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 position in optoelectronics. Especially, ferroelectric crystals in this family can be potentially used as polarized light detectors because photocurrent, induced by the ferroelectric bulk photovoltaic effect (BPVE), is the function of the intersection angle between the polarization directions of polarized light and the spontaneous polarization ( P s ) direction of ferroelectric crystals. Herein, exceptionally strong polarization responses to polarized light are achieved in ferroelectric crystals of (isopentylammonium) 2 CsPb 2 Br 7 ( 1 ), which is closely involved with the P s -directed BPVE. Structurally, the alternate packing of organic spacers and inorganic sheets leads to its intrinsic anisotropy of optical dichroism (α c /α a ∼ 3.1), thus creating sinusoidal photocurrents with a polarization ratio of ∼1.2 at 10 V bias. It is noteworthy that the exceptional polarization responses with a large polarization ratio of ∼7.2 can be further obtained based on its BPVE at zero bias (self-powered mode). This figure-of-merit is significantly superior to that of some 2D materials, nanowires, and homologues, e.g., ReS 2 (∼3.5), GeSe (∼2.16), CsPbBr 3 nanowire (∼2.6), and ( n -butylammonium) 2 (methylammonium)Pb 2 Br 7 (∼2.0). This work sheds light on the optimization of photoelectric behaviors on the targeted optoelectronic device applications by ferroelectric BPVE.