Molecular Miscibility Enables Single‐Phase Organic Scintillators for High‐Resolution Conformal X‐Ray Imaging

Flexible organic scintillators are attractive for conformal x‐ray imaging but are fundamentally limited by a thickness–transparency–resolution trade‐off, as the film thickness required for efficient x‐ray absorption generally increases light scattering from dispersed phosphor domains. Here, we overcome this limitation by introducing molecular miscibility as a design principle for single‐phase organic scintillators. A water‐soluble carbazole–quaternary phosphonium copolymer is co‐processed with poly(vinyl alcohol) to form a fully amorphous film in which the emitter is molecularly integrated within the polymer network. This architecture suppresses refractive‐index scattering while rigidifying the phosphorescent chromophores, simultaneously enabling high optical transparency and efficient room‐temperature phosphorescence. The optimized scintillator exhibits 88.1% transmittance at 300 µm thickness, a light yield of 16 533 photons MeV − 1 , and a spatial resolution of 12 lp mm − 1 , while supporting large‐area fabrication, multicolor scintillation through molecular co‐doping, and conformal x‐ray imaging of curved objects with reduced geometric distortion. This work establishes molecular miscibility as a general strategy for minimizing morphology‐induced optical losses, providing a pathway toward flexible scintillators that combine efficient x‐ray stopping with high‐resolution imaging.