Intrinsic Point Defects and Dopants Ce3+ in SrLiAl3N4: Thermodynamic and Spectral Properties from First Principles

Lanthanide-doped SrLiAl3N4 are among the most promising phosphor materials for solid-state lighting due to their superior luminescence properties. Native point defects occur naturally during their synthesis at high temperature and may act as charge-compensating centers for aliovalent lanthanide substitutions or as trapping centers of electrons from the conduction band, but their nature and influence on luminescence properties are not well understood. Herein, we perform a systematic study on intrinsic point defects and dopants Ce3+ in SrLiAl3N4 by combining hybrid density-functional theory (DFT) and multi-configurational ab initio calculations. DFT-based defect formation energies predict that Li substitution at the Sr site (LiSr) is the most favorable acceptor-type point defect, and nitrogen vacancies provide electron-trapping levels with suitable depths for realizing persistent luminescence at room temperature. Calculated Boltzmannweighted occurrence probabilities and 4f -> 5d transition energies of Ce3+ reveal that the emission in SrLiAl3N4:Ce originates mainly from Ce3+ located at the Sr2 site, whereas the emission tail on the long-wavelength side arises from Ce3+ at the Sr1 site, both chargecompensated by intrinsic LiSr defects. On this basis, geometric parameters in the local coordination structures are identified to interpret the relative spectral shift of Ce3+ at the Sr1 and Sr2 sites. The present results can also serve as a theoretical basis for the engineering of nitridolithoaluminate-based phosphors with targeted luminescence properties.