Exceptionally Strong Self-Powered Polarization Behaviors Involving with Bulk Photovoltaics in Highly Anisotropic 2D Hybrid Perovskite Ferroelectric Crystals

Two-dimensional(2D) hybrid perovskites take an emerging positionin optoelectronics. Especially, ferroelectric crystals in this familycan be potentially used as polarized light detectors because photocurrent,induced by the ferroelectric bulk photovoltaic effect (BPVE), is thefunction of the intersection angle between the polarization directionsof polarized light and the spontaneous polarization (P (s)) direction of ferroelectric crystals. Herein, exceptionallystrong polarization responses to polarized light are achieved in ferroelectriccrystals of (isopentylammonium)(2)CsPb2Br7 (1), which is closely involved with the P (s)-directed BPVE. Structurally, the alternatepacking of organic spacers and inorganic sheets leads to its intrinsicanisotropy of optical dichroism (& alpha;(c)/& alpha;(a) & SIM; 3.1), thus creating sinusoidal photocurrents with a polarizationratio of & SIM;1.2 at 10 V bias. It is noteworthy that the exceptionalpolarization responses with a large polarization ratio of & SIM;7.2can be further obtained based on its BPVE at zero bias (self-poweredmode). This figure-of-merit is significantly superior to that of some2D materials, nanowires, and homologues, e.g., ReS2 (& SIM;3.5),GeSe (& SIM;2.16), CsPbBr3 nanowire (& SIM;2.6), and(n-butylammonium)(2)(methylammonium)-Pb2Br7 (& SIM;2.0). This work sheds light on theoptimization of photoelectric behaviors on the targeted optoelectronicdevice applications by ferroelectric BPVE.