White light LED will trigger a revolution in lighting technology

Global white light LED development progress: White light LED is divided into single chip, dual chip, triple chip and quad chip. The following will be introduced according to this classification:

1. Single chip LED

InGaN(blue)/YAG phosphor

This is a relatively mature product, of which 1W and 5W Lumileds have mass-produced products. These products use a flip-chip structure to improve luminous efficiency and heat dissipation. Improvements in the phosphor coating process can increase color uniformity by 10 times. Experiments have shown that the increase in current and temperature causes some blue and red shifts in the LED spectrum, but has little effect on the fluorescent spectrum. The life test results are also good. After 12,000 hours of operation, the light output of a Φ5 white light LED drops by 80%, while this power LED only drops by 10% after 12,000 hours of operation, and is estimated to drop by 30% after 50,000 hours of operation.

InGaN (blue)/red phosphor + green phosphor

Lumileds uses 460nm LED with SrGa2S4:Eu2+ (green) and SrS:Eu2+ (red) phosphors, and the color temperature can reach a good result of 3000K-6000K, and Ra reaches 82-87, which is higher than the above products.

InGaN (UV) (red + green + blue) phosphor

Cree, Nichia, Toyota and other companies are all vigorously developing UV LEDs. Cree has produced 50mW, 385nm-405nm UV LEDs; Toyota has produced such white light LEDs, whose Ra is greater than or equal to 90, but the luminous efficiency is not ideal; Nichia has recently produced 365nm, 1mm, 4.6V, 500mA high-power UV LEDs, which will have better effects if made into white LEDs.

2. Dual-chip LED

It can be made of blue LED + yellow LED, blue LED + yellow-green LED and blue-green LED + yellow LED. This kind of device is relatively cheap, but because it is white light formed by two colors of LEDs, the color rendering is poor and it can only be used in occasions where the color rendering requirements are not high.

3. Three-chip (blue + green + red) LED

Philips uses 470nm, 540nm and 610nm LED chips to make devices with Ra greater than 80, and the color temperature can reach 3500K. If 470nm, 525nm and 635nm LED chips are used, the yellow tint is lacking and the Ra can only reach 20 or 30.

The use of wavelength compensation and luminous flux feedback methods can reduce color shift to an acceptable level. American TIR Company uses Luxeon RGB devices to make system products for landscape lighting and Lumileds to make LCD TV screens (22 inches), and the performance of the products is good.

4. Four-chip (blue + green + red + yellow) LED

White light LEDs with Ra greater than 90 can be made using 465nm, 535nm, 590nm and 625nm LED chips.

In addition, Norlux uses 90 three-color chips (R, G, B) to make 10W white light LEDs. Each device has a luminous flux of 130lm and a color temperature of 5500K.

Currently, there are three main types of white light LED technologies:

First, use the three-primary-color principle to mix the three ultra-high-brightness LEDs of red, green, and blue into white light;
second, add a small amount of yttrium aluminum garnet-based phosphor to the InGaN blue LED core;
third, use ultraviolet LED to excite the three-primary-color phosphor or other phosphors to generate multi-color light mixed into white light;

All three technologies have been industrialized, and the latter two technologies are developing faster. The semiconductor lamps manufactured in this way are small, reliable, long-life, low-voltage, energy-saving, and pollution-free. They can be called green light sources and a revolution in lighting methods. White light LEDs can save 80% to 90% of electricity compared to incandescent lamps, and their lifespan can exceed 100,000 hours. The main problem at present is the high cost of chips, but judging from the development law of the cost-effectiveness of electronic products, it is not far away for semiconductor LEDs to enter ordinary households. At present, high-performance LEDs are widely used in some special places, such as military equipment, mining, diving, exploration and other industries. It can be said with certainty that high-performance LEDs are becoming a very competitive new light source, and its commercialization will inevitably bring about a revolution in lighting technology.

Overview of white light LED market size:

The biggest potential application of LED is general lighting. With the advancement of technology, high-brightness white LED is gradually entering the lighting market with huge potential. According to statistics from Frost & Sullivan, the current annual growth rate of the global lighting market is about 5.5%. In 2000, the market size of incandescent lamps and fluorescent lamps alone reached 4.5 billion US dollars. The LED industry generally believes that the white light LED lighting market is expected to mature around 2010. It is expected that in the next few years, high-brightness LED will have a huge impact on the global lighting industry.