The integration of real‐time and flexible imaging has significantly advanced X‐ray scintillator imaging technologies. However, combining both functionalities into a single scintillator material remains a fundamental challenge. To address this, we designed a zero‐dimensional cerium (Ⅲ)‐based organic‐inorganic hybrid halide scintillator, MPH₂CeCl₅·3H₂O (MPH = morpholine), using low‐cost solution processing and leveraging Ce (Ⅲ)'s inherently nanosecond‐scale 4f–5d transitions. La³⁺‐alloying induced a dual effect, enhancing the photoluminescence quantum yield to 2.75 times the original value while maintaining a short decay time of approximately 22 ns. Combined with heavy‐atom effects, this nanosecond‐scale decay prompted investigation of X‐ray scintillation performance, revealing a respectable light yield of 10,400 photons/MeV and a low detection limit of 96.73 nGy_air/s. By embedding the optimized MPH₂CeCl₅·3H₂O into poly(methyl methacrylate) (PMMA), we fabricated a high‐performance flexible film that mitigates material hygroscopicity while enabling outstanding flexibility and dynamic imaging capabilities. This film achieved motion‐artifact‐free dynamic imaging at 100 fps, clearly resolving blades rotating at 560°/s. This work demonstrates Ce (Ⅲ)‐based halide hybrids as promising platforms for advanced medical and industrial imaging, offering high light yield, rapid response, and superior processability.

Lead-free bismuth-based halide perovskites and their analogues have attracted research interest for their high stability and optoelectronic properties. However, the morphology-controlled synthesis of bismuth-based perovskite nanocrystals has been rarely demonstrated. Herein, we report the colloidal synthesis of zero-dimensional (0D) Cs₃BiCl₆ nanosheets (NSs), Cs₃Bi₂Cl₉ NSs/nanoplates (NPs) and Cs₄MnBi₂Cl₁₂ NPs through a hot-injection method. We demonstrate that the Cs₃BiCl₆ NSs, as an initial product of Cs₃Bi₂Cl₉ and Cs₄MnBi₂Cl₁₂ NPs, can transform into Cs₃Bi₂Cl₉ NSs or Cs₄MnBi₂Cl₁₂ NPs via Cl-induced metal ion insertion reactions under the templating effect of Cs₃BiCl₆. This growth mechanism is also applicable for the synthesis of Cs₄CdBi₂Cl₁₂ nanoplates. Furthermore, the alloying of Cd²⁺ into Cs₄MnBi₂Cl₁₂ lattice could weaken the strong coupling effect between Mn and Mn, which leads to a prolonged photoluminescence lifetime and an enhanced photoluminescence quantum yield (PLQY). As a proof of concept, the alloyed Cs₄Mn_xCd_1–xBi₂Cl₁₂ NPs are used as a scintillator, which show a lowest detection limit of 134.5 nGy/s. The X-ray imaging results display a high spatial resolution of over 20 line pairs per millimeter (lp/mm). These results provide new insights in the synthesis of anisotropic bismuth-based perovskite nanocrystals and their applications in radiation detection.