Scintillation Response of 0D Cs₃Cu₂I₅ Thin Layers to Light‐ and Heavy‐Ion Irradiation

Low‐dimensional copper halides with perovskite–analogue structure are a rapidly growing material family for light‐emitting and X‐ray screening devices. Among them Cs 3 Cu 2 I 5 exhibits exceptional optoelectronic properties (large Stokes shift, high emission yield), due to the strong confinement effect of its 0D structure. However, its radioluminescence response to energetic ions has only marginally been explored and to heavy ions fully ignored due to the detrimental effect of luminescence quenching. Herein, the scintillation response of Cs 3 Cu 2 I 5 thin layers to ions in a wide range of atomic mass and ionization density, as well as to electrons using the Compton‐coincidence technique, is investigated. The photon yield, linearity, and energy resolution are investigated as key parameters of the spectroscopic performance. Different semiempirical quenching models are used to better understand the relationship between the luminescence yield and the ionization density. The spectroscopic capability of polycrystalline Cs 3 Cu 2 I 5 thin films is found on par with that of single‐crystal CsI:Tl to detect heavy ions. This makes easily processable thin‐film copper halides an attractive addition to the scintillator landscape.