Scalable, High‐Efficiency, and High‐Resolution X‐Ray Scintillator Films Enabled by Industrial Blow Molding of Ag‐Doped Cs 3 Cu 2 I 5 @Polyethylene Composites

X‐ray imaging plays an irreplaceable role in global security inspection, medical diagnostics, and industrial nondestructive testing, yet conventional single‐crystal scintillators suffer from high costs, complex fabrication, and poor flexibility. Here, we report a flexible x‐ray scintillator film (Cs 3 Cu 2 I 5 :Ag@PE) that uniquely combines industrial‐scale processability with ultra‐high luminescence efficiency. Ag doping can cause lattice expansion and increase material density, boosting x‐ray absorption and luminescence. Notably, the film is fabricated via scalable ball milling and industrial blown film extrusion. Compared to a maximum quantum efficiency of 43.3% typically achieved via the micropatterned method, our large‐scale extrusion strategy delivers a remarkable PLQY of 75.4%. The film also exhibits excellent stability (89.6% retention after 2000 h) and radioluminescence efficiency comparable to commercial LuAG:Ce. Furthermore, it achieves an ultra‐low detection limit of 212.5 nGy/s and a superior spatial resolution 175% higher than commercial CsI:Tl. This work highlights a scalable and highly efficient route toward high‐performance flexible x‐ray imaging for clinical and industrial applications.