Efficient and Reabsorption‐Free Radioluminescence in Cs₃Cu₂I₅ Nanocrystals with Self‐Trapped Excitons

Radioluminescent materials (scintillators) are widely applied in medical imaging, nondestructive testing, security inspection, nuclear and radiation industries, and scientific research. Recently, all-inorganic lead halide perovskite nanocrystal (NC) scintillators have attracted great attention due to their facile solution processability and ultrasensitive X-ray detection, which allows for large area and flexible X-ray imaging. However, the light yield of these perovskite NCs is relatively low because of the strong self-absorption that reduces the light out-coupling efficiency. Here, NCs with self-trapped excitons emission are demonstrated to be sensitive, reabsorption-free scintillators. Highly luminescent and stable Cs₃Cu₂I₅ NCs with a photoluminescence quantum yields of 73.7%, which is a new record for blue emission lead-free perovskite or perovskite-like NCs, is produced with the assistance of InI₃. The PL peak of the Cs₃Cu₂I₅ NCs locates at 445 nm that matches with the response peak of a silicon photomultiplier. Thus, Cs₃Cu₂I₅ NCs are demonstrated as efficient scintillators with zero self-absorption and extremely high light yield (≈79 279 photons per MeV). Both Cs₃Cu₂I₅ NC colloidal solution and film exhibit strong radioluminescence under X-ray irradiation. The potential application of Cs₃Cu₂I₅ NCs as reabsorption-free, low cost, large area, and flexible scintillators is demonstrated by a prototype X-ray imaging with a high spatial resolution.