Precise Tailoring of Unprecedent Layered Perovskite‐Type Heterostructure Ferroelectric via Chemical Molecular Scissor

Abstract Precise stacking of distinct two‐dimensional (2D) rigid slabs to build heterostructures has renewed the portfolio of 2D materials, e.g., magic‐angle graphene, due to the emergence of exotic physical properties. Recently, single‐crystal heterostructures of layered perovskites have emerged as an exciting branch, while it remains scarce to achieve strong ferroelectricity in this new heterostructure family. Here, we present the first ferroelectric of 2D perovskite heterostructures as single crystal, (EA 3 Pb 2 Br 7 )EA 4 Pb 3 Br 10 ( 1 , EA=ethylamine), by precisely tailoring inorganic sheets via a chemical molecular scissor. It has notable ferroelectricity of large spontaneous polarization ( P s ~5.0 μC/cm 2 ) and high Curie temperature ( T c ~375 K). Structurally, its inorganic framework adopts a unique 2D heterostructure that contains two different rigid slabs of {EA 3 Pb 2 Br 7 } n and {EA 4 Pb 3 Br 10 } n . This motif is self‐assembled by layer‐by‐layer clipping of rigid prototype sheets, using extra neopentylamine as a molecular chemical scissor. Unlike epitaxial growth, such a molecule‐level stacking facilitates the growth of heterostructure single crystals. Combining its strong ferroelectricity and inherent anisotropy, crystal‐based device of 1 exhibits an ultrahigh polarized‐light sensitivity up to ~37 in self‐powered mode, being the highest level of 2D perovskite ferroelectric family. Our work will facilitate the further development of ferroelectric materials for optoelectronic device applications.