Exploring the structural stability and optical properties of rare-earth doped K₃LuSi₂O₇ phosphor from first-principles calculations

The newly developed rare-earth doped K₃LuSi₂O₇ phosphor have promising applications in phosphor-converted light-emitting diodes that achieve broadband high-efficiency near-infrared emission. However, the further development of such luminescent materials is hindered by the difficulty in establishing the quantitative relationship between the microstructure and optical properties from experiments. This work performed first-principles calculations to study the optical properties of K₃LuSi₂O₇:x (x = Eu, Nd, Pr) compounds in relation to the atomic structure and external pressure, within the framework of hybrid functional. It is found that the direct band gap of K₃LuSi₂O₇ can be dramatically narrowed by doping rare-earth elements into K sites and applying external pressure, with distinct microscopic mechanisms. We predicted the energy-dependent absorption spectra of these compounds by assuming that the probabilities of different atomic configurations appearing follows the Boltzmann distribution when the real material is in a thermodynamically stable state. The results demonstrate that the absorption spectrum of K₃LuSi₂O₇:x (x = Eu, Nd, Pr) can be effectively tuned in the visible and near-infrared regions, making it a phosphor with specific luminescence characteristics.