Organic Cation Modulation in Hybrid Zirconium Halides for High-Performance Flexible X-Ray Imaging

Exploiting novel materials featuring high-quality zero-dimensional structure, remarkable lattice stability, and minimal defects represents an efficacious strategy for enhancing the detection performance of X-ray scintillators. Here, we design and synthesize two novel zirconium-based organic-inorganic hybrid metal halides (OIMHs), C₁₄H₄₀N₄ZrCl₈ and C₆H₁₆N₂ZrCl₆. Based on the steric hindrance effect of organic cations, the distance between [ZrCl₆]^2- polyhedra was designed, and the electronic coupling interactions among polyhedra were adjusted, thus precisely engineering excellent zero-dimensional materials. Simultaneously, the stronger N─H⁺···Cl^- bond is introduced to avoid structural instabilities and more defects due to the bigger organic cation in C₁₄H₄₀N₄ZrCl₈. As expected, C₁₄H₄₀N₄ZrCl₈ exhibits more remarkable luminescence behavior compared to C₆H₁₆N₂ZrCl₆. The photophysics process involving self-trapped excitons and defects is elaborately expounded using first-principles calculations, luminescence properties, and stabilities. Finally, a flexible and large-area scintillation screen based on C₁₄H₄₀N₄ZrCl₈ is fabricated and attains a high spatial resolution of 21.35 lp mm^-1 and a lower limit of detection of 2.270 µGy_air s^-1, outperforming the resolution of most blue-emitting scintillation screens. These results imply that the zirconium-based OIMHs possess significant potential applications for medical diagnostics, security scanning, and non-destructive testing.