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Chemistry: Publication in Angewandte Chemie
Virtually all light-emitting diodes used today require phosphors based on so-called rare-earth elements, which are expensive and challenging to obtain. In a collaborative research project between Heinrich Heine University Düsseldorf (HHU) and the University of Innsbruck, chemists have now demonstrated that the element manganese is in principle also suitable for such applications. In the scientific journal Angewandte Chemie, they show that this approach enables white light to be generated from a single manganese-based phosphor.
Light-emitting diodes – for short: LEDs – are energy-efficient and flexible, making them a key technology for sustainable lighting. Current white-light LEDs typically comprise a blue semiconductor LED, the light of which is then converted by two layers of photoactive materials into green light and red light. Combining these light colours creates the desired white light.
The phosphors used in current LEDs almost all contain rare-earth elements such as europium or cerium. However, obtaining these elements is costly and they are only extracted on a large scale in a few regions around the world, primarily in China. This presents significant strategic disadvantages.
A research team headed by Assistant Professor Dr Markus Suta (Inorganic Photoactive Materials working group at HHU) and Professor Dr Hubert Huppertz (Department of General, Inorganic and Theoretical Chemistry at the University of Innsbruck) has now sought alternatives, which are more widely available and easier to handle. They identified the transition metal manganese (for short: Mn) – more precisely the twofold positively charged manganese ion (for short: Mn2+) – as promising. By contrast with rare earths, manganese is much more abundant in the earth’s crust, can easily be mined and extracted from ores, and also offers straightforward handling.
So why has manganese not already been used for LEDs in the past? Professor Suta explains: “One fundamental disadvantage is the highly inefficient absorption of Mn2+, meaning that the luminescence decays relatively slowly. High power densities are therefore needed to achieve sufficient brightness.” By contrast, the ion Mn4+ is already in use – it emits narrow-band red light in fluorides and is mostly used for display screens. However, the production of the corresponding phosphors involves hydrofluoric acid, which is problematic.
In the renowned scientific journal “Angewandte Chemie”, the researchers now report on their examination of the luminescence – the radiation properties – of a special compound: of the Mn2+ ion in so-called alkali lithosilicates. The working group headed by Professor Huppertz already identified this class of compounds as potentially promising candidates for cyan-emitting narrow-band emitters for display screens several years ago, albeit still with europium as the emitter at that time.
Professor Suta: “In contrast to europium ions, manganese ions are much smaller and more flexible when it comes to the selection of specific coordination geometries. Mn2+ ions emit narrow-band green light in proximity to four oxygen atoms, but emit red light when surrounded by six to eight oxygen atoms. With the right structural details, the brightness of the luminescence retains a high level of thermal stability, which is important as LEDs with such inorganic phosphors reach operating temperatures of around 150°C.”
Professor Huppertz states a further advantage: “Together with the blue light of the semiconductor LED, efficient white light can thus be generated using a single phosphor obtained from available raw materials.” Two different europium-based phosphors are currently mixed to achieve this. Suta adds: “This offers the potential to create a white light-emitting LED with wide colour tunability.”
The researchers stress that further investigations are needed to determine the power densities required for excitation. Professor Huppertz concludes: “We need to see whether the brightness and power consumption of an LED with a manganese-activated phosphor based on our concept can actually compete with current LEDs.”
L. M. Träger, J. I. Ekeya, A. Liesenfeld, M. Wieczorek, H. Huppertz, M. Suta. Mn2+-Activated Alkali Lithooxidosilicate Phosphors as Sustainable Alternative White-Light Emitters. Angewandte Chemie 2025, Early View, e202504078; Angewandte Chemie International Edition 2025, Early View, e202504078
DOI: 10.1002/ anie.202504078
Crystal structure of an alkali lithooxidosilicate, the site occupation of Mn2+ and the resulting emi ...
Copyright: (© 2025 L. M. Träger et al., Angewandte Chemie International Edition published by Wiley-VCH GmbH
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Crystal structure of an alkali lithooxidosilicate, the site occupation of Mn2+ and the resulting emi ...
Copyright: (© 2025 L. M. Träger et al., Angewandte Chemie International Edition published by Wiley-VCH GmbH
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