Highly efficient LEDs could potentially slash global electricity consumption. To date, however, widespread adoption is hindered by costs, limited availability of raw materials and difficulties in achieving acceptable light quality. Researchers at Rutgers University state that they have overcome these obstacles and developed a less expensive, more sustainable white LED.

To achieve the soft white light that consumers expect, current LED technologies use a single semiconductor chip to produce blue light and then rely on a yellow-emitting “phosphor” coating to shift the color to white since LEDs do not emit a white light. The phosphor is made from materials, such as cerium-doped yttrium aluminum garnet, composed of rare-earth elements. The elements are expensive and in limited supply and available from mining operations outside the U.S. Light output of these phosphors tends to be harsh, cold colors.

The Rutgers team is developing hybrid phosphor-based technologies that are more sustainable, efficient and low-cost. They combine earth-abundant metals with organic luminescent molecules to produce phosphors that emit a controllable LED white light. By varying the metal and organic components, the researchers can tune the color of the phosphors to regions of the visible light spectrum acceptable to the human eye. The team continues its research to develop other rare-earth-free LED phosphors based on different metals and organic compounds.

Many combinations are possible and a computational approach is used to sort through the possibilities and predict the color of light various metals and organics combinations will emit. The approach shows promise for use in general lighting applications, the researchers say.

In order to achieve success, the team optimized reaction conditions including temperature and the addition of a solvent and developed a procedure to make a compound with a high yield.

Experiments indicate that the technology may cut LED costs by as much as 90% from current methods that rely on rare-earth elements. The team has several granted and pending U.S. patents and are exploring manufacturing possibilities. The Rutgers research shows that substituting one LED light for a common incandescent light bulb in every American household could potentially save the nation $700 million annually in energy costs.

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