Efficient Near‐Infrared Emitting Halide Scintillators with Mitigating External Light Crosstalk for Portable X‐Ray Imaging

Abstract Portable X‐ray imaging technology plays a crucial role in enabling prompt diagnosis and treatment outdoors. Nevertheless, the persistent challenge of external optical signal crosstalk poses a significant bottleneck to its advancement. Herein, a solution utilizing near‐infrared (NIR) light to effectively mitigate optical crosstalk is proposed, thereby demonstrating the feasibility of portable X‐ray imaging even under ambient light. A series of rare earth ions doped Cs₂Ag_xNa_1‐xIn_yBi_1‐yCl₆ halide scintillators is reported, which possess bright broadband visible and NIR emissions. Taking Cs₂Ag_0.6Na_0.4In_0.95Bi_0.05Cl₆: 5%Tm as an example, it shows decent thermal quenching resistance, high PLQY up to 76.3%, and compelling light yield up to 33500 photons MeV⁻¹. The highly efficient NIR emission is attributed to the energy transfer from the optimized host to lanthanide ions. A flexible scintillation film is prepared by mixing poly(dimethyl‐siloxane) with Cs₂Ag_0.6Na_0.4In_0.95Bi_0.05Cl₆: 5%Tm powder, realizing a low X‐ray detection limit of 55.2 nGy_air/s and a high spatial resolution of 11.2 lp mm⁻¹. Due to the efficient NIR emission, the scintillation film enables clear X‐ray imaging under bright LED illumination with the simple addition of filters, avoiding the necessity of a complex imaging apparatus. This work sheds light on NIR emissive scintillator for rapid outdoor response and portable X‐ray imaging.