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

Two-dimensional 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, we report a new composition of lead-free 2D perovskite-4-fluorophenethylammonium bismuth iodide [(F-PEA)3 BiI6 ]. An oriented bulk 2D material with a large area of 1.33 cm2 was obtained by tableting disordered 2D perovskite powders under a pressure of 280 MPa, resulting in different anisotropy resistivities of 5 × 1010 and 2 × 1011 Ω·cm in the lateral and vertical directions, respectively. This four-fold conductivity difference of the large-area wafer is already comparable to that of 2D perovskite single crystals. Trivalent Bi3+ ions were employed to achieve a stronger ionic bonding energy with I- ions, which intrinsically suppressed the ion migration effect. Thus, the oriented wafer presented 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 showed 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. This article is protected by copyright. All rights reserved.