Ultrafast and high-resolution X-ray imaging based on zero-dimensional organic silver halides†

Supersensitive and fast X-ray imaging is of great importance in medical diagnosis, industrial flaw detection, security and safety inspection, and frontier science exploration. As the core of detection devices, new generation scintillators require small self-absorption capacity, short fluorescence lifetime, simple film-making protocol, excellent stability and non-toxicity. Herein, a new type of lead-free organic silver halide TPPAgX₂ (TPP = C₂₄H₂₀P and X = I, Br, and Cl) is rationally developed with a large Stokes shift (176 nm) and ultralow photoluminescence decay (3.8 ns lifetime). It achieves an ultrafast fluorescent response that is the best among all the Pb-free perovskite scintillators. Temperature-dependent PL and DFT calculations together confirm that TPPAgCl₂ follows an emission mechanism in which a triplet exciton can be rapidly upconverted via thermal activation. A series of TPPAgX₂-based flexible scintillator films were fabricated and tested. A detection limit of 0.447 μGy_air s⁻¹ was obtained for TPPAgCl₂, which is one order of magnitude lower than the medical X-ray diagnosis requirement. In addition, it exhibits a superior X-ray imaging resolution of 11.87 lp mm⁻¹. The excellent performance and simple preparation methodology are expected to be potentially applicable for large-scale manufacturing.