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

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 kVp 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.