American Scientists Have Successfully Invented LED Phosphors Without Rare Earth Elements

- Aug 09, 2019-

American researchers claim to have successfully developed white LEDs that are cheaper and last longer. They will discuss the invention at the recent 250th Annual Meeting of the American Chemical Society (ACS) National Conference and Expo.

Zhichihao Hu, a team member from Rutgers University who participated in the study, said: "If more people in the United States use LEDs at home or in business, the country's electricity consumption can be cut in half." At the time, he was A graduate student. Now, he is a postdoctoral fellow at Rutgers University, where he focuses on the field of rare earth elements.

Current LED technology typically uses a single semiconductor chip to produce blue light and then converts the color to white by virtue of a yellow light-emitting phosphor coating. This phosphor is made of yttrium-doped yttrium aluminum garnet (composed of rare earth elements). These rare earth elements are very expensive and have limited supply, mainly from mining operations outside the United States.

The research team is developing a hybrid phosphorus-based technology that claims to make LEDs last longer, more efficient, and less expensive. They combine a common soil-rich metal and organic luminescent molecules to produce a controllable LED white phosphor. By changing the metal and organic components, researchers can systematically adjust the color of the visible light spectrum of the phosphor in the most acceptable region of the human eye. They also continue to experiment with the development of other rare earth-free LED phosphors based on different metals and organic compounds.

Many materials have the potential to be combined, so they initially calculated the possibility of sorting, predicting what color of light will be emitted by various combinations of metals and organisms, and then experimenting to find the best combination.

Their method allows the bandgap and light emission covering the entire visible range including yellow and white to be fine-tuned by the system. Therefore, the LED lights they developed can fine-tune a warm white light, similar to cheap and inefficient incandescent lamps. This is of great importance in general lighting applications.

American scientists successfully develop rare earth-free LED phosphors


(Left: LED with yellow phosphor, off state; right: open state)

Hu pointed out: "One of the challenges we have to overcome is to find the right conditions to synthesize the compound. Just like cooking, this synthesis also requires a 'recipe'. It is often not simply mixing the raw materials together. The product we need. We need to optimize the reaction conditions - temperature, solvent addition - and then make simple steps to obtain high yield compounds."

Tests on certain materials have shown that the team can reduce the cost of LEDs by 90% using current methods. They have applied for US patents and are exploring the possibility of production.

Funding for the project was provided by the National Science Foundation and Rutgers University. Hu is currently funded by the National Institute of Energy's Key Materials Institute.