Nd 3+ Doping Induced Anti‐Thermal Quenching in Rare‐Earth Lead‐Free Halide Double Perovskite Toward High‐Resolution X‐Ray Imaging

ABSTRACT Flexible scintillator screens with excellent stability and high spatial resolution are crucial for non‐planar X‐ray imaging applications. Lead‐free rare‐earth halide double perovskites (DPs) have emerged as formidable contenders in the scintillator field due to their unique advantages, environmental friendliness, high quantum efficiency, facile synthesis, and tunable emission wavelength etc. Herein, Nd 3+ ‐doped Cs 2 NaScCl 6 (CNSC) micron crystal with a high near‐infrared (NIR) emission quantum efficiency of 76% were successfully synthesized using a simple hydrothermal method. The systematic optical characterization unveiled, for the first time, anti‐thermal quenching effect induced by Nd 3+ doping in DPs. Subsequently, large‐area, flexible CNSC: Nd 3+ @PDMS scintillator for X‐ray imaging were developed, demonstrating excellent mechanical stability (Without attenuation after 5000 bendings), ultra‐high spatial resolution (24 lp/mm), and exceptional operational stability (The signal intensity was enhanced after continuous irradiation). These research results not only enhance the understanding of anti‐thermal quenching in DPs, but also promote the development of NIR high‐efficiency ultra‐flexible scintillator.