Oriented 2D Perovskite Wafers for Anisotropic X-ray Detection through a Fast Tableting Strategy.

Abstract

2D perovskite single crystals have emerged as excellent optoelectronic materials owing to their unique anisotropic properties. However, growing large 2D perovskite single crystals remains challenging and time-consuming. Here, a new composition of lead-free 2D perovskite-4-fluorophenethylammonium bismuth iodide [(F-PEA)₃ BiI₆ ] is reported. An oriented bulk 2D wafer with a large area of 1.33 cm² is obtained by tableting disordered 2D perovskite powders, resulting in anisotropic resistivities of 5 × 10¹⁰ and 2 × 10¹¹  Ω cm in the lateral and vertical directions, respectively. Trivalent Bi³⁺ ions are employed to achieve a stronger ionic bonding energy with I^- ions, which intrinsically suppress the ion-migration effect. Thus, the oriented wafer presents good capabilities in both charge collection and ion-migration suppression under a large applied bias along the out-of-plane direction, making it suitable for low-dosage X-ray detection. The large-area wafer shows a sensitive response to hard X-rays operated at a tube voltage of 120 kV_p with the lowest detectable dose rate of 30 nGy s^-1 . Thus, the fast tableting process is a facile and effective strategy to synthesize large-area, oriented 2D wafers, showing excellent X-ray detection performance and operational stability that are comparable to those of 2D perovskite single crystals.