X‐Ray Quantum Cutting Scintillator Based on CsPbClxBr3−x:Yb3+ Single Crystals

Abstract Metal‐halide perovskites, especially for 3D halide perovskite single crystals (SCs), are emerging as the promising scintillators. However, the strong self‐absorption and low light yield of these perovskites restrict their practical applications. Quantum cutting can convert a high energy photon into multiple low energy photons, endowing a large Stokes shift and high photoluminescent quantum yield (PLQY). Here, this work reports a novel quantum cutting material, CsPbCl x Br 3− x :Yb 3+ perovskite SCs, with the PLQY of 149% and a Stokes shift >550 nm, successfully conquering the issues of poor PLQY induced by the thermal quenching and the large self‐absorption in perovskite SCs. Benefiting from the extremely high PLQY and negligible self‐absorption effect, the first high‐performance quantum cutting scintillators based on CsPbCl x Br 3− x :Yb 3+ perovskite SCs are developed, exhibiting high transmittance, large X‐ray absorption/conversion efficiency, outstanding light yield of ≈1.12 × 10 5 photons MeV −1 , and a detection limit as low as 176.5 nGy air s −1 . Finally, a single‐pixel X‐ray imaging is achieved by integrating CsPbCl 3 :Yb 3+ SCs with silicon photomultiplier. This work sheds light on exploring highly competitive scintillators beyond the scope of traditional perovskites.