Review of the development of LED light efficiency

The history of LED development has been for decades, but the application in the field of lighting is still new technology. With the rapid development of LED technology and the gradual improvement of its luminous efficiency, the LED application market will be more extensive. Especially in the context of the global energy shortage worry, the prospect of LED in the lighting market has attracted worldwide attention. In the face of huge market opportunities, the world's major companies have accelerated the pace of research and development. High-power white LEDs have reached 157 lm/w in the laboratory, and high-power white LEDs close to 100 lm/w are about to enter commercialization. The three major bottlenecks of high power, high luminous efficiency and low cost are being gradually broken. It can be said that the dawn of white LEDs entering the field of general lighting has already appeared.

Here we take the white LED of 100lm/W light effect in June 2006 as a milestone, and make a simple combing of the development process of LED light efficiency in recent years.

(October 2008) Cree releases white LED with 157lm/W light efficiency

Cree announced at a GaN seminar in Switzerland that its laboratory level of white LEDs has reached 157 lm/W, and its 102 lm/W products will be mass-produced soon.

(July 2008) Toshiba will launch a white LED with a luminous flux of 90 lm

Toshiba (USA) Electronic Components Co., Ltd. mass-produced the input current of 250mA, the beam is 90lm white LED "TL12W02-D". The new LED is packaged from two LED chips with a beam current of 40 lm at an input current of 250 mA. When the input current is 250 mA and the temperature is 25 ° C, white light at the CIE chromaticity diagram coordinates (x = 0.32, y = 0.31) can be obtained. Heat dissipation is improved by using a low thermal resistance package. The operating temperature range is -40 to +100 °C and the junction temperature is up to 110 °C. The forward voltage at a forward current of 250 mA is 6.8V. The maximum power consumption is 2.4W. The external dimensions of the surface mount model are 10.5 mm x 5.0 mm x 2.1 mm. It is envisaged to be applied to industrial equipment and civil equipment. The price is $2.90 for every 10,000 batch purchases.

(May 2008) JLEDS revised blueprint for white LED development for general lighting

The Japan LED Lighting Promotion Association (JLEDS) has unveiled a blueprint for the development of high-power white LEDs for lighting fixtures, and proposed white light ordinary products (high-efficiency type), high color rendering products, and bulb color products (bulb color). The luminous efficiency target as of 2020. According to the target, the luminous efficiency is expected to reach 150 lm/W around 2015. Under normal circumstances, the luminous efficiency of high-efficiency products in fluorescent lamps is about 100lm/W, the high-efficiency products of white LEDs will reach about 100lm/W in 2008, the high color rendering will exceed 80lm/W, and the color of light bulbs will reach 70lm/ W or so. In 2010, it is expected to reach about 130 lm/W, 120 lm/W and 90 lm/W or more. In 2015, it is expected to reach 160 lm/W or more, 140 lm/W or more and 130 lm/W, respectively. Regarding the spread of LED lighting, the technology development blueprint indicates that it will be popularized around commercial facilities around 2010, when luminous efficiency exceeds 100 lm/W. LED lighting will be popularized in the office and residential areas around 2015, when light quality (light tones such as white LEDs) is improved.

The technology development plan also mentions the issues facing the promotion of universal access. Point out that the biggest issue in achieving universal access is cost. The cost of LED lighting fixtures is 5 to 10 times that of fluorescent fixtures and HID appliances. This is because white light LEDs are two digits higher in terms of the unit price of the light source (yen/lm), and heat sinks, power supplies, and lenses are also required. JLEDS believes that not only is it necessary to reduce the cost of the light source, but it is also important to reduce the cost of peripheral components. In addition, indoor lighting places great emphasis on color temperature and color rendering, so it is also necessary to improve light quality.

(September 2007) Nichia Chemicals releases 134lm/W high power white LED with 350mA

Nichia Chemical Industry has released the next generation of high-power white LEDs positioned as 1W LEDs. At 350mA current input, the luminous flux is 145lm and the luminous efficiency is 134lm/W. The efficiency of the light output corresponding to the input electrical energy is 39.5%. The product is a YAG phosphor and a blue LED chipset and the chip size is 1mm square. It is intended to be used in general lighting equipment with a color temperature of 4988K, which is close to 5000K for general lighting equipment. For the convenience of measurement, a pulse current input method is also adopted. The specific production time has not been determined.

