Forced Intergrowth of NaYS₂ Phase in Sulfur‐Rich Environments with Fluorescence Remodeling of Upscaled Full‐Spectrum

Abstract Optimization of the host lattice is a novel strategy to achieve efficient up‐conversion luminescence (UCL) with multi‐peak full‐spectrum emission. Herein, lattice optimization is performed in a non‐vacuum sulfur‐rich environment, where the ultra‐low phonon energy NaYS₂ heterogeneous phase is forced to intergrow, which overcomes the limitations of the conventional vacuum preparation method and achieves high‐efficient UCL. Remarkably, the lattice sites are preferentially occupied by S²⁻, which causes lattice distortion and generates layered NaYS₂/Y₂O₂S hybrid crystalline with high inversion asymmetry to reconfigure excitation mechanism and exhibit distinct luminescence centers at the multi‐peak full‐spectrum. Moreover, owing to longer lifetime of excited state energy levels of Er³⁺ after lattice modification and ordered segregation of Er³⁺ in the YS₆ layer restricting the negative energy exchange process, the luminescence intensity is increased by about six times, and the remodeling of full‐spectrum‐efficient UCLs is realized. This work reports an innovative approach for lattice optimization and a facile preparation of ternary sulfides, which provides a new direction for achieving highly efficient UCLs with promising applications in biomedical imaging, near‐infrared detection, and temperature sensing synergy.