LED produces warm white light from a single phosphor

"Right now, white leds give off a bluish, cool light that people tend to dislike, especially in indoor lighting," said Zhengwei Pan, an associate professor in the department of physics at the University of Georgia. "Our material achieves a warm colour temperature while at the same time giving highly accurate colour rendition, which is something no single phosphor converted led has ever been shown to do." To create the new phosphor, Pan and his team combined minute quantities of europium oxide with aluminium oxide, barium oxide and graphite powders. They then heated the powdered materials to 1,450°C in a tube furnace. According to Pan, the vacuum of the furnace pulls the vaporised materials onto a substrate, where they are deposited as a yellow luminescent compound. When the yellow luminescent compound is encapsulated in a bulb and illuminated by a blue led chip, the result is a warm white light. Although his team's results are promising, Pan emphasised that there are still hurdles to be overcome before the material is used to light homes, businesses and schools. The researchers are now working to overcome issues such as low efficiency, and are looking at ways of scaling the production to an industrial scale. "We still have more work to do," Pan said, "but the colour temperature and rendition that we have achieved gives us a very good starting point."