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:Ce(3+) phosphors have been investigated by using first-principles calculations. Four categories of typical substitutions (i.e., the doping of the Ce(3+) without the neighboring dopants/defects and with the neighboring VO(••), AlSi', and VCa″) are taken into account to simulate local environments of the Ce(3+) 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 Ce(3+). On the basis of the optimized crystal structures, the electronic properties of γ-Ca2SiO4:Ce(3+) 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 Ce(3+) are derived from the ab initio 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:Ce(3+) phosphors have been explored. Such information is vital, not least for the design of Ce(3+)-based phosphors for the white light-emitting diodes (w-LEDs) with excellent performance.

Identifying the Emission Centers and Probing the Mechanism for Highly Efficient and Thermally Stable Luminescence in the La3Si6N11:Ce3+ Phosphor

“…Therefore, identifying the emission centers of this phosphor experimentally is mainly restricted by the synthesis of La 3 Si 6 N 11 :Ce 3+ pure phase. Recently, wave function-based embedded cluster ab initio calculations were successfully used to calculate the energies and relative oscillator strengths of the 4f → 5d transitions of Ce 3+ ions, based on which the theoretical absorption spectra of Ce 3+ at different sites can be simulated. − Thus, this method is successful in identifying different types of luminescence centers independent of the experiment.…”

Highly Robust Oxynitride Phosphor against Thermal Oxidization and Hydrolysis

“…To further confirm the site occupancy of Ce 3+ in Sr 2 Al 3 Si 7 ON 13 , DFT calculations were performed. The total energies of different configurations were calculated because total energy is related to the stability of each configuration: the lower the total energy is, the more stable the configuration will be. ,− Therefore, Ce 3+ occupying Sr1 and Sr2 sites can be different conformations for evaluation to study the occupancy preference. Details of the model construction and calculation configuration are depicted in Figure S2 and a description in the Supporting Information.…”

Site Occupancy and VUV–UV–Vis Photoluminescence of the Lanthanide Ions in BaY2Si3O10

“…Subsequently, the Eu 3+ −O 2− CT energy is usually ascribed as the energy difference between the top of the valence band (VB) and the 4f ground states of Eu 2+ because the top of the valence band (VB) of silicates is primarily formed by the O 2− ligand 2p orbit, as confirmed by ab initio calculations. 50 In addition, the energy difference between the top of the VB and the bottom of the conduction band (CB) is described as the energy band gap and its value is approximately 1.08 times larger than the E ex value. 48 Consequently, the binding energies of the top of the VB, the bottom of the CB, and the exciton level are −9.53, −0.57, and −1.24 eV, respectively.…”