Achieving Efficient X‐ray Scintillation of Purely Organic Phosphorescent Materials by Chromophore Confinement

Abstract Scintillators have attracted significant attention due to their wide‐ranging applications in both industrial and medical fields. However, one of the ongoing challenges is the efficient utilization of triplet excitons to achieve high radioluminescence efficiency. Here, a series of purely organic phosphors is presented for X‐ray scintillation, employing a combined rigid and flexible host‐guest doping strategy. The doped crystals exhibit a remarkable maximum phosphorescence efficiency of 99.4% under UV excitation. Furthermore, upon X‐ray irradiation, the radioluminescence intensities of the doped phosphors are markedly higher compared to their single‐component crystal counterparts. Through systematic investigations, it is demonstrated the crucial role of confining isolated chromophores in enhancing scintillation efficiency. Additionally, a transparent scintillator screen fabricated with the doped phosphor exhibits excellent X‐ray imaging performance, achieving a high spatial resolution of 18.0 lp mm⁻¹. This work not only offers valuable insights into suppressing non‐radiative transitions of triplet excitons during scintillation but also opens a new avenue for designing highly efficient purely organic phosphorescent scintillators.