Polymorphism‐Dependent Organic Room Temperature Phosphorescent Scintillation for X‐Ray Imaging

Abstract Organic phosphorescent scintillating materials have shown great potential for applications in radiography and radiation detection due to their efficient utilization of excitons. However, revealing the relationship between molecule stacking and the phosphorescent radioluminescence of scintillators is still challenging. This study reports on two phenothiazine derivatives with polymorphism‐dependent phosphorescence radioluminescence. The experiments reveal that molecule stacking significantly affects the non‐radiation decay of the triplet excitons of scintillators, which further determines the phosphorescence scintillation performance under X‐ray irradiation. These phosphorescent scintillators exhibit high radio stability and have a low detection limit of 278 nGys⁻¹. Additionally, the potential application of these scintillators in X‐ray radiography, based on their X‐ray excited radioluminescence properties, is demonstrated. These findings provide a guideline for obtaining high‐performance phosphorescent scintillating materials by shedding light on the effect of crystal packing on the radioluminescence of organic molecules.