A Bright Future for LEDs
Two inch diameter chips.
Much larger chips will be developed over the next decade, up to the size of whole 8 inch diameter wafer.
A single wafer-level LED chip that produces more than 150 Watts of light output has been made in work form China. This level of output from a single chip makes applications for LEDs in high power lighting from stadiums to runways feasible, and the researchers have long term plans for a new way to light buildings and towns.
The efficiency and long life of LEDs have allowed their use in lighting to spread right into our offices and homes, with unit costs falling all the time. However, the maximum output power of a single LED chip is around 10W, so their use in high power lighting applications requiring kilowatt level output would require hundreds of chips, driving costs above acceptable levels for customers.
With the cost of the LED chips falling, the cost of packaging the chips and assembling them with other components to form an LED lamp is becoming more important. The ideal scheme in terms of packaging and assembly costs would be to use one LED chip per lamp, but the limited output power of single chips seriously curtails the use of this scheme.
Light and heat
Xiangneng HuaLei Optoelectronic Co. Ltd. and several Universities in China, report successful creation of a single wafer level LED chip producing more than 150W output, using a single chip assembly approach.
This approach allows the creation of LED chips with areas a hundred times bigger than the highest-power LED chips previously produced. It required a combination of other smaller advances, as team leader Prof. Yong Cai explained: "We developed several technologies, including series and parallel network designs, resistor matching, active liquid heat dissipation and plug-in electrodes, to successfully fabricate this chip."
The team also intend to develop the cooling system to allow recycling of the heat energy produced in a lighting system, but this is part of their longer term development plans. They are currently working to improve the wall-plug efficiency (WPE) of their high-power WL-LED chip.
The team hope that the WL-LED they have produced may prove to be the first step towards this. They expect that much larger chips will be developed over the next decade, up to the size of whole 8 inch diameter wafers, allowing light outputs in the tens of kilowatts. Whether the idea of 'central lighting' will prove feasible or not, it is clear that WL-LEDs have a strong future in more conventional applications of high-power lighting.
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