Polar 2D hybrid perovskite crystals with intrinsic strong linear dichroism for polarization-sensitive and self-powered detection

Abstract

Two-dimensional (2D) hybrid perovskite, which has inherent optical anisotropy and structural properties shows broad application prospects as a polarization-sensitive candidate. In particular, the polar members that enable the bulk photovoltaic effect (BPVE) show great potential in self-powered photodetection. Here, by incorporating a brominated aromatic cation as an interlayered spacer, we have succeeded in synthesizing a polar 2D hybrid perovskite, (BBA)₂(MA)Pb₂I₇ (1, where BBA⁺ is 4-bromobenzylammonium, MA⁺ is methylammonium). The inherent structural anisotropy caused by the alternate placement of inorganic perovskite sheets and organic-spaced cations permits substantial linear absorption dichroism with a high ratio of ∼4.2 (at 520 nm). Moreover, the bromination of the organic spacer favours the electric polarity of 1. The electric spontaneous polarization (P_s) results in notable BPVEs in 1, which directly drives the separation and transport of photoexcited carriers and further supports its self-powered capability. As expected, the self-powered photodetector of 1 exhibits strong polarization sensitivity to linear polarized light, showing a polarization ratio of 4.8. This figure is even larger than that of conventional inorganic GeSe nanosheets (∼1.09 at 532 nm). This work will facilitate the potential application of 2D polar perovskite candidate materials for self-powered photodetection.