LEDs with more natural light developed

US researchers say they've developed an LED that emits a warm light rather than the bluish, cold light that's held LEDs back from use in indoor lighting. University of Georgia scientists say the LED is the first that emits a warm white light, using a single light emitting material, or phosphor, with a single emitting center for illumination. "Right now, white LEDs are mainly used in flashlights and in automotive lamps, but they give off a bluish, cool light that people tend to dislike, especially in indoor lighting," physics Professor Zhengwei Pan said. "Our material achieves a warm color temperature while at the same time giving highly accurate color rendition, which is something no single-phosphor-converted LED has ever been shown to do." Warm white light can be achieved with a blue LED chip coated with light emitting materials but combining the source materials in an exact ratio can be difficult and costly, Pan said -- and the resulting color often varies because each of the source materials responds differently to temperature variations. "The use of a single phosphor solves the problem of color stability because the color quality doesn't change with increasing temperatures," co-researcher Xufan Li, an engineering doctoral student, said. There are still design and production hurdles to be overcome before the material is used to light homes, businesses and schools. "We still have more work to do, but the color temperature and rendition that we have achieved gives us a very good starting point," Pan said.