Efficient and Reabsorption‐Free Radioluminescence in Cs(3)Cu(2)I(5) 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 Cs(3)Cu(2)I(5) 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 InI(3). The PL peak of the Cs(3)Cu(2)I(5) NCs locates at 445 nm that matches with the response peak of a silicon photomultiplier. Thus, Cs(3)Cu(2)I(5) NCs are demonstrated as efficient scintillators with zero self‐absorption and extremely high light yield (≈79 279 photons per MeV). Both Cs(3)Cu(2)I(5) NC colloidal solution and film exhibit strong radioluminescence under X‐ray irradiation. The potential application of Cs(3)Cu(2)I(5) NCs as reabsorption‐free, low cost, large area, and flexible scintillators is demonstrated by a prototype X‐ray imaging with a high spatial resolution.