In the village of repair two said the use of blue LED white LED will disappear sooner or later

"The use of blue LED white LED will disappear sooner or later. "

According to the Nikkei technology online reports, say this sentence, is due to the development of blue LED and won the 2014 Nobel prize in physics at the University of California-Santa Barbara (UCSB) Professor Nakamura Shuji. This is the village held a seminar in July 24, 2015, GaN energy revolution, said in a speech.

LCD backlight and lighting, such as the use of white LED, mainly by the blue LED chip and yellow phosphor combination. Nakamura pointed out that this type of white LED, the presence of blue light peak intensity is high, easy to cause sleep disorders, which is called the blue light problem". The solution introduced in the village is the United States Soraa sales of white LED.

Soraa is a joint venture in the village (co-founder) to set up a LED venture enterprise, mainly in the sale of purple LED chip combined use of red (R), green (G), blue (B) phosphor white LED. In the village, this white LED "through the purple LED to stimulate the phosphor to obtain blue light, so the peak intensity of blue light is not too high". In addition, all the light in the visible wavelength range can be output, so that the ideal white light can be realized.

Efficiency increased by about 50%

Purple LED chip itself has many advantages. For example, the purple LED chip is stacked on the GaN substrate class GaN semiconductor to produce, belonging to the GaN on GaN type LED. Therefore, the crystal quality of GaN semiconductor layer is very high. There is no difference in the lattice constants between the substrate and the GaN type semiconductor layer, so it is difficult to find a crystal defect called "dislocation".

The ordinary blue LED chip is made on sapphire substrate. The lattice constants of GaN semiconductor and sapphire are different, so they are prone to dislocation.

Purple LED chip shape is also very unique, for the triangle. Compared with the conventional LED chip, the shape of the four chip is the same as that of the LED chip, and the efficiency of the light emitted from the light-emitting layer of the triangular chip is higher than that of the chip.

According to the village, due to the purple LED crystal quality and light extraction efficiency is very high, so the light output divided by the input power obtained by WPE (wall-plug efficiency, electro-optical conversion efficiency) can reach 84%. The average blue LED WPE is only 50 ~ 60%.

Another feature of the purple LED chip is not easy to appear light effect down (droop) problem. In order to improve the luminous intensity and increase the driving current density, the decrease of luminous efficiency is a phenomenon that is caused by the decrease of luminous efficiency. The GaN on GaN products are of high crystal quality, compared with the sapphire substrate products, it is not easy to reduce the effect of light. Therefore, compared with the sapphire substrate products, GaN substrate products can increase the current density to 5 ~ 10 times.

However, GaN substrate based products can not solve the problem of light efficiency decline, the current density of the existence of a limit.

Laser lighting for the third generation of products

Therefore, Nakamura Ichino in the study of the use of semiconductor laser lighting. If the sapphire substrate products as the first generation of SSL (solid state lighting: solid lighting), then the GaN substrate product is the second generation, and laser lighting is the third generation of products.

In the village, the use of semiconductor lasers, then, even if the current density increased to nearly 1000 times the LED, it will not affect the efficiency of the light-emitting.

Therefore, the chip area required to achieve the same brightness can be greatly reduced. For example, to get a white light 60W, sapphire substrate type LED requires 28 mm2 area, and the use of semiconductor lasers, then, only need to be 0.3 mm2.

At present, the cost and efficiency of blue semiconductor lasers. Nakamura said, the cost is 10 times the blue LED, and efficiency (WPE) is only about half, only about half of the blue LED. Therefore, the cost must be reduced to 1/10, efficiency increased to two times". He is full of confidence in solving these problems.

Under the advice of famous investors

Speech, the village also referred to the reasons for the establishment of Soraa. The company was founded in 2008 by three professors, including UCSB. To this end is the opportunity to provide a well-known venture capital investor Vinod Khosla (Vinod Khosla). The research team saw Khosla village published 2006, persuaded in the village of entrepreneurship.

Soraa began selling LED lights in the United States in 2012, starting in 2013 and other countries outside the United States sales. 2014 sales reached about 4 billion yen to achieve rapid growth.

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