Influence of N Doping on the Electronic Structure and Absorption Spectrum of Ca$lt;inf$gt;2$lt;/inf$gt;SiO$lt;inf$gt;4$lt;/inf$gt;: Eu$lt;sup$gt;2+$lt;/sup$gt; Phosphor

The electronic structure and absorption spectrum of Ca 2 SiO 4 : Eu 2+ was studied by using density functional theory. It is found that N atoms substituted provide many states around the Femi level, which leads to narrow optical band gap and interband transition originating from N2p to the Eu4f. In the N-doped Ca 2 SiO 4 : Eu 2+ phosphor, Eu 2+ ions experience a strong nephelauxetic effect and crystal field due to the coordinating nitrogen ions around the activated centers, which results in Eu4f and 5d states splitting. Thus, the red-shift of the absorption spectrum and high absorption band in the wavelength of 220-470 nm takes place for the N-doped Ca 2 SiO 4 : Eu 2+ phosphor.