Rutgers group develops rare earth free LED phosphor
White LEDs are fast replacing conventional lighting sources, however, there are concerns that the rare earth materials used in their phosphors could become scarce and more expensive. White LEDs are made using a blue-emitting InGaN/GaN diode with a coating of a yellow-emitting phosphor such as cerium-doped yttrium aluminum garnet or (YAG):Ce3.
Scientists at Rutgers University in the US have now designed some new materials for making these yellow-emitting phosphors without rare earth elements. The group led by Jing Li has developed an inorganic-organic hybrid phosphor family made out of copper iodide, an abundant compound. They report their development in ACS' Journal of the American Chemical Society.
This family of I-VII binary semiconductor materials can be synthesised by a simple, low-cost solution process and are easily scalable, according to the group. Moreover band gap and emission energy, intensity, and colour can be systematically tuned by incorporating ligands with suitable electronic properties. High quantum efficiency is achieved for some of these compounds. Such features make this group of materials promising candidates as alternative phosphors for use in general lighting devices.
The group tuned the phosphors to glow a warm white shade or various other colors using a low-cost process.
"Combining these features, this material class shows significant promise for use in general lighting applications," they conclude.
