New manufacturing method could lead to LED TVs

Researchers at Rensselaer Polytechnic Institute have taken a big step forward in the development of high-quality LED televisions and displays.

The team says it’s developed a new method for manufacturing green-colored LEDs with greatly enhanced light output.

“Green LEDs are proving much more challenging to create than academia and industry ever imagined,” says professor Christian Wetzel.

“Every computer monitor and television produces its picture by using red, blue, and green. We already have powerful, inexpensive red and blue LEDs. Once we develop a similar green LED, it should lead to a new generation of high-performance, energy-efficient display and illumination devices. This new research finding is an important step in the right direction.”

The team etched a nanoscale pattern at the interface between the LED’s sapphire base and the layer of gallium nitride (GaN) that gives the LED its green color. Overall, they say, the new technique results in green LEDs with significant enhancements in light extraction, internal efficiency, and light output.

Sapphire is among the least expensive and most widely used substrate materials for manufacturing LEDs, so Wetzel’s discovery could be put into practice rlatively easily. Wtzel says his new method should also be able to increase the light output of red and blue LEDs.

The color of light produced by LEDs depends on the type of semiconductor material used. The first LEDs were red, with blue coming years later.

The holy grail of solid-state lighting, however, is a true white LED, Those used in applications such as key chains or auto headlights, and grocery freezers, are actually blue LEDs coated with yellow phosphorus – which adds a step to the manufacturing process and also results in a noticeable bluish tint.

The key to true white LEDs, Wetzel says, is all about green. High-performance red LEDs and blue LEDs exist. Pairing them with a comparable green LED should allow devices to produce every color visible to the human eye – including true white.