Technologies | Light Conversion | Phosphors | White LEDs | Apr 24, 2019

Energy-Saving New Red LED Phosphor Developed at University of Innsbruck

The human eye is particularly sensitive to green, but less sensitive to blue and red. Chemists led by Hubert Huppertz have now developed a new red phosphor whose light is well perceived by the eye. This increases the light yield of white LEDs by around one sixth, which can significantly improve the energy efficiency of lighting systems.

Light emitting diodes or LEDs are only able to produce light of a certain colour. However, white light can be created using different colour mixing processes. "In a white LED, red and yellow-green phosphors are excited by the light from a blue diode. The particles emit light in the red and green range, and in combination with the blue light they produce white light," describes Hubert Huppertz from the Department of General, Inorganic and Theoretical Chemistry at the University of Innsbruck, Austria. He and his team are working on improving the red and green phosphors. In cooperation with OSRAM Opto Semiconductors, his team has now succeeded in synthesizing a new red phosphor that has excellent luminescence properties and can make LED lighting significantly more energy-efficient.

Color shift improves luminous efficacy

The powerful red phosphor Sr[Li2Al2O2N2]:Eu2+, named SALON by the researchers, meets all the requirements for the optical properties of a phosphor. The development goes back to research carried out by Hubert Huppertz at the University of Bayreuth. As part of his doctoral thesis, he developed nitrides doped with europium that are fluorescent. These were then further optimised by the working group in Munich and are now widely used. These red phosphors are partly responsible for the fact that LEDs no longer only glow cold white, but also warm white. Interestingly, the human eye reacts most sensitively to the colour green. In the blue and red areas, the eye is less sensitive. Although these phosphors emit red light in the visible range, a large part of the energy goes into the infrared range, which the human eye does not perceive. The fluorescent material developed in Innsbruck has now succeeded in slightly shifting the light emission from red towards blue.

"Since initially only a few very small particles were available in a very inhomogeneous sample, it was difficult to optimise the synthesis," said doctoral student Gregor Hoerder. The breakthrough came when the researchers were able to isolate a single-crystal from one of the most promising synthesis products and thus determine the structure of the new material. "The substance is synthesised in such a way that it emits more orange than red," says Hubert Huppertz. "With SALON we have less energy loss, it emits exactly in the red range we can see."

Acknowledgements:

OSRAM Opto Semiconductors, a strong industrial partner, the Fraunhofer Institute for Microstructures of Materials and Systems IMWS in Halle and Dirk Johrendt's research group at the Ludwig Maximilian University in Munich were also involved in further characterizing the new material. The development has already been registered for patent.

References:

The original paper has been published under the title Sr[Li2Al2O2N2]:Eu2+—A high performance red phosphor to brighten the future" at https://www.nature.com/articles/s41467-019-09632-w

Publishing researchers: Gregor J. Hoerder, Markus Seibald, Dominik Baumann, Thorsten Schröder, Simon Peschke, Philipp C. Schmid, Tobias Tyborski, Philipp Pust, Ion Stoll, Michael Bergler, Christian Patzig, Stephan Reißaus, Michael Krause, Lutz Berthold, Thomas Höche, Dirk Johrendt & Hubert Huppertz

For details and additional information, please contact Prof. Hubert Huppertz using this link: https://www.nature.com/articles/s41467-019-09632-w/email/correspondent/c1/new 

FEATURED

A Cree® J Series® 2835 LED for Every Application on Your List

A Cree® J Series® 2835 LED for Every Application on Your List Cree's J Series 2835 LEDs combine high efficacy and lower power consumption. J Series 2835 LEDs are optimized for low density applications requiring high efficacy and smooth appearance, such as downlights, troffers, and panel lights. Thirteen models of J Series 2835 LEDs are available in 2200 K - ... Read more »

EDITORIAL

Porotech Launches Groundbreaking Micro-LED Product

Porotech Launches Groundbreaking Micro-LED Product University of Cambridge spin-out Porotech has today announced the launch of its first product based on its breakthrough gallium nitride (GaN) production technique that is set to transform the electronics industry. The company has launched the world's first commercial native red LED epiwafer for ... Read more »

EDITORIAL

Luminus Releases XFM-5050 UVC LEDs and Opens New Possibilities for Disinfection and Sterilization

Luminus Releases XFM-5050 UVC LEDs and Opens New Possibilities for Disinfection and Sterilization Luminus Devices today introduced its new XFM-5050 UVC LED series that sets new benchmarks for output, and lowers the $/mW another 20% compared to previous Luminus UVC LEDs. The series offers 2, 3, and 4 chip options with nominal power levels of 120, 180, and 240 mW of disinfection power. Read more »

EDITORIAL

Transform Your Space with Thorn's New VCT Technology

Transform Your Space with Thorn's New VCT Technology VCT technology (Variable Color Temperature) brings a new dynamic to your space. It is now possible to set dedicated color temperatures for specific areas of your space, ranging from 2700 K to 6500 K. The VCT enables you to manually and automatically adjust light levels and to set pre-defined ... Read more »