What is being claimed as the world’s first single-material white phosphor has been made by researchers in Taiwan.
Currently white LEDs are made using RGB phosphors and a UV LED, or a blue LED and a yellow phosphor.
However, by heating compounds containing gallium, zinc and phosphorus in water and acid for several days, Sue-Lein Wang and colleagues at Tsing Hua University produced a material that emits white luminescence when exposed to 365nm UV light.
The structure of the material, a zinc gallophosphate, features areas of order and disorder, and the functional mechanism proposed by the researchers involves blue light emission from the ordered regions, and yellow from the disordered.
When exposed to light at wavelengths longer than 420nm, emission is all yellow. At less than 420nm there are both yellow and blue parts, due to increased emission at 433nm. And when exposed to light at 390nm the two intensities are equal, resulting in the emission of white light.