First-Principles Study on Structural, Electronic, and Spectroscopic Properties of γ‑Ca₂SiO₄:Ce³⁺ Phosphors

Abstract

In the present work, geometric structures, electronic properties, and 4f → 5d transitions of γ-Ca₂SiO₄:Ce³⁺ phosphors have been investigated by using first-principles calculations. Four categories of typical substitutions (i.e., the doping of the Ce³⁺ without the neighboring dopants/defects and with the neighboring V_O^••, Al_Si′, and V_Ca″) are taken into account to simulate local environments of the Ce³⁺ located at two crystallographically different calcium sites in the γ-Ca₂SiO₄. Density functional theory (DFT) geometry optimization calculations are first performed on the constructed supercells to obtain the information about the local structures and preferred sites for the Ce³⁺. On the basis of the optimized crystal structures, the electronic properties of γ-Ca₂SiO₄:Ce³⁺ phosphors are calculated with the Heyd–Scuseria–Ernzerhof screened hybrid functional, and the energies and relative oscillator strengths of the 4f → 5d transitions of the Ce³⁺ are derived from the <i>ab initio</i> embedded cluster calculations at the CASSCF/CASPT2/RASSI-SO level. A satisfactory agreement with the available experimental results is thus achieved. Moreover, the relationships between the dopants/defects and the electronic as well as spectroscopic properties of γ-Ca₂SiO₄:Ce³⁺ phosphors have been explored. Such information is vital, not least for the design of Ce³⁺-based phosphors for the white light-emitting diodes (<i>w</i>-LEDs) with excellent performance