Ultrabroadband-Emissive Lanthanide Chalcogenide for X-ray Scintillation

We report herein the synthesis and optical properties of a lanthanide chalcogenide scintillator, CeCsSiS₄, which crystallizes in the orthorhombic space group Pnma and adopts a two-dimensional layered structure. CeCsSiS₄ exhibits ultrabroadband emission spanning 400-950 nm with a record full width at half-maximum (fwhm) of 207.3 nm among Ce³⁺-based inorganic emitters. The emission originates from the combined contributions of the Ce³⁺-5d → 4f transition and Ce-5d → S-3p charge-transfer transitions. The material shows a high photoluminescence quantum yield of 51.6%, a fast decay time of 26.4 ns, strong X-ray radioluminescence, and excellent radiation and moisture stability, demonstrating promise for robust X-ray detection.