Molecularly thin, two-dimensional all-organic perovskites.

Recently, the emergence of all-organic perovskites with three-dimensional (3D) structures has expanded the potential applications of perovskite materials. However, the synthesis and utilization of all-organic perovskites in 2D form remain largely unexplored because the design principle has not been developed. We present the successful synthesis of a metal-free 2D layered perovskite, denoted as the Choi-Loh van der Waals phase (CL-v phase), with the chemical formula A2B2X4, where A represents a larger-sized cation compared to B and X denotes an anion. The CL-v phase exhibits a van der Waals gap enabled by interlayer hydrogen bonding and can be exfoliated or grown as molecularly thin 2D organic crystals. The dielectric constants of the CL-v phase range from 4.8 to 5.5 and we demonstrate their potential as gate dielectrics for thin-film transistors.