the electro-optical conversion power efficiency of silicon-based green light (520nm @ 20A / cm2) reached 41.6%. During the 13th Five Year Plan period, it is expected to make a breakthrough in this technical route.
The second way is to upgrade and upgrade the existing technology of monochromatic LED excited yellow phosphor. There are two ways:
The first one is to activate polychromatic phosphor by blue chip, and improve the color index by improving the phosphor. In technology, we need to obtain blue fluorescent powder with high excitation efficiency, further improve the excitation efficiency of yellow powder, green powder and red powder, and improve the related packaging technology. The advantage of this method is that the technical difficulty is relatively small, the product development speed is fast, but there are still high-intensity blue wave peaks, the spectral continuity is insufficient, and the intensity of each wave band is very different from that of sunlight.
The second one is to excite polychromatic phosphor with violet chip to realize continuous spectrum. Although the light efficiency of this scheme is greatly sacrificed and the cost is high, it can achieve the maximum close to the solar spectrum, not only to achieve high reduction degree and high saturation, but also to avoid the emergence of short wave blue light. At present, many enterprises have launched full spectrum LED products through this technical scheme.
It can be said that the current high-quality full spectrum LED technology is still a long way from the real health lighting, but the concept of health lighting has been recognized by more and more consumers. At present, full spectrum LED products are mainly used in surgical lights, eye protection lights, museum lighting, high-end place lighting and other fields with high spectral quality requirements. In some high-end lighting products, the concept of sun like light and full spectrum is also highlighted. With the continuous improvement of technology and the promotion of healthy lighting concept, the market share of full spectrum LED products will increase significantly, especially in the field of indoor lighting.
