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

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journal contribution
posted on 23.07.2015, 00:00 by Jun Wen, Lixin Ning, Chang-Kui Duan, Shengbao Zhan, Yucheng Huang, Jie Zhang, Min Yin
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 VO••, AlSi′, and VCa″) 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 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:Ce3+ phosphors have been explored. Such information is vital, not least for the design of Ce3+-based phosphors for the white light-emitting diodes (w-LEDs) with excellent performance.