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 [Sb 2 I 9 ] 3- of the bi-octahedral structure of PEA 3 Sb 2 I 9 is split into corner-shared [SbI 6 ] 3- by intermolecular interactions and steric hindrance of FPEA + ions in 2D FPEA 3 SbI 6 . Two Sb 3+ ions share three octahedral [SbI 6 ] 3- , leaving one-third of Sb 3+ vacancies in the framework of FPEA 3 SbI 6 . Furthermore, Sn 2+ 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.