Two‐Inch Low‐Dimensional Perovskite Microcrystal Composite Scintillation Screen for Sub‐Nanosecond X‐Ray Imaging

In radiological imaging, scintillation screens play a critical role in converting ionizing radiation into visible light, directly influencing imaging sensitivity. Enhancing the light yield (LY) and scintillation speed of these screens is essential for reducing radiation dose and improving image quality. However, materials combining high LY with ultrafast decay time are typically associated with high fabrication costs, severely restricting their practical implementation. Here, we report a cost‐effective strategy for fabricating large‐area scintillation screens based on (C 6 H 5 C 2 H 4 NH 3 ) 2 PbBr 4 (PEA 2 PbBr 4 ) microcrystals, a material known for its high LY and fast decay time. The resulting composite screens maintain the intrinsically high LY of PEA 2 PbBr 4 while achieving an ultrafast decay time of 0.986 ns. Through an optimized microcrystal dispersion process, the screens achieve horizontal scalability while maintaining uniform scintillation performance, enabling large‐area X‐ray imaging applications. Moreover, the PMMA matrix provides substantial thermal protection, giving the PMMA/PEA 2 PbBr 4 composites significantly improved thermal stability compared with the pure microcrystals. This work offers a promising pathway toward the development of scintillators that combine high sensitivity with high detection efficiency for next‐generation radiation imaging.