Cation Engineering\nof Cu-Doped CsPbI<sub>3</sub>:\nLead Substitution and Dimensional Reduction for Improved Scintillation\nPerformance

To date, inorganic halide perovskite nanocrystals show\npromising\ncontributions in emerging luminescent materials due to their high\ntolerance to defects. In particular, the development of cesium lead\niodide (CsPbI<sub>3</sub>) has shown its efficiency for light-harvesting\nproperties. However, further implementation is hindered due to the\ntoxicity of the lead content. Therefore, in this study, we introduced\nCu atoms to partially substitute Pb atoms (5% Cu) in the CsPbI<sub>3</sub> lattice as a solution to reduce the Pb toxicity. Partial\nsubstitution of Pb with Cu atoms in CsPbI<sub>3</sub> host lattice\nincreases the Stokes shift (∼67 nm) compared to pristine CsPbI<sub>3</sub>, thereby preventing the undesired self-absorption. An outcome\nis focused on the champion of a fast component (τ<sub>1</sub>) decay time of ∼0.6 ns. Temperature-dependent radioluminescence\noutlines an incremental change in the emission intensity marginally\ncentered at 713 ± 16 nm, which indicates that Cu-doped CsPbI<sub>3</sub> is not greatly affected by temperature. In addition, we report\nthat the light yield pristine CsPbI<sub>3</sub> after doping is increased\nto 3.0 ± 0.8 photons/keV. Our work provides physical insights\ninto a tunable scintillation property using transition metal doping\ntoward lead-free-based scintillating perovskites.