Green phosphors are a core component of white LED lighting, yet most commercial systems still rely on materials based on garnet structures that require high processing temperatures and depend on specific raw materials. Researchers in Austria and Germany have now reported a new class of lithium-based phosphors that could provide a viable alternative. The work, led by Professor Hubert Huppertz at the University of Innsbruck, demonstrates that these newly synthesized compounds can match the performance of established commercial phosphors while offering advantages in material flexibility and production conditions.
Rießbeck, K. M., Seibald, M., Stoll, C., Köbler, A., Suta, M., & Huppertz, H. (2025). Ce 3+ ‐Activated Lithium Rare‐Earth Oxonitridolithosilicates: A New Class of LED Phosphors with Similarities to Garnets. Advanced Functional Materials, 35(44). https://doi.org/10.1002/adfm.202515406
White LEDs typically generate green light using phosphors that convert blue LED emissions into longer wavelengths. These phosphors must be efficient, stable, and capable of operating under elevated temperatures for extended periods. The most widely used materials meet these requirements but involve energy-intensive manufacturing and rely on compositions that can be sensitive to supply constraints. In response, researchers have been searching for alternative phosphor systems that maintain optical performance while reducing processing demands.
The Innsbruck research team focused on a group of compounds known as lithium rare-earth oxonitridolithosilicates. These materials combine lithium, rare-earth elements, oxygen, nitrogen, and silicon within a crystalline structure that differs significantly from conventional garnet-based phosphors. The inclusion of nitrogen alongside oxygen in the lattice was a key design strategy, as it allowed the researchers to adjust electronic environments around activator ions responsible for light emission.
Synthesis of these materials required developing new chemical routes and formulation strategies. The goal was to create a stable host lattice capable of accommodating rare-earth activator ions, particularly cerium, which is commonly used in LED phosphors. By carefully controlling the arrangement of atoms within the crystal structure, the researchers were able to create conditions that support efficient green luminescence.
One notable feature of the new compounds is their layered structural organization. The lattice consists of interconnected silicate tetrahedra arranged into four-membered rings, linked by lithium tetrahedra. This configuration creates a flexible framework that tolerates chemical substitutions more readily than many traditional phosphor materials. As a result, the team successfully synthesized thirteen distinct compounds within the same structural family, each maintaining similar luminescent properties.
Another distinguishing characteristic lies in the coordination environment surrounding the activator ions. In these materials, cerium ions are positioned within a square-antiprismatic arrangement formed by four oxygen and four nitrogen atoms. This configuration differs from those typically observed in commercial phosphors and contributes to the optical behavior of the material by influencing how energy is absorbed and re-emitted as visible light.
To evaluate performance, the researchers conducted detailed photoluminescence measurements, including temperature-dependent testing. These experiments showed that the new phosphors maintain stable green emission across a range of operating conditions. The results indicate that the materials could achieve high efficiency if implemented in industrial LED manufacturing processes.
The research was carried out in collaboration with Heinrich Heine University Düsseldorf, where spectroscopy studies provided insight into the mechanisms responsible for light emission. An industrial partner, ams OSRAM, also participated in the project, enabling the fabrication of prototype LEDs incorporating the new phosphors. Testing of these prototypes confirmed that the materials can compete with existing garnet-based phosphors in terms of performance.
Beyond efficiency, one of the key advantages of the new materials is their lower synthesis temperature. Reduced processing requirements could translate into lower energy consumption during manufacturing, which is an important consideration given the scale of global LED production. Additionally, the different chemical composition may help diversify supply chains for phosphor materials, reducing dependence on specific resource streams.
The work reflects a broader trend in materials engineering toward designing functional properties through structural control at the atomic level. By tailoring crystal frameworks and chemical coordination environments, researchers can influence how materials interact with light without relying solely on conventional compositions.
While further development and industrial scaling will be required before widespread adoption, the study demonstrates that alternative phosphor systems can achieve performance comparable to established technologies. As demand for energy-efficient lighting continues to grow, such materials could play a role in improving both the sustainability and resilience of LED manufacturing.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
