Japanese experts to discuss the latest LED technology progress

In energy and energy saving components with a "Green Device Exhibition 2010" and "Green Device seminar Forum 2010", held by LED, OLED lighting and semiconductor lasers and other solid light source technology seminar "a new generation of lighting forum". The domestic and foreign manufacturers in the field of solid light source from the five aspects of luminous efficiency, brightness, life, color rendering, surface light source and point light source, introduces the latest progress.

Japan's PHILPS company (Philips LumiledsLighting lumens) Koyama Hiromiyuki to the white LED efficiency as the center of the relevant technology in the future was prospected. According to Koyama Hiromiyuki introduction, according to the rate of increase in the efficiency of ordinary white LED light-emitting point of view, will be more than 200lm/W in recent years. Although the light bulb LED in terms of luminous efficiency is inferior to ordinary white LED, but has now reached 90~100lm/W, will soon exceed 200lm/W. In the future, it is necessary to achieve the same level of high efficiency at high current density. The specific approach is to reduce the current density is higher but the lower the luminous efficiency of the "Droop" phenomenon.

Japan PHILPS lumen to solve this issue, is changing the white LED and bulb color LED light source - blue LED chip structure. Although the details were not released, but has been in the blue chip light emitting LED quantum well layer region and partition layer near the interface, used to prevent the accumulation of electrons or holes layer structure, the electrons and holes are easy to combine again. In this way, the external quantum efficiency of the 1mm square chip can be up to 65.5% when the current is 350mA, and the efficiency can be as high as when the current is 1A.

Through the above method and the reduction of the forward voltage technology, we hope that in the future, when the current density is 2A/mm2, the luminous efficiency can reach 150lm/W, and the luminous flux can reach 1000lm in the 1mm chip. This requires an increase in the internal quantum efficiency to 80% (currently at 53%), the external quantum efficiency increased to 72% (currently at 47%), the phosphor conversion efficiency increased to 252lm/Wopt (currently 228lm/Wopt).

Japan OSRAM Opto Semiconductors (OsramOpto Semiconductors GmbH) MichaELSchmitt also introduces high output power white LED technology to reduce the decline phenomenon. This is a technology called "UX:3" that will be located inside the N electrode in LED. The current is uniformly distributed inside the chip, so as to control the current density and improve the efficiency. In addition, by canceling the electrode on the chip surface, the light inside the chip is easier to be released to the outside of the chip.

The company revealed the characteristics of the current output power to the 1mm square chip. Compared with the ideal characteristics of the optical output power (which has no decay phenomenon) with the increase of the current, the output power of the current in the 350mA~1A range is about 15% lower than that of the ideal one.

Effective from chip to improve the reliability of heat.

In the extension of the life of the light source, TOYOTA synthesis Yamaguchi Zuo delivered a speech. It is pointed out that in the aspect of high output power white LED for lighting, the method of heat dissipation of the blue chip of LED is very important. As a cooling technology applied to the company's products, first of all, on the high thermal conductivity of the ceramic substrate on the blue chip LED flip chip packaging, the heat source of the chip light-emitting layer close to the ceramic substrate. Then, the electrode of the LED chip is connected with the electrode of the ceramic substrate by a gold tin (AuSn) solder. There is gold tin solder the LED chip to facilitate heat released from the electrode. In the reliability test, even after twenty thousand hours of use, the brightness is only about 5% reduction. In the frequent White LED turn on the lights, turn off the lights, the flow of LED chip will also reduce the hot pressing, so this method can also be used to extend the life.

TOYOTA also introduced the company developed a white LED. glass packaging glass material package is characterized by higher reliability compared with the ordinary resin packaging white LED (short wavelength light will not weaken); linear expansion coefficient, the LED chip and package substrate was very close, not easy to produce hot pressing caused by temperature change. The company in the development of the field of optical glass and cooperation. Currently, plans to use some of the chips in the small part of the product to expand the technology, the latest data, the current through the 20mA light-emitting efficiency reached 104.9lm/W (the current specification is 76.5lm/W). First of all, it will be used for special purposes, such as testing equipment and endoscopes, and will also be used in a wider range of applications in the future.

LED want to be the protagonist of lighting, not only to have high energy efficiency, full brightness and long life, but also to pursue the light is comfortable. From this perspective to promote the development of white LED is MITSUBISHI chemical. In the "GreenDevice Forum 2010", MITSUBISHI chemical orido Wen Fu said that the color and color performance of white light color in the future will be more and more important.

Folding households believe that only the average color rendering index (Ra) as a judge of the color of the white LED is not good enough. Because the evaluation of color rendering of bright red color high chroma does not contain Ra. In response, the company has highlighted the benefits of the company's red phosphor CASN (CaAlSiN3; Eu2+) added to white LED phosphor practice.

Folding households pointed out that, in order to further improve the color rendering, can be used in near ultraviolet LED red, green, blue three kinds of phosphors. MITSUBISHI chemical has developed a white LED using near UV LED with a luminous wavelength of 405nm. Although there is still a decrease in efficiency due to the Stokes effect, the light wavelength