At the "Green Device Forum 2010" seminar held at the same time as the "Green Device 2010" exhibition of the energy and energy-saving components exhibition, a seminar on the solid-state light source such as LED, organic EL and semiconductor laser for lighting was held. The domestic and foreign manufacturers in the field of solid-state light sources have introduced the latest developments in terms of luminous efficiency, brightness, lifetime, color rendering, surface light source and point source.
Japan's Philips Lumileds Lighting's Shenshan Bosuke is focusing on the future of related technologies, focusing on the high efficiency of white LEDs. According to Shenshan Bo Xing, according to the improvement speed of ordinary white LED luminous efficiency, it will exceed 200lm/W in recent years. Although the bulb color LED is inferior to ordinary white LED in luminous efficiency, it has reached 90~100lm. /W, will soon exceed 200 lm / 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 "Droop" phenomenon with higher current density and lower luminous efficiency.
In order to solve this problem, Philips Lumen of Japan is changing the structure of the blue LED chip, which is the light source of white LED and bulb color LED. Although specific details have not been disclosed, a layer structure for preventing accumulation of electrons or holes has been employed in the vicinity of the interface between the quantum well layer and the barrier layer in the light-emitting region of the blue LED chip, so that electrons and holes are easily recombined. In this way, the external quantum efficiency of the 1mm square chip can reach 65.5% when the current is 350mA, and the efficiency can reach 59% when the current is 1A.
Through the above method and the reduction of forward voltage technology, it is hoped that the luminous efficiency of the current density of 2 A/mm 2 in a 1 mm square chip can reach 150 lm/W, and the luminous flux can reach 1000 lm. This requires an internal quantum efficiency of 80%. (currently 53%), the external quantum efficiency is increased to 72% (currently 47%), and the conversion efficiency of the phosphor is increased to 252 lm/Wopt (currently 228 lm/Wopt).
Michael Schmitt of Osram Opto Semiconductors GmbH in Japan also introduced high-output white LED technology to reduce degradation. This is a technique called "UX: 3" where the n-electrode is placed inside the LED. The current is passed evenly inside the chip to control the current density and improve efficiency. In addition, by eliminating the electrodes on the surface of the chip, the light inside the chip is more easily released to the outside of the chip.
The company revealed the characteristics of the optical output power when a current is applied to a chip of 1 mm square. Compared with the ideal characteristic (no decay phenomenon) in which the optical output power increases linearly with increasing current, the optical output power when the current is in the range of 350 mA to 1 A is about 15% lower than the ideal characteristic.
Effectively radiate chip heat and improve reliability
Toyota's Yamaguchi Shoufu gave a speech on extending the life of the light source. It is pointed out that in the high output power white LED for illumination and the like, the heat dissipation method of the light source blue LED chip is very important. As a heat dissipation technology applied to the company's products, first, a blue LED chip is flip-chip packaged on a ceramic substrate having a high thermal conductivity, and a chip light-emitting layer serving as a heat source is brought close to the ceramic substrate. Then, the electrode of the LED chip and the electrode of the ceramic substrate were connected by gold-tin (AuSn) solder. The presence of gold tin solder allows the heat of the LED chip to be easily dissipated from the electrode. In terms of reliability testing, even after 20,000 hours of use, the brightness is only about 5% lower. When the white LED is turned on and off frequently, the hot pressure flowing to the LED chip is also reduced, so that the life can be extended by this method of use.
Toyota Synthetic also introduced the white LED developed by the company in a glass package. The glass package is characterized by higher reliability than ordinary white LEDs packaged in resin (short-wavelength light does not become weak); In terms of coefficient, since the distance between the LED chip and the package substrate is very close, hot pressing due to temperature change is less likely to occur. The company has cooperated with Sumita Optical Glass in its development. At present, it is planned to develop this technology in some products using small chips. In the latest data, the luminous efficiency when the current is 20mA is 104.9lm/W (the existing specification is 76.5lm/W). First, special-purpose lighting for inspection equipment and endoscopes will be used in the future in a wider range of lighting.
In order to become the protagonist of lighting, LEDs must have high energy efficiency, sufficient brightness, long life, etc., and whether the light is comfortable. From this perspective, the development of white LED is Mitsubishi Chemical. In "GreenDevice Forum 2010", Mitsubishi Chemical's discounted man, Wenfu, said that the color of white light such as color rendering and color expression will become more and more important in the future.
The discounted household believes that it is not enough to use the average color rendering index (Ra) as a numerical value for judging the color rendering of white LEDs. Because Ra does not include the color rendering evaluation of high chroma colors such as bright red. In this regard, the discount emphasizes the company's benefits of adding the red phosphor CASN (CaAlSiN3; Eu2+) to the white LED phosphor.
The discounted household pointed out that when it is desired to further improve color rendering, three kinds of phosphors of red, green and blue can be combined on the near-ultraviolet LED. Mitsubishi Chemical has developed a white LED that uses a near-ultraviolet LED with an emission wavelength of 405 nm. Although there are still problems such as a decrease in efficiency due to the Stokes effect and deterioration of the package material due to a short emission wavelength, Ra exceeds 95. The color rendering of high chroma red (R9) exceeds 90. However, the luminous efficiency of white LED is relatively low at a color temperature of 2700K, only 25lm/W. The company will focus on improving luminous efficiency in the future.
In the speech, the discounted user mentioned the Color Quality Scale (CQS), a new color rendering standard with 15 saturated colors as the color card. Although Ra is low but CQS is high, the objects under illumination can be clearly seen. This CQS is currently being Accepted by CIE TechnicalCommittee.
Sound Bar,Rgb Light Sound Bar,Gaming Sound Bar,Hifi Soundbar Speaker,Echo Wall
Comcn Electronics Limited , https://www.comencnspeaker.com