A pyridinium cation engineering strategy to achieve high-performance X-ray scintillation of antimony halides.

While organic-inorganic hybrid metal halides (OIMHs) have emerged as promising X-ray scintillators, a major challenge lies in the precise control of their structural dimensionality and exciton behavior to optimize the scintillation performance. Here, we introduce a pyridinium cation engineering strategy to address this issue. A one-pot reaction of SbCl with a pyridine derivative, in the presence of HCl, yields either a 0D or 1D Sb-based OIMH. The 0D structure featuring isolated [SbCl] polyhedra imposes strong quantum confinement, leading to enhanced electron-phonon coupling. This results in an orange-red self-trapped exciton emission at 630 nm, characterized by a large Stokes shift of 262 nm and a near-unity photoluminescence quantum yield. This 0D material demonstrates high-performance X-ray scintillation with a light yield of 20 718 photons MeV and a low detection limit of 0.31 µGy s, enabling high-resolution imaging. In contrast, the 1D material consists of corner-sharing inorganic chains. It shows green emission from organic free excitons and poor scintillation performance. This study establishes that pyridinium cation engineering is a potent and promising strategy for the design and optimization of metal halide-based emitters and scintillators.