Dual fluorescence properties and enhanced thermal stability of SrSi₂O₂N₂:Eu²⁺ phosphors by coupling with g-C₃N₄

Nowadays, considerable efforts have been extensively devoted to explore a general strategy for improving the color uniformity and thermal stability of phosphors, which is vital for its applications in health and comfort lighting. In this study, the SrSi₂O₂N₂:Eu²⁺/g-C₃N₄ composites were successfully prepared via a facile and effective solid-state method to improve their photoluminescence properties and thermal stability. The coupling microstructure and chemical composition of the composites were demonstrated by high-resolution transmission electron microscopy (HRTEM) and EDS line-scanning analyses. Notably, the dual emissions at ∼460 nm (blue) and ∼520 nm (green) were observed for the SrSi₂O₂N₂:Eu²⁺/g-C₃N₄ composite under near-ultraviolet (NUV) excitation, attributed to the g-C₃N₄ and 5d-4f transition of Eu²⁺ ions, respectively. The coupling structure will be beneficial to the color uniformity of the blue/green emitting light. Further, SrSi₂O₂N₂:Eu²⁺/g-C₃N₄ composites exhibited a similar photoluminescence intensity compared with the SrSi₂O₂N₂:Eu²⁺ phosphor even after thermal treatment at 500 °C for 2 h due to the protection of g-C₃N₄. The decreased decay time (1798.3 ns) of green emission for SSON/CN compared with SSON phosphor (1835.5 ns) indicated that the coupling structure suppressed the non-radiative transition and improved photoluminescence properties and thermal stability. This work provides a facile strategy to construct SrSi₂O₂N₂:Eu²⁺/g-C₃N₄ composites with coupling structure for improved color uniformity and thermal stability.