The reason for achieving high efficiency of white LEDs this time is to achieve high efficiency of the blue LED chips used. The blue LED has an optical power of 651 m/W and a wavelength of 444 nm when driven at 350 mA. The external quantum efficiency is 66.5% and the WPE is 60.3%. When driving at 1A, the optical power can reach 1.7W. The problem with the next generation of products released this time is that the forward voltage is higher. In the future, we will begin to optimize the epitaxial growth method to reduce the forward voltage.

(September 2007) Citizen Electronics developed a 540lm white LED for lighting

Citizen Electronics has developed a white LED "CL-L102-C7" series for lighting that achieves 540 lm of luminous flux when inputting 700 mA. Samples are scheduled to be available from October 2007 and will be available in volume production in January 2008. The white LED developed this time is a high-power product of the "CL-L102-C3" series that the company is selling (light flux of 245lm when inputting 350mA current). The new product has higher luminous efficiency, 74 lm/W at 700 mA input and 90 lm/W at 350 mA input. When the amount of light is 150 lm, the input current can be reduced by 160 mA, and the luminous efficiency can be greatly improved by 110 lm/W. The new product has a 50mm x 7mm x 2mm form factor. The color temperature is 5000K, and 2900K varieties will be introduced in the future.

(August 2007) OSRAM releases red and orange LEDs with a luminous efficacy of 85 lm/W

Osram Opto Semiconductors of Germany has launched AlGaInP LEDs with a maximum luminous efficiency of up to 85 lm/W. There are 5 products, 2 of which are red, and the rest are reddish orange, orange and yellow. Mainly for automotive interior lighting, LED displays and entertainment equipment. This LED is equipped with an LED chip using "Thinfilm" technology. By using this chip, the luminous efficiency of red-orange LEDs has increased to about 3.5 times that of the company's original product "Lx T67F" series. The maximum and minimum values ​​of light intensity, the peak wavelength of light emission, and the luminous efficiency are as follows (all values ​​when inputting 20 mA current): red LED brightness is 280-900 mcd, illuminating peak wavelength is 633 nm, and luminous efficiency is 47 lm/W; The corresponding values ​​of the red LEDs are 355 to 1120 mcd, 625 nm, and 65 lm/W, respectively. The red-orange LED is 560-1800mcd, 617nm, 85lm/W; the orange LED is 560-1800mcd, 606nm, 85lm/W; the yellow LED is 355~1120mcd, 590nm, 60lm/W. All products are available in a surface mount package. The size is 3.5 mm x 2.8 mm x 1.9 mm. The radiation angle is 120 degrees. The operating temperature range is -40 to +100 °C.

(February 2007) CAO Group Dynasty series LED light efficiency up to 100lm/W

The typical luminous efficacy of CAO Group's Dynasty® LEDs has increased from the previous 50-70 lm/W to 50-100 lm/W. The Dynasty series of LEDs integrates multiple standard LED chips to achieve high light energy, reducing the cost per lumen by less than expected and extending the working life. The butterfly beam optical design with horizontal 360 degrees and 270 degrees vertical, the package diameter is only 9mm, in addition to the traditional surface mount, screw-in, twist-in placement. Its 3D structure makes lamp replacement more convenient, which is especially important for the replacement of individual components of the LCD backlight. The color of the product is divided into red light, blue green light, green light, yellow light and blue light, and the white light color temperature is 5000--7000K.

(January 2007) Lumileds white light LED current 350mA light efficiency up to 115lm / W

Philips Lumileds announced that its chip-based high-power white LED (size 1mm x1 mm) broke through the 100lm/W mark for the first time, revealing the true potential of solid-state lighting: at 350 mA, the light efficiency is 115lm/W (luminous flux is 136lm), relevant Color temperature (CCT) 4685K; at 2000 mA, the luminous flux is 502 lm, and the luminous efficiency is 61 lm/W. In particular, the correlated color temperature is much lower than the typical values ​​reported previously.

