Near-infrared organic scintillators for efficient X-ray imaging via singlet and triplet to doublet energy transfer

Near-infrared (NIR) organic scintillating materials are in high demand in a variety of fields, such as radiography, X-ray radiation therapy, and medical diagnosis. However, efficient organic NIR materials with high X-ray absorption are rarely reported. Here, we developed NIR organic X-ray imaging scintillators based on a typical organic radical with emission from a spin doublet excited state. The energy transfer strategy from thermally activated delayed fluorescence (TADF) sensitizers to the radical emitter was exploited to enhance X-ray absorption capability. The optimized scintillators with an Au(III)-TADF complex as the sensitizer exhibited intense NIR radioluminescence peaking at 746 nm upon X-ray excitation. High-quality X-ray imaging with a high spatial resolution of 15.3 lp mm⁻¹ was demonstrated, suggesting great potential for real applications. This work provides an effective strategy for the development of NIR organic scintillators.