Unraveling Broadband Near-Infrared Luminescence in Cr 3+ -Doped Ca 3 Y 2 Ge 3 O 12 Garnets: Insights from First-Principles Analysis.

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr³⁺-doped Ca₃Y₂Ge₃O₁₂ garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr³⁺ activator ions, which revealed a pronounced preference for the Y³⁺ sites over the Ca²⁺ and Ge⁴⁺ sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states ²E and ⁴T₂, along with their optical transition energies relative to the ground state ⁴A₂ in Ca₃Y₂Ge₃O₁₂:Cr³⁺, were successfully modeled using the ΔSCF method. Calculation convergence challenges were effectively addressed through the proposed fractional particle occupancy schemes. The constructed host-referred binding energy diagram provided a clear description of the luminescence kinetics process in the garnet, which explained the high quantum efficiency of emission. Furthermore, the accurate prediction of thermal excitation energy yielded insights into the thermal stability of the compound, as illustrated in the calculated configuration coordinate diagram. More importantly, all calculated data were consistently aligned with the experimental results. This research not only advances our understanding of the intricate interplay between geometric and electronic structures, optical properties, and thermal behavior in Cr³⁺-doped garnets but also lays the groundwork for future breakthroughs in the high-throughput design and optimization of luminescent performance and thermal stability in Cr³⁺-doped phosphors. [ABSTRACT FROM AUTHOR]