Emergence of a Lanthanide Chalcogenide as an Ideal Scintillator for a Flexible X-ray Detector

The development of high-performance X-ray detectors requires scintillators with fast decay time, high light yield, stability, and X-ray absorption capacity, which are difficult to achieve in a single material. Here, we present the first example of a lanthanide chalcogenide of LaCsSiS₄  : 1 % Ce³⁺ that simultaneously integrates multiple desirable properties for an ideal scintillator. LaCsSiS₄  : 1 % Ce³⁺ demonstrates a remarkably low detection limit of 43.13 nGy_air  s^-1 and a high photoluminescence quantum yield of 98.24 %, resulting in a high light yield of 50480±1441 photons/MeV. Notably, LaCsSiS₄  : 1 % Ce³⁺ exhibits a fast decay time of only 29.35±0.16 ns, making it one of the fastest scintillators among all lanthanide-based inorganic scintillators. Furthermore, this material shows robust radiation and moisture resistance, endowing it with suitability for chemical processing under solution conditions. To demonstrate the X-ray imaging capacity of LaCsSiS₄  : 1 % Ce³⁺ , we fabricated a flexible X-ray detector that achieved a high spatial resolution of 8.2 lp mm^-1 . This work highlights the potential of lanthanide chalcogenide as a promising candidate for high-performance scintillators.