Researchers from the Chinese Academy of Sciences and the University of Science and Technology of China have developed a method to boost upconversion luminescence in oxide perovskites, which tend to display good thermal and chemical stability but limited optical efficiency.
At the core of their approach is a dual-cation substitution strategy applied to titanate perovskites. By precisely adjusting the sodium-to-lithium ratio at the crystal’s A-site, the team induced a controlled structural transition that enhances energy transfer between rare-earth ions, leading to a significant increase in luminescence intensity and quantum yield.
The demand for efficient and stable luminescent materials continues to rise, driven by applications in solid-state lighting, full-color displays, and advanced anti-counterfeiting technologies. While fluoride-based upconversion materials can achieve high efficiency, they often suffer from poor long-term stability. Oxide perovskites, though far more robust, have been limited by low efficiency and susceptibility to thermal quenching.
In this study, the researchers synthesized a series of dual-cation titanate perovskites with the formula Li(1−x)NaxLaTi₂O₆, doped with Yb³⁺/Er³⁺ or Yb³⁺/Tm³⁺ ion pairs. Substituting Li⁺ with Na⁺ induced a phase transition from a tetragonal to a rhombohedral structure, altering the local crystal field around the luminescent ions and enabling more efficient energy transfer.
Among the tested compositions, Li₀.₁Na₀.₉LaTi₂O₆:Yb³⁺/Er³⁺ delivered the best performance. Compared with baseline materials, the optimized phosphor achieved up to a 32-fold enhancement in upconversion intensity and a more than 70-fold improvement in quantum yield while maintaining excellent thermal stability.
Under 980 nm laser excitation, these phosphors emit bright, tunable green and blue light across a wide temperature range, underscoring their promise for high-performance lighting systems and durable anti-counterfeiting applications.
