Unlocking novel halogen germanate phosphors for full-spectrum lighting and ultra-sensitive temperature sensing

Exploring multiple emission bands from single rare-earth doped phosphors and developing design principles to enhance brightness and temperature sensing capabilities are key challenges in advanced optical applications and research. Herein, we report a novel Sr 6 Ge 2 O 7 Cl 6 :Eu 2+ (SGOC:Eu 2+ ) phosphor and that exhibits three emission bands at 400, 501, and 670 nm. These bands are resolved into four Gaussian peaks, attributed to 5d-4f transitions of Eu 2+ ions occupying four distinct Sr 2+ sites. Resolved into four Gaussian peaks, attributed to 5d-4f transitions of Eu 2+ occupying four distinct Sr 2+ sites. Energy levels were quantified via Van Uitert equation and lattice distortion analysis. The unique thermal quenching disparity between high-energy (400 nm) and low-energy (501 nm) emissions enables superior temperature sensing, achieving absolute and relative sensitivities of 3.07 % K −1 (298 K) and 15.22 % K −1 (498 K), respectively, via fluorescence intensity ratio (I 400 /I 501 ). Ge/Si substitution enhances Eu 2+ incorporation, elevating luminescence intensity by 282 % and quantum efficiency from 23.6 % to 57.5 %, attributed to suppressed non-radiative losses and modified local lattice symmetry. A white LED fabricated with SGOC:Eu 2+ exhibits exceptional color rendering (Ra = 96). This work highlights the critical role of multi-site engineering in designing high-performance phosphors for ultra-sensitive optical thermometry and efficient solid-state lighting, providing a blueprint for next-generation photonic materials.