Centimeter‐Sized Single Crystals of Two‐Dimensional Hybrid Iodide Double Perovskite (4,4‐Difluoropiperidinium)₄AgBiI₈ for High‐Temperature Ferroelectricity and Efficient X‐Ray Detection

Abstract

Abstract Ferroelectricity and X‐ray detection property have been recently implemented for the first time in hybrid bromide double perovskites. It sheds a light on achieving photosensitive and ferroelectric multifunctional materials based on 2D lead‐free hybrid halide double perovskites. However, the low T c , small P s , and relatively low X‐ray sensitivity in the reported bromide double perovskites hinder practical applications. Herein, the authors demonstrate a novel 2D lead‐free iodide double perovskite (4,4‐difluoropiperidinium) 4 AgBiI 8 (1) for high‐performance X‐ray sensitive ferroelectric devices. Centimeter‐sized single crystal of 1 is obtained and exhibits an excellent ferroelectricity including a high T c up to 422 K and a large P s of 10.5 μC cm −2 . Moreover, due to a large X‐ray attenuation and efficient charge carrier mobility (μ)–charge carrier lifetime (τ) product, the crystal 1 also exhibits promising X‐ray response with a high sensitivity up to 188 μC·Gy air −1 cm −2 and a detection limit below 3.13 μGy air ·s −1 . Therefore, this finding is a step further toward practical applications of lead‐free halide perovskite in high‐performance photoelectronic devices. It will afford a promising platform for exploring novel photosensitive ferroelectric multifunctional materials based on lead‐free double perovskites.