Technically the LEDs produce light by passing electrons through a semiconductor material, in combination with materials called phosphors that glow when excited by radiation from the LED. “But it’s hard to get one phosphor that makes the broad range of colors needed to replicate the sun,” said John Budai, a scientist in ORNL’s Materials Science and Technology division in a release. “One approach to generating warm-white light is to hit a mixture of phosphors with ultraviolet radiation from an LED to stimulate many colors needed for white light.”

via Scientists growing new crystals to make LED lights useful for office, home.