(December 2006) Edison's single-chip white LED with a maximum brightness of 250lm

Taiwan's packaging factory Edison Optoelectronics has released KLC8 series products, which can provide single-chip package brightness up to 250lm@1A, and has the highest luminous efficiency of 100lm/W@350mA, and the product life can reach 50,000 hours. Its wide range of dynamic operating characteristics (0mA ~ 1A), suitable for energy-saving lighting, situational lighting and other variable lighting applications. KLC8 generally has a luminous efficiency of 85lm/W at 350mA operating current. This series offers white light (4,500-10,000K) and warm white (2,800-3,800K) LED light sources. The warm white LED has a luminous efficiency of 70lm/ W@350mA, this series is available in a film-package package for lead-free processes and is highly productive.

(December 2006) Seoul Semiconductor's single-chip white LED light efficiency up to 100lm/W

Seoul Semiconductor of South Korea introduced a single-chip white LED-P4 with a luminous efficacy of 100 lm/W. P4 has a luminous flux of 240 lm at maximum drive current, 100 lm/W at 350 mA, and 80 lm/W for another. Seoul Semiconductor evaluated that traditional LEDs can achieve more than 100 lm of luminous flux from multiple chips, but P4 is a white LED with a luminous flux of 240 lm on a single chip. Seoul is expected to achieve a breakthrough in its performance: it is expected to achieve 135 lm/W of light efficiency next year and 145 lm/W at the beginning of 2008.

(December 2006) Nichia White LED luminous efficiency increased to 150lm/W

Nichia Chemical Industry has developed a white LED with a forward current of 20 mA and a luminous efficiency of 150 lm/W, which is 1.5 times that of the current product. If only focusing on the luminous efficiency compared with other light sources, the luminous efficiency of the white LED reaches about 1.7 times that of the fluorescent lamp with improved color rendering (the luminous efficiency is 90 lm/W under the same conditions), which is an incandescent lamp (the same condition) The lower luminous efficiency is 11.5 times that of 13 lm/W, and even exceeds the high-pressure sodium lamp (luminous efficiency of 132 lm/W) which is generally considered to have the highest luminous efficiency. This white LED is a combination of a blue LED chip and a YAG-based yellow phosphor, just like a normal LED. It adopts the same package as the company's "NICHIARAIKOH" model, and emits 9.4 lm of light flux when the current is 20 mA (color temperature is 4600 K). The average color rendering index (Ra) was 95. The white LED is a development product, and the production date has not yet been determined. In the future, Nichia Chemical Industry plans to improve production technology to realize the practical use of 150lm/W products as early as possible.

(July 2006) Cree develops white LEDs with luminous efficiencies of 131 lm/W

In July 2006, Cree Corporation of the United States announced the development of a white LED with a luminous efficiency of 131 lm/W. The company said that the product will become a new benchmark in the LED industry, highlighting its high luminous efficiency. It is reported that this luminous efficiency value has been confirmed by the National Institute of Standards and Technology (NIST). The white LED was prototyped using Cree's GaN-based LED chip "EZBright". The luminous efficiency of 131 lm/W is a value obtained when a current of 20 mA is applied. The color temperature is 6027K.

(June 2006) Nichia Chemicals Releases White LED with 100lm/W Light Efficiency

Nichia has developed a white LED with a luminous efficiency of 100 lm/W and has begun to supply samples. It is planned to start mass production in December of the same year. In terms of luminous efficiency, performance exceeds that of popular fluorescent lamps, and it can be compared with varieties with higher luminous efficiency. In 2005, the company said that it will mass produce 100lm/W products around 2010. The news announced this time will lead the production time by 3 to 4 years. The white LED that Nichia Chemical Industry will supply samples will get 6 lm of luminous flux at an input current of 20 mA. It belongs to a small power type with input power of only 0.06W. The specific price is not fixed. Nichia has published 113lm/W white LED development products at the academic conference. Nichia also announced a blueprint for development beyond 2007. It is reported that the development of 150 lm / W products will be completed in 2007. Previously, other manufacturers have said that they will start production of 90 lm/W ~ 100 lm / W products from 2006 to 2007, and Nichia Chemical Industry only announced a conservative value.