Centimeter-Sized Single Crystal of a One-Dimensional Lead-Free Mixed-Cation Perovskite Ferroelectric for Highly Polarization Sensitive Photodetection.

Linear dichroic anisotropic photonic materials are highly attractive due to their great potentials in many applications, which in combination with the ferroelectric properties could broaden their research and applications. However, to date, the linear dichroism conversion phenomenon has not been observed in one-dimensional (1D) large-size single-crystal materials: in particular, lead-free perovskite ferroelectric crystals. Here, we propose a new ferroelectric design strategy: namely, partial organic cation substitution for precisely designing 1D polarization-sensitive perovskite ferroelectrics. As an example, the 1D mixed-cation perovskite ferroelectric (n-propylammonium)(methylammonium)SbBr5 was synthesized, which exhibits a fascinating ferroelectricity with a notable reversible polarization of 2.9 μC/cm2 and a large ferroelectricity-driven polarization ratio of 6.9. Importantly, the single-crystalline photodetectors also exhibit superior optoelectronic anisotropic performances at the paraelectric phase, having a large photoelectric anisotropy ratio (∼35), an excellent polarization-sensitive dichroism ratio (∼1.31), highly sensitive detectivity up to ∼109 Jones, and a fast response rate (∼45/68 μs). This finding provides a significant and effective pathway for the targeted design of new functional lead-free linear dichroic anisotropic photonic ferroelectrics.