Perovskite Dimensional Evolution Through Cations Engineering to Tailor the Detection Limit in Hard X‐ray Response

Halide perovskites with various compositions are potential candidates in low-dosage X-ray detection due to their large sensitivity and tunable optoelectronic properties. Here, cations engineering induced dimensional evolution of halide perovskites between 0D, 2D, and 3D is reported. Centimeter-sized 2D lead-free perovskite single-crystal of 4-fluorophenethylammonium antimony iodide (FPEA(3)SbI(6)) is synthesized. In contrast to the 0D phenethylammonium antimony iodide (PEA(3)Sb(2)I(9)), face-shared [Sb2I9](3-) of the bi-octahedral structure of PEA(3)Sb(2)I(9) is split into corner-shared [SbI6](3-) by intermolecular interactions and steric hindrance of FPEA(+) ions in 2D FPEA(3)SbI(6). Two Sb3+ ions share three octahedral [SbI6](3-), leaving one-third of Sb3+ vacancies in the framework of FPEA(3)SbI(6). Furthermore, Sn2+ ions can be filled into the vacancies to form continuous 2D frameworks to tune the anisotropic conductivity and device sensitivity to hard X-rays. The dimensional evolution of perovskite single-crystals from 3D to 2D or 0D to 2D maximizes the signal/noise ratio to facilize the adjustability of detection limit in hard X-ray detection, which is determined by both device sensitivity and device noise current. A record low detection limit coefficient of 0.65 is achieved in the 2D FPEA(3)SbSn(0.5)I(7) single-crystal sample, which results from selective charges collection over mobile ions/noise current in the 2D perovskite structure.