Alloying n‐Butylamine into CsPbBr3 To Give a Two‐Dimensional Bilayered Perovskite Ferroelectric Material

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Abstract
Cesium‐lead halide perovskites (e.g. CsPbBr3) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr3, we design the first cesium‐based two‐dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C4H9NH3)2CsPb2Br7 (1). Strikingly, 1 shows a high Curie temperature (Tc=412 K) above that of BaTiO3 (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm−2), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs+ ions. To our knowledge, such a 2D bilayered Cs+‐based metal–halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large “on/off” ratios of photoconductivity (>103).
Funding Information
  • National Natural Science Foundation of China (21525104, 21622108, 21601188, 91422301, 21571178, 51502288, 51502290)
  • Youth Innovation Promotion Association of the Chinese Academy of Sciences (2015240, 2016274)

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